Funny for in my DSET case it is mostly about a primitive equalization in MF. Well, almost.

I god a few other versions of 2A3, one more 604 and a few 45. I in fact like the 45s, even though with my attenuator wide open I have ~2dB less gain then I would like when I use 45s and 25:1 loading. So, I need to research if I can remove the divider from the grid of the driver stage (where I burn 3db). I can remove it but I need to learn it with max signal I would not drive the 5E6P into grid current.

Then I kind of know what kind tube I would like to use in output stage. I would like to use the soft sounding tube but I would like to drive it very contrasty (higher loading ratio, fast core, perhaps higher current to drive impedance lower). What I would like to accomplish sonically is following. I like generally how DH Sound and some of the DHT has VERY interesting HF. They are not strong and in way rolled off (here is where most of the people feel the vintage sound) but they are also very lucrative and flavorsome. The character of the upper range of some DHT is intriguing and I can only describe it with effect of a butterfly landing on you shoulder. It is there but it is also almost “not there” or at least it is not defined in the terms of HF event. So, what I would like to have is a higher amplitude of that butterfly effect of I need to learn how to drive “some” soft-sounding 45, 2A3, 604 and 186 harder to accent their HF region.

I found an interesting flow in the sound of my current OPTS and while it will be certified I am experimenting with park of amorphous core transformers that left over from my former projects. I am trying to remap my Tribute but it is just 40mA. It might be enough for RE604 and YO186 as the run at 35mA but it is not good for 2A4 as some of them go up to 40mA. I have 50mA Lundahl 1623A that I used for my failed headphone project and how use for my fundamental channel. The leading battle is a very interesting amorphous transformer. It is 5-6H, make custom for me with limited turns, specifically foe my DSET configuration. It uses a large core and can handle even 100mA. I kind of slowly am experimenting with them.

At this point I very much know what I need I need – I heed the HF extensions, not the response itself – all of them are good for couple hundreds of kHz according to measurements but I am looking for the subjective auditable HF extensions while the transformers are running the “soft” DH tubes. I almost looking for a “bright” output transformer, sure if I found one then I will be bitching that it corrupted my DH’s “butterfly effect” (read above). Still among the few transformers that I have in THIS specific configuration I like more those that give me more HF from my DH tubes. Can I blame myself?

The key I see in this that with more “punchy “extension of HF from my MF channel I can implement the Macondo’ drivers integration model that I would like to. Otherwise it will be not the best case in my application. I always have my full range Milq (injection channels) with amorphous 6C33C that give me an idea how fur the S2 driver might be taken…

I got few inspirations recently that made me to dedicate today for building another DH MF for second amp. It is end of the day and the conversion of the second amp is done, including the PS, marking and drilling the holes, driver stage and the DH stage – everything. In fact the amp was working perfectly fine right after assembly and each voltage and current was right spot on.

I will keep it for another day or two open and I am experimenting with removing the voltage divider from input filter and then the saga with Melquiades 2009 modification will be over. The final decision about the output transformer I made is that the transformer I need 25:1. No taps, no re-mapable coils, no loading change. The strait coils 25:1 and it will be it. Perhaps there is a way to do it without loosing anything but I am not in business to write the audio theory and make more experiments. The 25:1 will be it. It might be a bit rough for 2A3 (remember, I load to 16R) but I can shunt my LPAD with extra résistance and it shall not have any negative effect, not like shunting the S2 driver…

The friends of mine who observe this project advised me a kinky techniques how to make my Nickel core transformer to sound much “expedited” then it is, so the VERY ideal 25:1 with additional “expediting” will be plenty to suck all HF out of my DHT.

Hm, I was playing with options to get rid the 3dB divider in the MF channel input and I realized that I was a moron somewhere. I was operating under presumption that I was getting 2V on the driver cathode in MF channel that made the swing voltage on the grid valuable to drive the input tube into gird current. This is where the idea of the input voltage divider comes from. I person who observe my project informed me a couple day back that it might not be 2V.

