Thanks guys,
Right now I am not using VDR and so far it's OK. Didn't fry any transistors. Actually this might be OK because I lowered AC feedback
by putting 47K resistor between ground and last cap in feedback
(I have string of caps in feedback instead of only one).
This mod. improved linearity on high freq. and protects drive stage.
Also instead having one 7Mohm feedback resistor I have 30 240Kohm
resistors which improves thermal stability.
Regards.
Right now I am not using VDR and so far it's OK. Didn't fry any transistors. Actually this might be OK because I lowered AC feedback
by putting 47K resistor between ground and last cap in feedback
(I have string of caps in feedback instead of only one).
This mod. improved linearity on high freq. and protects drive stage.
Also instead having one 7Mohm feedback resistor I have 30 240Kohm
resistors which improves thermal stability.
Regards.
Told you this tube looked ok !
There must be more suitable tubes out there that nobody is using anymore.
The absence off oscillations could also be because you lowered overall feedback. I did this also in my design and the result is a more wide and deep soundstage.
I also use strings off carbonfilm resistors iso one resistor.
High voltage resistors are rare and expensive, so this is the easy way to get it done.
DJ
There must be more suitable tubes out there that nobody is using anymore.
The absence off oscillations could also be because you lowered overall feedback. I did this also in my design and the result is a more wide and deep soundstage.
I also use strings off carbonfilm resistors iso one resistor.
High voltage resistors are rare and expensive, so this is the easy way to get it done.
DJ
Finally done!!!
I am happy to say it is done!
Acoustat X clone is up and running.
At first, disappointment. Not enough volume and it sounds distorted
at max. I was ready to promise my self and sign to my wife
no more building. Not to mentioned being very upset about this.
But than, after I cooled down I started to think what could be the problem. I knew I have enough drive ( confirmed by scope )
that leaves only one factor, bias voltage. In this circuit bias voltage is taken from B+ (5KV) which also should be OK.
Still, I connected bias voltage previously used with my speakers and
voila ear splitting sound level and distortions gone!
I still don't understand why is this better but it is.
I know that this PS has 1.5Kv more voltage but difference in sound level is huge and no distortions, which is confusing.
Anyway it is OK now and sound is fantastic. Most noticeable was
much better transients and tighter bass .
Was it worthy of trouble? Absolutely Yes!
I expect for sound to be even better after burn-in time that tubes need after 25-30 years of sleep.
Regards.
I am happy to say it is done!
Acoustat X clone is up and running.
At first, disappointment. Not enough volume and it sounds distorted
at max. I was ready to promise my self and sign to my wife
no more building. Not to mentioned being very upset about this.
But than, after I cooled down I started to think what could be the problem. I knew I have enough drive ( confirmed by scope )
that leaves only one factor, bias voltage. In this circuit bias voltage is taken from B+ (5KV) which also should be OK.
Still, I connected bias voltage previously used with my speakers and
voila ear splitting sound level and distortions gone!
I still don't understand why is this better but it is.
I know that this PS has 1.5Kv more voltage but difference in sound level is huge and no distortions, which is confusing.
Anyway it is OK now and sound is fantastic. Most noticeable was
much better transients and tighter bass .
Was it worthy of trouble? Absolutely Yes!
I expect for sound to be even better after burn-in time that tubes need after 25-30 years of sleep.
Regards.
Congratulations too, Sasha.
About your bias problem, beside different bias voltage, there are probably different resistors used, hence the difference in sound level.
The original bias resistor in the X is 500Mohm, which is quite high.
Reducing the value can improve performance, this is because of natural leakage which lowers the bias voltage on the foil.
DJ.
About your bias problem, beside different bias voltage, there are probably different resistors used, hence the difference in sound level.
The original bias resistor in the X is 500Mohm, which is quite high.
Reducing the value can improve performance, this is because of natural leakage which lowers the bias voltage on the foil.
DJ.
Big thanks to all of You for support and help in building this amp.
This was on my mind for past 3 years and since than I was collecting
the parts and infos and waited for some free time to build it.
Bigwill's thread was remainder to finally do it.
Rcavictim gave valuable pointers and yes You are welcome to come. Djmiddelkoop provided schm. and tips.
Thanks again to all.
P.S.
Even with 100Kohm bias resistor was no change until I didn't
connected separate PS.
Djmiddelkoop, I think You should give it a try in Your amp
and maybe it will work out for You as it is for me.
This was on my mind for past 3 years and since than I was collecting
the parts and infos and waited for some free time to build it.
Bigwill's thread was remainder to finally do it.
Rcavictim gave valuable pointers and yes You are welcome to come. Djmiddelkoop provided schm. and tips.
Thanks again to all.
P.S.
Even with 100Kohm bias resistor was no change until I didn't
connected separate PS.
Djmiddelkoop, I think You should give it a try in Your amp
and maybe it will work out for You as it is for me.
Hi Zelter,
If I remember correctly, not much signal to the grids.
Around 15Vpp.
For info on tubes try: http://hereford.ampr.org/
Regards.
If I remember correctly, not much signal to the grids.
Around 15Vpp.
For info on tubes try: http://hereford.ampr.org/
Regards.
I know this is an old thread but i'm building ESLs for a science project.
I just one the regional fair and am going to the international science fair in New Mexico soon. My problem is due to budget constraints my ESL uses welding rods as stators, there aren't enough and the diaphragm to stator spacing is 3/32 in. I am using a 5500v bias supply.
I use 4 70V PA transformers in series parallel for step-up. I recently got an s-5 tube amp kit. My question is could I simply run the transformer from the tube amp backwards and then have it driven with the tubes. Is there anything wrong with this approach? It doesn't seem like its ever done but it seems like its possible to do.
