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04-17-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 61
Post ID: 16090
Reply to: 16084
Closing the Gap
fiogf49gjkf0d
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 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 62
Post ID: 16093
Reply to: 16090
Missing miliampers
fiogf49gjkf0d
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.
GU81M_screen.gif

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
04-18-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 63
Post ID: 16095
Reply to: 16093
BAT Man
fiogf49gjkf0d
N-set, I see you are determined to live and die with the charts.  So be it. Prost.

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.

Best regards,
Paul S
04-18-2011 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 64
Post ID: 16097
Reply to: 16095
Why?
fiogf49gjkf0d
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
04-18-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 65
Post ID: 16099
Reply to: 16095
Are commercial PSETs made?
fiogf49gjkf0d
 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
04-18-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 66
Post ID: 16100
Reply to: 16099
Wrong Again...
fiogf49gjkf0d
Yes, of course you know about the BAT but, once again, I should fact check before posting, eg., "BAT SET"; or better yet, just put a sock in it.

I think the candidates are up the thread...

..instead of posting, maybe I'll dig out Beethoven's PS #15...

Best regards,
Paul S

05-06-2011 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 67
Post ID: 16219
Reply to: 16066
Non-linear electric chair
fiogf49gjkf0d
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:

GU81M_20Hz_2Vrms_wave.JPG

The FFT of the waveform above:

GU81M_20Hz_2V.JPG

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

GU81M_50Hz_2V.JPG

Pentode infierno at 100Hz:
GU81M_100Hz_2V.JPG

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
05-07-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 68
Post ID: 16221
Reply to: 16219
I would look at the problem wider.
fiogf49gjkf0d
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 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 69
Post ID: 16222
Reply to: 16221
Starting point?
fiogf49gjkf0d
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
05-11-2011 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 70
Post ID: 16240
Reply to: 16222
Welding and other activities
fiogf49gjkf0d
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
05-11-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 71
Post ID: 16241
Reply to: 16240
Unfortunately no one is looking in this direction.
fiogf49gjkf0d
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 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 72
Post ID: 16243
Reply to: 16241
SS cheap trick
fiogf49gjkf0d
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
05-11-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 73
Post ID: 16244
Reply to: 16243
Gain, Phase and Corrected Frequency
fiogf49gjkf0d
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 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 74
Post ID: 16247
Reply to: 16243
A cheap trick
fiogf49gjkf0d
 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 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 75
Post ID: 16249
Reply to: 16244
Multistage considerations
fiogf49gjkf0d
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
05-12-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 76
Post ID: 16250
Reply to: 16249
Too many unknowns in both cases
fiogf49gjkf0d
 N-set wrote:
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

It is 3 stages total not 5. You do not need 3 dedicated filtering stages to write 24dB filter. The same Marchanhd crossover does it via 2 stages, I am sure it would possible to use only one extra stage to with two LC filters as a supplement to  two-stages idea Of cause no one would use the  low-pass OTP slope as at this slope a transformer has a LOT of distortions. You want to be at least 2-3 octaves from low-pass slope….
 N-set wrote:
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.

If Romy were be testing any hybrid then it would be identically in complexity question: what would be proper harmonics structure at a given volume and how to control it. The ONLY excuse would be that it is very narrow band amp and it might be much more forgiving in harmonic inaccuracy…
 


"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 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 77
Post ID: 16252
Reply to: 16250
The only way seems to try and compare
fiogf49gjkf0d
Sure, me idiot. I wanted for some reason multiply the harmonic imprints.
2 LC will not give a chance to try 3rd order, no? Or is this
option not really needed?
Also the driver should be kept for what it's meant--driving the output, so no filtering
duties on it as it'll be fighting the grid currents etc. Still looking for the output tube...





Cheers,
Jarek
05-12-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 78
Post ID: 16253
Reply to: 16252
Overall Gain
fiogf49gjkf0d
Maybe the best way to think about the X/O is that one way or another, it's effectively part of the amplification chain.

Don't the "2 stages" in the Marchand include offset for X/O losses?  Sure, if the X/O is interstage, then it will need to clean up its own mess before the output tube cranks it up.  However, no free lunch no matter where you X/O, with respect to level, phase, distortion and noise.  Smaller parts at line level is nice; but it does have to stay at that level. 

The only advantages I see for transistor, op-amp or whatever are efficiency and/or signal/noise.  Op-amps can be made very quiet -- with some serious feedback.

ULF might be servo, with the coil in the power loop.  Talk about feedback...

