Did some changes

[Tdale]

I finally got rid of the shielded wires to the send/return pots yesterday. I also got rid of the switch I had, to put the loop out of the circuit.

I noticed some changes in the sound. First of all, I discovered that I had had the switch in the "loop" position the last few days, giving me a muffled sound, due to the cap-effect of the shileded wires.

The sound opened up more, and is both brighter and and more "nasal" sounding now...almost like a slight wah effect, and I like it.

I'm also about to do something with the OT primaries...I might even put them on the outside, as someone suggested.

I'd also like to experiment a little with tone stack cap values, but I'm not sure what to try. I could just go ahead and try all sorts of values, but I don't like to solder and re-solder too much, so any suggestions would be helpful. I have 0.1 for bass and 0.047 for mid now. I also have a 0.001 for the treble, with a switchable 500pF in series.

I'm generally pretty happy with the tone controls, but the effect when I turn them is not very dramatic, much more subtle than on other amps I've had. In one way that's pretty nice, as long as the 12 o'clock sound is roughtly the way I like it. I followed the hybrid-a wiring, including the cap on the bass pot.

I have no idea what those 100K and 10K resistors, and the 0.005 and 0.001 caps do to the sound..could they be tweaked in some way?

I did not put in the 100K resistor between the master wiper and the "preamp out" jack. Is it a good idea to put it in?



Tommy

[Bob-I]

I'd also like to experiment a little with tone stack cap values, but I'm not sure what to try. I could just go ahead and try all sorts of values, but I don't like to solder and re-solder too much, so any suggestions would be helpful. I have 0.1 for bass and 0.047 for mid now. I also have a 0.001 for the treble, with a switchable 500pF in series.

500pF seems high to me. I'd go with a 390pF or even 330pF.

I have no idea what those 100K and 10K resistors, and the 0.005 and 0.001 caps do to the sound..could they be tweaked in some way?

The .001uF smooths out the bass a tad, it's a pretty subtle difference so I'd leave it. The 10k raises the tone stack from ground reducing the load it places on the gain, again leave it.

Which 100K are you asking about?

I did not put in the 100K resistor between the master wiper and the "preamp out" jack. Is it a good idea to put it in?

I'm not sure what it does, other than maybe changes the level of the loop. I didn't use it either.

[Tdale]

It goes from the rock/switch to the input of the volume pot.

By the way. If I think the overall sound is a bit thin, or lacks bottom, what cathode bypass cap is best to increase the value of to make it a bit beafier?

Tommy

[Bob-I]

It goes from the rock/switch to the input of the volume pot.

By the way. If I think the overall sound is a bit thin, or lacks bottom, what cathode bypass cap is best to increase the value of to make it a bit beafier?

Tommy

Depends, what do you have there now?

[Tdale]

I have 4.7 - 10 - 4.7 - 4.7 now.

I'll try a smaller cap for the mid boost circuit. The mid-boost is activated when the small cap is bypassed, right?

Tommy

[Bob-I]

The real question is what is causing the amp to lack bottom. The bypass caps sound fine, so you're losing bottom end somewhere. It may be in the coupling caps, the phase invertor, the coupling caps, the filter caps, or even the output transformer.

Maybe some more details about the ckt might help. Which schematic did you use?

[Tdale]

Hybrid-a. Mostly the same values as the schem, but I went for 250K mid pot. 180K before the od entrance. Other than that, all the values are the ones in the schem...or values suggested by dogears here on the forum.

I'm plyaing a strat and a tele, so that might be one reason for the bright sound.. Also, if I get used to the sound, maybe it isn't all that bright after all... I'll try to make some clips.

I'll also make some clips, showing what the tone controls do to sound.. as I said, the tonal range isn't very dramatic, but that might be normal?

Tommy

[dogears]

.047 midcap = lack of bass

Been saying .01 is the way to go.

[Bob-I]

Hybrid-a. Mostly the same values as the schem, but I went for 250K mid pot. 180K before the od entrance. Other than that, all the values are the ones in the schem...or values suggested by dogears here on the forum.

When you start messing with values in the TS you get odd results sometimes. The 250K pot really should have a .01uF not the .047uF.

I'm plyaing a strat and a tele, so that might be one reason for the bright sound.. Also, if I get used to the sound, maybe it isn't all that bright after all... I'll try to make some clips.

Of course Fender's will be bright. You might want to lower the bright cap on the master volume, 47pF is pretty big, try a 22pF or remove it.

I'll also make some clips, showing what the tone controls do to sound.. as I said, the tonal range isn't very dramatic, but that might be normal?

Tommy

Yes, Dumble's tone controls are more subtle than Fender's.

[Pete]

Hybrid-a. Mostly the same values as the schem, but I went for 250K mid pot. 180K before the od entrance. Other than that, all the values are the ones in the schem...or values suggested by dogears here on the forum.

I'm plyaing a strat and a tele, so that might be one reason for the bright sound.. Also, if I get used to the sound, maybe it isn't all that bright after all... I'll try to make some clips.

I'll also make some clips, showing what the tone controls do to sound.. as I said, the tonal range isn't very dramatic, but that might be normal?

Tonal range is capable of being pretty dramatic. Is there a fair amount of Bass with the Bass control all the way (or nearly) up?
What speaker are you playing?

I did not put in the 100K resistor between the master wiper and the "preamp out" jack. Is it a good idea to put it in?

personally, I like it. it can mellow things a little. ... and I agree with dogears, .01 is the way to go on mid.

[Tdale]

I will put in a 0.01 today!

I'll report back when it's done.

By the way, this guy:

http://www.myspace.com/eivindaarset

Will try out my amp next week. A bit non-traditional but still one of Norway's best guitarplayers in his field.

Tommy