| Search | Login/Register
   Home » Melquiades Amplifier » Planning my DSET (132 posts, 7 pages)
  Print Thread | 1st Post |  
Page 3 of 6 (132 items) Select Pages:  « 1 2 3 4 5 » ... Last »
08-08-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 51
Post ID: 21837
Reply to: 21821
LPad in Channel F
fiogf49gjkf0d
Hi Romy,

I am calculating crossover scenarios for the HF Channel (Channel F) and am hoping that you can remember a reasoning for using a 20K LPad instead of a larger value such as 30K or even 50K?  As the larger impedance is used the value of the capacitors reduces and the size of the inductor increases, which I would have thought to be a good thing in terms of the actual performance of the inductor compared to its design specifications.  Unless your aim was to minimise the inductor size or you were just using the LPad that you had available?

I am not sure how increasing the LPad from 20k to 50k would affect the operation of the filters in the other channels.

Regards,

Anthony
08-10-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 52
Post ID: 21839
Reply to: 21837
It does not matter.
fiogf49gjkf0d
 anthony wrote:
I am calculating crossover scenarios for the HF Channel (Channel F) and am hoping that you can remember a reasoning for using a 20K LPad instead of a larger value such as 30K or even 50K?  As the larger impedance is used the value of the capacitors reduces and the size of the inductor increases, which I would have thought to be a good thing in terms of the actual performance of the inductor compared to its design specifications.  Unless your aim was to minimise the inductor size or you were just using the LPad that you had available?

I am not sure how increasing the LPad from 20k to 50k would affect the operation of the filters in the other channels.
  
There is no aspects of minimization of the inductor size. You can go to 30K, or 50K, or 100K input LPAD. The LPAD (which is not inductive switched attenuators with good resistors) anyhow sites behind the filter, so the input impedance of the attenuators will be “visible” by other channels only at HF, so the value of the attenuators is semi-irrelevant. The reasons why I went with 20K is because I would like to keep the value of the resistors that formed the attenuators lower. If I use S102 resistors that have no inductance of any kind then the value of the resistors would be absolutely irrelevant. I use very good resistors for attenuator (RN/CMF55/60), they are metal film and non-indicative but they still have “some” residual inductance and my presumption was that higher value the more inductance. I warn you that this is such an irrelevant minor thins that we can talk about it but I very confident that it has no practical impact to the sound you will get out of it. So, in term of the input attenuators for HF you can do anything you want.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-12-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 53
Post ID: 21847
Reply to: 21839
A few power supply changes
fiogf49gjkf0d
 Romy the Cat wrote:
 
There is no aspects of minimization of the inductor size. You can go to 30K, or 50K, or 100K input LPAD. The LPAD (which is not inductive switched attenuators with good resistors) anyhow sites behind the filter, so the input impedance of the attenuators will be “visible” by other channels only at HF, so the value of the attenuators is semi-irrelevant. The reasons why I went with 20K is because I would like to keep the value of the resistors that formed the attenuators lower. If I use S102 resistors that have no inductance of any kind then the value of the resistors would be absolutely irrelevant. I use very good resistors for attenuator (RN/CMF55/60), they are metal film and non-indicative but they still have “some” residual inductance and my presumption was that higher value the more inductance. I warn you that this is such an irrelevant minor thins that we can talk about it but I very confident that it has no practical impact to the sound you will get out of it. So, in term of the input attenuators for HF you can do anything you want.

Thanks Romy, that is just the information I was after.


I am planning to add an extra power supply just to run the DHT channel.  In the course of things this lets me scale down the power transformer and choke for the first stages of Channels A, B, C (that choke is a monster!) and it eliminates the 56R resistor on the DHT B+ which may or may not be affecting things.  

Also I am scaling down the power transformer for the second stages of Channels A, B, C to roughly half of the specified current rating.  I have a feeling that that trafo is rated 3A because at the beginning of the 6-Channel project there was the potential for 6 x 6C33C, but in the course of development that is now reduced to three.  The smaller power transformer should operate closer to its nominal voltage rating as a result and the chokes that follow will probably operate closer to their rating as well.

Regards,

Anthony
08-12-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 54
Post ID: 21850
Reply to: 21847
The opportunities are endless.
fiogf49gjkf0d
Anthony, there is many areas for power supply scaling down if you want to. You can put an extra 440V coil on your power transformer that driver output stage and have PS for driver stage and perhaps bias. Do not forget that this high voltage do not suck a whole a lot of current, so it will not drive VA and price for the transformer too much up. You can have one dedicated high voltage with filter and from it to power the driver stage AND bias. So, you will effectively have juts 3 transformers: filament, 220V and 440V. It is not to mention the PS for MF-DHT that you will do. I do not know what it will be. It would be nice to have your DHT to be driver by Milq’s driver but it allow would be nice to have a complete departure from Milg for MF and to have DHT driver for MF.
 
