Depth Mod 2204 Help!

[Charvel_King]

I am adding a depth control to my 2204 build and i have seen it wired in two ways on different layout diagrams.

1) Wire from NFB resistor to wiper (middle lug) of pot, 4 ohm tap connected to the outside lug. With 0.0047uf cap across two lugs

2) Wire from NFB resistor to outside lug of pot, 4 ohm tap connected to wiper (middle lug). With 0.0047uf cap across two lugs.

Which is correct?

Also neither of the two layout show the empty lug being ground on the back of the pot, is this not required?

Thanks

 

[glip22]

Just solder the open outside lug to the wiper or connect them through the cap leg. Either way. Use the second diagram. Also when you ad the cap in it will change your am's tone. It will be darker. You can play around with the NFB resistor to compensate up to 100k. In the 50k range works well but every amp is different. Raising the value will let more high frequencies through.

 

[LP Freak]

I always use the second diagram and it works great.

 

[Charvel_King]

Thanks for the replies.

I have now tried it both ways and neither of them seem to have any affect.

I was expecting a similiar sweep to the Presence knob, or at least similar equivilant change in tone, but i don't notice any difference.

I am runing a standard 100k NFB.

I figured it would bring in a lot of low end like on other amps i have played with depth/resonace controls. Any ideas?

 

[londaxe]

Thanks for the replies.

I have now tried it both ways and neither of them seem to have any affect.

I was expecting a similiar sweep to the Presence knob, or at least similar equivilant change in tone, but i don't notice any difference.

I am runing a standard 100k NFB.

I figured it would bring in a lot of low end like on other amps i have played with depth/resonace controls. Any ideas?

Does your amp have a PPIMV? If so, does the resonance control have any effect when the PPIMV is turned up?

I've got two amps (2203 and 2204 clones with tweaks) wired like in the second image. Both 47k NFB with the wire going to the speaker jack, but the 2203 has a .0033uf cap instead of .0047uf.

Works a bit better on the 2204 for some reason.

 

[Charvel_King]

Thanks for the replies.

I have now tried it both ways and neither of them seem to have any affect.

I was expecting a similiar sweep to the Presence knob, or at least similar equivilant change in tone, but i don't notice any difference.

I am runing a standard 100k NFB.

I figured it would bring in a lot of low end like on other amps i have played with depth/resonace controls. Any ideas?

Does your amp have a PPIMV? If so, does the resonance control have any effect when the PPIMV is turned up?

I've got two amps (2203 and 2204 clones with tweaks) wired like in the second image. Both 47k NFB with the wire going to the speaker jack, but the 2203 has a .0033uf cap instead of .0047uf.

Works a bit better on the 2204 for some reason.

My amp is bassicly a straight 2204 clone. 100NFB to 4 ohm tap on impedance switch.

I have it wired like you then, ie diagram 2, but it is doing nothing.

I understand lowering the NFB to a more plexi-ish value, like you, (47K) would give more -ve feedback and make the presence/depth have a greater affect.

My amp has no Post PIMV, just the stock Pre PIMV.

 

[londaxe]

Wait, that layout isn't the one I used. Try this.

note how the 3rd lug is used in this one.

 

[Charvel_King]

I think i have figured this out!

I haven't removed the orignal wire that goes from NFB to 4 ohm tap!

I was looking at the Soldano XL mod, which is a fixed depth/resonance mod, and it suddenly hit me!

What a rookie error!

I guess when you are looking at something for so long you miss things like that!

I'll 86 that wired tomorrow!

 

[Charvel_King]

Wait, that layout isn't the one I used. Try this.

note how the 3rd lug is used in this one.

Yeah that's it, i couldnt figure out why there was a un-used lug.

Your diagram is correct, also pointed out by glip22

Thanks!

 

[Jofipe]

How does it sound?

I wanna try with my '72 JMP with a PPIMV...

 

[Charvel_King]

How does it sound?

I wanna try with my '72 JMP with a PPIMV...

I'll report back tomorrow!

