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10-26-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 51
Post ID: 17235
Reply to: 17234
I think you will do more experiments….
fiogf49gjkf0d
KOTriode, I was not criticizing your DAC, whatever it is. I was saying that system-design-wise if your preamp was able to inflict such a dramatic change in Sound then in my view it just highlighted the problem with DAC. Take another DAC, or any commercial CD/DVD player from your kinds room, or a phonostage or a tuner or a tape-machine of any another front end you have and try to make the same experiment. It will instantly give you the idea if what you observe is the preamp generic sound or it was the weakness of preamp to drive your speakers directly. General what you describe is very common for DACs that has passive output stage, or just one transformer right after decoder…..

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
11-02-2011 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 52
Post ID: 17274
Reply to: 17235
Lower hum on 6C33C preamp.
fiogf49gjkf0d
After spending considerable amount on the hum problem, one way to fix it is tho remove transformer and place it in a different chassis, the noise level will improve more than 15 db to -74db. But that cause too much hassle, so I got it improved to 62db (by 4-5 db) by wrapping the transformer with a piece of foam to remove transformer vibration from chassis, then 2 pieces of old VPI magic brick on the output transformer. Now the level is low enough that I can hear just a little bit sitting 7-8 feet away from the speakers with volume all the way up. 


 
11-02-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 53
Post ID: 17277
Reply to: 17274
What kind noise is it after all?
fiogf49gjkf0d
KOTriode, am and not exactly following what you are saying. You are talking about mechanical noise coming from a transformer or that fact that transformer arouses mechanically of inductively some noise that you can hear from loudspeakers? 

THe Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
11-02-2011 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 54
Post ID: 17285
Reply to: 17277
60Hz hum
fiogf49gjkf0d
IMG_6229_a.JPG
It's 60Hz hum, caused by both mechanical and magnetic field coupling to the output transformer. I used a toroidal transformer and thought it would not caused this problem but it did. When using an external power supply for both B+ and heater (AC), the noise went down to around -74db, another 12db improvement. The output transformer is 1:1 and does not have magnetic shield, it picked hum easily. So, for now I just use the preamp the way it is, but in the future, if I build another 6C33C preamp, which I certainly will, I will have the power supply on separate chassis.
11-02-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 55
Post ID: 17289
Reply to: 17285
Yes, that sucks...
fiogf49gjkf0d

 KOTriode wrote:
It's 60Hz hum, caused by both mechanical and magnetic field coupling to the output transformer. I used a toroidal transformer and thought it would not caused this problem but it did. When using an external power supply for both B+ and heater (AC), the noise went down to around -74db, another 12db improvement. The output transformer is 1:1 and does not have magnetic shield, it picked hum easily. So, for now I just use the preamp the way it is, but in the future, if I build another 6C33C preamp, which I certainly will, I will have the power supply on separate chassis.

Well, the sexy configuration of your chassis does certainly have toll. Whatever I even built, no matter how little it was used separate chassis for transformers and power chokes with the last cap on the control chassis. Well, I did built one headphone amp that had all together but that project went to nowhere as it sounded like crap.

I think with use good cans it is still possible to mount a good toroidal in soft wax and to hide it mechanically and magnetically from the rest of the circuit. It for sure shall not be sitting in the middle of chassis…

BTW, one very important think, did you check your PS for incoming DC? Toroidals are notoriously horrible if they see any DC on primary. Most of the RMS meter will not measure DC properly with 120AC, at least my Flukes do not do it. so, you might run juts for teat the am from some kind of 1:1 isolation transformer and to see it comfort your in chassis toroids. I have a good success to place the transformer on the fat sheets of sorbotan and isolated them with MuShield sheets. Still, nothing can beat the transformers sitting in … basement and rung a long cable to control unit. The long cable in this case acts as a wonderful decupler between the filtering stages….

The caT

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
11-02-2011 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 56
Post ID: 17292
Reply to: 17289
6C33C vs 845 preamp
fiogf49gjkf0d
One last thing I can do is buy some Mu metal sheet on Ebay and lined up the transformer can and potted with wax as you said, but that's too much work and probably do not work as well as on a separate chassis, so for now I will listen the way it is and compare with some other preamp, one of my favorite is a 845 transformer coupled preamp  that I build a few moons ago. 

IMG_6230_a.JPG
11-02-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 57
Post ID: 17294
Reply to: 17292
Regarding your transformers, make it flipable.
fiogf49gjkf0d

Ah, you use those gorgeous VPI boxes to host transformers. No wonder it does not sound well, what did you see the anything from VPI sound well? Seriously, I do have those VPI boxes, I do not remember where they come from to me but they are too good to wasted them and I keep in them cartridges mounting hardware.

Regarding your transformers. You might do what I did with my Melquiades. When I made my Super Melquiades 6ch chassis I was not experienced with the fact that it will be too many and too powerful transformers and chokes in there at very close proximity. So, I had quite a lot of mechanical noise. The Melquiades chassis is very strong – 4mm steel. Now I understand as it was a mistake and it had to be me non-ferromagnetic material for PS chassis. For the control unit there is nothing better than steel but the PS I would go only aluminum.