With all thing consider it is possible to make one large toroidal transformer to power all amps demands. Call to Maryland or Plitrone and they will give you a price. How affective would be sonically I do not know. 


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-13-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 55
Post ID: 21861
Reply to: 21850
The power supplies
fiogf49gjkf0d
At this stage I am looking at running the two 440V supplies from separate secondaries of the same transformer and likewise for the two 240V supplies.  The guy that is making the transformers thinks this will be the most effective way for my particular scenario.  So all up that will make 3 power transformers (440V + 240V + DHT420V) and two filament transformers.  I will leave some room in there for later on just in case I want to add another DHT channel or two.

I am not sure how large to make the filter caps for the DHT channel.  At this stage I think I will start at 3000uF and perhaps try altering it a little up or down once the system is stable.

On another point, I got to Sydney a couple of weeks ago and listened to Tax's 'Koshka' Melquiades running a heavily modified AG horn system.  I did enjoy my visit and am now quite confident that the Melquiades will suit my objectives.  Of course this is a few hours listening in a new room but I heard a lot of things that I like.
08-13-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 56
Post ID: 21865
Reply to: 21861
How did you do it?
fiogf49gjkf0d
 anthony wrote:
I am not sure how large to make the filter caps for the DHT channel.  At this stage I think I will start at 3000uF and perhaps try altering it a little up or down once the system is stable.

Hm, it is depends how stupid you are. The 3000uF is an average level of stupidity. In my amp I went for 36000 I believe that was accessibly stupid. In some amp DIYers make SETs with 8uF that is unsufficiently stupid. It is about how much you wiling your transformers, chokes and the rest PS and filter to be impactful to sound. Some folks make vintage tube rectification, use super-duper components in filtration and use very small last cap of a special type, let say paper in oil… Then the sound of the amp is 50% of the sound of PS. I do not say that it is bad and with proper tweaking all of it you can get fine result. I do not like this approach and I prefer to use large electrolytic to cancel out any sonic PS contribution. In my amp it is not about the contributive sound of passive elements but rather about unadulterated sound of active elements. Use the filtration to drive ripples to let say 1-3mMv and it would be good start.
 anthony wrote:
On another point, I got to Sydney a couple of weeks ago and listened to Tax's 'Koshka' Melquiades running a heavily modified AG horn system.  I did enjoy my visit and am now quite confident that the Melquiades will suit my objectives.  Of course this is a few hours listening in a new room but I heard a lot of things that I like. 

It is nice to hear BUT: if you heard the Tax's installation then how you concluded that sound you heard was result of “good Melquiades” but not the result of Tax’s heavily modified AG horn system? What I am asking is how you in the sound that you heard you were able to attribute what you liked to the amps but not to numerous other aspects?


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-13-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 57
Post ID: 21872
Reply to: 21865
Two things I really liked...
fiogf49gjkf0d
 Romy the Cat wrote:
 anthony wrote:
I am not sure how large to make the filter caps for the DHT channel.  At this stage I think I will start at 3000uF and perhaps try altering it a little up or down once the system is stable.

Hm, it is depends how stupid you are. The 3000uF is an average level of stupidity. In my amp I went for 36000 I believe that was accessibly stupid. In some amp DIYers make SETs with 8uF that is unsufficiently stupid. It is about how much you wiling your transformers, chokes and the rest PS and filter to be impactful to sound. Some folks make vintage tube rectification, use super-duper components in filtration and use very small last cap of a special type, let say paper in oil… Then the sound of the amp is 50% of the sound of PS. I do not say that it is bad and with proper tweaking all of it you can get fine result. I do not like this approach and I prefer to use large electrolytic to cancel out any sonic PS contribution. In my amp it is not about the contributive sound of passive elements but rather about unadulterated sound of active elements. Use the filtration to drive ripples to let say 1-3mMv and it would be good start.


When I read your text above I instantly realised that the '3000uF' filtering caps that I was talking about were for the two single stage channels and not the DHT channel.  In your DSET schematic you use a 8000uF filter cap that shares the load for three first stages and the entire DHT channel, so perhaps a value around there is a better place to start.  Driving the ripples as you suggest is what I will do.  For a power supply that is driving the DHT channel alone, would you stick with one large filter cap or would you go for multiples of say 1000uF?


 Romy the Cat wrote:

 anthony wrote:
On another point, I got to Sydney a couple of weeks ago and listened to Tax's 'Koshka' Melquiades running a heavily modified AG horn system.  I did enjoy my visit and am now quite confident that the Melquiades will suit my objectives.  Of course this is a few hours listening in a new room but I heard a lot of things that I like. 

It is nice to hear BUT: if you heard the Tax's installation then how you concluded that sound you heard was result of “good Melquiades” but not the result of Tax’s heavily modified AG horn system? What I am asking is how you in the sound that you heard you were able to attribute what you liked to the amps but not to numerous other aspects?


