ah, thanks
never thought about resistor specsheet
you refer to dielectric resistance, right?
I looked at one alu housed
had both power voltage specs, and dielectric
dielectric power rating was twice as high as working voltage rating
with another cast type, there was only voltage rating on dielectric specs
no specs on working voltage
In case anyone is interested 
here's a link to the resistor used. Its a HS25 25W 50k. Voltage proof to 2500V but with a working of 550V.
To be absolutely honest, I've pretty much ignored voltage ratings on resistors before, but I've never used something as big as this with that kind of voltage drop either. The best I could find at short notice was more of the same resistor, but I'll be keeping an eye out for either a higher rated one, or some other means of dropping ~600V or so.
At least I now know that the amp works OK and that its fairly likely (but not guaranteed) that nothing else is wrong.
Fran
here's a link to the resistor used. Its a HS25 25W 50k. Voltage proof to 2500V but with a working of 550V.To be absolutely honest, I've pretty much ignored voltage ratings on resistors before, but I've never used something as big as this with that kind of voltage drop either. The best I could find at short notice was more of the same resistor, but I'll be keeping an eye out for either a higher rated one, or some other means of dropping ~600V or so.
At least I now know that the amp works OK and that its fairly likely (but not guaranteed) that nothing else is wrong.
Fran
Hi,
no, not yet... in the next few days I will be checking. No obvious bulging or damaged electrolytics though. I need to take out the pcb though to get at the caps to see what the story is with the filter caps.
I managed to find a 50k resistor with a 1250VDC working voltage so that's what I'll use in that position.
Fran
no, not yet... in the next few days I will be checking. No obvious bulging or damaged electrolytics though. I need to take out the pcb though to get at the caps to see what the story is with the filter caps.
I managed to find a 50k resistor with a 1250VDC working voltage so that's what I'll use in that position.
Fran
Who knows what was in mind of the original designer; I once saw an amp that used paralleled sections of 12AU7 on less than 1 mA current total.
14 mA / 50K would mean like 700V of voltage drop. That means small power from such an oven, according to the available voltage to drive output tubes...
14 mA / 50K would mean like 700V of voltage drop. That means small power from such an oven, according to the available voltage to drive output tubes...
Ran this amp last night for a few hours to see how it sounds. Sound is warm, but very good bass. More than I expected from my horns. That resistor gets very hot though, estimate about 75 deg C. Chassis where the resistor is mounted gets to about 65. Still well under the 200deg rating but hot enough to worry about reliability.
Fran
Fran
Hi, Do you have a manual or schematic of this amp. A friend has one that appears to have never been used (his late fathers). The valves are 2 off 211/VT4C, 2 off 12AX7A, 4 off 12AT7WC. We can't start to look at it as we don't know which sockets to fit the 12's into or what ohms speakers we should use.
The 211 is a very special tube that can sound excelent if properly used.
From my experience it should operate with at least 1100V, 1200V even better.
Needs a high impedance output transformer (0ver 10.000 Ohm) and needs a huge swing in the grid. Best to use a good interastage transformer.
If you want to skip this, better use another tube, like the 845 or GM70...
From my experience it should operate with at least 1100V, 1200V even better.
Needs a high impedance output transformer (0ver 10.000 Ohm) and needs a huge swing in the grid. Best to use a good interastage transformer.
If you want to skip this, better use another tube, like the 845 or GM70...
The amp appears to be unused, still has the plastic film stuck to it. One of the 211's has a loose component rattling around inside so we will need to get one of those. As I said in my earlier post, it is the possitioning of the 6 smaller valves that we are stuck for and what ohms speakers to use. Anyone know? Thanks
I designed a 211SET amp. I ordered it to a Chinese small manufacturer
as a custom order with the following job split.
*Circuit design by me
*Circuit Design brush up by the manufacturer
*Mechanical Design and Amp manufacturing by the manufacturer
The final circuit schematic is shown in the below url. As you can see,
THD=3.6% @ 40.5W can be obtained.
http://www.bezdz.com/images3/T10A-6-100V-115V-230V.bmp
Photographs and descriptions are shown in my Web page as below
(sorry written in Japanese).
211 SET
I like 211's sonic rather than indirect heated cathode.
as a custom order with the following job split.
*Circuit design by me
*Circuit Design brush up by the manufacturer
*Mechanical Design and Amp manufacturing by the manufacturer
The final circuit schematic is shown in the below url. As you can see,
THD=3.6% @ 40.5W can be obtained.
http://www.bezdz.com/images3/T10A-6-100V-115V-230V.bmp
Photographs and descriptions are shown in my Web page as below
(sorry written in Japanese).
211 SET
I like 211's sonic rather than indirect heated cathode.
Sorry, I am refering to the Gamma Acoustics Rythym Ref Amplifier. Can anyone help with any details of this amp?
If you contact Peter Qvtrop @ AudioNote UK, he can tell you a good bit about the GAmma amps. From what I heard a good few years ago, they were always noisy (hum) and took a lot of sorting out. THey were also said to be unreliable. The guy who built them in Staines/Slough had worked for AudioNote and left to build these for himself.
To find a good schematic is difficult and without doubt the best of them were designed and made by Be Yamamura. It is difficult to say much more about them other than that each one was different to the others! I had one on loan from Be for a couple of years. It had early WE tubes - and was probably the best amp I have heard…..the rest of my system was simply not of high enough quality to do it justice. Most of these were fitted with Telefunken ex. German Airforce tubes…..complete with Swastika decals. His transformers and Chokes were made at great expense by Tamura to his own specification. All I can remember of the circuit is that it was valve rectified, choked PS, and a single RCA input stage with interstage transformers. It made the most beautiful music with great emotional enjoyment……wish I still had it!
There is an Italian design in the defunct Sound Practices magazine. I have the mag on disc and can probably send it in .pdf format. Its late now, so I will do this tomorrow and if poss will post it on this thread.
To find a good schematic is difficult and without doubt the best of them were designed and made by Be Yamamura. It is difficult to say much more about them other than that each one was different to the others! I had one on loan from Be for a couple of years. It had early WE tubes - and was probably the best amp I have heard…..the rest of my system was simply not of high enough quality to do it justice. Most of these were fitted with Telefunken ex. German Airforce tubes…..complete with Swastika decals. His transformers and Chokes were made at great expense by Tamura to his own specification. All I can remember of the circuit is that it was valve rectified, choked PS, and a single RCA input stage with interstage transformers. It made the most beautiful music with great emotional enjoyment……wish I still had it!
There is an Italian design in the defunct Sound Practices magazine. I have the mag on disc and can probably send it in .pdf format. Its late now, so I will do this tomorrow and if poss will post it on this thread.
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