5F1 Champ w/ Capacitor Coupled One-Tube 6BM8 Reverb (Eric Barbour/Ampeg-style)

[Splash Zone]

Thanks to you both. This was my understanding on both accounts: likely a typo, and that the capacitor type could be interchanged, but that electrolytics have a design that requires polarization to make them work correctly.

Banana sized capacitor....this is funny.

[Splash Zone]

Great news, this circuit works in my Skylark! I’m posting prematurely because I’m excited, but there are a few tweaks to make and then I’ll share the schematic for others. Nice work dchang0!!

[Splash Zone]

Here’s the final schematic and some sound samples. In my opinion, the choke is a must with a tube rectifier (where you can’t increase the filtering of the power supply).

I have a 1 meg resistor following the reverb intensity pot and I don’t know why so high but it sounds quite good here like this. I think I might be running the reverb driver a little hot calculating 20 mA, when 10 to 15 mA are sufficient. Sounds just fine to me so not going to mess with it…



Voltages:



Sound clips to hear what the reverb can sound like:


Gibson GA-5TR

https://youtu.be/YUlXPeAiLNg

[Chuck H]

Not a lot of reverb.?. But enough I think. Great tone overall. (<period) And that's what matters.The 1M series resistor doesn't reduce the reverb much at all but it does help to keep the mixed dry signal stronger. It may reduce a little top end on the reverb signal and it might be worth experimenting with a capacitor parallel to that 1M resistor since reverb is mostly in the HF. That may reduce top end on the dry signal a little but it should add sparkle to the reverb. Values in the 47pf to 220pf range I think (based on instinct and not simulated or tested). But the tone you have now is really good so if there's too much detriment to the dry signal tone you can always undo any mods.

Kudos I actually wasn't a believer on this one but even a subtle reverb effect while keeping some amp grit sounds stellar. This is what that 1M resistor is doing for you. Happy accident. Or not. I'm sure you experimented as well. Anyway... Do try a capacitor parallel to that resistor and see what happens.

[Pedro Vecino]

I would try connecting the pentode in pentode mode to drive the tank more and get more intensity and liveliness. And with more gain I would experiment with other things like connecting a capacitor in parallel with the tank input (180K resistor) to create more emphasis on the highs if necessary, etc.
Finally I would look at the 1M resistor if necessary. On the 68 Deluxe reverb (new silverface) it significantly reduces the sensitivity of the effect and its presence. I usually use a series sum of 470K + 220K/330pF in parallel to replace it. Similar to what Chuck proposes.
These are just ideas with the circuit already assembled and working.