Although Tax has tuned his system to his tastes which are close but do not _exactly_ align with mine the system was capable of playing many genres of music which tells me that it was not a one-trick-pony tuned for a particular 'sound'.  This system-wide determination reflects on the amplifiers as well, because I have heard several SET amps that blatantly impart their signature on the music from all genres particularly when used on lower sensitivity speakers (which Taxes are not).  I don't want to hear the same sounds in all my music and I did not get that from Tax's system even though there were a couple of 'tunings' that I would like to do to align it properly with my tastes.

My biggest take home from the visit was the systems ability to swing in a balanced and cohesive way.  The night before I had been to see Bruckners Eighth at the Sydney Opera House and as you are well aware this piece has large swings in which it seems as though the entire orchestra must throw caution to the wind and just 'do'.  Even in the systems that I have enjoyed there always seems to be a 'compression' with these large swings, and this compression seems to be mostly influenced by the amplifier (and sometimes the source) that is driving the speakers, whatever they may be.  With Tax's system the swing from light to dark to light and the way that it handled the transients in general was always composed and balanced and comparatively non-compressed.  The fact that these transients were handled so well even with Tax's midrange that is a little 'heavy' or 'dark' for me tells me that the amplifier in use is very capable indeed. 

10-18-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 58
Post ID: 22101
Reply to: 21693
Splitting the DSET
fiogf49gjkf0d

So I am currently working towards this concept for my Macondo (see below) and I have just the Upperbass horns left to turn and prep. 
 My Macondo 1.jpg

My Macondo 2.jpg
I am thinking about how to best integrate the DSET with Macondo and have come up with something like this…

My Macondo Aerial 1.jpg

Perhaps it will be possible to build the amplifiers as part of the frame of Macondo and then package the power supplies so that they will fit under the Upperbass Horn.  This will hide them from view and reduce the footprint of the entire audio system in the room. 
Romy, the thing that worries most is heat.  I am concerned that the 6C33C’s and other tubes will cause the drivers above to warm too much if I snuggle the tubes in too close to the frame and I am hoping for your input here.  Are you able to give some indication from your experience with this gear?

I thought that I would set the amplifier section on a platform to the inside of the horn stack (because the bass will go on the outside of the stack, and run cables from the hidden away power supply up to the platform.  Some effective vibration isolation will be installed for both the power supply and the amplifier.

With this arrangement I could hard-wire the speaker cables and the only cables in or out would be a power cord and the interconnects.
I had also thought about splitting the amplifier section into three as follows:  6C33C x 3 Channels down with the power supply;  DHT channel right next to the MF horn;  two single stage channels up high next to their drivers.  However I thought it best to have the crossovering all in one place.  A split amplifier section would require setting up two more bias supplies but I am sure that is achieveable. 
 

Regards, 

 
Anthony
 
10-18-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 59
Post ID: 22104
Reply to: 22101
I do wish you to come up with something in this direction.
fiogf49gjkf0d
Anthony, yes, it is a perfectly legitimate question and I asked myself this question many times. I do think that if you make horn from wood then heat will damage them but if your upper bass horn is from concrete  (like Jessy did) then it does open some possibility. I did not do anything in this direction. As a partial consideration of the subject you might consider to locate the binding post on the amp on a very strategic side to accommodate the location of the horns. There are cons and pros for this solution as you would never know what life prepared to you and where yoou will be moving to a new listening room.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
10-20-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 60
Post ID: 22136
Reply to: 22104
The heat issue
fiogf49gjkf0d
I am certainly looking into an integrated solution.  The first thing that I need to do is determine a safe distance to keep those 6C33C's from the wood or drivers.  I have listened to Tax's fullrange Melquiades once but was not thinking at the time about the proximity to other things as I am now, otherwise I would have made my experiments at that time.  I am still waiting on some final parts to arrive before I build a fullrange Melquiades myself.  In the meantime it would be nice to decide if this could be implemented or not and whether the idea should be dropped.

Romy, are you able to give me some advice on what you think is a safe horizontal separation between 6C33C and the timber?  It would be much appreciated.  Perhaps just use your hand and estimate what you think would be a safe distance so as not to disturb paint or make something too hot in general.  Or perhaps use a thermometer or temperature sensor on your multimeter to get some idea of the temperature gradient from the valves.

I will give Tax a call and ask the same of him, but of course he is just running a single 6C33C.

Regards,

Anthony
10-20-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 61
Post ID: 22137
Reply to: 22136
Be carefully however.
fiogf49gjkf0d
Anthony, I truly do not know. I presume any rise of a temperature around a wood would make wood prone to crack. From different perspective it is possible to come up with some thermal multilayered shields. I am sure if to make it as objective then with today materials it possible to do anything you want and to protect wood. Find somebody who knows and I am sure they would assist you. The only think that I would recommend is to re-asses your objective and make sure that you really want to integrate acoustic system with amps. I admit it sounds very lucrative BUT it also bind the amp with speakers. Generally those binding solutions might be blessing or a souse of major pain in ass in future. So, be very positive that it will be your last amp, last room and last speaker. I was very positive about it at least 5 times....


