Hey all, I am going to be starting a tube amp project - a 6H30 (gain stage) / 12BH7 (phase splitter) / KT88 (output) tube amp (kinda like a Quicksilver 8417 or Bogen MO100), and I have all the components. The output tranny is a edcor 60W and 3500 ohm primary impedance, and 4 and 8 ohm tap output.
Now what I really wanted to do was drive a pair of either ML CLS, or a setup consisting of a series of acoustat panels, using a modified acoustat MK-121 interface. This setup would be for frequencies over 200hz....
But I was wondering if there was a tranny I could use instead of the edcor that would have the 3500 ohm primary impedance on the KT88 plates (just like the edcors) , but secondary be a 7- 1 step up to the 3500v - 5000v direct to the ESL panels. The B+ of the tube amp should be around 475v.
Not exactly direct drive (as I am not driving directly from the plates), but sorta...
Anyway, would this work, and does such a tranny exist? 7:1 to 10:1 step-up and 3500 ohm impedance on plate side? What would the impedance need to be on the esl side?
Go easy on me if it is a ridiculous idea...I'm thenthitive....
Now what I really wanted to do was drive a pair of either ML CLS, or a setup consisting of a series of acoustat panels, using a modified acoustat MK-121 interface. This setup would be for frequencies over 200hz....
But I was wondering if there was a tranny I could use instead of the edcor that would have the 3500 ohm primary impedance on the KT88 plates (just like the edcors) , but secondary be a 7- 1 step up to the 3500v - 5000v direct to the ESL panels. The B+ of the tube amp should be around 475v.
Not exactly direct drive (as I am not driving directly from the plates), but sorta...
Anyway, would this work, and does such a tranny exist? 7:1 to 10:1 step-up and 3500 ohm impedance on plate side? What would the impedance need to be on the esl side?
Go easy on me if it is a ridiculous idea...I'm thenthitive....
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The idea is not bad at all!
Actually it´s a very good idea!
I have that ide myself 🙂
I will use a 300B drivin an interstage Lundal 1677 transformer drivin two GM70 tubes on the output.
From there i have custom built output transformer 1:3.5 from SOWTER.
The GM70s is fed with 1350volts and is loaded with coils 50H on each GM70.
That way I will get the double swing output 2*1100V=2200Volts and multiplied with the transformer turn ratio 3,5 it will give me a total sving on the plates of 7000 volts.
Good enough i think.
4 coils and 4 transformer was hand made by Mr Brian Sowter himself...
I guess he like challanges!
He could meet my spec with wery low capacitance which is important also the isolation capability.
So a short answer to your question is YES! This is the way to go!
Good luck!
Bear in mind... everything above 48Volts is really dangerous.
300volts requires lot of skills.
1200volts is for experts only or really really stupid guys.
I´m the later one i guess...
Actually it´s a very good idea!
I have that ide myself 🙂
I will use a 300B drivin an interstage Lundal 1677 transformer drivin two GM70 tubes on the output.
From there i have custom built output transformer 1:3.5 from SOWTER.
The GM70s is fed with 1350volts and is loaded with coils 50H on each GM70.
That way I will get the double swing output 2*1100V=2200Volts and multiplied with the transformer turn ratio 3,5 it will give me a total sving on the plates of 7000 volts.
Good enough i think.
4 coils and 4 transformer was hand made by Mr Brian Sowter himself...
I guess he like challanges!
He could meet my spec with wery low capacitance which is important also the isolation capability.
So a short answer to your question is YES! This is the way to go!
Good luck!
Bear in mind... everything above 48Volts is really dangerous.
300volts requires lot of skills.
1200volts is for experts only or really really stupid guys.
I´m the later one i guess...
This has been discussed before and is not practical.
The more voltage you have on the primary the more turns it takes to keep the core from saturating at a given frequency and core area.
This means that many more turns on the secondary and this will raise the transformers parasitic capacitance dramatically.
Doing this can lower it's resonate frequency well below 20khz and will severely limit the transformers bandwidth.
Yes, it seems logical but it doesn't work like that and is not practical unless you have some really big iron to hold all of the extra turns while still providing enough room for some thick insulation in between the turn layers in order to keep the transformer capacitance at a minimum.
The more turns you have the more copper losses you have as well!
