GoodSoundClub - Romy the Cat's Audio Site

04-17-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	51
Post ID:	16079
Reply to:	16074

2 stage

Paul, I'm not rushing to the breadboard. I'm trying to visualize if Romy's constraints
can be satisfied. I have to gather more data on GU81 to think of doing anything.
How linear it is?? Perhaps this tube is an audio no-go as you've mentioned?

Going to 3 stage would defy the whole GU81 exercise. If alowing the 3rd stage I'd go with 304tl A1
in the first place or 833A A2. Both seem to have a +/- good reputation in audio.
And reputation is what unfortunately I have at my disposal at this stage. Same applies to 6E5P.
I agree that 6E5P seems to give just right enough gain to approach 0Vbias
(2Vrms x 32=90Vmax), without margin,
but anyway I'd parallel
the drivers than add one more stage. I've somehow bought the Romy's sense of elegance
with 2 stages.

PS caps are seemingly not a big problem: find the Nichicon part number, google it,
put your spam-friendly email in the pages which locate parts for you, in the next 2 days you'll
receive 40 offers from Asia. Some seemingly serious, but I haven't tried so far.

I'm not in love with transformers, but not affraid of them either (so far...)
Again driven by the sense of elegance rather,
I'm attracted by a simple design with few stages and one big tube. I of course can be
very wrong, as I said at ULF small dissincronizations of paralled tubes should not
matter (no time-domain smearing). Transformer will have to handle the power anyway,
so it will be big, but the compromises with HF are absent, as have already been mentioned 1000 times.

Cheers,
Jarek
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04-17-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	52
Post ID:	16080
Reply to:	16079

Only one transformer per amp.

It is unfortunate that this thread will not lead to anything practical or tangible to me personally, so any talk from me are very much worthless. Still from the purely conceptual perspective I would like to explain why I would prefer non-transformer coupling. I am thinking about low knee decay and I would like it to be as low order as possible. The OPT will have own roll off slope, whatever order it will be there is no escape from it. A second coupling transformer will have another roll off. So, pretend that each of them have second order at bottom, it means the entire amps will have 4^th order roll off. Consider that I am crazy but I would like to have as slow roll off at the bottom as possible… So I feel that it has to be only one transformer in amplifier. Do not give me Sacuma as example – his amps sound like shit. BTW, the notion of one transformer per amp was inspired in me by Dima….

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

04-17-2011

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Paul S
San Diego, California, USA
Posts 2,660
Joined on 10-12-2006

Post #:	53
Post ID:	16081
Reply to:	16079

Gap

What is the "reverse engineering" version of an SET circuit that would accomplish - in terms of audible results - what you want? The reason I suggest 3 stages is only because I see a gap between required input and necessary output for the proposed driver versus the desired output tube, versus the plate curves. YMMV, of course.

Surely, the answer lies somewhere between Ockham and Einstein: something like, "make it as simple as necessary."

Re: buying in to the sense of 2-stage elegance, don't forget the difference in gain between your own stated wants and Romy's DSET, starting from the same point.

Best regards,
Paul S

04-17-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	54
Post ID:	16082
Reply to:	16080

You've promissed...

...to assist spiritually!

Interesting view on IT. Indeed the multichannel SET with line-level crossover changes the perspective
on the coupling techniques. This rules A2 out (unless cathode follower...blah blah blah)

And paralled drivers? May I ask why you wanted to avoid them but would accept paralled output tubes?

Cheers,
Jarek
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04-17-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	56
Post ID:	16084
Reply to:	16081

How big a gap?

Paul S wrote:
What is the "reverse engineering" version of an SET circuit that would accomplish - in terms of audible results - what you want? The reason I suggest 3 stages is only because I see a gap between required input and necessary output for the proposed driver versus the desired output tube, versus the plate curves. YMMV, of course.

Surely, the answer lies somewhere between Ockham and Einstein: something like, "make it as simple as necessary."

Re: buying in to the sense of 2-stage elegance, don't forget the difference in gain between your own stated wants and Romy's DSET, starting from the same point.

Best regards,
Paul S

Paul, I assume the standard 2Vrms input. If in A1 GU81 is still ok with 40mA, 8W drive, then 6E5P gives
just enough gain, unless I'm overlooking something. If doubled, 16W should be ample enough.
A SET would require a linear 600W triode to give 150W A1, easy to drive, high gm, medium mu.