I just measured it on this second amp and it is 3.25V. That is VERY BIG difference as my signal at full volume does not go over 2.2V behind the filter and 20K resistor.  So, bye-bye the input divider on MF. I have no idea why O flipped with the cathode voltage measurement. Perhaps what I did it I had a current-dead driver. Not I have 332R resistor and 3.25V. That make on the tube 10.8mA, which is right where, is shall be. Now, I need to figure out where my out stage will be clipping with more voltage from driver…

The Cat

It is it, I eventual got what I was striving for a while and now my MF DHT channel is done and the most important is that it now sounds exactly how I need it to sound. The new 25:1 loading turned out to be the key. It is “fast” enough and I did not play with distribution of gap – it is good as is.

I call it a “few steps back” solution because it is how I used my S2 driver before I went for single stage. Before I used a half of 6C33C loaded to 1150R, which is very-very light for that tube. I know very well the sound of under-loaded S2 and it was pretty much how I used it since 2002. Then I went for damping S2 with plate, ending with 550R load and with 15:1 on the 6E5P plate. Now with DHT and 25:1 I somewhere near my 1100R on ½ of 6C33C and – boy this driver sings again.

With today configuration the “bright” and “bold” DHT tube are hardly useable – the single-plate Chinese tubes, some version of 2A3 and Valvo LK460 for instance are too brutal and too amusical. However the softer sounding 2A3, the 45 with plate of 1.7K and my 4V tubes are singing like canary – the very direct hit.

Actually my YO186 and Telefunken RE604 and Klangfilm KL71403 do the very best in the new configuration. The Telefunken and Klangfilm need one and a half dB less help from tweeter the YO186 needs 1.5 more but even with no tweeter they do amazingly pleasant and VERY VERY different. I matched a pair of YO186 and when I first time put them with both channels and the full system it was just an amassing gratification. It is not the go things and not the “my playback” complex – with the YO186 my playback do sound differently… I just went over a deep 2 hours listening meditation, thinking about this new sound, listing a few CDs of ….Jimmy Scott. I know, it is not my music but I always liked him and it is very interesting to see how the bottom region of YO186 handles the Jimmy Scott’s unique phrasing. The simplicity of Jimmy Scott is a great help in what I was interested to hear and boy – you need to see what YO186 did with Scott’s inimitable articulation!

Anyhow, it is fan in here and I am planning on this weekend my becoming ritual ceremony of trashing my Weller solder station. Since the 2002 it will be the third one….

Yes, the people in the beginning of the thread were right – the DHT two stage solutions do sound more interesting than one stage amp. Still, it does not suggest that if I have 12dB more gain on my single-stage triode I would not be able to load my single-stage to 9K-10K ten I would have worst result.  Well, where to get a low-voltage triode with gain of 60-80 and able to dissipate 5-8W on plate? The reason I still have doubts because loaded to identical 15:1 the DH and single-stage amp, having a virtually the same plate impedance sounded remarkably similar.

Still, we are not taking about the theory but the practical rendering of tangible solution and in practicality the two stages MF with DHT in output, idly relatively running against S2 truly turned out to be victorious over my former single-stager. For a last could day I am like a pig in shit, experimenting with different settings trying to put the benefit of the more prominent output from my MF into a full use.

The MF with my new amp is different and it needs to be used differently in Macondo. I did not figure out how yet and I would say that all together Macondo does not sound now as I would like it to. However, I do see some very tremendous potentials and I very much look forward to caponize on some advantages the I go from putting the DHT double-stages into the game.

Once again, thanks for all supporters and clique people who stayed along with this project.

I need to finish posting in this thread as the subject of this thread is practically over. Still, here are a few comments that I would like to make.

A few years back, driving the S2 with 6C33C I was pitching the harder loading, trying to damp the S2 resonances with 3c33c PLATE. The last month with my DHT I obviously went to opposite direction. Do not forget that the plate of my DHT does not see the S2 driver and loaded to 16R LPAD. I discard the changing out impedance of LPAD as the S2 has no exertion and therefore no returning current.