I am not saying it can't be done but it is not cost effective nor will you gain any performance.
FWIW !!
jer 🙂
The more voltage you have on the primary the more turns it takes to keep the core from saturating at a given frequency and core area.
This means that many more turns on the secondary and this will raise the transformers parasitic capacitance dramatically.
Doing this can lower it's resonate frequency well below 20khz and will severely limit the transformers bandwidth.
Yes, it seems logical but it doesn't work like that and is not practical unless you have some really big iron to hold all of the extra turns while still providing enough room for some thick insulation in between the turn layers in order to keep the transformer capacitance at a minimum.
The more turns you have the more copper losses you have as well!
I am not saying it can't be done but it is not cost effective nor will you gain any performance.
FWIW !!
jer 🙂
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Well i am all about Diy but ......Jim Did this with the Acoustat tube sevos..... just copy this....Go for it....Less you need to Make a new mouse trap??
I had the Xs Thay were a pr of M3s type on the floor....
The Tube Sevos Sounded Great....These Amps Will drive ANY ESL.....ML ,SL,Quad,......What was the Down side an why did i move on to the 121 interfaces......The THD was so low that you just wounted more an more Output....an it Not going to happen.....
To me it like a 500 Watt pr ch Mcintosh SS amp.....Sounds Sweet.....but has no headroom becase of the autio-fourmers on it outputs.....you can use all it output with Low THD....leves mOST wonting More...
An this is not just me.... I sold Mc an saw a lot of people who lov the sound move away from the Mc SS Amps....just did not have the drive thay wounted for ribbons are Even Mc own speakers...
With mods the 121 can sound as good an can be driven with my OTLs M60s ....60watt tube amps....Goodluck
I had the Xs Thay were a pr of M3s type on the floor....
The Tube Sevos Sounded Great....These Amps Will drive ANY ESL.....ML ,SL,Quad,......What was the Down side an why did i move on to the 121 interfaces......The THD was so low that you just wounted more an more Output....an it Not going to happen.....
To me it like a 500 Watt pr ch Mcintosh SS amp.....Sounds Sweet.....but has no headroom becase of the autio-fourmers on it outputs.....you can use all it output with Low THD....leves mOST wonting More...
An this is not just me.... I sold Mc an saw a lot of people who lov the sound move away from the Mc SS Amps....just did not have the drive thay wounted for ribbons are Even Mc own speakers...
With mods the 121 can sound as good an can be driven with my OTLs M60s ....60watt tube amps....Goodluck
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Tyu, the servos did not have output trannies, but I was enquiring about having a reverse output tranny on my tube amp - a stepup instead of conventional step down - to drive the esls
Did mean go too far off the topic......
I have used.... edcor tranfourmers.... thay will wind any tranfourmer you can come up with......if it can be made thay well do it... An there $$ is as good as any i have found.....
But i see the sevos type tube amps as a ezer way to drive a ESL if this is someing anyone wonts to do.........Goodluck...
I have used.... edcor tranfourmers.... thay will wind any tranfourmer you can come up with......if it can be made thay well do it... An there $$ is as good as any i have found.....
But i see the sevos type tube amps as a ezer way to drive a ESL if this is someing anyone wonts to do.........Goodluck...
As i mentioned... write down your requirement specification and send it out to transformer suppliers and let dem send you a quote.
Sowter fullfilled my specifications at a reasonable price i have to say, and YES, there is many layers of insulation here and there.
And a massive piece of iron i can tell.
Remember that the secondary on those transformers is probably much better than the QUAD ESL63 original transformers....
The weight only is more than double, on each transformers.
Sowter fullfilled my specifications at a reasonable price i have to say, and YES, there is many layers of insulation here and there.
And a massive piece of iron i can tell.
Remember that the secondary on those transformers is probably much better than the QUAD ESL63 original transformers....
The weight only is more than double, on each transformers.
Dumb question - what would the output impedance need to be on such a tranny connecting to the ESL?
As we all know ESLs already have matching transformers. I expect the allure of eliminating one transformer in the signal train is powerful.
I would certainly give it a shot despite admonitions to the contrary. The only thing that would concern me is that bias voltage on the secondary side. Just as an output transformer can saturate when there is too much unbalanced DC current through the primary, so to can it saturate on the secondary side.