Cheers,
Jarek
STACORE

04-17-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	57
Post ID:	16085
Reply to:	16083

2kV-3kV of B+ vs. 1A of plate current

N-set wrote:
And paralled drivers? May I ask why you wanted to avoid them but would accept paralled output tubes?

I would for sure avoid any paralleling, would it be driver or output. Still, driver provides voltage gain and output stage - current gain. The difference between the paralleling tube will be more affecting voltage gain stage then current, at least it is what I feel but I do not insist the I am right.

gordan wrote:
Guys, you seem to be perfectly comfortable with 2kV of plate voltage in your rooms?

We are perfectly comfortable to talk about it. No one put any 2kV in anybody room. We are talking about what conceptually might be done. I would personally be much more comfortable with parallel 6C33C, which might be even sonically preferable as they would have ultra low Rp and very high current. (Higher current = higher rise time as less sensitive to any capacitance). The problem is that now one would say what the factual result is as no one, of very-very few would experiment with all of those options.

Another subject you are losing, gordan. I do not know him personally but if you see what N-set then you recognize the he is very experienced builder. The people who do not afraid 2kV-3kV power supplies are ether ignorant or stupid. N-set neither ignorant nor stupid and he knows how to deal with what he is dealing with. I, with my experience would not touch 2kV-3kV, in fact the people who advise me explicitly prohibited me to do it. However, for well experienced person it is not a big deal. Do not forget that somebody work on 750.000.000 power lines – if to know how to do it then voltage is not a problem – ignorance is. I am very sure that a well-built 2kV power amp made to the appropriate standards will be in home as dangers as a kitchen toaster. After all in older color TV we has 36.000V, so how many people were damaged?

BTW, if I sometimes to assemble the Dima’s Zarathustra II hybrid then …it has 5A idle current in output stage. The PS for it also VERY obnoxious. It is class A so it is huge input chokes with 4 by 270.000uF per channel. The power transformers if I remember correctly are rated for 70V/25A. I can’t not even move the box with parts of Zarathustra II power supply…

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

04-17-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	58
Post ID:	16087
Reply to:	16085

HAHAHAHA!

Please, guys, I'm not an experienced builder at all!!Please don't offed a real experienced builders!
I'm rather both hopelessly stupid
and ignorant. Knowing that, I'm trying to be carefull. That's all.
My active participation here, apart from the spiritual motivation to hear an unheard trace
of the voice of God, is simply because I have an unfnished, idiotic, lifetime project over which I've
spent countless hours, down to designing the PS transformers myself and getting
German EI laminations for them. Then the experience came from my winders, they've showed me
few tricks. Now that project may get a new, less idiotic, life now. At least on paper...

Paralleling: good points! Although this is the transformer which changes V's to A's, but true
a tube like 6c33c is somewhat closer to that function than many other tubes. Parallel drivers would
have to be matched, which with 6E5P will not be costly.

2-3kV: I look at those Wavac's ect to see how they protect the tubes. The topcaps
are fully covered, probably in teflon. If you touch whatever part, including the tube, you are
potentially safe from HV. I'd add a faraday cage around the tube. Not only for safety but also to shield
the strong fields from the powertube. Inside: HV potted transformers and chokes, RF HV cable (I have 80m of
a prime RG something, good to few kV). This also answers Paul: use RG coax for the connections.

And I'd definitely try Slagle's cancellation technique in the OPT too: an additional winding
carrying 11A of the heater current to cancell some of the 350mA DC magnetization.
This should make the OPT even more tangible: low effective DC magnetization, no MF nor HF,
just power and inductance. The magic of DSET.

Cheers,
Jarek
STACORE

04-17-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	59
Post ID:	16088
Reply to:	16087

There is nothing to laugh.

N-set wrote:
Please, guys, I'm not an experienced builder at all!!Please don't offed a real experienced builders!
I'm rather both hopelessly stupid
and ignorant. Knowing that, I'm trying to be carefull. That's all.
My active participation here, apart from the spiritual motivation to hear an unheard trace
of the voice of God, is simply because I have an unfnished, idiotic, lifetime project over which I've spent countless hours, down to designing the PS transformers myself and getting
German EI laminations for them. Then the experience came from my winders, they've showed me few tricks. Now that project may get a new, less idiotic, life now. At least on paper...

