Compression problem with a Non HRM ODS

[tonejunkie]

Hey guys, I have had this amp built for a while and put it aside. I am in the first stages of trouble shooting. I will post the voltages soon but here is the problem. On the clean channel with no dumbleator when I turn up the volume on my guitar from 9 to 10 i get a large jump in volume and gain which makes the amp unusable in live settings. (I have been using it for a practice amp for a while now).

Here is what I have tried when I plug a guitar into the dumbleator input and set the dumbleator to drive the amp as hard as it was going just through the clean preamp section it does not have the same symptom. This leads me to belive the problem is in the circuit between the guitar input and the preamp output.

I have checked the circuit many times. If we assume it is a bad part and not a circuit mistake what would you check first? (I have already tried several tubes).

[JD0x0]

wait youre plugging your guitar into the dumbleator!?

it goes in the effects loop.

[JD0x0]

[quote="tonejunkie"]On the clean channel with no dumbleator when I turn up the volume on my guitar from 9 to 10 i get a large jump in volume and gain which makes the amp unusable in live settings.

quote]

you should get more volume turning it up. can you elaborate how it is unusable live? does it just not work? is it too much gain?

what settings are on your amp?

[tonejunkie]

The amp is unusable live because there is such a large volume and gain jump between 9 and 10 on the guitars volume knob. I think I will make a MP3 of this. I have built many amps and never had this problem. Yes plugging strait into the dumblator input bypasses the preamp section of the amp. This allows me to say that it does not seem like the problem lies in the phase inverter or power amp section of the circuit because the same issue does not happen.

[ayan]

The amp is unusable live because there is such a large volume and gain jump between 9 and 10 on the guitars volume knob. I think I will make a MP3 of this. I have built many amps and never had this problem. Yes plugging strait into the dumblator input bypasses the preamp section of the amp. This allows me to say that it does not seem like the problem lies in the phase inverter or power amp section of the circuit because the same issue does not happen.

A couple of thoughts. Number one would be that you have one of those 10% audio taper tops on your guitar, which have a huge change towards the last end of the pot's travel. However, as I believe you have other amps, I presume you have pkayed this guitar through some of them without incident. What kind of a guitar is this (I meand pickups and pots, the rest is irrevelant) and, is the pot wired the usual way, that is, deriving the output from the wiprer of the pot? I also wheether your amp's input impedance is 1 Meg, or if there could be something off there. Have you measured it?

Gil

[talbany]

If it's not a pot or a wiring/ pickup issue .... A large jump there at the end could be some kind of a loading issue...That's a good one


Tony

[nickm57]

Same with different guitars? or Just fender style ones?

[tonejunkie]

I have several guitars (strat, tele, 335, Les Paul, etc.) all of which work fine with all of my other amps. All of the same guitars do the same compression/volume jump thing with this particular amp.

In terms of "loading issue" what would cause that?

[heisthl]

Cold solder joint on V1a RK bypass cap? Conducts when the signal gets big enough....

[briane]

Yes, I had a similar issue with a cold solder joint, though I cant recall the specifics. Turned out it was a fast build, through most of the night, and I had missed soldering one of the cathode bypass caps. I wrap my joints, so it conducted most of the time, but not all the time.

wait youre plugging your guitar into the dumbleator!?

it goes in the effects loop.

Yes it goes in the effects loop...but try it as a tube overdrive (into the input), its pretty interesting...

I like to think thats what roy orbinson might have done.

[JD0x0]

Yes it goes in the effects loop...but try it as a tube overdrive (into the input), its pretty interesting...

I like to think thats what roy orbinson might have done.

I have a BK butler tubedrive for that

i actually tried it in the effects loop once and set it for clean and it sounded pretty good. My amp sounded HUGEE

to this date i still dont have a proper d-lator. i think i'm going to wait for Nik at ceriatone to release a tube one. provided it's not too expensive

[angelodp]

Sorry if this is meandering but, can you elaborate on the use of the dumbleator on the front end.

ange

[JD0x0]

Sorry if this is meandering but, can you elaborate on the use of the dumbleator on the front end.

ange

It acts as a boost pedal. or like having a preamp in your guitar. Just boosts the signal into the amp giving more drive

[heisthl]

SideHatch (Shane) uses one when he has to record straight into a board to warm up the signal on the way. Just plug your guitar straight into the input jack of the D'lator and connect it's output jack to your amp or mixing board. Set the send and return levels to taste.

[bcook]

I had this same issue arise when I dropped my guitar cable in water. So if not the cable, perhaps you've got a partial short to ground between the input jack and V1. As Gil said, measure it.