So the actual device might have to be of the cut-core variety. The other issue is that there is likely a learning curve for anyone fabricating such a part. Be prepared to built between 5 and 20 units getting it right.
If there is an argument for going direct-drive, that latter issue may well be it.
I would certainly give it a shot despite admonitions to the contrary. The only thing that would concern me is that bias voltage on the secondary side. Just as an output transformer can saturate when there is too much unbalanced DC current through the primary, so to can it saturate on the secondary side.
So the actual device might have to be of the cut-core variety. The other issue is that there is likely a learning curve for anyone fabricating such a part. Be prepared to built between 5 and 20 units getting it right.
If there is an argument for going direct-drive, that latter issue may well be it.
Yikes!!
The secondary CT of this step up tranny would be grounded, and ESL bias placed on the diaphragm, just like a MK-121.
Hate to start this and have to quit as it may be over my head, especially since I have all the components for the tube amp AND all the interface already.
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The devil is not so black as it's painted
Well, it will take you not more than a month of full time work or so, depending on learnability and money supply. I would suggest to look on so-called cable transformer by Finnish diyer to derive some knowledge.
If you don't have bias on the secondary that will help!
If it were me I would go to someone that already makes matching transformers for ESLs- maybe even the one that made the transformers in your unit. They might have a better chance of getting it right.
If it were me I would go to someone that already makes matching transformers for ESLs- maybe even the one that made the transformers in your unit. They might have a better chance of getting it right.
Didn't we just have another thread about this? In the other thread, I mentioned that one of Dayton-Wright's earliest speakers around 1972 had just that kind of amp.
While I think direct HV drive is audibly better (than anything in the universe), your concept may be second best, if Fry's concerns can be addressed.
Say, why not just make it direct drive and have no transformer? Unless you have little kids around the house!
Personal opinion: I think ESLs are so great a way to make sound waves (compared to shaking heavy cardboard pieces in the air) that even kind of faulty drive systems (that is, transformer-borne) or various beaming limitations that they still sound wonderful. So twice as good, if you can own a direct-drive ESL.
Ben
While I think direct HV drive is audibly better (than anything in the universe), your concept may be second best, if Fry's concerns can be addressed.
Say, why not just make it direct drive and have no transformer? Unless you have little kids around the house!
Personal opinion: I think ESLs are so great a way to make sound waves (compared to shaking heavy cardboard pieces in the air) that even kind of faulty drive systems (that is, transformer-borne) or various beaming limitations that they still sound wonderful. So twice as good, if you can own a direct-drive ESL.
Ben
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Hi,
well as mostly, I tend to disagree with Ben 🙄 *lol*
From a technical viewpoint most direct drive amplifiers are quite limited, either in output voltage, output current and bandwidth.
As to my taste most DD-amps I heard didn´t sound as well as a good tranny driven by a fine Tubeamp, say a SE-Triode, especially when driven hard.
Similar to a transformer the amplifier needs to be designed after the panels requirements. A segmented wire stator panel certainly asks for different conditions than a fullsized metal stator. The first aks for rather high driving voltages while the second asks for more current capability.
In any case will it become difficult to achieve a similar dynamic range, bandwidth and low THD as with a good transformer. Not to mention safety, power demand and reliability issues.
jauu
Calvin
well as mostly, I tend to disagree with Ben 🙄 *lol*
From a technical viewpoint most direct drive amplifiers are quite limited, either in output voltage, output current and bandwidth.
As to my taste most DD-amps I heard didn´t sound as well as a good tranny driven by a fine Tubeamp, say a SE-Triode, especially when driven hard.
Similar to a transformer the amplifier needs to be designed after the panels requirements. A segmented wire stator panel certainly asks for different conditions than a fullsized metal stator. The first aks for rather high driving voltages while the second asks for more current capability.
In any case will it become difficult to achieve a similar dynamic range, bandwidth and low THD as with a good transformer. Not to mention safety, power demand and reliability issues.
jauu
Calvin
Lots of differing opinions on this subject, kinda like a Obama/Romney debate....yikes.
I called Galaxy Transformers (company that made Acoustat trannies) and they were too busy to take on another project (the guy was polite about it)...
"Idiot Shield On" Can't I just take a beefy standard 120V -12VCT toroidal transformer run backwards with a pair of series resistors on primary to the plates to get the 3500 ohms resistance/impedance, and the step up side direct to the ESLs? "Idiot Shield Off".