Anyhow, to redo everything was too much pain in ass and I kept fighting with mechanical noise coming from stray felids of my transformer and chokes.

http://www.goodsoundclub.com/Site_Images/SuperMilq5.jpg

Then when I a few year I went for toroids I came with a cool idea to lift the transformers from the surface of chassis and to orient their stray fields parallel to the chassis and perpendicular to each other. The frame the attached the toroids to chassis I made from aluminum.

http://www.goodsoundclub.com/Site_Images/SuperMilq_6Ch_3.jpg

so, today I have 4 small pieces of magnetic inside:

http://www.goodsoundclub.com/Site_Images/SuperMilq_6Ch_50.JPG

 and 8 outside:

http://www.goodsoundclub.com/Site_Images/SuperMilq_6Ch_53.JPG

The noise is very low, practically negligible is there is no DC in power lines but I use PP2000 that have my ass with DC.

So, you might do something similar or even kinkier. Put your power transformer in a can or on the box you have it now but make the cable that run to chassis loose. Then attach an expendable arm from chassis to transformer can that would flip and extend the transformer from the chassis. If you go very crazy then you can put a micro switch under the transformer and as the transformer sit in it default transporting position then the amps is off and if the transformer is lifted and extended off the chassis then the amp turn on.

Rgs,
Romy the Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
11-02-2011 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 58
Post ID: 17296
Reply to: 17294
It's OK for now.
fiogf49gjkf0d
I used those VPI magic brick sitting on top of the transformer, my audio analyzer tell me that these bricks helped the noise by about 1db, may be the 6 lbs or so weight does damp the xformer vibration, so I leave them on, just trying everything to keep the hum low. 
You have a good point about changing the position of the toroidal, I have thought about standing it up, but the wire I cut was too short to move the transformer. The hum from magnetic field must be pretty high from these toroidal, because when I remove the can and the toroidal is exposed naked, the hum was higher by 3db!
For now, the hum level is slightly audible, good enough for me to go on and compare the 6C33C preamp sonic to other. Onto the 6C33C amp, on my second set of tube (not the golden grid), which has about 50 hrs of playing in the amp, are pretty stable now, the bias current reach to the exact 200ma setting after about 15 minutes every time, so far no surprise.... I never have problem with hum in this amp, I guess with the step down ratio of 600:4, it is not sensitive as the preamp 1:1 in therm of noise and magnetic field.
03-14-2012 Post mapped to one branch of Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 59
Post ID: 17962
Reply to: 17296
6C33C amp/preamp follow up
fiogf49gjkf0d
Wow! I did not realized that almost 4 months have passed since I wrote last.
Quite a few things have happened the last 4 months that I have played with the 6C33Camp/preamp combo. I have tried at least 3 different vendors on the Ulyanovsk type, the Gold Grid plate (from Bulgaria) and Svetlana. The amp ran without any problem, I have modified the amp power supply by changing the power transformer to a beefier 400W toroidal, twice as much VA, so that I can experiment the 6C33C tubes with plenty more current and voltage. I changed the rectifier tubes from 5R4WGY to 5AR4. I ran the output tubes at around 220V and 240ma, that's about 53W of plate dissipation. The Bulgarian tubes after about 60 hrs of playing, showed instability in bias on both tubes, the current would changes every 15 minutes after I bias them to 220ma sometimes it will go up to 240ma, sometimes go down to 200ma, tube bias just dont want to stay put. After I got 20 new Svetlana tubes, I picked random 2 tubes, burn-in the heater for about 5 hrs, put on power, biased them at 230ma, it will stay the same times after times of power up and during long listening session. I have played more than 50 hrs on the Svetlana and quite happy with them. Few days ago I checked prices of these tubes, and was surprised that the asking price now is twice of what I have paid (and from same seller!) . The 6C33C Ulyanovsk in the preamp dissipate 6W of plate power ,worked without any problem, and very stable bias current. These 6C33C are suprising low in microphonic for an output tubes, I would say its microphonic level is as low as a good 9 pins or octal tube and much lower than any other output tubes.

I started to break-in the preamp/amp mostly with DAC sources but change to vinyl at about the 100 hrs mark and up to now, I believe I am familiar with the 6C33C tubes sound characteristic.

- Upon listening, one would recognize these 6C33C has huge and big sound, not too different from 845 tubes in what Romy characterized as Elephant Sound which not many other tubes that I have tried shares this same trait, and it is the main reason that I like the sound of 845.- The second character that stand out the most of the 6C33C tubes is the schockingly level of micro detail and focuses that these tubes revealed without adding a touch of brightness to the music when listening to a recording like John Klemmer Arabesque from Nautilus direct-to-disc. On a guitar recording of Kiyoshi Shomura playing Danza Espanola on the first cut, you can clearly hear the sound of the guitar string plucked and each breath the artist takes when playing. By comparison the 845 sounded dark and the leading edge transient is soften.- On dynamic, the 6C33C tube showed its ability to go deep in the bass on Ray Brown trio recording of Soular Energy which is excellent for a 15W SE , the 845 amp can do better, but not by much, but probably because of its 25W output give it more headroom than the 6C33C.- One always think that you have to use directly heated triode to get the best midrange out of a tube amplifier, the 6C33C proves that it is no longer necessarily true. The 6C33C is simply so revealing and coherent on pair of stacked Quad, it just sound much better than many amp in my stable, and that's include a pair of Futterman OTL 3.

