Volume: OD vs. clean

[lionaird]

Hi everyone,

I have a big volume discrepancy between the clean and the OD channel of my #183. Now, I can adjust the 100K OD trimmer and it does change the volume. But the clean channel is still much louder, even when I set the OD trim to 0 Ohm. That's not how it's supposed to be, is it?

Cheers,
Toby

[CHIP]

Try this, Set pre amp vol. to 1 o'clock,the drive(level) 11 o'clock, the volume(ratio) to approx. 1 o'clock. set the trim(trigger) to approx. 23k ohms from wiper to ground. Then adjust the volume(ratio) pot to try and match clean volume and OD volume.
If you adjust the drive(level)for more or less dirt, then you have to adjust the volume(level) pot accordingly.

[lionaird]

Try this, Set pre amp vol. to 1 o'clock,the drive(level) 11 o'clock, the volume(ratio) to approx. 1 o'clock. set the trim(trigger) to approx. 23k ohms from wiper to ground. Then adjust the volume(ratio) pot to try and match clean volume and OD volume.
If you adjust the drive(level)for more or less dirt, then you have to adjust the volume(level) pot accordingly.

With those settings I have to put the master volume past 12 o'clock to even hear the OD channel. Which makes the clean channel extremely loud. Even with everything cranked up to full (including the OD trimmer gain), the OD is far from being what you would expect from a 100 Watts amp...

[ayan]

Try this, Set pre amp vol. to 1 o'clock,the drive(level) 11 o'clock, the volume(ratio) to approx. 1 o'clock. set the trim(trigger) to approx. 23k ohms from wiper to ground. Then adjust the volume(ratio) pot to try and match clean volume and OD volume.
If you adjust the drive(level)for more or less dirt, then you have to adjust the volume(level) pot accordingly.

With those settings I have to put the master volume past 12 o'clock to even hear the OD channel. Which makes the clean channel extremely loud. Even with everything cranked up to full (including the OD trimmer gain), the OD is far from being what you would expect from a 100 Watts amp...

Might I suggest that you probably have a bad connection somehwere along the way? The wire from the wiper of the Lead Master volume connects to the channel switching relay; the overall Master Volume is one of the poles on that relay. You can try a fairly simple test: disconnect the wiper of the Lead Master Volume and the wire at the input of the overall Master Volume. Temporarily, directly connect those two points -- you will be hard-wiring the output of the overdrive this way, bypassing the switching. Do you still have a very low volume on the Lead channel? If not, then you have something strange going on at the relay conenctions, or perhaps (but less likely) a bad relay. If you still don't have enough volume, there is something wrong in your overdrive section; since you don't complain about lack of distortion, I would pressume the problem would likely be at the output of V2.

I hope this helps,

Gil

[lionaird]

Try this, Set pre amp vol. to 1 o'clock,the drive(level) 11 o'clock, the volume(ratio) to approx. 1 o'clock. set the trim(trigger) to approx. 23k ohms from wiper to ground. Then adjust the volume(ratio) pot to try and match clean volume and OD volume.
If you adjust the drive(level)for more or less dirt, then you have to adjust the volume(level) pot accordingly.

With those settings I have to put the master volume past 12 o'clock to even hear the OD channel. Which makes the clean channel extremely loud. Even with everything cranked up to full (including the OD trimmer gain), the OD is far from being what you would expect from a 100 Watts amp...

Might I suggest that you probably have a bad connection somehwere along the way? The wire from the wiper of the Lead Master volume connects to the channel switching relay; the overall Master Volume is one of the poles on that relay. You can try a fairly simple test: disconnect the wiper of the Lead Master Volume and the wire at the input of the overall Master Volume. Temporarily, directly connect those two points -- you will be hard-wiring the output of the overdrive this way, bypassing the switching. Do you still have a very low volume on the Lead channel? If not, then you have something strange going on at the relay conenctions, or perhaps (but less likely) a bad relay. If you still don't have enough volume, there is something wrong in your overdrive section; since you don't complain about lack of distortion, I would pressume the problem would likely be at the output of V2.

I hope this helps,

Gil

Thanks. Will give that a go. Actually there is lack of distortion of the OD channel...

[lionaird]

Could somebody please double check for me that I wired the relays correctly. I'm using the PCB's from agbamplifiers http://agbamplifiers.com/pcb/UNIVERSAL% ... 0NOTES.pdf

Relay 1 (preamp boost)

[img764]http://i638.photobucket.com/albums/uu10 ... cd368d.jpg[/img]

Far left wire (yellow): to middle pins of preamp boost switch
2nd wire from left (red): to middle pole of bass pot
3rd wire from left (yellow): to left middle and right lower pin of Rock/Jazz switch
4th wire from left (red): to right middle pin of Rock/Jazz switch
5th wire from left (yellow): to left pole of treble pot

Relay 2:

[img764]http://i638.photobucket.com/albums/uu10 ... 146aeb.jpg[/img]

Far left wire (green): to middle pins of OD switch
2nd wire from left (blue): to right pole of Master Volume pot
3rd wire from left (green): to 220K resistor of preamp board
Empty eyelet
4th wire from left (black): chassis ground
5th wire from left: coaxial to middle pole of OD volume
6th wire from left (yellow): to 503K cap on preamp board

Is that correct?

[ToneMerc]

Do you have the NC jumpered to the NO terminal?

TM

[ayan]

Thanks. Will give that a go. Actually there is lack of distortion of the OD channel...

Then your problem is more likely to be at the input of the overdrive. Check your wiring against the schematics and if that checks out OK, inspect your solder joints.

Gil

[CHIP]

Do you have the NC jumpered to the NO terminal?

TM

That's the problem, if the eyelets empty.

[lionaird]

Do you have the NC jumpered to the NO terminal?

TM

That's the problem, if the eyelets empty.

Oh. I forgot to jumper NC to NO... Fixed now but can't hear any difference. Back to checking my wiring I guess

[CHIP]

Post some good pics of your build if you don't find the cause of your problem.

[lionaird]

Will do. Thanks

[ER]

Maybe try checking R across lugs 1&3 on all the pots to make sure they're the proper values, sometimes it can change with too much heat etc.,

Check under the boards to make sure nothing is getting grounded.

Check all shielded runs on OD for no connection from hot lead to shield (taking into account the pots value). Sometimes a stray shielding strand or too much solder heat can short the hot lead to ground.

Good luck.

Yes, I had a couple defective pots that got passed me into my build.
They were NOS Allen Bradley 1M pots that jumped resistance early in their rotation.

[Structo]

Just to be clear, the J. Border PCB is a bit different from the traditional relay board since it is made to handle any of the relay duties on the amp.

The OD relay must be jumpered as shown but you only have to use one jumper, either or.

The black dotted line that goes diagonal, would be an under board wire while the Blue jumper can be done on top of the board.

[lionaird]

Just to be clear, the J. Border PCB is a bit different from the traditional relay board since it is made to handle any of the relay duties on the amp.

The OD relay must be jumpered as shown but you only have to use one jumper, either or.

The black dotted line that goes diagonal, would be an under board wire while the Blue jumper can be done on top of the board.

Just to clarify: so you either jumper between the eyelets (blue connection) or under the board (diagonal black connection)? Not both?

OD volume pot measures 260K, OD Drive pot measures 235K. Preamp volume pot measures 242K with wire (to treble pot) attached to lug 3 and 1M when wire unsoldered from lug 3. Measured coaxials hot to ground but seems ok