Where would be the best place to insert a reverb circuit into a tweed tremolux 5G9?

[Dandrix]

Those numbers are good. Noise gone is good. Tell me, does the amp sound pretty much as it did before the reverb was added? I ask because it should sound almost exactly the same so if it doesn't that could be a symptom. The only difference is that your signal is flipped 180 degrees. So there may be some small nuances that will be different if you always sit in the same place WRT the amp.

So the reverb is no longer breaking into static noises? Just oscillation and feedback? Also, do you have ample reverb at 5 before the problem starts. I expected the circuit to have too much reverb when we started this actually. Last question, does the static noise start at the same time as the oscillation or does happen anywhere you rotate the control?

The sound is good, good mix. if i said it sounds a little brighter than i last remembered? would love to hear a real fender 5g9... bucket list.
no static noise, alittle hum. figured it was part of the reverb needing some dialing in? feedback low hum to high pitch squeal (oscillation and feedback?)
plentiful amount of reverb up to five. would be enough
" Last question, does the static noise start at the same time as the oscillation or does happen anywhere you rotate the control?" After 5 on the dial for sure.

Questions for you:

The reverb pot makes a staticy sound as it is raised(wiper noise?)up in level. The wire that comes from the node of 510k and 470k (yellow wire in my pictures) to the reverb pot middle lug. did you want me to use interconnect cable for that connection? if i tap it or move it around it makes noise in the circuit.
let me know what you think

[Chuck H]

The wire that comes from the node of 510k and 470k (yellow wire in my pictures) to the reverb pot middle lug. did you want me to use interconnect cable for that connection? if i tap it or move it around it makes noise in the circuit.
let me know what you think

Planning to move that lead above board. I'm not sure what you mean by "interconnect cable" but I'll guess it's the same thing the rest of us call shielded cable? I never intended it to travel under the board. That's why it wasn't a dotted line in the layout I constructed. Looking at your actual layout I can see that the lead is longer than what I perceived. So I think a shielded cable, as short as possible and not run under the board would be best. Ground the shield at the reverb level pot ground.

You'll need to add a series resistor to the reverb circuit following the dual pot. On the layout I did I was counting on one of the unused mid board eyelets for this. You've layed things out a little differently, but I can see that you'll know how to manage this. So take the shielded output from the dual reverb level pot to a 220k resistor on the board and then to the mixer stage grid. I also didn't include any top end bleeders to mitigate HF oscillation. Sometimes you can get by without them. Add a 100pf cap from anywhere on the reverb pot that manages signal to the ground on that pot. If I've failed to describe this well enough I'll post a modification to the layout image.

[Dandrix]

Planning to move that lead above board. I'm not sure what you mean by "interconnect cable" but I'll guess it's the same thing the rest of us call shielded cable? I never intended it to travel under the board. That's why it wasn't a dotted line in the layout I constructed. Looking at your actual layout I can see that the lead is longer than what I perceived. So I think a shielded cable, as short as possible and not run under the board would be best. Ground the shield at the reverb level pot ground.

You'll need to add a series resistor to the reverb circuit following the dual pot. On the layout I did I was counting on one of the unused mid board eyelets for this. You've layed things out a little differently, but I can see that you'll know how to manage this. So take the shielded output from the dual reverb level pot to a 220k resistor on the board and then to the mixer stage grid. I also didn't include any top end bleeders to mitigate HF oscillation. Sometimes you can get by without them. Add a 100pf cap from anywhere on the reverb pot that manages signal to the ground on that pot. If I've failed to describe this well enough I'll post a modification to the layout image.

If I've failed to describe this well enough I'll post a modification to the layout image.

yes, that would be totally awesome. so there is no confusion on my part. ty

shielded cable i meant." interconnect" maybe the name of the manufacturer?
as for the 100pf cap i will have to order that. i think i only have a 10pf and a silver mica 500pf cap left in the arsenal?

[Chuck H]

as for the 100pf cap i will have to order that. i think i only have a 10pf and a silver mica 500pf cap left in the arsenal?

Fender uses a 220p cap. You could series three 500p caps for 166p. A good tweener value. No one looking inside but you

EDIT: About the "sounds a little brighter than i last remembered?"... The mixing stage has a low impedance output. This would make for a little less HF damping at the PI input than the stock amp. It's not so much brighter as more clear. I've found it to be an improvement most often but that can be adjusted too. The upside is that the mixing stage your using has overall MUCH lower distortion than the 3.3M/10p mixer. That thing distorts like crazy. And not the good kind of distotion. More like a phase error that makes the waveform look sorta wonky. The mixer you're using now is the better choice for keeping the amps stock character.

[Chuck H]

Here you go. I made a note on the drawing, but I'll say it again here. Keep the reverb signal leads short. I'd even shorten the jumper on the dual pot. Run the reverb lead from the pot over the board, keep it short and suspended as shown. I know that soldering three leads to that ground lug on the reverb pot is a little bit of a PITA but you'll have to manage. Additions in blue.