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
12-21-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 62
Post ID: 22331
Reply to: 22137
All about bass
fiogf49gjkf0d
Hi Romy,

So it is time to think about the bass output transformer in my DSET.  My bass channel will be 8 x 25W/8565-00 each side set in a sealed box and will cover the frequency range below say 100Hz.  These drivers can be wired anywhere between 1R and 64R which gives quite a bit of flexibility for adjusting the amplifier/speaker system damping factor.  Reading your threads about your Scanspeak arrays it is evident that the system damping factor is important for the bass channel and is influenced by the OPT decisions, how the 6C33C is loaded and most likely by how the speaker is wired.  

I propose to wire the drivers in parallel so that they present a nominal load of 1R to the amplifier which in effect will maximise the system damping of the drivers, which from what I take from your writings could be a good thing.  Then I will have a bass OPT wound with a secondary of 1R or 1.1R that will pass 450mA and cover say 5Hz - 800Hz before rolling off.

Romy, given your experience with the amplifier and the drivers, are you able to offer any advice regarding the OPT or wiring of the drivers before I give the transformer winder my final specs?

Regards,

Anthony
12-22-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 63
Post ID: 22334
Reply to: 22331
Approaching the LF DSET
fiogf49gjkf0d
 anthony wrote:
Hi Romy,

So it is time to think about the bass output transformer in my DSET.  My bass channel will be 8 x 25W/8565-00 each side set in a sealed box and will cover the frequency range below say 100Hz.  These drivers can be wired anywhere between 1R and 64R which gives quite a bit of flexibility for adjusting the amplifier/speaker system damping factor.  Reading your threads about your Scanspeak arrays it is evident that the system damping factor is important for the bass channel and is influenced by the OPT decisions, how the 6C33C is loaded and most likely by how the speaker is wired.  

I propose to wire the drivers in parallel so that they present a nominal load of 1R to the amplifier which in effect will maximise the system damping of the drivers, which from what I take from your writings could be a good thing.  Then I will have a bass OPT wound with a secondary of 1R or 1.1R that will pass 450mA and cover say 5Hz - 800Hz before rolling off.

Romy, given your experience with the amplifier and the drivers, are you able to offer any advice regarding the OPT or wiring of the drivers before I give the transformer winder my final specs?
   
Anthony, this is a very good and a very complicated question.  The question is boil down to the following: to connect in parallel and drive low impedance or to connect to series and to drive high impedance. There is no right answer to it in my view as not one did a methodologically clear experiment and got the empirical answers. I would outline for you my thoughts on the subject and what I would do, under no circumstances take it as “right way” to do it as there is no right way. Examine my reasons yourself and with your other advisers and make a decision for yourself.
There are 5 main points that shall be taking under consideration when you think about the subject: output tube, transformer, cables, drivers, usability. Let me to describe each of them.
 
The Output Tube. I personally do not think that there is any difference for the tube to drive low or high impedance behind a proper transformer.  Let pretend your tube wants to “see” 1.500R.  If you have on secondary 0.5R or 64R it would not be any difference for tube with appropriate transformer that converts 0.5R or 64R to 1.500R. It would be a different transformer ratio (and to a degree a deferent transformer design) but I doubt that tube will see some kind of “reactance” on secondary. Consult on the subject with some smart tube amp designers (good luck to find them) but my vote goes to the statement “tube does not care”. 
 
Output transformer. Here is what the thing become complicated. Of you drive ultra-low impedance with step down transformer then your secondary turns will decrease. They primary will have whatever they have for all case but secondary will go lover and lower as load impedance drop and might even become foil-made. That is for sure will make the transformer faster and better for transients BUT your need LF DSET transformer it means you need inductance. As you will be losing your turn on secondary you will be losing inductance and the only way to get it back would be to increase the core size.  You need to put your transformer maker on the task and see if you will be able to obtain a transformer core for half amper gap, no secondary turns and 5Hz at full power. That will be a small refrigerator size piece of iron and it might be very expensive. 
 
Cables. Driving 1R you will be driving current. Driving 64R you will be driving voltage. Some of the cables/connectors behave differently under voltage vs current conditions. Also if you drive 1R with low voltage then you might pick some on like interferences. 
 
Drivers. If you go with 8 x 25W/8565-00 then make sure that your make the right boxes and over dump them. I would use 4 individual boxes by 2 drivers each. I do not think that drivers would care how they are connected. The difference would be in case of driver mismatch. In real world all drivers will be slightly different. You are not a large speaker builder and you won’t be able to pick among 100s driver the best matching drivers. So, if one driver has Fs 20Hz and another 24Hz then the question is: would it be betters for them to be connected in parallel or not. I do not know the answer and I am not informed enough to make a guess. You need to consult with somebody else, BTW, if you do them post a received answer. 
 