OK I said it.
I know the difference between tanformer series resistance and series impedance are different, but can they be made to better match output tube plates (the tube amp design) by adding a series resistor is the question?
The popular Antek AN-1206 100VA (dual primary/secondary 120V - 6V) comes to mind...too bad they are still out of stock (going on 4 months now...sigh)
I called Galaxy Transformers (company that made Acoustat trannies) and they were too busy to take on another project (the guy was polite about it)...
"Idiot Shield On" Can't I just take a beefy standard 120V -12VCT toroidal transformer run backwards with a pair of series resistors on primary to the plates to get the 3500 ohms resistance/impedance, and the step up side direct to the ESLs? "Idiot Shield Off".
OK I said it.
I know the difference between tanformer series resistance and series impedance are different, but can they be made to better match output tube plates (the tube amp design) by adding a series resistor is the question?
The popular Antek AN-1206 100VA (dual primary/secondary 120V - 6V) comes to mind...too bad they are still out of stock (going on 4 months now...sigh)
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john65b,
You can take any transformer and do anything. But that doesn't mean it will sound any good.
Toroidal xfmrs do not have good bandwidth when used for audio (a few minor exceptions apply) so forget that idea completely.
What you are looking for is more or less a 1:1 transformer. Aka "mod transformer" or modulation transformer, as used in broadcast transmitters. You need a pair. That's not easy to find and usually expensive. You'd want to use a HV tube for the primary so that you can swing enough voltage. Something with B+ at 1,500-2,500v probably. Big, hot, heavy. Dangerous. (sexy though)
You can NOT use the usual interface on an ESL with a HV drive source, they want speaker level and impedance input.
Plus the MK-121 uses two transformers.
No you can't use resistors in series with the primary, that will cause a massive voltage drop and other negative effects (frequency response changes).
Your best bet is to build an amp that is *designed* to drive the ESL that you actually *have*. Usually that means something in the 100w-200w class of amp.
[for example Bob Cummings (you may not know who he is) built a pair of 211 in SE parallel with a custom OT at 2 ohms to drive a pair of ML CLS. Worked very nicely]
Or to build a DD type amp (hot, heavy, dangerous).
And a bit tricky to find appropriate tubes these days.
What you *can try* as an experiment is to take a standard, appropriately sized output transformer and run *it* backwards off the secondary of a tube amp - the "primary" of this transformer now produces voltage equal (or similar to) the voltage on the plates of the output tubes. This can be used to run the stators directly. (getting flat output from the ESL using this method is another design issue, as it is with any matching transformer).
_-_-bear
You can take any transformer and do anything. But that doesn't mean it will sound any good.
Toroidal xfmrs do not have good bandwidth when used for audio (a few minor exceptions apply) so forget that idea completely.
What you are looking for is more or less a 1:1 transformer. Aka "mod transformer" or modulation transformer, as used in broadcast transmitters. You need a pair. That's not easy to find and usually expensive. You'd want to use a HV tube for the primary so that you can swing enough voltage. Something with B+ at 1,500-2,500v probably. Big, hot, heavy. Dangerous. (sexy though)
You can NOT use the usual interface on an ESL with a HV drive source, they want speaker level and impedance input.
Plus the MK-121 uses two transformers.
No you can't use resistors in series with the primary, that will cause a massive voltage drop and other negative effects (frequency response changes).
Your best bet is to build an amp that is *designed* to drive the ESL that you actually *have*. Usually that means something in the 100w-200w class of amp.
[for example Bob Cummings (you may not know who he is) built a pair of 211 in SE parallel with a custom OT at 2 ohms to drive a pair of ML CLS. Worked very nicely]
Or to build a DD type amp (hot, heavy, dangerous).
And a bit tricky to find appropriate tubes these days.
What you *can try* as an experiment is to take a standard, appropriately sized output transformer and run *it* backwards off the secondary of a tube amp - the "primary" of this transformer now produces voltage equal (or similar to) the voltage on the plates of the output tubes. This can be used to run the stators directly. (getting flat output from the ESL using this method is another design issue, as it is with any matching transformer).
_-_-bear
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OK, Thanks Bear...