Best regards,
Paul S
05-22-2011 Post does not mapped to Knowledge Tree
N-set
Gdansk, Poland
Posts 454
Joined on 01-07-2006

Post #: 79
Post ID: 16299
Reply to: 16252
Have the cake and eat it
fiogf49gjkf0d
Although the spiritus movens of the whole idea seems to have found the
bass solution, the idea continues to live.

Thanks to the invaluable help of Stephie B, I've comeback to the GU81M like
a boomerang with some progress. There are 3 new things:

1) FFT vs Sound: as an ad hoc assumption let's accept that the limit of torelability is when
the 3rd hamonic starts to dominate the 2nd; weather it's right or not I guess only
the experiment will show

2) Selectable Ultralinear connection as one more degree of freedome to play with
power/distortion ratio

3) Incorporated low-pass filter around 12AX7 (I know nothing about x-overs, so correct me if there are mistakes).

Here are two versions: LC (Butterwoth???) filter and RC Sallen-Key type (Linkwitz-Riley):

GU81Mv3LC.gif


GU81Mv3SK.gif

Now the comments: there is a mistake, 6E5P has +214V on the plate of course.
Everything is DC coupled a la Chimera's Axiom,
 which makes up for 73265876 power supplies
to supply 3 tubes (although the +/-200V 2mA is nothing). the -3dB point sims show at 5.5Hz.
The 6E5P driver is biased at -4V and not -3.5V to give it some
headroom. I'd love to have some provisions to adjust in some small limits
the bias of the driver and the ouput individually, as this all is very senitive.

Ad1) The sims show that the +/- optimum load is 2.9k giving 160W at the point when 3rd harm=2nd
(at I think around 10% THD).
(Stephie claims to have reached 187W with 6E5P pent. mode, but I could not reproduce it).
The tube can give much more, in excess of 200W but at considerable clipping. The search over
GU81M shows that amateur radio peple do use&abuse it quite hard, 450W free air is realistic,
and there are reports it can survive quite some more for years. Unfortunately I could not get
any feedback from audio users of GU81M.

Ad2) Thanks to Stephie I've resolved how to add an UL posibility -- since the grid needs it's own
supply the only chance is to add another winding on the OPT. This makes the OPT complicated, but
for a completely different reason than usually: the primary side now has 3 windings: the main plate load,
the selectable 0-20%-30%-40% screen load, and the compensating winding caryying filament current
to reach 130H@300mA with a reasonable core. I think the switchable UL shoud add some nice
degree of freedome, apart from changing the load. I could not simulate the UL as LTspice
gets stucked, so no idea how it "performs".

Ad3) I've assumed 12AX7 CF with 157k to be a good solution, following Romy's experience.
I know nothing about active filters, please educate me. The most "economical" seems to be
LC filters, but 99% of x-overs I've found googling (incl. the Marchand) are Sallen-Key RC
with positive feedback. Now, is S-K so popular because it sounds good or because
it uses cheap tubes and RC instead of costly chokes??? Any input highly appreciable.
I'm not even sure if my implementation of S-K is correct? Have to sim it.

The input sensitivity without the filters (still have to sim them) for 3=2 point is around 1.7Vrms.

Cheers,
N-set



Cheers,
Jarek
05-22-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 80
Post ID: 16300
Reply to: 16299
Drifting Away
fiogf49gjkf0d
N-set, I am not the one to double check your mathematical solutions, that's for sure.  I wonder if in practice the curve values here are effectively tied to variables?  I like the Chimera idea, but it has no "locked curves" to contend with, and it uses diodes everywhere, even out, to help temper tank circuit effects and (it appears) to provide a sort of "feedback", or "anti-blowback".

I think the reasons for S-K RC with feedback include usual trafo noise and also to counter drift.  This is what I meant by "corrected", above.  Of course I like dial-a-bias, even if only to try to secure the active curve.

By the way, I somehow feel safer at "only" 500V.  Now, caps might even fit in the chassis!

Best regards,
Paul S
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  »  New  More power from Melquiades? More powerful tube?..  A new Icon Audio's MB81 Mono Blocks...  Melquiades Amplifier  Forum     19  172808  09-01-2007
  »  New  NAT Audio Magna -160 Watts of Single-Ended Class A..  The KR Audio ways....  Audio Discussions  Forum     5  49442  11-12-2007
  »  New  Claude Perrier and his tube seremony..  Claude Perrier and his tube seremony...  Audio Discussions  Forum     0  9967  01-05-2008
  »  New  Getting more power from SET vs. properly distorting SS...  Sound Board...  Audio Discussions  Forum     4  31909  05-09-2011
  »  New  The ULF cannel for my new listening room...  The crossover is ready to go....  Audio Discussions  Forum     34  3212  07-29-2018
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