Usability. That is bitch. First thing first: how do you know how much your tube need to be loaded? Pretend that it is 6C33C and pretend that you need to load it with 600R to get a balance MF sound. Idle tube more you dive you less harmonics, faster sound, in a way over-burned transients. Loading the tube more five you “slower”, more euphonic sound and more power. That would be true for MF but at LF you will have much less negative impact of tube idling and you might find VERY beneficial to load your 6C33C with 1 kR or 1.2kR. That are not exact number but I just give you an idea. Also, the differences at 1R load are huge. Each change of 0.1R loading will give you a large difference in sound. You will need to hit very prissily and you as you start will not know where to aim. I can only presume that you will be in the realm of 1200-1500R, or perhaps higher but with “odd” transformer and a few other variable it is very hard to predict anything. Do not also forget that with limited wiring on the secondary you will have very limited opportunity to have multiple taps on your transformer as the filling of the barbing will be suffering. 
 
Usability continue. There are more ugly things: as you ideal more your bass tube and get better sound (to a degree) you will be losing power. Even with 8 drivers and let say a single 6C33C you will need a sealed room of let say no more than ~300sq feet or you will be driving your 6C33C into A2, which is a clipping for this tube.  If you have a normal listing room of 600+ with open floor plan then you are way out of your DSET capacity with 6C33C unless you super load the tube and then you have shity sound. Even if you did resolve your problem with power somehow then the ugly truth that it will take time for you to understand what type of bass you need. My estimation that it would be good to stay with properly doe bass for 2-3 months in order to “get” where/how to move next with bass.
 
So, from all that I said above if I were in your position I would not go final DSET solution with bass now but rather did it incrementally.  Make your bass sections, connected them conventionally, let say 16R each and drive them with some kind of SS amp. Then take the SET that you would like to use as DSET and drive it into the bass channel. Play with loading, find the best configuration and make a judgment about sufficiency of power. Then go for a DSET that would be against a conventional load. 4x16R in parallel = 4R. That would be a conventional load and you can use many different amps to try, including your SET, If you test everything with your SET, find a proper loading and get conformation about power then you can converts the found transformer ratio to any another load. 
 
That is basically what I did over the time and this is what I would do if I do it again. Do not forget that your situation might be very different from what mine was in my old city home. Your bass channel will be running under 100Hz and your room dissipation at 100Hz might be very different then at 40hz, so you might need much more power than you might think. It is nice to learn about it experimenting with SET then to pay a lot of money for DSET OPT and then learns that you have not enough DC gap to add another tube in parallel or that you need to lose another 10% turns on secondary and the cost of shipping of the transformers will cost more than a pair of new one.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
12-22-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 64
Post ID: 22335
Reply to: 22334
Many thanks
fiogf49gjkf0d
 Romy the Cat wrote:

Output transformer. Here is what the thing become complicated. Of you drive ultra-low impedance with step down transformer then your secondary turns will decrease. They primary will have whatever they have for all case but secondary will go lover and lower as load impedance drop and might even become foil-made. That is for sure will make the transformer faster and better for transients BUT your need LF DSET transformer it means you need inductance. As you will be losing your turn on secondary you will be losing inductance and the only way to get it back would be to increase the core size.  You need to put your transformer maker on the task and see if you will be able to obtain a transformer core for half amper gap, no secondary turns and 5Hz at full power. That will be a small refrigerator size piece of iron and it might be very expensive. 

I can't see the transformer being small under any circumstances.  My transformer winder is very smart and level headed so I think that I have a good chance of getting a good result with the OPT if I can tell him what to build.

 Romy the Cat wrote:
   Cables. Driving 1R you will be driving current. Driving 64R you will be driving voltage. Some of the cables/connectors behave differently under voltage vs current conditions. Also if you drive 1R with low voltage then you might pick some on like interferences. 

I had not even though about cables, but of course you are right.

 Romy the Cat wrote:
 
Drivers. If you go with 8 x 25W/8565-00 then make sure that your make the right boxes and over dump them. I would use 4 individual boxes by 2 drivers each. I do not think that drivers would care how they are connected. The difference would be in case of driver mismatch. In real world all drivers will be slightly different. You are not a large speaker builder and you won’t be able to pick among 100s driver the best matching drivers. So, if one driver has Fs 20Hz and another 24Hz then the question is: would it be betters for them to be connected in parallel or not. I do not know the answer and I am not informed enough to make a guess. You need to consult with somebody else, BTW, if you do them post a received answer. 

I am a little worried about driver mismatch.  The first thing for me to do in this regard is to run them in on signal for a while and then measure their parameters, matching them driver by driver into groups.  I know just the person to talk to about driver matching so I will give him a call after Christmas to pick his brain.
 
