The Amp Garage

Jumpering across the 2k2 between B+2/4 gives 280/285 close enough to what 102 has (and highest I can get). I understand this combines the two power stages and puts the filtering caps in parallel. Is this going to cause any adverse affects? Any reason not to replace this 2k2 with a wire? If you do t...

Franco, DC balance and AC balance are two different things. First, get the DC balance (idle bias current) of the power stage to match as closely as possible. Use matched tubes and/or swap pairs from side to side for the best balance. With four power tubes, this just means put the tube with the highe...

imo1 wrote: ↑Wed May 29, 2024 1:49 pm Those changes are all the ones I implemented...

Fixed a couple of things in the mark-up. Where did B+ land? Any changes to the dropping string?

Ok, cool. I'll fix up the schematic based on the above.

I was thinking the same thing... I read through the thread and tried to capture the changes in the attached.

(updated)

But JFETs lack an equivalent to a triode’s grid current, which IIRC is supposed to play a significant role in the DCCF’s compression effect.

Thanks for the run down on using the ratio pot. I recall HAD saying in some article or interview that the Ratio control was a great feature on the ODS. Must have been shortly after its introduction. I may give the scope a try again before boxing up the amp. I remember when I built the #102, that I c...

How is this flyback voltage generated. The individual claimed it was from an open circuit on the secondary. I had heard people claim an open circuit secondary leads to shorted turns because the insulation is damaged, but I haven’t heard it affecting the parts in primary. Given that the amp in quest...

Very nice! If you find that you are using one setting for the Ratio control, you could replace it with a fixed divider, but I'm interested to hear how you are using it. IMO the ODS was a continuously evolving concept, with the changes HAD made over the generations being improvements. For the PI bala...

I was talking to someone on You Tube about the octal sockets burning between pins 2 and 3. His opinion was that it’s caused by flyback from a speaker connection going open circuit. I don’t know if I entirely believe this (of course I could be wrong) as it would be easier for the arc to go through a...

I don't know how similar the effect would be, but I'd guess that a JFET source follower would be a better bet.

Is anyone actively administering this forum at this point? I see two posts by a new user at the top of Technical Discussion and Garage Talk which appear to be AI-generated or something in that vein. I think those have been taken down now. If you spot something, it seems like the thing to do is clic...

You're right, of course, he's no James Brown, but nobody is... https://www.youtube.com/watch?v=zieXmNwHGYA

GAStan wrote: ↑Sat May 25, 2024 2:35 amThe bleeder is definitely a good idea.

I made a small tweak to the eyelet board .pdf on this. Increased the current limiter to 47R, and decreased the bleeder to 150k. Should have it drained in a minute or so.

The SSS bipolar driver supply board in the first post has been updated again with some fine tuning. The bleeder resistor mentioned above has been reduced to 150k to balance the current draw on the positive and negative sides, and to allow the voltages on both sides to drain in about a minute after s...