- Distortion: the 6C33C is not very linear, in audio amplifier it exhibits the highest level of distortion than any power tube.

The 6C33C tube got to be the best buy tube in history, it provide so much level of musical enjoyment for such a price. In a multi-amp system, I would prefer to use the 6C33C for midrange and high, 100Hz up, I think it's hard to beat the 6C33C it's unfortunate that its power output is inadequate to power woofer even with one 100db/w sensitivity.
03-14-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 60
Post ID: 17964
Reply to: 17962
Feedback to the 6C33C review.
fiogf49gjkf0d
 KOTriode wrote:
On dynamic, the 6C33C tube showed its ability to go deep in the bass on Ray Brown trio recording of Soular Energy which is excellent for a 15W SE , the 845 amp can do better, but not by much, but probably because of its 25W output give it more headroom than the 6C33C. .

I do know the sound of 845 and 211 tubes and I feel that properly implemented 6C33C shall way over-perform them in dynamic and bass. The advantage that 845 has is by the fact that it is a 845 direct heated tube and by definition the direct heated might gently enter the grid currents and run in A2. 6C33C in contrary is indirect heated and it even theoretically can’t operate properly with grid currents. If eve if you give to 6C33C super powerful driver than as soon swing in grid approaches the bias voltage the tube will just clip. The direct heated do not clip, the run higher distortions but the still are operational in A2. This gives to people who do not care HOW the amp running a feeling that 845 has more bass sand more dynamic.  The reality is that one need to be certain if the sensitivity of his acoustic system is enough to be able to use 6C33C in A1 , if not then all bets are off. I was laughing to see the idiots big-Willson user who claim that that bough Lamm ML3 and feel that it has more dynamic and more bass then Lamm ML2.0. I did ask them if any of them ever seen on scope what happen when 18W Lamm SET begin to drive the dead 15” Willson ported woofer. Of cause they have no idea what I even asked – they are too “big” reviewers to pay attention to such “small” things. Anyhow, if the 6C33C is not stressed to A2 then I do feel that 6C33C has better bass then any 845 I heard.
 KOTriode wrote:
One always think that you have to use directly heated triode to get the best midrange out of a tube amplifier, the 6C33C proves that it is no longer necessarily true. The 6C33C is simply so revealing and coherent on pair of stacked Quad, it just sound much better than many amp in my stable, and that's include a pair of Futterman OTL 3.

I do not necessary agree with it. The “best midrange” is a complex subject. I have absolutely no problems with 6C33C midrange but there is more to it. If you run multi-way installation then you have you own custom objective to the sound of MF channels. You change the compression driver; crossover, you play with wires and with many other aspects, I went even further and added tonal injection as I was not able to get tone I needed from one MF. The 6C33C has very nice and clean midrange but it has only one type of midrange. If one would like to add own specific twist into out of midrange MF channel then 6C33C, in my view, does not give a lot of options. You can get many different productions of 6C33C and they all will sound the same more or less. With directly heated triodes we have fallibility to find the character we want among many options. As I went for DHT I was paling with dozens of different tubes unit I found the one that doe the best in context of the rest of my efforts. If you compare the 6C33C midrange with the midrange on my current MF DHT tube (YO186) than the DHT will be laughable. I guess it produced a huge amount of distortions but you would never seen a person who walked out of my room and did not claim the it was the cleanest and the most interesting MF s/he even heard. The point that I am trying to make is that in context multi-ampling the 6C33C is not the most flexible tubes if one goes for any custom characters for given channel. The 6C33C is very clean and too straight forward for “some” applications.

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-14-2012 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006
Post #: 61
Post ID: 17966
Reply to: 17964
Driving Miss Daisy
fiogf49gjkf0d
KOT, with the ML2s I found very little difference in the sound of various 6C33Cs, but the old Svetlanas certainly "held to spec" better (and longer..).  I find the 6C33C to be more "direct" sounding than 845 or 211, but this in the context of a 3-stage amp, and I was limited in my choice of 2nd stage tube.  The input tube was certainly a factor, so I ass-u-me the driver matters as well (as with most tube amps).

I have to say I think any low-power amp will be (and should be) critically limited as far as loading, rather than over-driven.  IMO, A2 is nice only to give more A1 headroom; but with the IHT I think feedback "helps the ML2 drive more difficult speakers", and I think parallel output would be the only option for more power from 6C33Cs, if to attempt 15" drivers.