One of my major fears that I had is to over-idle the plate, making sound to barbarically-impressive. I do have some signs of it with 2A3 as my 25:1 is too low load for it. With RE604, 45 and YO186 that have higher plate impedance the 9.5K looks like absolutely perfect load (in my situation). The driver has the very right amount of “zippiness” and “color” where it needs to be “zippy” and “colorful” but it turns very disinterested and almost monotonously-flat when the music is called upon.  I made quite a few control listening and I am very pleased with result. I think if I take a few more turn from the transformer secondary then it will be too light load and it will “fracture” the sound.

Now is the most important thing. The high contact and high transient capacity of the new MF driver kind of cracked down the imaging. However, here is what the wonder of the very capable MF drivers come to surface: the imaging might be moderated by…. attenuation of MF level.  Get this: an attenuation for 2.5dB of MF driver is practically not auditable in term of volume but it useful in order to settle down the proper imaging. Here is where a very few smart readers who have ears and an experience in systems setup would say: Romy over-idled the MF out tube if the change of volume for 2.5dB is not auditable. Well, trust me – I am an academic in it: I did not over-idled the plate – it is the unique benefits of S2 driver by soft tube. For whatever reason the S2 now does not dive into “collision mode”, it go very fast and super transient but still holding the sound together with no artifact of  the typical under-loaded plate. I do not know what is responsible for this: the special quality of my DHT of the special character of the David Slagle’s Nickel transformer? I have no idea but I certainly very welcome the results…

I assure you that my experience has very little meaning to others as I do not look for “better tube” but look for a tube that would go the best in my specific DSET application and in very custom application of Macondo MF channel. Also, a local guy snatched my Sun Audio amps and I have no way to play my DHT tubes full range…

With all lower MF range magnificence of YO186 it a bit roll of at it’s HF and this is exactly what I would like to punch in my MF channel. The best German RE604-type and other 4V tubes are more balanced. Marconi are strange, Philips sounds like cotton, one Mullard and one PX4 that I got turned out to be very much used  and not as fresh as I would like them to be.

Here is what I got a tube that so far answered my play - it was type 45. I bought a few RAC and Tang-Sol used and one pair of brand new Philco from 30-40s. this 45 are very good, particularly the new Philco. They are more extended then my 2A3 and my 4V tube and they are more EXCITING I would say. Also, they are incredibly clean.  I will stay for a while with 45s and I do like what I am getting with them. Any, specific 45 that you might suggest me to try?

Thanks, KM.

I did read a few days again all that you told about the 45 before and have order a two pairs of new (promised) Sylvania from 30s and 40s. From what I tried the Sylvanias never wee bad.  I did not try 50sa or 245, perhaps I will. I am interesting is my specific application – an ability of the tube to push very strong into HF but very clean and very discriminatively. Some of my 2A3 very much punch but they do all HF in the same way. I do not know if it is a sign of coloration or absent of coloration but I like very much what this Philco 45 does – it very high, not thin, not lean and has still where it operate very high some integrity how it show favoritism to tones. It is very much reminds me how my single-state sounded but this time it is a bit more contrasty (thanks for loading). I do not want a tube to be stupidly extended (like Valvos for instance) but I would like it to be “stupidly able to be extended” if it called upon.

Interesting that from RE604 is very extended and superbly clean but the 45has some “Zippines” (positivly speaking) that ads some "excitement". Perhaps it is because my RE604 are used buy my 45 are new? The RE604 run at 36mA but 45s at 41mA. I do not know… Still, the 45 are not expensive and I have plenty of gain to put in there whoever can birth. Oh, if I would not be too lazy I would try my brand new 10Y… BTW, while listening the tubes I do EQ then by gain with .25dB precision, so the gain is not a factor at all that might the a case in a multi-channel installation…

Paul S wrote:

I know zip about using the 50, except it is another very "clear" tube that seems to have more "qualities" than the 45, and some folks attach +/-

cv wrote:

I've only heard the 801 in class A2, but I can easily imagine that the 10Y or 801 with nickel output would offer the purest possible sound in the 1k-10k range, such that it is the S2's true voice you are hearing. It's something I'm going to pursue when I have time/funds... Alas I do think that your existing amp platform (i.e. B+ voltages) is not optimal for 10Y; the DC coupling would be out etc and this may well swamp the differences between tubes.

