Lamington reverb tweaks

[Sonny ReVerb]

So I built a version of the Lamington Reverb into one of my amps. It is underwhelming overall. There is reverb present, but the levels of the send (dwell?) and return need to be 7-8 to hear it. I would like more. Maxing the levels doesn't add much and is a less pleasing sound.

Did my circuit changes lower the reverb level somehow? The bypass caps C15 and C19 are not installed yet. Install one or both? Any idea what signal levels I should look for by scope at the various tube outputs?

Any help is greatly appreciated.

[Bieworm]

Did you manage to get it Hum free? I never did... but it sounded awesome!!!

[sluckey]

Need to post a complete schematic. That reverb circuit should produce more verb than you need. But improper interface with your other circuitry may be killing the reverb.

[Sonny ReVerb]

Did you manage to get it Hum free? I never did... but it sounded awesome!!!

No hum. The amp is nearly silent at idle.

Need to post a complete schematic.

Just plug my Lamington fragment into this schematic:
https://el34world.com/Forum/index.php?topic=23894.msg257236#msg257236

The Ampeg reverb variant also had somewhat weak reverb. Maybe there's a fix to get more reverb out of both of these amps!

[sluckey]

Your gain pot also controls the reverb send level. Is that intentional?

[Sonny ReVerb]

Yes, that's from the original design. A friend played the amp at a local blues bar. He ended up with the gain maxed and the master dialed back. I think he was looking for more drive, not more reverb. Sounded great, though.

[sluckey]

The 4EB2C1B tank you show only has a 600Ω input. The 4FB3D1B has an input of 1475Ω and would be better suited. Should give more reverb.

Why did you choose the 4EB2C1B?

[Sonny ReVerb]

The Lamington used an 8EB2C1B...

[sluckey]

Well, assuming your circuit is correctly wired IAW that schematic, I'd want to hear another tank in the same circuit.

     https://www.tubesandmore.com/products/reverb-tank-accutronics-4eb2c1b-medium-decay-2-spring

     https://www.tubesandmore.com/products/reverb-tank-mod-4fb3d1b-long-decay-2-spring

[Sonny ReVerb]

I have a 4FB3D1B on hand. I'll give it a try.

[Latole]

I have a 4FB3D1B on hand. I'll give it a try.

Wrong reverb tank could be a issue, impedances are different

[Sonny ReVerb]

The 4FB3D1B has an input of 1475Ω and would be better suited. Should give more reverb.

The 4FB3D1B does sound much better. I know Ampeg used that tank for their tube driven circuit, but I was trying to stick close to the Lamington example.

Chalk up another success, Mr. Luckey!

[Keppy]

What's with the values of C18/20? Any signal that makes it through the 1n cap ought to pass right through the 10n to ground. I don't see how you're getting anything at all with that arrangement.

[sluckey]

What's with the values of C18/20?

Good question. That certainly did not come from the original Lamington.

[Sonny ReVerb]

No clue.

It comes from the Amplified Nation Wonderland, which is the basis for this amp. It does work.

[sluckey]

Humor us. Disconnect one end of the 10nF across the pot. What happens? I'm betting you'll get happy.   

[Sonny ReVerb]

I swapped the cap for a 1000pF. It has more reverb, but it's not night and day. The genesis for these amps is the John Mayer Sig. One clone shows a choice of caps from 470-2200pF, so 10,000pF might be a bit large.

[sluckey]

Try it with ***NO CAP*** across the reverb pot.