[Dandrix]

i am replacing my yellow lead with your dotted blue wire(shielded wire) attaching were the the yellow was on the pot? blue (0) on the pot is messing with me. sorry for the confusion

[Chuck H]

Ha ha. The blue O just represents that the lead is "encircled". Notice there's one on either end of the dotted blue line. The blue dotted line would be the shield. It's a schematic symbol for a shielded lead.

[Dandrix]

You had me on the blue circle! all good. BORROWED 100pf cap from a treble bleed cap from one of me guitars. i will buy a new one for the guitar. lol
the reverb is dead quiet. 1-4 not very noticeable. 5 is my happy spot for now. over 10 is about it. anything over that gets messy. the trailing end of a chordwhen you strum it once, sounds like it roaring still, Dwell is to long?
I also tried that with the amp volume dimed. which the amp is naturally distorted and would make the reverb nasty. not complaining, just trying to give feedback
Is there any tweaks that could be made to change the characteristics of the reverb (components) that would change? trailing end dwell, more reverb less reverb etc...
and good job!
thanks for sticking with me.
I have enjoyed tinkering and experimenting again.

[Chuck H]

I'm not sure I'm understanding this. Is the reverb doing what a reverb should? That is, no more non reverb noises are happening?

Any trouble with acoustic feedback from the tank springs themselves?

Over 10 get's messy is good. Any knob on the amp should be able to give you 'too much' if only so you know you have enough

Hows the hum level with the reverb up? A little is normal. But if it's objectionable it can almost always be reduced.

It might be possible to reduce the decay time a little. To reduce it a lot would require a different tank. The old Fender stand alone reverbs had a control knob labeled "dwell". It reduced the signal to the driver tube. By driving the springs less they didn't sustain as long. It could also be used to make the reverb less "boingy". So you could try reducing drive to the tank. If you want to maintain the same reverb level you have now you would have to balance the lower drive by reducing the value of the 220k resistor you just put in to increase volume.

As to the tone of the reverb, we can only control the EQ. And even then only a little. I don't think we could make it much brighter, but we could probably make it a little fuller if it sounds too thin.

[Dandrix]

I'm not sure I'm understanding this. Is the reverb doing what a reverb should? That is, no more non reverb noises are happening?

Any trouble with acoustic feedback from the tank springs themselves?

yes, the reverb is good! hence the thumbs up ion guy. no more noises exactly. not even feeding back at full dial "12"

[Dandrix]

lower drive by reducing the value of the 220k resistor you just put in to increase volume.

i will try a 150K or 100K res.
there's probably a give and take with this?

[Chuck H]

Simply reducing the load at the driver tube grid isn't the way to do it.

There's that 1M load resistor at the driver tube grid now. You would need to create a "voltage divider" as if that were a 1M pot. Exact resistances aren't critical though. So if, say, you wanted to cut the drive in half you could use a pair of 470k resistors. One to the grid after the 500p capacitor and the other as the load resistor from the grid to ground.

If your reverb volume drops too much you can restore it by decreasing the value of the 220k resistor from the reverb pot to the mixing stage grid.

[Dandrix]

It might be possible to reduce the decay time a little. To reduce it a lot would require a different tank. The old Fender stand alone reverbs had a control knob labeled "dwell". It reduced the signal to the driver tube. By driving the springs less they didn't sustain as long. It could also be used to make the reverb less "boingy". So you could try reducing drive to the tank. If you want to maintain the same reverb level you have now you would have to balance the lower drive by reducing the value of the 220k resistor you just put in to increase volume.

Hey chuck, I am interested in reducing the decay. Could you walk me through what could be done? Hopefully a component or two change? Lol
Everything else is working great.

[Chuck H]

Ok. I'm going to describe it and I hope that will be sufficient. It's actually a pretty good effort to arrange the drawings and such that I've put together so far. And I'll do it if needs be, but lets try this first...

There's a 1M resistor as the grid load for the reverb driver tube input. Imagine that is a volume pot. You can create a voltage division with a series resistor and a dropping resistor to the ground with the total sum being near the 1M value. Incidentally, you could even wire a 1M pot there temporarily. Wire it JUST LIKE A VOLUME CONTROL. Signal from the 500p goes to the right lug, left lug grounded and the center lug feeds the grid of the driver tube. Now you can alter the drive to that tube. If you find a level that sounds better to you, remove the pot and measure the values at each end. Replace the pot with fixed resistors. Easy peezy. THEN...

If you limit drive to the reverb you may/will lose some reverb volume. You can regain any lost volume by reducing the value of the 220k resistor that feeds the mix stage triode. A smaller value will increase the wet to dry level.

[Enzo]

Why make it temporary? Wire a small 1 meg trimmer pot right on the part board in place or the 1 meg resistor. Dial it all the way up and the circuit is stock. Want less drive, dial it down to suit. And if you ever change your taste in reverb, there is nothing to un-modify. Just adjust the trimmer.


If you lose some reverb volume, I should hope there would be plenty of room left on the panel control. I don't know anyone who plays it on 10. Or 11...