Yep, this is one of the reasons why I do not do it. I have some very cool 10Y but the plug-and-play with 10Y will not work with my current Milq platform. If I can go away with 6.3V on filament then I will not be able to go away with 410V driving 10V. That would bring another B+ supply and so on. People have no idea how much I hate to do that DIY soldering crap! The second reason, probably the biggest one that for now I do not feel frustrated with the result I got from 2A3/RN604/YO186/45. My rules of the engagement no one cancels yet:

http://www.romythecat.com/Forums/ShowPost.aspx?PostID=432

cv wrote:

Anyway, whilst you do have the urge to experiment, you really, really should try a tapped filter choke at the front for gain adjustment instead of the attenuator at the S2.

This is a good one. I have a number of conversations with David about it. I do not exactly subscribe the idea of his tapped filter chokes and autoformers. In fact I feel that conceptually they are faulty. In regular resistive attenuator a signal flows across a resistor that is more of less free from any none-linearity. In a tapped chokes the attention happens via inductive resistance where the whole series signal flows across none-linear galvanic element. So, in theory I feel that restive attenuation is less devastating. I never used autoformers and frankly I have no motivations to do it. David, argues that a magnetic element is better than resistive and is willing to prove it to me by sending to me his speaker-level autoformers. I a very skeptical and I would rather to pay for a very high resolution (1/6dB) resistive speaker-level steps-attenuator with constant impedance. I am contemplating to commission the 16R LPAD if I find a right person….

cv wrote:

If it's not too much a departure from the subject of the thread, I'm a little surprised to see the back of the "Newton bias" scheme; does the 6E5p still retain its special qualities in this application with the more pedestrian bias arrangement here (IIRC the Newton scheme's primary benefits were at LF?), or might it now be worth experimenting with a filament-biased DHT at the front (and dropping some gain in the process...)?

Good point, I have thought about it as well. The 6E5P with "Newton Bias scheme” is not a panacea but a solution with well defined objective: to eliminate any explicit capacitor from a stage. How would you bias a tube? A buttery in grid or cathode do not sound right, not to mention that they are in a way the “capacitors”. A fix bias would imply a coupling cap or transformer, all versions of cathode bias would imply a cap in cathode. What you call the “Newton Bias” (actually the Newton Bias was another notion and it had nothing to do with Milq – that was a bias in Zaratustra amp) is affective way to bias with signal flows across juts a resistor – in my book the least damaging element. In the MF channel you see that I return to cathode bias but it was different. Since the objective was to lower the gain of my driver stage the 6E5P is use with no bypassing cathode cap –just a series resistor -means no negative problems in my book. 

Another point that I make is that I know how the 6E5P sounds with no caps and “Newton Bias”. I presume that it might be another application that might be fine but I would like do not spend time to evaluate many other options. In Milq tweeter channel of the “Newton Bias” on 6E5P in my view is not good idea at all as the 6E5P is quite capacitive bitch but what is the alternative? I have a single gain stage with a single resistor in a series signal path – what might be more kosher then this? I would like to have less capacitive tube with more gain and more power for HF channel, however….

cv wrote:

You might ask Dave if he knows of any 9-pin DHTs with mu of about 18 and Ri of about 1k... or have me send some old Limey tubes - begging your pardon, sire - valves to try...

I did ask about that type of tube before. Any interesting DHT candidates with high gain have too high plate impedance. If I find one that can do 20 times gain, have plate of 500R-700R and able to care 5W-7W on plate then I would go for one DHT stage. Unfortunately I do not know such a tube, with exception of high power transmitting tube that would run at 1kV and that I do not need.

cv wrote:

On the matter of the DHT having a plate resistance of 500-700... you do realise that running the 6E5p with an unbypassed cathode resistor is giving you an effective Rp of about 12k, right? The formula is, IIRC, Rp + (mu+1)Rk.

