The Amp Garage

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...

That isn’t going to work because the grid can’t be lifted from a 220k leak to a 2M2 leak resistor no matter what. It has to retain the 220k resistance whether it’s a parallel of the MV control or a fixed resistor. It’s going to pop loudly also because it’s an open circuit while the contact switches...

GAStan wrote: ↑Sat May 25, 2024 2:35 am The bleeder is definitely a good idea. The +170 volt caps were still at 50vdc after sitting overnight before I added it.

Credit Tony D for that idea.

Looks great! Your questions and feedback have led to quite a few updates to the documentation, so there is some great synergy going on here.

Hope that solves it!

The speaker output should be in phase with the PI input.

Yours will be the first with the new resistors added to the bipolar supply. I’ll be interested to hear how that works in hardware.

I just found a really thorough introduction to Thermal Resistance and Heat Dissipation, and I wish I had found this a few years ago. basics_of_thermal_resistance_and_heat_dissipation_an-e.pdf If the Texas Instruments pdf above was too specific for your tastes, this Rohm Semiconductor lesson covers ...