I just one the regional fair and am going to the international science fair in New Mexico soon. My problem is due to budget constraints my ESL uses welding rods as stators, there aren't enough and the diaphragm to stator spacing is 3/32 in. I am using a 5500v bias supply.
I use 4 70V PA transformers in series parallel for step-up. I recently got an s-5 tube amp kit. My question is could I simply run the transformer from the tube amp backwards and then have it driven with the tubes. Is there anything wrong with this approach? It doesn't seem like its ever done but it seems like its possible to do.
ak_47_boy said:
It is the voltage field gradient that initiates an arc discharge, not the current. Current only comes into play once the ionized path is created.
That said, hot spots will become thermally activated emitters, so I suspect could tend to initiate a ionization path if the tube was being used at the hairy edge of sparking.
BTW, when you refer to transmitted tubes are you referring to tubes that appear out of nowhere due to matter teleportation like in star trek?
Am I right to assume you want to use the tube amp's output transformer backwards, ie connect the 8 ohm side to the tube plates and the other end directly to the esl?? 
That sounds like a pretty sure way to blow up your output tubes, they don't like to see an impedance of a few ohms only.
A series resistor might prevent that but would have to be several KOhm in value. That results in almost zero output and bandwidth as the resistor forms a voltage divider with the load.
Better use the trannie the way it should be and connect your 4 PA transformers to the output side to stepup to your esl.
If you want a transformer that can be placed directly between the output tubes and the esl you'll have to design a specialized one, with much low turns ratio and designed for the high voltages present. That can be done (even has been done) and can even sound pretty good, but is quite a challenge.
That sounds like a pretty sure way to blow up your output tubes, they don't like to see an impedance of a few ohms only.
A series resistor might prevent that but would have to be several KOhm in value. That results in almost zero output and bandwidth as the resistor forms a voltage divider with the load.
Better use the trannie the way it should be and connect your 4 PA transformers to the output side to stepup to your esl.
If you want a transformer that can be placed directly between the output tubes and the esl you'll have to design a specialized one, with much low turns ratio and designed for the high voltages present. That can be done (even has been done) and can even sound pretty good, but is quite a challenge.
ESL tube amps
The Sanders electrostatic speaker and amplifier. A modified version of the Hermeyer electrostatic (issue 3/1972 and 4/1972). Part 2. Modification of the Hermeyer electrostatic amplifier, a smaller, lower-powered version.
AUDIO AMATEUR 1/1976 [May 1976] (v.7#1) pg. 12
Added Info AUDIO AMATEUR 2/1976 [Jul 1976] (v.7#2) pg. 39 (AR amplifier)
Correction AUDIO AMATEUR 3/1976 [Oct 1976] (v.7#3) pg. 39
I have used the Hermeyer 813 amp on a big ESL array; it sounds great. A lot of work and dangerous as mentioned.
My experience is get some good audio transformers and live happy ever after.
The Sanders electrostatic speaker and amplifier. A modified version of the Hermeyer electrostatic (issue 3/1972 and 4/1972). Part 2. Modification of the Hermeyer electrostatic amplifier, a smaller, lower-powered version.
AUDIO AMATEUR 1/1976 [May 1976] (v.7#1) pg. 12
Added Info AUDIO AMATEUR 2/1976 [Jul 1976] (v.7#2) pg. 39 (AR amplifier)
Correction AUDIO AMATEUR 3/1976 [Oct 1976] (v.7#3) pg. 39
I have used the Hermeyer 813 amp on a big ESL array; it sounds great. A lot of work and dangerous as mentioned.
My experience is get some good audio transformers and live happy ever after.
This is my first visit to this forum. Hope I can supply you with something useful later on.
Jumped on to this thread as it concerns what I am working on.
I have begun constructing a direct-drive tube-amp for the panels of a pair ML Scripts that I just traded in. Think they will be adaptable as they work only down to 500Hz and will not need too extreme signal-levels.
The step-up transformers is around 1:50 I guess (4:10000 ohms). And for some reason they do not use the center-tap for the EHT, it is connected to one of the secondaries. Can supply you with a schematic of filter and transformer later today.
In a bridge-mode amplifier I do not think that a B+ of over 1000V will be needed. If we assume that max input will be 25W this corresponds to a needed signal voltage of around 250V rms from each side (700V ptp over the panel). My guess seems a little low so maybe I have missed something here?
If I am right, two pairs of SRPP- or Mustage-connected EL34´s(not in triode mode) would do.
Does anyone have an electrical model of a typical ESL-panel? This would make it easier to do a lot of the prototyping in Pspice. Do not think the model is as easy as just a capacitor.
Brgds
Lars
Jumped on to this thread as it concerns what I am working on.
I have begun constructing a direct-drive tube-amp for the panels of a pair ML Scripts that I just traded in. Think they will be adaptable as they work only down to 500Hz and will not need too extreme signal-levels.
The step-up transformers is around 1:50 I guess (4:10000 ohms). And for some reason they do not use the center-tap for the EHT, it is connected to one of the secondaries. Can supply you with a schematic of filter and transformer later today.
In a bridge-mode amplifier I do not think that a B+ of over 1000V will be needed. If we assume that max input will be 25W this corresponds to a needed signal voltage of around 250V rms from each side (700V ptp over the panel). My guess seems a little low so maybe I have missed something here?
If I am right, two pairs of SRPP- or Mustage-connected EL34´s(not in triode mode) would do.
Does anyone have an electrical model of a typical ESL-panel? This would make it easier to do a lot of the prototyping in Pspice. Do not think the model is as easy as just a capacitor.
Brgds
Lars
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