You be careful with your self-assessments. I did show your proposals to people I trust and they observing your circuits inform me that you are not an idiot and that you know what you are doing. I would still be looking voice of God in different place, primary from within, but it is a free country and everyone has own rights to pursue own happiness.

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

04-17-2011

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Paul S
San Diego, California, USA
Posts 2,660
Joined on 10-12-2006

Post #:	61
Post ID:	16090
Reply to:	16084

Closing the Gap

N-set, my primary reason for trying to run tubes "conservatively" is only because that's consistently what has worked best for me over time. Or, put another way, I really like to be able to "tune" all my active gain devices according to sound. If you are comfortable with simply running at or near the theoretical margins, then you should just go for the single driver tube, le voila'. Or, sure, just "cheat" with a "single" paralleled driver. Extra headroom will certainly give you more options for tuning the tubes via loading, etc.

Not that it makes a difference here and now, but I have said at this site before (but not in this thread) that I hear "more A1" from a proper A2-capable drive, given the "right" output tube. By the same token, in my limited experience, the jump into A2, proper, brings a lot of audible distortion. Basically, like everything in audio electronics, it only makes so much "sense" in actual practice. Again, YMMV.

Best regards,
Paul S

04-18-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	62
Post ID:	16093
Reply to:	16090

Missing miliampers

Paul, 6E5P may strech very much, but maybe just enough to close the gap.
In such a racing car there is a little margin, it's not a usual 10W+ design.
Biased at -3.5V 6E5P will produce +40Vmax on the grid, driver driven to the limit
The grid will eat 50mA@200V (the endpoint of the proposed loadlines)
according to the datasheets, 40mA@400V. The 6E5P is on 40mA...
Anyone has a GU81M spice model?

I've been somehow missing some current, which I've finally found: the screen!
According to the data eats up to 300mA at 0V bias.
The 20k resistor is an idiocy, the screen needs a dedicated supply, IMHO, it's a 120Wmax anode!
I'd also be happy to find somewhere take few negative volts to be able to adjust the
GU81M bias without changing the driver's current.

2 signal tubes, very simple signal topology...and 6 different supplies!!!What can one do?
Physics...
The VR's are screened from the load as I'm affraid the G2 current impulses
may extinguish the them. The last cap should be the biggest possible, G2 acts as an anode
and conducts all the impulses!

I've been thinking about paralled 6c33c and I will not go into that. To get 150W A1 how many 6c33c's
one needs? 10? this is over 400W of the heater power alone, 1kW with anodes max.
Now go ahead implement, maintain and
stabilize that mastodont! I think this pig won't fly, the tubes will drift thermally,
unless the chassis occupies 2/3 of the room surface. One-two big tubes are easier to
implement, eventhough they sit at few kV and need 39656 supplies....and much more elegant.

Cheers,
Jarek
STACORE

04-18-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	64
Post ID:	16097
Reply to:	16095

Why?

Not at all! How would you start anyway? By a random walk?
Random tube at a random point?
Charts is what I usually start with. I know nobody who measured
hmself GU81M and can provide a reliable data. If you know, please
put me in touch.

Paralleled 6c33c-- I don't go into that. Take 10 6c33c, space at 1.5 tube diameter.
How much space that occupies?

Cheers,
Jarek
STACORE

04-18-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	65
Post ID:	16099
Reply to:	16095

Are commercial PSETs made?

Paul S wrote:
I think, BTW, Romy knows more than he tells about the parallel 6C33Cs. In any case, there are stable commercial examples to draw from, eg., the many examples from BAT. Don't forget, space around the tubes.

I do not think that commercial parallel SETs are made and I am sure no one does the parallel DSETs. BAT does not do parallel SET but their amps are PP amps. Audio Mirrors I think does parallel 6C33C but I remember it was with some kind of twist that I did not like. There were plenty of OTL with parallel 6C33C but I did not see too much SETs. I do not why I need to know more than I tell about the parallel 6C33Cs. I do not have any opine about parallel 6C33C besides that it would be relatively easy to try.