I should work well with your amp.

BUT as you have a PPIMV the effect will be less noticible the more the PPIMV turned down as you will be limiting th -ve feedback that the depth/resonace & presence rely on.

At loud volume where the PPIMV is set high it would be fine.

Go for it! If you want to add low end without mush and retaining definition in the gain i would do it.

 

[MrDan666]

I think i have figured this out!

I haven't removed the orignal wire that goes from NFB to 4 ohm tap!

Yup that's it right there.. Should work fine once that is fixed as others said, it won't have as much impact with higher NFB resistor values.

 

[Charvel_King]

I think i have figured this out!

I haven't removed the orignal wire that goes from NFB to 4 ohm tap!

Yup that's it right there.. Should work fine once that is fixed as others said, it won't have as much impact with higher NFB resistor values.

Thanks Dan!

I'm going to experiment with that, might replace the NFB with a 33K and a 250/500k pot and have a play with it. Kinda like a "feel/dampening" knob

Or will stick in 47k like in a plexi see how that feels. Could definitly benifit from the added tightness too with the higher -ve

 

[Jofipe]

Dan knows a thing or two

Would you mind snapping a picture of the finished install?

Thanks!

Just spend a minor fortune setting my '72 back to stock with NOS parts.. don't wanna fuck it up now that is has the correct bite an tone

 

[Charvel_King]

Dan knows a thing or two

Would you mind snapping a picture of the finished install?

Thanks!

Just spend a minor fortune setting my '72 back to stock with NOS parts.. don't wanna fuck it up now that is has the correct bite an tone

Thats cool. It should be easy to install and just as easy to reverse. Borrow a hole from a speaker jack..

Sure thing, i'll snap a pic after work tomorrow

 

[londaxe]

I'm going to experiment with that, might replace the NFB with a 33K and a 250/500k pot and have a play with it. Kinda like a "feel/dampening" knob

Or will stick in 47k like in a plexi see how that feels. Could definitly benifit from the added tightness too with the higher -ve

Definitely try 47k. You could also add a variable NFB control. Maybe something that goes from 27k (JTM 45 value) up to 100k (metal face value)

Also, as for the 72 mentioned in the above posts, it's also possible to just use a fixed value and not add the pot at all. I have a JMP 2204 which just has a .0047uf cap in there and no pot - didn't want to mess with it too much and wanted to keep the stock look.

 

[Charvel_King]

I'm going to experiment with that, might replace the NFB with a 33K and a 250/500k pot and have a play with it. Kinda like a "feel/dampening" knob

Or will stick in 47k like in a plexi see how that feels. Could definitly benifit from the added tightness too with the higher -ve

Definitely try 47k. You could also add a variable NFB control. Maybe something that goes from 27k (JTM 45 value) up to 100k (metal face value)

Also, as for the 72 mentioned in the above posts, it's also possible to just use a fixed value and not add the pot at all. I have a JMP 2204 which just has a .0047uf cap in there and no pot - didn't want to mess with it too much and wanted to keep the stock look.

Yeah thats what i meant, have it variable on a pot.

The fixed depth mod would be similar to the Soldano XL mod. Good idea if you dont want to drill any holes.

 

[Charvel_King]

Dan knows a thing or two

Would you mind snapping a picture of the finished install?

Thanks!

Just spend a minor fortune setting my '72 back to stock with NOS parts.. don't wanna fuck it up now that is has the correct bite an tone

If you do want to give this a try without a pot to control it, as mentioned above. You can do it fixed by adding a resistor+cap in parallel, in series with the NFB resistor.

You could add the pot first and dial in what you like, then once you have that measure the resistance the pot is set to and use a fixed resistor in it's place.

On Soldano HR w/ XL mod its a 22nF (o.o22uF) cap and 1M ohm resistor. Also they have a 39K NFB resistor (compared to typically 47k in a 1959/1987 or 100k in a 2203/4) so those amps have a greater -ve feedback meaning the presence & depth will have a more prominent affect.