Sure, some won't "like" the 6C33C because it is not "magical"; but I like that it allows fine tuning in other areas.

By the way, one should NOT get "elephant sound" from 6C33Cs (and I think this may be one reason why some don't "like" them...).

Maybe keep playing with operating points...

Best regards,
Paul
03-14-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 62
Post ID: 17967
Reply to: 17964
6C33C amp/preamp follow up
fiogf49gjkf0d
The reason that I built the 6C33C preamp was to explore the 6C33C true musical potential like I did with the 845. Not only did I compare the sound of these tubes in power amp, but also in preamp. The reason is that with power amp you might hit some limitation with commercially available output transformer. For 845 there are many excellent choice of output transformer, but it is very limited with the 6C33C. For preamp since the bias current is much lower you can basically use the same preamp output transformer for both tubes, which is what I did. The 845 gives much more bloom in the bass, goes much deeper and give you sense of plenty power, the 6C33C while quite good, has very tight bass but there some sense of dryness (where is the beef?) . But from 100Hz up it is where the 6C33C really shine, the 6C33C can focus on voice and instrument fantastically which I think the low microphonic level of this tube has something to do with it, the 845 imaging is blurred when compared to 6C33C. And then, the 6C33C high is so airy opened and extended, which would make it an excellent tweeter amp. I also think the power is the 6C33C Archille's heel, the linearity of the tubes rank probably at the bottom of your power tube list once you pushed them over 4-5 watts, yes you can corrected with feedback, but then you will loose some of its magic quality, which I dont implement in this amplifier.Now, I have forgot to mention the speaker type used when I raved about the midrange of the 6C33C. I tried them in 3 different system, a Supravox based 8in Field Coil and ribbon tweeter, an Open baffle Supravox field coil bass, midrange and RTR electrostat, and the Stacked Quad. All these systems, even with the 100db sensitivity of the Supravox would need more than 10W to drive, so that eliminates all the flea power amp such as 10Y, 2A3, VT62.... which does not leave much for choice as DHT amplifier. In the future, I would like to try the 6C33C in a horn system, which probably happen in the next 6 months or so, with the compression driver 1-2 watts power required, there will be more player.  So, the term "best midrange" so far would apply only to the speakers that I have tried. It is also very interesting that out of 4 different 6C33C tubes that I have tried, they are all sounded very familiar but my preference is the Svetlana labeled tubes so far, they performed as what a good tube should be, no crackling sound, no bias drift, no surprise.... so far.Regarding the "elephant sound", what I meant is that the 6C33C do throw a very large soundstage, depth, a big sound. What the 6C33C did that the 845 does not is the ability to focus on instrument and voices, the image size is just correct, not bloated like the 845, if you happen to compare the 845 side by side with the 6C33C you will feel like you just put on corrective lens with the 6C33C, the image become so sharp, you can hear every little detail but the size of the landscape still is the same as the 845.It is unfortunate that there is not many output transformer choice available out there to explore the 6C33C full potential, it would be nice that there is a transformer available for PSE 6C33C with 40 watts capability, I completely agreed with Paul that any 15 and even 12 inches woofer would appreciate 30-40 watts of power, even the ones with 100db sensitivity. Just for fun, you can see the Stereo 6C33C in action here in action in a tri-amp Supravox field coil + RTR electrostat system along with 845PP and 300BPSE but please dont judge the sound quality of the system through a $100 video camera.
http://www.youtube.com/watch?v=3qvoyh1jznQ
03-14-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 63
Post ID: 17968
Reply to: 17967
It will wary with implementation…..
fiogf49gjkf0d
I see now. Quad can’t be driven by single 6C33C. This is well know fact and I did a lot of experiments with Quads and Lamm ML-2.0. For whatever reason as ML-2.0 drives Quads it produces Stingy Sound. I can’t explain it but it is not the sound that ML-2.0 and Quads are capable under the best conditions. When I sold my Lamm then one of my ML-2.0 was interned to by a guy from West who was a big Quads devotee. I did tell him many times that it will not sound as ML-2.0 is able to sound but he bought them anyhow. He reported that he loved it but I never believed him, or cared. Warn you that ML-2.0 runs global feedback and it has to be able to drive Quads better then something like Melquiades. I never tried Melquiades with Quads but I think ti will be even worth then Lamms.

Also about the sub 100H bass.  For whatever reasons the amps with 6C33C are very sensitive to plate loading when they do lower bass.  I have seen the situation that 1/2R of secondary impacted bass hugely.

