Fizzy, grainy distortion from ODS

[jakehop]

Hi guys,

I just built a ODS-101, and i'm getting great clean-sounds, but the OD is fizzy and grainy, lacking the smoothness I've been hearing from these models, as well as the dynamics and sustain.

I've recorded a clip. It doesn't show the great clean channel, but you can get an idea of how it sounds - especially the bad OD-sound: http://www.jakehop.com/dumble1.mp3

I've been messing with all the controls like mad. It sounds to me like some kind of bad blocking distortion, or a misbiased stage in the amp, but all the stages measure normal - about 200V on the plates, and a couple of volts at the cathode.

I've been reading about troubleshooting this beast on the forum for the last couple of days, but nothing's worked! It's a 100W HRM model with SkyLiner EQ. I've been trying some 124 and BluesMaster values here and there, but nothings changed.

Thanks in advance!

[boldaslove6789]

Give it some burn in time, I know it " may be mythical " but you gotta give it a bit. Is this your 1st d-style amp?

[ChrisM]

Give it some burn in time, I know it may be mythical but you gotta give it a bit. Is this your 1st d-style amp?

Burn in is not mythical. Certainly not with caps, tubes and speakers.

Transformers and the rest is up to the mojo police.

[JD0x0]

Give it some burn in time, I know it may be mythical but you gotta give it a bit. Is this your 1st d-style amp?

Burn in is not mythical. Certainly not with caps, tubes and speakers.

Transformers and the rest is up to the mojo police.

+1 but im going to chalk resistors and transformers up to non mythical as well. Regaurdless of what "burns in" or not there is a definite tonal change in new amps after some playing time.

[kd]

That has been my experience also. Give the amp time to burn in before making an mods. A Dumbleator will also help smooth the amp. Might as well build one while your waiting on the amp to break in.

Ken

[phsyconoodler]

Try some trimpot settings too.It sounds like it's a bit shy on gain.
What guitar are you using?It also sounds like there's no treble and not much mids in the tone.

[jakehop]

As much credit as I give burn in for changes in tone, I don't think it'll cure my problem here.

The overdrive sounds like a misbiased tube, even though all values are withing spec. I think I'll leave it on till the next weekend, and see what happens. Any other advice is appreciated!

[moj067]

Are you playing single coils? Sounds like it. Like Psych said try playing with your internal gain trimpot. Cause it sounds like you've got the ocean trying to come thorough a straw. If that not it it look over your connections. V1 sounds a little too high if 200v. Alot of guys like it in the 180-190 range,it can make a difference. But you've got to chase this problem down first. Then tweak the other stuff. Check around your grounds,etc.

Good luck.

[jakehop]

Thanks buddy!

I've tried every possible connection with the trim, volume and drive. I'm thinking it might be a connection problem. It has the internal loop as well - I've been A/B'ing with the clean channel and I don't *think* it's the loop. But to be scientific about this stuff, I'll try to bypass it, and check my soldering as well.

I've been using single coils and humbuckers with the same results. I think it might be a cold solder or something like that.

[ChrisM]

Got any pics of the amp?

[bluesfendermanblues]

As much credit as I give burn in for changes in tone, I don't think it'll cure my problem here.

The overdrive sounds like a misbiased tube, even though all values are withing spec. I think I'll leave it on till the next weekend, and see what happens. Any other advice is appreciated!

If everything is soldered correctly, your amp could suffer from a phenomenon called 'parasitic oscillation' which is caused by ringing at very high frequences - sometimes in the Mhz range.

Cowboy trick
You could try a 10pf capacitor across the input jack (hot to ground), alternatively from od input (hot) to ground. If either of the above mentioned caps gives a smoother od sound, the origin of the oscillation problem wiill probably stem from bad lead dress wiring.

You can leave the caps in the amp or check the lead dress wiring in your amp. There's a lot of fine pictures of nicely build DIY amps at this forum to be inspired by.

If your decide to leave the small 10 pf caps in the amp, the peceived sound will not suffer since they cut off high freqencies at about 10kHz .....and your guitar speaker will not play wery much above 6 khz.

[Bob-I]

That's definitely not a matter if burn in, something is wrong.

It sounds to me like all the stages are not amplifying correctly and gain is being lost. Double check all the voltages and the values of the components on V2. Check the signal going in and out of each stage, there should be an increase in gain at each stage.

[Structo]

Yes, I agree that something is wrong.
Double check all wiring to and from the OD tube, especially the relay if you are using one.
The switching and relay wiring can be a bit of a challenge to newcomers to these amps.

Just trace out the wiring compared to the layout or schematic.

[jelle]

The soundclip is not working for me.

Got pics?

[ampdork]

Cap leaking DC?