The DHT that I meant was a candidate for a single stage gain with DHT. To find a DHT to substitute just my 6E5P driver is not too difficult.

cv wrote:

Regarding the inductive attenuator - in using an LR filter at the input, the series R will give the inductor a chance to express any non-linearities in voltage terms. With a 6db attenuator, the signal is tapped half-way through the core, so I can almost visualise cancellation of non-linearities in each half...whatever they might be. Then there is also the benefit of the driver tube seeing 1/4 of the filter R.

… and the part of the signal that need to be NOT attenuated still will be flowing through the part of the coil. The flowing across the DCR of the tap is not a big deal but it is INSIDE of a choke and theoretically it is influenced by all issues of magnetic non-linearity.   Do not forget that to the magnetic non-linearity exposed the part of the signal the shunted to ground AND the part of the signal that shall flow top load with no impact. This is my theoretical beef with the idea of magnetic attenuation.

nl wrote:

Why do we use DHT tubes?

You mean the driver DHT tubes?  Yes, it might be an interning idea but at this point I see no need.

nl wrote:

In Romy's case, I would suggest experimenting with various driver stages. The primary quality is how it sounds -- how it combines with the DHT sound to make an appealing overall result.

nl, what in your view might be the “appealing overall result” that you feel might be accomplished by substitution of my driver with DHT? I understand that you never heard the sound I get from 6E5P and I never used the DHT driver and therefore there are no points of reference, still what would you your hypoteti9cal assumptions?

nl wrote:

Why are we experimenting with DHTs at all here? It is because of the possibility of a different sound character than the 6E5P.

I do not looking for “different sound character”. That is what most of the DIYers do not get. I am looking for the very specific character of sound that I know, understand and comprehend. The differences that many “soldering people” are getting out there are completely irrelevant to me as I very seldomly experienced that DIY build any “tailored” or sensible sound. it does not mean that I shall not experiment with DHT drivers but it means that a promise of “ the different sounds” is not something that motivates me.

nl wrote:

Thus, it doesn't make a lot of sense to me to keep the 6E5P as a driver tube. Why not try something else? I would suggest a 6SN7 or possibly a signal DHT like a 26, 112, 01A, 30, etc. etc. Direct coupled with resistor load (as already exists) is fine. Some people like the combo of a high-gm tube like 417, 6H30, 6S45, etc. etc. as a driver tube. Other people find them hard, glassy, and not emotionally involving -- the typical complaints of the high-gm series. The main advantage is that they allow the elimination of a gain stage. Also, they provide a rather low Rp to drive the output tube harder.

Interesting, those people who “like” or “do not like” something about the DHT drivers, do they make their judgments in context of full-range SETs or in context of the narrow- band DSETs?

nl wrote:

The second thing I would suggest (again) is to try your DHT amp running the large horn (600hz up) as far up as it will go -- ie no lowpass filter. That should give a better idea of the overall sound quality of the DHT amp without having to make two to run both horns simultaneously.

That is interning as I thigh about it myself when I started to use my YO186. The YO186 has VERY lucrative lower range and it might be fun to expose it to my upperbass horn. I do not know about the run the upperbass with no lowpass filter but the notion to try YO186 full-range very much crossed my mind. A local guy snatched my prototyping San Audio amp otherwise I would put the YO186 in full-range use and would try to drive with it different things. I still do not know if it will be able compete with 6C33C as the 6C33C drivers my upperbass with VERY idle plate. The DHT tubes would not have power to idle plates too much. If I put the YO186 with 45:1 transformer then it will suffocate to drive my upperbass driver.  Still, the idea is worth trying…

floobydust wrote:

Paul, I suppose that new vs old between the 45 and RE604 could account for some differences, but it's more of an "apples to oranges" comparison. Pushing the 45 beyond it's ratings is not a great idea... especially the cathode current as it will certainly shorten it's life... I always run the 45 around 34-36ma and never any more. You can run the plate a bit beyond 10-watts (the final revised rating) provided you have adequate airflow and keep the cathode current down.