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

05-06-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	67
Post ID:	16219
Reply to:	16066

Non-linear electric chair

I've been pushing this intellectual excersise (masturbation?) of solving Romy's constraints on a powerfull bass SE amp.
Thanks to Stephie Bee the humanity have now a decent model of GU81M, so before electro-cutting
onself, one can see if the electrocution will be linear. Who wants to be electocuted by an ugly, distorting
electric chair?

Below are some simulation outputs for 6E5P(triode)-DC-GU81M. The input is 2Vrms for plots. The out power 185+W into 1 Ohm.
The opearion is A1, there is enough gain, big 6E5P!moreover it seems, at least in simulations, that 6E5P can drive Gu81M into a mild A2 too.
Very strangely, the higher the frequency, the uglier the simulated spectrum. The inductord are 100H driver load
and 130H OPT primary. The load GU81M wanted to see is strangely 4k.

The waveform at 1 Ohm load 20Hz. The charging effect I've mentioned is clearly visible at the first couple of peaks:

The FFT of the waveform above:

The same at 50Hz. Really ugly. What do the dips mean?

Pentode infierno at 100Hz:

This is all assuming the ideal PS, the ideal transformer/choke, etc. One observation is that the higher
order harmonics would be cut by the OPT.

How this all relates to the Sound (if at all)??? I have no idea. It all looks ugly to me.
How sensitive is the ear to the distortion at ULF? No idea. F-M curves suggest more than to
MF or HF distorion as the sesnitivity of the ear to ULF harmonics is higher than to the fundamental
(unless I mess something up).
Is it worth trying based on the above curves? No idea. Would rather see a PSET with 2x250W triodes,
but the only candidate which comes to my mind is 212E at the cost superpassing
all the tube price idiocy out there.

Cheers,
N-set

Cheers,
Jarek
STACORE

05-07-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	68
Post ID:	16221
Reply to:	16219

I would look at the problem wider.

The 185+W into 1 Ohm is not a lot indeed but I do not understand all of those simulations and I do not know how the distortions of simulations affect the actual results.

N-set, when you are mentioned the “Romy's constraints on a powerful bass SE amp” then I would like to say that I see now a problems a bit wider. To have a lot of SET power is great but also it is very important to be able to use this power. So, thinking about a powerful bass DSET I would like to think about the whole package that would include optimal crossovering, phase adjustment, gain adjustment, impedance matching, etc. I mean that even a great powerful DSET is not an assurance of great ULF as lower bass need to be viewed in context of enter installation where the given ULF DSET is used.

Rgs, Romy

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

05-07-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	69
Post ID:	16222
Reply to:	16221

Starting point?

I fully agree with you on the holistic approach, I have been just trying to see if one can get at least one element of the package.
Or at least a +/- reasonable starting point for getting it. I reffered to your "school of thought"
on SE amps: 2 stage, no IT, no cathode followers, no multiple drivers, etc etc.
The excercise is to see if those constraints have any reasonable solution (without burning 1kW at 3kV power
to get 160W, which is doable with 2xGU48).
I have no idea how to interpret the results myself, hence I dared to post them here in a hope that
somebody would try to interpret them. You've mentioned elsewhere checking your B2 out and seeing distortion.
How does it compare to the ugly 20Hz waveform I've posted?

Still, before all that FFT fortune telling practices,
one basic question has no answer : how sensitive we are to the ULF distortion?
Romy, others, from your experience, how does it look like?

I would completely disagree on the power: 185W from 2 stage into 1 Ohm IMHO is very good!!!
This is a 450W tube, not a 1kW monster!
But the price of distortion seems very high?

Cheers,
Jarek
STACORE

05-11-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	70
Post ID:	16240
Reply to:	16222

Welding and other activities

I think this GM81M does not justify itself. It's good only for welding and tesla coils?
Due to a seeming common unknowledge of
how to relate spectra to sound at ULF as a bare minimum I tried to get a decreasing
spectrum of harmonics. This brought the power down to 90+W,
which is already doable with 833A at much lower distortion.

Cheers,
Jarek
STACORE

05-11-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	71
Post ID:	16241
Reply to:	16240

Unfortunately no one is looking in this direction.

N-set, at this point I am under impression (not conviction however) that a hybrid with some kind of harmonic correction circuit can do the job but spend much less blood. I have to admit that the best hybrids that I head had (Lamm M1.1) no where remotely as interesting bass as better SET did (Lamm ML2.0). I still do believe in ultimate sound of bass DSET but for all intended purpose I think a SS devise with properly colored sound by a tube driver might do the job well.