 Romy the Cat wrote:
Usability. That is bitch. First thing first: how do you know how much your tube need to be loaded? Pretend that it is 6C33C and pretend that you need to load it with 600R to get a balance MF sound. Idle tube more you dive you less harmonics, faster sound, in a way over-burned transients. Loading the tube more five you “slower”, more euphonic sound and more power. That would be true for MF but at LF you will have much less negative impact of tube idling and you might find VERY beneficial to load your 6C33C with 1 kR or 1.2kR. That are not exact number but I just give you an idea. Also, the differences at 1R load are huge. Each change of 0.1R loading will give you a large difference in sound. You will need to hit very prissily and you as you start will not know where to aim. I can only presume that you will be in the realm of 1200-1500R, or perhaps higher but with “odd” transformer and a few other variable it is very hard to predict anything. Do not also forget that with limited wiring on the secondary you will have very limited opportunity to have multiple taps on your transformer as the filling of the barbing will be suffering. 

Yes, the tube loading is something that I need to play with in order to more fully understand its effects.  To be honest this is the part that worries me most.

 Romy the Cat wrote:
 
Usability continue. There are more ugly things: as you ideal more your bass tube and get better sound (to a degree) you will be losing power. Even with 8 drivers and let say a single 6C33C you will need a sealed room of let say no more than ~300sq feet or you will be driving your 6C33C into A2, which is a clipping for this tube.  If you have a normal listing room of 600+ with open floor plan then you are way out of your DSET capacity with 6C33C unless you super load the tube and then you have shity sound. Even if you did resolve your problem with power somehow then the ugly truth that it will take time for you to understand what type of bass you need. My estimation that it would be good to stay with properly doe bass for 2-3 months in order to “get” where/how to move next with bass. 

The room is 280sq feet and sealed.  It has a raked ceiling but to offset that there is also a degree of soundproofing which reflects energy back into the room.  I had considered to use a SS amplifier for the bass as a benchmarking tool...I think that I would be foolish not to.
 Romy the Cat wrote:
 
So, from all that I said above if I were in your position I would not go final DSET solution with bass now but rather did it incrementally.  Make your bass sections, connected them conventionally, let say 16R each and drive them with some kind of SS amp. Then take the SET that you would like to use as DSET and drive it into the bass channel. Play with loading, find the best configuration and make a judgment about sufficiency of power. Then go for a DSET that would be against a conventional load. 4x16R in parallel = 4R. That would be a conventional load and you can use many different amps to try, including your SET, If you test everything with your SET, find a proper loading and get conformation about power then you can converts the found transformer ratio to any another load.
That is basically what I did over the time and this is what I would do if I do it again. Do not forget that your situation might be very different from what mine was in my old city home. Your bass channel will be running under 100Hz and your room dissipation at 100Hz might be very different then at 40hz, so you might need much more power than you might think. It is nice to learn about it experimenting with SET then to pay a lot of money for DSET OPT and then learns that you have not enough DC gap to add another tube in parallel or that you need to lose another 10% turns on secondary and the cost of shipping of the transformers will cost more than a pair of new one.

This is a much more balanced approach than I was considering.  Yes, I should build the bass arrays first and test them in my room with SS to be sure that a SET can power them in that situation.  That has to be step number one.  Then, if warranted, experiment to sort out the DSET OPT specs.  Luckily, my transformer guy in Australia has finally agreed to build this OPT, so freight will be inconsequential compared to the international transit that I was facing a while ago.

Thanks Romy for your thoughtful and and considered input here.  It is very much appreciated.

Regards,

Anthony

12-22-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 65
Post ID: 22336
Reply to: 22335
SS amps do generally very bad bass.
fiogf49gjkf0d
Interesting. with sealed 280 sq feet and 8 drivers per side along a long wall you very much migh be able to use a singe 6C33C. With proper loading, good trasformer, DSET and these drivers you should be able to get bass that I doubt you will be able to get from any SS amp.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
12-24-2015 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 66
Post ID: 22352
Reply to: 22336
The long wall?
fiogf49gjkf0d
Romy, I have seen you mention setting speakers up across the long wall before but never got to the base of your reasoning?  Could you please elaborate?  Is it to do with the delay of first reflections?

12-24-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 67
Post ID: 22354
Reply to: 22352
Multiple reasonings…
fiogf49gjkf0d
 anthony wrote:
Romy, I have seen you mention setting speakers up across the long wall before but never got to the base of your reasoning?  Could you please elaborate?  Is it to do with the delay of first reflections?