I have a question. I have a situation in here that needed a minor correction. It might be left as is but still I would like to fix it. Sine I have my hard is set not at 45 tube I would like them to run very much equal. My amps not have rig and left channel run ~5mA different. With the same tube the left amp has (K-G-A) 191V-155V-407V and the right amp has 198V-161V-407V. That makes left amp to have 5mA less currant then right and I would like to make them the same (with the same tube). I can match the DC that comes from driver tube (155V vs. 161V) but the voltage drop on my cathode is different, probably due to the not exact value of the power resistor.

So, I probably will not remount it but will put a large resistor in parallel to the higher one and will make the cathode resistors the same. My question is: how much you advise to drive my 45. Usually people think how to get more power but I do not need power. So, I do not have the “best” operation point that would assure the most power but I rather can driver it wherever I wish. So, how much shell I wish?

The 45 is 10W tube. I have 407V-191V or 208V on the tube and I run it at 35mA and 40mA or at 7.5W and 8.3W. Where do you fee; it the good point to me settle: 35mA and 40mA? Sonically I hear no deference…

floobydust wrote:

The final ratings on later ST-style glass 45s was 10 watts on the plate and 300 volts cathode to plate max. Recommended bias current is between 34-36ma max. Short answer... I prefer no more than 34ma on the 45 cathode. It's a coated cathode type on a thin filament wire and pushing them will run them down quicker. If you can manage 35ma and match the set I'd say you're good to go. The only problem is your available supply voltage. As you're "backing into" a set of fixed parameters (plate voltage supply is already defined), you might need to alter your driver operating point to get the 45 in this range and maintain optimal performance. Of course, you know better than I about the driver stage and where it's optimal operating point is. I would do some (bias) trimming on the driver stage first and see if you can reduce the 45 idle current to no more than 35ma while keeping the driver stage operating properly. If not, you might end up trimming the cathode resistor to get there.

Floobydust,

I hear what you are saying but I do not know if I agree with you. It kind of odd – I ask advice and I disagree with the advice but it is not that disagrees but rather it does not conform to my view of “common since”. Let me to lay down my view, perhaps my view is inaccurate and you will be able to point out where I am wrong. 

The source of my disagreement is 35mA as some time of absolute number that has own meaning. Yes, the typical operation of 45 reportedly 250V and 35mA that makes 8.7W. Furthermore I presume that it is high possible that you guys who are experienced with this tube found that at this operation point the 45 does the best.  Highly possible and I would not debate it. However, let remind to each other that a proper operation point is a subject of voltage, current, load and the most important from my point of view – a symmetrical clipping under the given voltage, current and load. Only with context of the symmetrical clipping the tube give up max power and experience no voltage and no current starvation under any signal amplitude (until it clips).

Now, let see what happens in my case. Firs my channel runs no LF and it is DSET. In classic SET configuration power is derivative of LF as inductance dies first. In case of SET employed as DSET and has not LF the consideration of power as current vs. voltage are not there. My MF amp would hardly clip by power of output stage but rather by overdriving the stage very deep into A2 and by clipping the driver stage. If so the symmetrical clipping of the output stage might not be a subject and therefore is might not be the only right operation point. In my case I run the tube at 208V and at 35mA and 40mA or at 7.5W and 8.3W, what is near the same plate dissipation as 250V/35mA (8.7W). If I do not have objective to get max power from the tube then why 208V/40mA might be worse than 250V/35mA? You suggests that “it's a coated cathode type on a thin filament wire and pushing them will run them down” but current does not burn cathode, I presume temperature does as a derivative of power. It you have a fuse that goes off at 1A and 120V then it will not go off at 1A and 12V. This is my argument, I do not know if I right but it makes “common sense” to me.

There is another subject. The common practice to use 45 is to load it against 6KOhm. I am loading it against 9.5K and will be soon against 11K. This is 2 times idler load and I am sure that power-perfect operation point will be moved from 250V/35mA. So, do I need to worry about 40mA in my case or I might use whatever stick to the wall as long it is within 8W?