What is important in her is not just add tube like harmonic distortion to suck an amp but to find a very proper dynamic pattern how those harmonics are change with volume. This is VERY complex and way above the heads of most of the today designers. No one have made a SS amp to sound similar to SET but I have to admit that for LF ONLY the task might be much simpler.

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

05-11-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	72
Post ID:	16243
Reply to:	16241

SS cheap trick

I'm monitoring your progress constantly, so I'm well aware of your discovery. But I find it
somehow a cheap trick. This is a purely irrational feeling, absolutely irrelevant for you and your
system. Since I have the breadboards I keep looking for a bass SET solution...
Waving the 2 stage constraint by adding the active crossover does simplify the things
and now I understand better what you meant by the " bass package".

Cheers,
Jarek
STACORE

05-11-2011

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Paul S
San Diego, California, USA
Posts 2,660
Joined on 10-12-2006

Post #:	73
Post ID:	16244
Reply to:	16243

Gain, Phase and Corrected Frequency

N-set, this might be a case where you can start with the 6E5P without working it so hard and still have enough gain , and correct as you go, because of the diminished frequency range requirements, and because of the third stage. Am I talking heresy to mention error correction at this point? Basically, you will have an active X/O as a 2nd stage, like a psycho phono corrector; a corrected psycho phono corrector, ultimately working into a reactive load.

Only a really greedy person (like me...) would want accessable "quasi-parametric" voltage scrubbers, too.

Why would corrected 90 W from 833 not be OK?

Best regards,
Paul S

05-11-2011

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Romy the Cat

Boston, MA
Posts 10,161
Joined on 05-28-2004

Post #:	74
Post ID:	16247
Reply to:	16243

A cheap trick

N-set wrote:
I'm well aware of your discovery. But I find it somehow a cheap trick. This is a purely irrational feeling, absolutely irrelevant for you and your system.

I world not call it irrational, in fact it is very rational and I very much share this feeling. I do agree that it is a cheap trick and nothing more them a half-ass solution. To have 4 active tube stages for a stinky filters – ridicules. However, this is what I have in my disposal and let agree that gong from a tube crossover with 12AX7 and a mass-consumer power amp to 150W DSET amp is a LARGE move.

I am under no delusion that what I doing now with ULF amplification is architecturally non-kosher. However, I also would like to know how much REAL practical difference the 150W DSET would make against a PROPERLY IMPLEMENTED “bass package". BTW, I do not feel that I have properly implemented “bass package”. I have what I have and in my estimation the properly implemented “bass package” shall be much better then what I have now and I have very specific list of things the I do not like in my bass now. Still, the whole direction where I went with my bass I do feel promising.

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

05-12-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	75
Post ID:	16249
Reply to:	16244

Multistage considerations

Paul, if by error correction you mean frequency correction then I was thinking about +/- the same.

i) Active filters; I have zero experience with crossing-over but people who seem to know what they
are talking about all agree that at ULF active is the way;
ii) If Roman is right, 24db/oct slope with a provision to change to 18db/oct
iii) User adjustable freq. and gain
iv) I would not rely on the OPT 12db natural slope as it's hardly adjustable

That all will give 5 stages if I'm not overlooking some posibility: 3 filtering stages, with the first one bypassable, the driver being
at the same time the last filtering stage and the output with multitapped OPT.

Why not 90W from 833?It's too little power I guess? Then to get those 90W A1 means 2.5-3kV
which is a pain. At 1.5kV one could pile up big Nichicon's, at 3kV...$$$$. Good point about 833 is that
it can handle 450W FAC or even 550W (Pentalabs), and there are 4358757 versions of it, including
the euro TB3/1000. All pretty +/- available (I think the tube is still being used).
Again, 304tl/th is an interesting option with perhaps more power and 2x lower Rp.
Or double all that, consuming 240W heater power per channel...
Approaching this babe from behind, I'm still searching for a propoer output tube.

BTW, I said that my feelings are irrational and irrelevant as it remains unknown what is the proper
implementation. It may as well happen that the hybrid Romy is testing IS the way to go and Bass SET (BSET)
is a waste of time and money and power.

Cheers,
Jarek
STACORE

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