Now about the “some sense of dryness”. Yes, I would confirm that it might be the case and in some designs 6C33C do have a tendency to sound like SS amp. I think it is a properly of des but the property of the tube. In fact I feel that it is in many cases the properly of the driver. If you make 6E5P-6C33C two stages then you will see that the amp has some dry SS feeling. Add to the amp the Melquiades-style biasing of the driver stage and you will get superb most feeling with bass 10 times better then it was with battery or fix-bias of 6E5P.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-14-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 64
Post ID: 17969
Reply to: 17968
Quad and 6C33C
fiogf49gjkf0d
Forgot to elaborate the Quad system.It is actually a tri-amp Quad system, below 100Hz is the Supravox 15in Field coil in open baffle, then it's a Stacked Quad ,and about 5Khz there were 5 RTR ESL cell. I did try the 6C33C amp in a single pair Quad by itself, and I understand what you mean by Stingy sound, there is nothing to write about it. But in a tri-amp stacked Quad system with 6C33C (I did try couple different amp including the 845), I would say wow! Even the guy who sold me the pair of bronze Quad heard it and could not believe such difference in Quad sound when you stacked them. Anyway, the 6C33C was used here as at its best driving the Quad from 100Hz- 5Khz.Using the 6C33C in the preamp, alone without any driver tube, I do detect the bass as described, but it is not a bid deal as you think,the difference is there, but  in fact it never bother me at all, since the sonic qualities of the 6C33C is already way beyond my expectations. 
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Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 65
Post ID: 17970
Reply to: 17969
The 6C33C dehumidifier.
fiogf49gjkf0d
I see, this tri-way Quad system for sure shall be much different from regular Quas. I kind of even understand why you stay with open baffle bas to support the system’s bass. For sure it will not Bruckner-style pressurize a room as non-dipole bass would do but it for sure shall go alone with Quads well. I would like like to hear the think, which city are in? So, essentially when you talk about bass from 6C33C you were talking about the 6C33C amp drive sub 100Hz woofer or effectively in might be a bass DSET?  Try to play with 6C33C loading. I do not know the Supravox drivers and particularly in open baffle and electromagnets drive but among the drivers that I experienced I have seen that 6C33C is very sensitive for loading. If you feel that it was “but too dryness” and if you need to get more “beef” than just make the tube to idle a bit less. You will pick up more harmonies (and get more “beef”) and you get slightly more power from the tube. I mean if you load your 6C33C to let say 600R then make it 500R or 550R. It will be much softer sound with more “round” corners. You might not feel that it is too dry anymore. As the very temporary test, juts to preview the result you might short your woofer with 30-100R power resistor. You will lose some transients in bass and some other attributes of quality but you will get a preview how the heavier loaded 6C33C might sound and a send if it is a good direction for you to go.

Let me know about the results.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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KOTriode
Posts 40
Joined on 07-20-2010
Post #: 66
Post ID: 17971
Reply to: 17970
6C33C bass.
fiogf49gjkf0d
I am not too worried about the 6C33C bass, since I have other alternative. Even if lower loading will improve it, the problem is to get more power out of the 6C33C to a 40W (PSE perhaps) level to be able to drive the 12in or 15in woofer, even then the level of distortion of these tubes at that power would have been in double digit or some kind of feedback will have to be used. It's just curiosity that led me to experiment the 6C33C driving the 15" at 100Hz as DSET and in another case, the 15" (with 150Hz passive low pass) together with the 8in (2Khz passive lopass) in the OB system. Also, the OB 15in might not give thunderous bass as the a vented box, but then with its electromagnet would give the sense of speed that would be perfect for a horn system to come in the next few months (when I got the mechanical mounting problem sorted out), trying to match a 15in woofer to a horn at 500-600Hz is no easy feat. You will be surprise how a simple OB with 6db roll off can easily rattle the windows of your room playing Reference Recordings Firebird Suite.
PS. I lived in The Silicon Valley.
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Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 67
Post ID: 17972
Reply to: 17971
The experiments very worth to undertake.
fiogf49gjkf0d

KOTriode. One of the reasons why I advance the idea of using 6C33C for sub 100Hz bass is because it is very easy to say objectively if it is enough power. You see, when you use 845 for instance the tube might jumps in and out if A2. Since it is DHT it will work more or less fine in A2 but each tube at each operation point, with each driver and in each way of being connected/powering will sound differently. There is nothing wrong with it but we greatly would attribute of use if each tube in A2 to the sound of the lower bass for this particular tube.  With 6C33C it will be no ambiguity in sound: if it stays in A1 then it will sound as it sounds and if it reaches A2 then it must not be used for a given amp gain (efficiency of speaker + room size). So, I think to compare metrologicaly properly the lower bass between 6C33C and 845 we need to compare BOTH of the tubes in A1. It is not difficult to detect if ether of your tubes run in A1.

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=6057#6057

Anyhow, I do understand how “simple OB with 6db roll off can easily rattle the windows” but in my view it is very different bass. I heard as large OB as largest Knlangfilm Bionors with both perm and electromagnets and even I do recognize some quality of THAT sound but I do not feel that anything below 50Hz is valuable for what I am interested.   It might not mean a lot but let agree to disagree as my position about OB for lower bass is well formed. BTW, Reference Recordings in my view has a bit idiosyncratic bass. For sure it is impressive but not the bass that I would recognize as too musical.  It is a bit overly-studio type of bass, I do like it but I do not find it to be my reference bass.

