I am looking to upgrade my 4 tube, 7189 mono tube amp from push-pull to ultra linear. What I am looking for, is any or all information pertaining to what primary impedance will work best for this amp in ul. I know eico made a amp like this in ul,and the primary impedance for their amp was 4000 to 4300 ohms. I believe healthkit also made a amp like this,but I do not have any information on their amp. Does anyone have any information on what primary impedance will work best for this type of tube amp? I have looked through several tube manuals,but no luck. My current set-up is 4-7189, in push-pull parellel,with a primary impedance of 3300 ohms.Any suggestions on what primary impedance will work best for this tube amp in ul would be appreciated. tv1143
Primary output transformer impedance
- Thread starter tv1143
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Jim McShane
Well-Known Member
There's a rule of thumb that may help you here too - lower primary impedance will give you MORE, more power & more distortion. Higher primary impedance will give you LESS, less power & less distortion.
Tom Bavis gave you a very good starting point, where you want to be in that range is to an extent dependent on whether you need more power or less distortion.
Thespeakerdude8
Super Member
To a certain point- once you go below a certain point you start straying away from the tubes optimal loadline and they will actually produce less power and more distortion. If you look on the tube chart, it will usually give the amounts needed on a power output+THD as a function of load impedance.
This probably doesn't help much with 4 tubes though,other than halving everything.
SET12
Super Member
While Jim and Tom are correct you should also be aware that a Pentode connected amplifier to my ears and others is simply more dynamic so when you go Ultra Linear expect lower distortion from it but there is a price to be paid. Its always give and take!
Also though not talked about much is dynamic conductance (Transconductance X The Load) so higher loads yield higher dynamics but everything works together! Power Supplies and so on.
You do have choices and as I like to say "nothing is written in stone"
Cheers
SET12
Jim McShane
Well-Known Member
Ahh, but to run pentode mode you need a very good screen supply too. So not only is nothing written in stone, there's no such thing as a free lunch!
But if the original poster is buying new iron he might as well buy it with U/L taps. He can leave them unconnected for pentode (or triode) mode - or follow through with his plan to go ultralinear (a.k.a. "partial triode").
BTW, a Citation II in U/L has incredible dynamics. U/L CAN be done with great results too. :thmbsp:
spkrman57
wrongsideofthetracks
Does running ulstra-linear change the primary impedance?
I'm one who has some knowledge of tubes, but not what I call a "expert".
If running UL vs pentode configuration, does the overall impedence change at the plate-to-plate connection.
OT: On single-ended amps run in "triode-strapped" mode have different impedence than pentode or UL mode?
Thanks to anyone who can answer my questions!!!
Thanks, Ron
Ahh, but to run pentode mode you need a very good screen supply too. So not only is nothing written in stone, there's no such thing as a free lunch!
But if the original poster is buying new iron he might as well buy it with U/L taps. He can leave them unconnected for pentode (or triode) mode - or follow through with his plan to go ultralinear (a.k.a. "partial triode").
BTW, a Citation II in U/L has incredible dynamics. U/L CAN be done with great results too. :thmbsp:
I'm one who has some knowledge of tubes, but not what I call a "expert".
If running UL vs pentode configuration, does the overall impedence change at the plate-to-plate connection.
OT: On single-ended amps run in "triode-strapped" mode have different impedence than pentode or UL mode?
Thanks to anyone who can answer my questions!!!
Thanks, Ron
SET12
Super Member
Ahh, but to run pentode mode you need a very good screen supply too. So not only is nothing written in stone, there's no such thing as a free lunch!
But if the original poster is buying new iron he might as well buy it with U/L taps. He can leave them unconnected for pentode (or triode) mode - or follow through with his plan to go ultralinear (a.k.a. "partial triode").
BTW, a Citation II in U/L has incredible dynamics. U/L CAN be done with great results too. :thmbsp:
No free lunch!
Its the same for Ultra Linear :yes:, Granted there are many fine sounding Ultra Linear designs and the Citation is a very fine example.
I agree he can try them all, to each their own.
Yes, supplies are part of the key. And a regulated screen can do wonders. But even non regulated screens are still more dynamic to my ears with a good powerful fast supply. With a slow wimpy supply for a Penetode vs a Good fast supply for the Ultra Linear I'd likely give the edge to the Ultra Linear.
Lets take a case in point. Like the Pentode connected EICO HF81
View attachment 124603
What do you see in this supply that is not the norm in most?
:yes: The screen taps are actually a form of feedback the tubes Rp (internal resistance) is lower. One can get by with less overall feedback I have even seen Pentodes running in SET mode with Ultra Linear Taps connected with little or no Global feedback.
And Triode Strapped Penetodes have considerably less plate resistance and often have no need feedback much of the time for a SET amp.
A Push-Pull amps actual tube load is 1/4 of the plate to plate impedance.
SET12
Thanks for all the replie's. Perhap's I can be a litle more specific in the application of which this amp is to be used. I want to use the amp in a tri-amp set up,3 amps per channel,with this amp being used for the low's, and crossed overed at 300 to 400hz.I would like at least 30 watts rms-or more- out of it, with "excellent" bass reproduction,with the lowest possible distortion.That is my goal.I have heard that ul give's better frequency reproduction and lower distortion.But I wonder, just how much power output I would lose going from p-p at 3300 ohms, to say ul at 4k to 4.3k?Also,I heard that lower primary impedance has better output frequency response. I this true?I am just trying to get "all" the facts before a purchace a new output transformer. I can get a edcor 60 watt tranny for $62.00 to $70.00 dollar's,and a hammond for about $20.00 more. Both with either 3300 or 4300 ohms with ul taps.I have not looked at the dynaclone tranny yet,but I believe these are 4300 ohm,35 watt units,with ul taps.I will check prices today.I would apreciate any or all information pertaining to this set-up and how to proceed.I am also using a ss rectifier with a slow start circuit for rectification.If you need any more information,please feel free to ask.Thank you for "all" of your time and replie's,tv1143
NOSValves
Super Member
I'll bite.....what? Pretty basic and barely up to the job? Typical EICO is you ask me...
Mike Stehr
Poverty Audio
That's what I thought. Seems pretty common hanging the B+ right off the rectifier with the first cap. Quite a few of the cheaper vintage amplifiers do this sort of thing, even some of the more expensive ones I would guess.
Unless I'm missing something.........
SET12
Super Member
Mike hit it on the head.
About a decade ago I converted a Pilot Integrated amp to a basic power amp.
In the original circuit was the typical 100 ohm resistor fed from the tube rectifier and its first cap which feed the second cap that feeds the output stage. Screens were fed from the second cap as well
On a hunch I removed the 100 ohm resistor and allowed the tube rectifier and its first cap to feed the output stage and screens. My buddy and I gave it a listen. And to our surprise that amp was dramatically more dynamic.
While the EICO does not have modern reserves it does have the same basic connection other than the screens which are fed from the second cap.
The DCR in the path has a substantial effect on an amplifiers dynamics.
Herb Reichert, Has really made a point about the importance of a low DCR path in his Flesh and Blood 300B Amplifier. And as he points out in his article its the DCR not the Henry's that count.
http://www.enjoythemusic.com/magazine/equipment/0801/fleshandblood.htm
And I have to concur based on what I have heard both from the Pilot and my own amplifiers.
If I was using chokes I'd just might consider these Toroidal chokes at Plitron like the PAT4174 a 10H choke with a 20 ohm DCR.
http://www.plitron.com/audio_chokes.asp
SET12