The Amp Garage

One other thing I thought of: Most octal power tubes like KT88 and 6L6 have Grid 3 internally connected to the Cathode. But the EL34 does not, so you need to make sure pin 1 and pin 8 are connected.

Okay, you had the variable bias circuit installed before, right? Then you took out the pot? If you left the 1 ohm resistor in that's good. If not I would suggest you put it back in the circuit. That's how you'll measure the bias current. It should be a 1 watt / 5% resistor (the more accurate your re...

I know how NFB reduces the gain. Still not clear on how that narrows the band from clean to distortion. I'll do some more research. However, I'm certainly with you on the tone. I have used Fender open backs, though it's been awhile. But I do want a responsive feel. Right now I'm using AX84 1X12 boxe...

Bravo for finding the problem. Well done. Also, I applaud you adding the second gain control. I find it most useful, especially with a lead/rhythm switch. The only problem I see is that you might want to do the math for your bias. An EL34 is a very different beast from KT88. I've got an EL34 in one ...

Your connections all sound right. That's how I did it on one of mine. On the other the connection points are the same but they go to a relay instead of a switch so I can use a footswitch - works great. You might try taking the switch out of the circuit and reattach R12 to R14/Pin6 to make sure that ...

Thanks for the info, guys. That 'tightens' my understanding of it. :^) I'm building my first amp with NFB and I've read, as Mant said, that the more there is, the tighter the bass becomes. And since 'tighter' doesn't necessarily mean less bass, as sliberty says, that's what I want and I'll use the 1...

I guess this is pretty duh question, especially from someone who has built a few amps. But there's a matter of terminology that I never quite got. When it is said that the bass, for instance, is "tight" or "loose" what exactly does that mean?

I appreciate your indulgence.

I've got 500 pF on both. Maybe I should try some alteration, like 270 on the first and 680 on the second. That's what I've got on hand.
Thanks for the tip!

For whatever reason, the particular parts, brands, etc. I used building my amp, it has a Lot of high end. If I want more 'chirp' I can crank the treble on the amp, or turn up the tone on my guitar. I run the amp's treble at just under half and the guitar's at just over half. So there's still plenty ...

I don't, but 500pF does work very nicely.

[img792]http://i269.photobucket.com/albums/jj55 ... Hybrid.jpg[/img]

I also saw a Dumble schematic from the '70s with 500pF snubbers.

Great! I thought that might the case. It's the only real difference I can find in Dumbles and various clones compared to other amps. I built a single ended amp and have been trying to get a smoother sound. I tried 270pF and they seemed to smooth it a little, so I put 500pf caps in it. Sounds great. ...

I saw this in a D'Lite schematic in the overdrive section:

[img:484:233]http://i269.photobucket.com/albums/jj55 ... rdrive.jpg[/img]

Schematics of Dumbles I've seen have caps in the same places but are 350pF. Are these for smoothing? Or do they have some other purpose?

One of the things about these amps (TrainWrecks) is that they can be controlled with the volume knob on your guitar. Here is Glen Kuykendall talking about the amp and what it is like using it. I highly recommend watching this. http://www.youtube.com/watch?v=Uc3Xi6aAG80&feature=related If you can use...