One more thing. Fell free to discard below – they are just the thoughts that pop up in my mind when I though about your loudspeakers.  I am sure that Quads in MF do fine and the RTR ESL panels do fine as tweeter but I have a filling (and I might be very wrong) that in this configuration the upper range will have some dynamic challenge. If it is what you feel then I would try to use “dynamic injection”. It might be very hard to at HF but still might be possible. You might try to use different type of tweeters that have the “dynamic injection” built-in juts for experiment to see if more virtual dynamics in tweeter would be appealing to you.  I do not want to suggest the models of tweeters at public forum as I know the ugly results of it but if you would like to experiment with “virtual dynamics” then contact me privately and I will pitch the tweeter for you. I personally do feel that if you add more dynamic tweeter above the Quads then you might make the Quad’s MF more fun. I do admit that more dynamic tweeter most likely will enrich the Quads but will not be VERY hard to make Quad’s FM and more dynamic HF to sound the same in context of one installation. Still, I think the experiment is very worth to undertake.

Rgs,
Romy the Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-14-2012 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006
Post #: 68
Post ID: 17973
Reply to: 17971
Giant Transformer
fiogf49gjkf0d
KOT, as you may know, the ML2 has a BIG transformer to make "36 Watts" at clipping; but even with this and the trick feedback it is not the first choice for large dynamic/OB drivers.  Of course I mention this because of your remarks about the 6C33C, big transformers and LF.  OTOH, if you give the 6C33C suitable input and a reasonable load, then it will not mess up what what it is presented with, including the amazing-to-me ability to not screw with any Tone that comes its way.  In this way (and in its "directness") it reminds me somewhat of the 2A3.

For many years I also used the RTR HF modules (6/side), but paralleled with XXXXXXXX dynamic tweeters, as far as they would go.  IOW, I agree with Romy about exploring the 6C33C with parallel "tone drivers", if only to also enjoy the 6C33C's "gift" to Tone.

Not to go too far, but I also like the "6C33C SET LF" very much...  as far as it goes...  In fact, one problem I'm having now is getting "more LF" that is anywhere as good as what I got from my 6C33C SET!

Maybe Class A SET input/drivers into Class A 6C33C PP...

Best regards,
Paul 
03-15-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 69
Post ID: 17974
Reply to: 17973
New 6C33C mono block amp coming.
fiogf49gjkf0d
Ok, I will try to lower the primary impedance like you suggested, but it will be on the new 6C33C mono block amplifier that I am building. The custom made chassis will be finished by next week and I have the better components waiting to get installled in these new amps. It's unfair to compare the stereo 6C33C with the mono block 845 with top grade parts.Now the thing about the dynamic tweeters, I would be very interested to see your suggestion as I always want to look for the best tweeters to match my systems and finally settle on these RTR, so Romy, please send me an email regarding these tweeters. Thanks in advance.
03-15-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 70
Post ID: 17975
Reply to: 17974
Would you like to try the Milq’s basing?
fiogf49gjkf0d
 KOTriode wrote:
Ok, I will try to lower the primary impedance like you suggested, but it will be on the new 6C33C mono block amplifier that I am building. The custom made chassis will be finished by next week and I have the better components waiting to get installled in these new amps. It's unfair to compare the stereo 6C33C with the mono block 845 with top grade parts.Now the thing about the dynamic tweeters, I would be very interested to see your suggestion as I always want to look for the best tweeters to match my systems and finally settle on these RTR, so Romy, please send me an email regarding these tweeters. Thanks in advance.

I do not see if any why it would be unfair to compare the stereo 6C33C with the 845 monoblocks. But to me more important for “compare” bass is to assure the both 6C33C and 845 has the same lower cut of full power. If one amp has -3dB at 20Hz and another -3dB at 26Hz then we do not compare bass but rather the amount of inductance of OPT for a given tube. if both amps have the same cut off (difficult to do) THAN whatever difference is will be the true difference in the tube bass character. The PS and other things let presume are the same.