About you Toroidal comment - that Antek AN-1206 transformer Interface I built sounded much better than the Acoustat MK-121 and the MK-141 (Medalion) Interfaces...the clarity was impressive, while the Acoustats were kinda blah on the CLS.
A Tube amp -> a second, identical audio transformer used in the tube amp wired backwards -> ESL stators basically becomes a 1:1 ratio, correct?
About you Toroidal comment - that Antek AN-1206 transformer Interface I built sounded much better than the Acoustat MK-121 and the MK-141 (Medalion) Interfaces...the clarity was impressive, while the Acoustats were kinda blah on the CLS.
A Tube amp -> a second, identical audio transformer used in the tube amp wired backwards -> ESL stators basically becomes a 1:1 ratio, correct?
Well, I am surprised at your report on the Antek for an interface to the Acoustat. Did you measure the resulting frequency response? One can be fooled due to variations in the response. A single impedance transformer can *only* match for a specific combination of bandwith vs. sensitivity. That's why Jim Strickland's patented interface uses two transformers - it extends the bandwidth without the sensitivity penalty.
The CLS are different than the Acoustat speakers, they probably have different capacitance, so need a different impedance ratio to match properly.
Yes, the basic idea on the reversed output transformer is correct, the ratio is reverted back. Of course if you use different taps or different transformers the ratios may or may not be 1:1.
_-_-bear
The CLS are different than the Acoustat speakers, they probably have different capacitance, so need a different impedance ratio to match properly.
Yes, the basic idea on the reversed output transformer is correct, the ratio is reverted back. Of course if you use different taps or different transformers the ratios may or may not be 1:1.
_-_-bear
1. In today's world, hard to imagine you can't produce an amp as good as you'd like to perform whatever you want. Seems arbitrary to argue otherwise.
Transformers now and always have been giant bundles of compromises, esp. when we are talking about an application that pushes their limits in a variety of ways all at once, as Fry said. Odd to hear that a tube amp (with its own limitations in power) is advocated along with an iron transformer (with limitations far more noxious to the ear) as better than DD.
2. As I pointed out at length in the other thread, my Sanders-like 2400 volt B+ DD amp really drove a bunch of power resistors (very cleanly) and the ESL capacitance which paralleled those resistors was not a major design factor (till I started sorting out the parasitic oscillations in the loop). In other words, characteristics of the ESL didn't matter to the amp. Although you might want to EQ upstream to drive your specific panels, of course.
Ben
Well all i can say is it good to see someone that HAS had a DDamp....give some input!
I well say My Acoustat sevo tube amps had a Eq in them.... an thay sound so Vary good to me an [others] ...
So when i was Saleing Audio in the 80-90s...
A Dr. i had done work for in his home..had a pr of Acoustat 1+1s....With one of pass,s big s/500s 250 watt pr ch Amps driving them...he wonted to Bet me...that there was No way that these Acoustat DD tube amps could give him more out put than the Big Pass...an sound better on top of that...
So i call him on the Bet....$2500+the pass s/500+ the 121 interfaces that were on his 1+1s.....
Well that was that...
I got the cash amp an 121...he got my Sevos tube amps...With Stock tubes... Amps were all stock ....
I lov the sound of the DD amps on my Xs that i paid $400 for the pr...but i was over driving them ...just could not get a nuff of that low thd, ,full,warm,honey sweet topend, big Full bass an sound stage that filled the room......So i never looet back....goodluck on you Trip with DD amps
I well say My Acoustat sevo tube amps had a Eq in them.... an thay sound so Vary good to me an [others] ...
So when i was Saleing Audio in the 80-90s...
A Dr. i had done work for in his home..had a pr of Acoustat 1+1s....With one of pass,s big s/500s 250 watt pr ch Amps driving them...he wonted to Bet me...that there was No way that these Acoustat DD tube amps could give him more out put than the Big Pass...an sound better on top of that...
So i call him on the Bet....$2500+the pass s/500+ the 121 interfaces that were on his 1+1s.....
Well that was that...
I got the cash amp an 121...he got my Sevos tube amps...With Stock tubes... Amps were all stock ....
I lov the sound of the DD amps on my Xs that i paid $400 for the pr...but i was over driving them ...just could not get a nuff of that low thd, ,full,warm,honey sweet topend, big Full bass an sound stage that filled the room......So i never looet back....goodluck on you Trip with DD amps
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