The line-arrays that I used do load rooms with MUCH less problems across the long wall, it pretty much any acoustic system topology has more linear lower octave behavior across long walls. The positioning of bass section outside of the horns makes the system spread wide long wall positioning give you a lot of room of maneuver. With wall positioning you have wider room to play and you can find that precise location when system drops center image and breaks the imaging curve. If you use a short wall then this location might be just a few inches from you on the left and right but you never get there because there will be a walls on your way.  I always love how any acoustic systems image extended toward to mid of the rooms and across long walls. I do not feel that good thinks can’s not be done across short walls but if I have a chose then I would always go wide.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
12-25-2015 Post does not mapped to Knowledge Tree
noviygera


Chicago, IL
Posts 142
Joined on 06-12-2009

Post #: 68
Post ID: 22356
Reply to: 22336
This is interesting!
fiogf49gjkf0d
 Romy the Cat wrote:
Interesting. with sealed 280 sq feet and 8 drivers per side along a long wall you very much migh be able to use a singe 6C33C. With proper loading, good trasformer, DSET and these drivers you should be able to get bass that I doubt you will be able to get from any SS amp.

Romy,why do you feel the SS amps will not provide as good bass as tube amp? Since there is such a big selection of SS amps, also hybrid one, is it a general rule, regardless of amp power and type? Is it the type of distortion that's inherent to tube amps that makes them specially enjoyable in the bass region? 
12-26-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 69
Post ID: 22357
Reply to: 22356
Why do you feel what I feel? I do not.
fiogf49gjkf0d
 noviygera wrote:
Romy,why do you feel the SS amps will not provide as good bass as tube amp? Since there is such a big selection of SS amps, also hybrid one, is it a general rule, regardless of amp power and type? Is it the type of distortion that's inherent to tube amps that makes them specially enjoyable in the bass region? 
Well, can answer a question why do I “think” and bring many existing theories why SS do not do bass well. I do not know what theory would be “right” but I do not particularly care “why”. So, what I do it use purely imperial evidence without caring too my “why”. If I look at the best SS amps that I even hear and compare the bass they produce with best SET that I heard then it is very clear to me that no SS amp can even close to state to a good SET in bass performance. If you do to bass DSET world and do proper uploading of Triode and manage to maintain bass still in Class A then in my view (feeling) you get the best bass audio is capable to produce. Why? Well, I have too much on my plate now to care. I would prefer to listen the Poulenc’s Organ Concerto then to wax poetry about reasons that will not able to proof anyhow.
 


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-28-2016 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 70
Post ID: 22690
Reply to: 22334
First bass OPT prototype...
fiogf49gjkf0d
 Romy the Cat wrote:

 
Output transformer. Here is what the thing become complicated. Of you drive ultra-low impedance with step down transformer then your secondary turns will decrease. They primary will have whatever they have for all case but secondary will go lover and lower as load impedance drop and might even become foil-made. That is for sure will make the transformer faster and better for transients BUT your need LF DSET transformer it means you need inductance. As you will be losing your turn on secondary you will be losing inductance and the only way to get it back would be to increase the core size.  You need to put your transformer maker on the task and see if you will be able to obtain a transformer core for half amper gap, no secondary turns and 5Hz at full power. That will be a small refrigerator size piece of iron and it might be very expensive. 


My transformer winder has completed the first prototype DSET bass OPT.  He was quite excited when he called me and used the word "phenonomenal" to describe its performance into a reflective 1R load.  At 4Hz it is down 0.5dB and at 10kHz and 20KHz it is down 1dB and 3dB respectively.  We were certainly not chasing the high frequencies but they seem to be there nonetheless...it is quite a full range OPT.  The tube load is 2kOhm, which is higher than intended, but it still puts out 9w at 5% distortion into 4Hz at 1R, virtually all 2nd harmonic.  The filter caps in the test circuit are only 680uF and they are visibly pulsing when seen on the oscilloscope so are struggling at that output but the 15kuF caps for the amplifier should improve the performance some more.  Lucas says the square wave at 1w is "almost perfect".

So, I have to make a decision regarding the direction for a second prototype, if indeed I should bother with a second at this stage. I think that 9w output into 1R will be fine athough if the plate is loaded more lightly then I may pickup another watt or more.  It is the 2kOhm plate load that concerns me...is it too high? Is it just right?  Who knows?  Shortening the primary or secondary is going to affect inductance but this may be overcome by going up not one, but two core sizes and using larger wire.  Then of course I could wire the speakers up so they load at 2R which would give more secondary wire, more inductance and the primary could be shortened to reduce the tube load to something more moderate.  

Could any of these things improve the sound?  Does the first prototype sound ok?  All questions with no real answers.  I am tempted to stay with the 2kOhm plate load as we have in the first prototype and see how well I can make it sound.

Anthony


07-28-2016 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 71
Post ID: 22691
Reply to: 22690
I do not know.
fiogf49gjkf0d
 anthony wrote:
My transformer winder has completed the first prototype DSET bass OPT.  He was quite excited when he called me and used the word "phenonomenal" to describe its performance into a reflective 1R load.  At 4Hz it is down 0.5dB and at 10kHz and 20KHz it is down 1dB and 3dB respectively.  

