PA amp assembled

[mrn1ngstr]

Its a Dukane 1U460A. This is my novice learning amp. I know its not going to sound great as-is for guitar. I have oodles of components and Im going to make changes and test. And repeat. So now Ive got this thing put back together almost completely with modern stock and Ive been doing some testing with the scope and I played my SG through it. Here are some things Ive noticed-

1. I ran 60Hz, 300Hz and 10KHz through it on an 8 ohm dummy. I noticed that at 10KHz the amp made a high pitch hum.

2. Its quiet. Way too quiet. Im not expecting to have my ears torn off but my tiny terror is louder than this thing through the same speaker. I played my SG through it and dimed out Im getting .383V.

3. Its got extremely little headroom. I imagine thats because there are 3 cascaded 12AX7 gain stages starting out the gate.

4. Its a PA amp. Right now it sounds a little muddy, not as much as I expected, but the tone isn't great. There are large couple capacitors that could be lowered and that will help some. The bass and treble controls don't seem to do much. That has to get remedied. Honestly I don't even know what style of tone stack this thing has. I have 4 unused holes for controls on the front that Im not entirely sure what to do with. Right now it has volume, bass and treble. Id like to add a master volume.

Im going to cut out the first gain stage. This amp doesn't need it. The second tube is going to be an ECC823. Im going to elevate the heater and change the PI to 12AT7. Im sure Ill think of other things as I go along.

Any ideas on points 1 and 2?

The voltages written on the schematic are a little lower than whats actually there. I haven't gotten around to putting the current voltages on paper and scanning it in.

[billc]

I converted a PA myself recently and wired it like a guitar amp with a similar tube lineup and that worked really well...it is PLENTY loud and sounds great. Did not wire a tone stack initially and now I'm not all that motivated to add one, sounds good to me as is...but will eventually for the sake of experimentation. FWIW I had a extra tube socket so I wired a second channel with a twin triode (6SC7 octal in my case, wired like an early Bassman) and paralleled the triodes ala Matchless and that worked out well. Anyway, I started with the bare minimum of the circuitry of a vintage amp I like, got it up and running and am expanding from that.

[mrn1ngstr]

Yeah I didn't do that. People told me to. Probably still won't. Im stubborn sometimes. Like I said, its a learning amp. Ill continue to have problems for a while, but Ill learn from them.

I did some thinking today about my low output problem and Ive thought of a few things to check and Ill report back what I find. Im hoping that something is just wired incorrectly. Im really hoping it isn't the OT.

Ill figure out the 10k/high pitch coming from the amp later.

[mrn1ngstr]

So I fixed the output problem. My two thoughts were 1. it was the output jack wiring, or 2. it was the output trannie secondary (which would have been upsetting to say the least).

I unsoldered the 4ohm output lead and that did it. The thing that I don't get is why that did it. Two cliff jacks, an 8ohm and 4ohm outputs. Anyway, Im now getting just under the 30W I expected it to do. This sucker is loud... But it also makes a pop when I switch it off now.

Now on to making it sound less like a pa and more like a guitar amp. First thing I think I need to do is build a new tone stack. The one thats on there really does not do much or sound good.

Second thing is lower some of those coupling cap values. Im very far from an expert but Im pretty sure they're way to big.

Any input?