Anyhow, KOTriode,if you build new 6C33C monoblockd and as I underrated you render some kind if your version then can you juts as a prototype try my Milq basing schema with Milq driver. You might very much like it but I would be very interested to see you feedback posted. I do find that the 6E5-6C33C amps are very brutal and not interesting but the Milq’s basing make sound truly magical, at last in my view. If you have your 6C33C power then to make a few voltage dividers from B+ or whatever driver you use, fast power two gas tubes and put Milq driver in temporary test would be a couple hours for you. You can make it only with one amp, something that I call “maket” and see what happens.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-16-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 71
Post ID: 17976
Reply to: 17975
Further thoughts
fiogf49gjkf0d
Romy, in the contrary, it is very unfair to compare my 845 amp with the 6C33C. The main reason is the 845 amp used the best output/interstage transformer available, while the 6C33C's output xformer is pretty good but far from being best for the 6C33C. I can see sine wave distortion on the 6C33C at full power (15W) below 30Hz, while the 845 has no problem down to 20Hz (limit of my audio analyzer). Since there are not much 6C33C transformer availability out there, I just have to settle with what I have, but that's in the amplifier department. 
Now, the main reason that I built the 6C33C preamp is to experience the pure sound of 6C33C, with one cathode bias resistor/cap and a transformer load , it is as pure as it can be. It even have double output, one is through the output transformer, the second output using the transformer primary as choke load and output through a capacitor. It's output is pretty flat from 20Hz-20Khz with low distortion, sine wave looked pretty good at 20Hz, this is what I compared with a 845 preamp (even though with different output transformer), both do not have any other inoput/driver tube to inject their own sound. And it was these two preamp that lead me to compare the bass of the two tubes.
When I described the 6C33C sound in the bass, I think you might have misunderstood that I criticized in a bad way. " On dynamic, the 6C33C tube showed its ability to go deep in the bass on Ray Brown trio recording of Soular Energy which is excellent for a 15W SE , the 845 amp can do better, but not by much, but probably because of its 25W output give it more headroom than the 6C33C"
After living with 845 tubes over 20 years, with no less than 7 845 amplifier built, including 2 pair of push pull class a 50W and 100W(to satisfy my curiosity, I made a Parallel push pull with 4 845 tube per side to get 100w), I can say thay 845 is king in the bass area that no other tube can approach, now if the 6C33C being second best in the bass department at my first shot at it, I would say this tube is a miracle, I was so ecstatic adding this tubes to my stable and racing toward implementing it in a mono block version. I wish there are more output transformer available for the 6C33C, the Tango is too small to be serious, that leave Sowter and Lundahl, I might have left some others but if anybody know something I dont then I am all ears.
Regarding the Milq, it's not easy to modify my amp to the Milq cricuit, my amp was designed with DC coupled, therefore the B+ is pretty high, at about 500V it has twice the voltage of the Milq, the regulator cant regulate down to 220V without problem (too much voltage and current for the pass tube). To duplicate the Milq, it would  require different power transformer, but that can be done and I will put some thought into it.
03-16-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 72
Post ID: 17977
Reply to: 17976
Bias with attitude, bass and transformers...
fiogf49gjkf0d
 KOTriode wrote:
Romy, in the contrary, it is very unfair to compare my 845 amp with the 6C33C. The main reason is the 845 amp used the best output/interstage transformer available, while the 6C33C's output xformer is pretty good but far from being best for the 6C33C. I can see sine wave distortion on the 6C33C at full power (15W) below 30Hz, while the 845 has no problem down to 20Hz (limit of my audio analyzer). Since there are not much 6C33C transformer availability out there, I just have to settle with what I have, but that's in the amplifier department.

Well, if you saw sine wave distortion at full power at 30Hz than whatever bass you heard from that amp was nothing to do with bass of 6C33C but it was just the inadequate quality of your output transformer. I hope you understand it.
 KOTriode wrote:
Now, the main reason that I built the 6C33C preamp is to experience the pure sound of 6C33C, with one cathode bias resistor/cap and a transformer load , it is as pure as it can be. It even have double output, one is through the output transformer, the second output using the transformer primary as choke load and output through a capacitor. It's output is pretty flat from 20Hz-20Khz with low distortion, sine wave looked pretty good at 20Hz, this is what I compared with a 845 preamp (even though with different output transformer), both do not have any other inoput/driver tube to inject their own sound. And it was these two preamp that lead me to compare the bass of the two tubes.

Yes. I do understand it but I have absolutely no experience with 6C33C in preamp. I know very well how 6C33C act as current buffer in power SET but I have no idea what the 6C33C needs at line level. It might have very different needed about wish I am not informed.
 KOTriode wrote:
When I described the 6C33C sound in the bass, I think you might have misunderstood that I criticized in a bad way. " On dynamic, the 6C33C tube showed its ability to go deep in the bass on Ray Brown trio recording of Soular Energy which is excellent for a 15W SE , the 845 amp can do better, but not by much, but probably because of its 25W output give it more headroom than the 6C33C"

Possibly it was your observation but it might be skewed by the specifics of your implementation. To have a common denominator for talking we need to talk about the publicly available 6C33C implementations. So, the only thing that I personally can testify is that I heard quite a few power amps with 845. I myself prefer amps around 211 as I feel it is softer sounding tube then 845 but it is not the point. The point is that any single power amp that I heard with 845/211 was absolutely no context in lower bass department to Lamm ML2.0. It is laughable how much ML2.0’s bass is better then pretty much any other SZET out there with 845/211 or pretty much with any other tube. The Lamm ML2.0 bass is better then any SS amp out there as well and in my view the Lamm ML2.0’s bass is the textbook bass as it has to be in audio, of cause if the amp has enough power to drive whatever it drives. That was my introduction to 6C33C bass and in my estimation the 6C33C still hold own, again, in my estimation.
 KOTriode wrote:
After living with 845 tubes over 20 years, with no less than 7 845 amplifier built, including 2 pair of push pull class a 50W and 100W(to satisfy my curiosity, I made a Parallel push pull with 4 845 tube per side to get 100w), I can say thay 845 is king in the bass area that no other tube can approach, now if the 6C33C being second best in the bass department at my first shot at it, I would say this tube is a miracle, I was so ecstatic adding this tubes to my stable and racing toward implementing it in a mono block version. I wish there are more output transformer available for the 6C33C, the Tango is too small to be serious, that leave Sowter and Lundahl, I might have left some others but if anybody know something I dont then I am all ears.