 
That all make sense ONLY if we are taking about max power. You will not get from your transformer 0.5dB at 4Hz and 3db at 20KHz at max power and the fact that your guy gives you the numbers at a fraction of power does not make me too happy about him….


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-29-2016 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 72
Post ID: 22692
Reply to: 22691
Yes, that is right...
fiogf49gjkf0d
 Romy the Cat wrote:
 anthony wrote:
My transformer winder has completed the first prototype DSET bass OPT.  He was quite excited when he called me and used the word "phenonomenal" to describe its performance into a reflective 1R load.  At 4Hz it is down 0.5dB and at 10kHz and 20KHz it is down 1dB and 3dB respectively.  

 
That all make sense ONLY if we are taking about max power. You will not get from your transformer 0.5dB at 4Hz and 3db at 20KHz at max power and the fact that your guy gives you the numbers at a fraction of power does not make me too happy about him….


That was all data given to me over the phone in real-time as he measured the setup late at night.  He did some more testing today and it turns out that there is a bit more there than 9.5watts at 5% distortion...it was not the opt running out of puff but the the amplifier he was using for the signal generator...the tube and opt were still quite accurately passing the signal as it came to it from the generator.  With that rectified and some full power testing for bandwidth it became clear that the tube is too stiff when loaded at 2kOhm and that the grid clips before the opt does, but at 5.1w into 1R (which is where the grid was clipping) the output was down 0.6dB at 4 Hz, so at full power it still should be well under 10Hz

So, after all that and studying the tube curves the decision made is that the tube definitely needs to be loaded closer to 1500R as was originally intended and to do that we need to go up two core sizes (no inductance gain if we go up only one core size) and use larger diameter secondary wire.
08-07-2016 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 73
Post ID: 22702
Reply to: 22692
DSET Grounding
fiogf49gjkf0d
Hi Romy,

I am designing the power supply chassis for the DSET at the moment and hope that you can remember some things about how you managed the grounding.

All power supply components up to but not including the filter caps for each power supply will be held in the PS Chassis with the remainder held in the Amp Chassis.  I assume that this is how you managed things.  My question is basically whether you amalgamated the DC ground inside the PS or whether you waited until the Amp Chassis to join to common ground?  If the grounds for the various power supplies are joined in the PS Chassis then we would get away with fewer ground wires in the power cables between the boxes but this is not an issue for me, there are plenty of wires in my cables and connectors.  

I suppose this question then extends to the Bias PS, the centre tap for the filament transformers and the electrostatic screens for the various transformers...do you ground those in the PS or Amp Chassis?  According to the schematic, the Bias PS will be attached to common ground in the Amp Chassis.

Thanks for your help,

Anthony 
08-08-2016 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 74
Post ID: 22703
Reply to: 22702
As far as I remeber.
fiogf49gjkf0d
Anthony, I do not remember details now but the basic was following. I selected on PS and Control chassis single locations that I considered the main grounding points. Within PS chassis if was a negative terminal of the last filtering cap and within Control chassis it was negative side of the input RCA jack.  Those locations I called main negative thermal and they were connected direct via thick cable between PS and Control units. The main negative thermals I made think. I think it was 4-6 8ga wires and flooded with solder. I connected everything to them as star join with a difference that I made main negative thermals long like snake and positioned them in the chassis strategically in order to optimize and shorten the length of the negative wires to the ground. Do not forget the in Milq the negative thermals are cathode supplies and it is kind of important.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
10-19-2016 Post does not mapped to Knowledge Tree
anthony
Posts 191
Joined on 08-18-2014

Post #: 75
Post ID: 22821
Reply to: 22703
DSET Bass OPT is wound
fiogf49gjkf0d
The Bass OPT's for my DSET have been wound.  We have come back to a 1000R plate loading and into 1R the 6C33C grid clips at 9.36W and 5.8% distortion.  The -0.5dB points at full power are 5.9Hz and 5kHz.

A nice result really, and about where I thought the power would end up, although obviously it would be nice to have a little more.  9W before grid clipping should be enough in my room, and even if things are pushed harder the 6C33C/OPT will still push 15W at 10% distortion into 1R.

I also had Lucas test the output into 5R, and we got 17W at grid clipping and about 2.7% distortion.

When using such a low speaker impedance as 1R, the quality and type of connections between the OPT and the transducers really makes a difference...so it looks like I am going to have to hard-wire this channel.  Think about the effect of a 0.5R binding post in addition to a 1R speaker load...that is a large percentage of the nominal.
Page 3 of 6 (132 items) Select Pages:  « 1 2 3 4 5 » ... Last »
Home Page  |  Last 24Hours  | Search  |  SiteMap  | Questions or Problems | Copyright Note
The content of all messages within the Forums Copyright © by authors of the posts