If you're trying to economize, why not go with a single chassis amp?
You could build it without the chokes, but they're there for a reason. Personally, I'd use one in a CLC config., but your PS trans should be no more the 300vAC, otherwise you're going to end up with way too much B+.
As Kevin points out, the Williamson has issues, and could result in an exercise in frustration. 6V6's are easy to drive with a concertina, and you can get away with cheaper OPT's.
What circuit were the other amps you built based on?
jeff
Yes, it usually involves space for more iron, hence a better power supply for each amp.
That's really 6L6 territory.
Which one sounds better?
jeff
The ps transformers came out of a couple of weird Moviola mdl#565. I have no idea what they were for but they had 1-5Y3, 2-6V6, 2-6J5, 1-5879, 1-OC3. A couple of 1/4" jacks labeled "OPT" and "MAG". So I figured they would be good for a 6V6 amp.
I liked the 6BM8 3-watt (which I just realized I posted the wrong schem, correct one below). I'm no audiophile and I've been doing living sound engineering for so long my hearing probably wouldn't pickup most of the anomalies talked about on this forum. But both amps seemed to be thin, lacking in low end 200hz and below maybe. And just not very loud. I listen to rock n roll and so a little volume is desirable.
I liked the 6BM8 3-watt (which I just realized I posted the wrong schem, correct one below). I'm no audiophile and I've been doing living sound engineering for so long my hearing probably wouldn't pickup most of the anomalies talked about on this forum. But both amps seemed to be thin, lacking in low end 200hz and below maybe. And just not very loud. I listen to rock n roll and so a little volume is desirable.
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Why don't you just stick with your original idea ? Buy 2 7-pin sockets that fit into a 9-pin sockethole and you are done. If you don't like the result change it into something else. In the mean time try this design to change your 6BM8 amp. I tried it and it sounds really good.
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@EssB: I didn't use anything but the power transformers from the Moviola chassis. I was just describing what I pulled the trannys out of in hopes that somebody knew what they were purely out of curiousity. thanks though
@Jaap: I've decided to save my stock of 6AU6 tubes for another build. I really want to find a design using 6SN7's and 6V6's. Thanks for the the upgrade, I think that's just what I need cause I really want to get to work on something.
@Jaap: I've decided to save my stock of 6AU6 tubes for another build. I really want to find a design using 6SN7's and 6V6's. Thanks for the the upgrade, I think that's just what I need cause I really want to get to work on something.
You can exchange the 12au7 for the 6SN7 without any problem, at least that is what I am going to do in the near future (with CCS and led on first tube). I prefer local feedback in all cases to global feedback, that is one reason why I want to try this design.
In a RCA handbook I saw that you can also scale this design up with parallel 6V6 in het outputstage and get 20 Watts from it.
Are you talking about the schematic below?
With the CCS, are you going to use the LED's voltage drop to derive the constant voltage for the CCS? What about using an LM317 regulator.
I posted a schema for what was identified as a Williamson type design with 2-6sl7 and 2-6v6. But I was informed it was not a good choice. So I'm still looking
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The reason I asked is that I'm troubleshooting a buzz that only occurs at about half volume. As I turn the volume up or down the buzz fades in about half way and then fades out . The chassis is a little on the small side and things are cramped so I'm not surprised, I'm actually surprised it's not worse. But I've been doing a lot of reading on proper wiring practices to prevent hum and other undesirable noise and read about twisting the HV DC lines
A buzz which disappears at max and min volume could be due to capacitive coupling to the volume slider and associated circuitry.
Twisting wires works when you have two wires carrying equal and opposite AC currents. Their magnetic fields then approximately cancel. It could also work, but perhaps not quite so well, if two wires carry equal but opposite AC voltages - then you can get some cancellation of the electric field (but screening is usually better).
Twisting wires works when you have two wires carrying equal and opposite AC currents. Their magnetic fields then approximately cancel. It could also work, but perhaps not quite so well, if two wires carry equal but opposite AC voltages - then you can get some cancellation of the electric field (but screening is usually better).
thanks DF96, I took a closer look and realized I had the wrong value coupling cap. Decimal points are so small.
One final issue with this build. I was changing the cathode to ground resistors on the 6V6's for biasing and noticed that a slight hum and mechanical vibration coming from my power trany. If I got the biasing too hot it was worse, too cold and it was less so it's related to current load. I don't know the mA rating of the transfomer, they're harvested from old equipment I had laying around. Unloaded it's secondary HV is 715VAC. Could my trany be toast or toasting, or just underrated. Is there any way to determine the amps rating for an unknown transformer?
One final issue with this build. I was changing the cathode to ground resistors on the 6V6's for biasing and noticed that a slight hum and mechanical vibration coming from my power trany. If I got the biasing too hot it was worse, too cold and it was less so it's related to current load. I don't know the mA rating of the transfomer, they're harvested from old equipment I had laying around. Unloaded it's secondary HV is 715VAC. Could my trany be toast or toasting, or just underrated. Is there any way to determine the amps rating for an unknown transformer?
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