There are no good ready to go transformer for 6C33C. Tangos are garbage.  The 20 years back Tangos were OK for small tubes but Tango is long gone and whatever crap they label by Tango in fact Chinese transformers agglomerate production. Lundahl, with glass core, are very good in my view but they have small core size. At 200mA gap you will have 20Hz but if you build a full bloom 6C33C then you do not want to stop at 200mA. Your voltage is 200V, at 200mA you will have 40W on plate – way to little power, particularly for bass. I do not know the Sowter but generally I would advise to find somebody who would make for you your own custom transformer. Go for 350-400mA gap and for inductance to support 12-15Hz at 20W. There was a guy at my site who ordered one in Europe, I do not know if he like the results – he did not post any feedback. I guess you are American, so you might want o talk with somebody like David Slagle from NY. He is kind of “project guy” and he might be a good source for not cookie-cutter transformers with fast cores. Anyhow, the sound of nay SET is made at 85% by the sound of OPT. If you used any temp OPT to test your 6C33C then you get temp results and temp bass. I do not insist but I think that it is possible that as you get better and deserving OPT for your 6C33C then your view about the 6C33C bass will change.
 KOTriode wrote:
Regarding the Milq, it's not easy to modify my amp to the Milq cricuit, my amp was designed with DC coupled, therefore the B+ is pretty high, at about 500V it has twice the voltage of the Milq, the regulator cant regulate down to 220V without problem (too much voltage and current for the pass tube). To duplicate the Milq, it would  require different power transformer, but that can be done and I will put some thought into it.

I see, you use 6C33C as DC coupled with driver setting the bias – a dangers game for THIS tube. Anyhow, the idea of Milq is not the output tube but the driver tube and the way to bias the driver tube. Of your use the Milq’s driver tube with cathode bias or fixed bias then it will be very different sound that I very much do not endorse. Only with the bias as Milq has it the amp shows the sound that I like. Ironically, when I used the same Milq-style bias on the output tube then6C33C sounded like shit. The Milq driver and the way to bias THIS driver is very lucky combination in my view. BTW, if you use fixed bias on 6E5P and compare it with Milq bias then you will see that Milq bias show much much much more interesting bass…
Rgs, Romy the Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-17-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 73
Post ID: 17978
Reply to: 17977
Milq Driver tube bias
fiogf49gjkf0d
Romy,I looked at your Melq schematic : http://www.goodsoundclub.com/PDF/Melquiades_SET.pdf  regarding the 6E5P bias. Would it be simpler to use two alkaline battery in place of R5 to provide 3V , or 3 Rechargeable for 3.6V in place of R5 ? Did you tried that?
03-17-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 74
Post ID: 17979
Reply to: 17978
It is about Sound, stupid.
fiogf49gjkf0d

 KOTriode wrote:
Romy,I looked at your Melq schematic : http://www.goodsoundclub.com/PDF/Melquiades_SET.pdf  regarding the 6E5P bias. Would it be simpler to use two alkaline battery in place of R5 to provide 3V , or 3 Rechargeable for 3.6V in place of R5 ? Did you tried that?

I for sure do NOT call you stupid but rather improvise upon the celebrated Bill Clinton’s 1992 presidential campaign slogan against George Bush. KOTriode, I think you are NOT understand my whole adventure with Melquiades. If all that is necessary is to supply right voltage to the 6E5P drip then it would be so much simpler and any amp with right voltage would sound “right”. I did explain at this site a lot about the motivation and reasoning to use this type of bias instead of just “voltage supply”. I do not insist that my explanations are correct but I feel that my findings are very much accurate.  BTW, if you have 6E5P with min 15K plate resistor driving 6C33C then to convert the 6E5P to battery, cathode or fixed bias will be for you the matter of a few minutes. So you will be able to make your judgment.  The Melq’s idea was to engage the 6E5P in two-stage operation and among what I have seen the use of the 6E5P in the way how Milq does it provide the most interesting sonic result. There are many other ways to drive 6C33C, including multiple stages but if you attempt to use 6E5P (and I do not know if you do) than I do advise my version, at least to try and to fitness what will happen with Sound.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-17-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010
Post #: 75
Post ID: 17980
Reply to: 17979
Just have to build one to hear.
fiogf49gjkf0d
Ok, I just read your "Melquides Remote biasing". This technic can not be duplicate in my amp due to DC coupling, the C3G (I dont use 6E5P) driver stage basically adjust the 6C33C current in the output stage. Just for curiosity, I will build a mono block version Melquiades and compare with my version, I believe I have extra chassis for it.
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