12xxxx Help.

[axeman]

I've been trying to make this amp sound like others in this form, and I can't figure it out. Today I rewired the power tube section and it actually did improve in tone, but still sounds horrible. May be one of you guys can figure it out by looking at these pic's.

Thanks

[Omn]

As an overview these pictures are OK. But how about more detailed ones? Inputs. PI, or rather the whole area around; mains, fuses, secondary side of PT, outputs and ohm-switch...
Anyway. The best way would be to offer some measurements/readings. Not that I would be the one to ask, but that way someone will probably chim in.
The NFB-wire; where is it connected? Seems to be at the back of one output-jack, ending up at the center lug of the switch... I would rather go to one of the "ohm-lugs".

[axeman]

I use to have the NF wire at the impedance selector 8 ohm tap. Any way, the amp sounds like someone is playing the octave notes when I strum a chord. . Stand by for some more picks and Voltage reading.

[axeman]

Ok guys, I rewired the power board and there was a drastic improvement. It sounds spongy now ( when I jump the channels) I need some one to post a clip to compare tones. Please


Thanks

[MarshallGeek]

Wiring the NFB to the speakeroutput will put the NFB to the selected impedance setting.
The "octave" notes you're hearing sounds like a parasitic oscillation problem...
Try to run the purple wire coming from the NFB resistor under the board, and let it come out on the far end of the circuitboard where the positive ends of the biascaps are located. The last turretboardpost will be the "exitpoint" of the purple wire.



The silver mica cap on the PI, correct me if I'm wrong, shouldn't that be a 47pF? Yours is a 100pF...

[Omn]

Wiring the NFB to the speakeroutput will put the NFB to the selected impedance setting.
That is fine. But it is also a limitation when it comes to tweaking. Loose (4 ohm) or tight (16 ohm) is not a choice anymore.
Another limitation is the use of a "normal" standby-switch instead of the triple toggle. Many find the 80% to their likings.

I would not twist the CT of the heater around the heater wires, but rather straight to ground. But who am I?
And I would trim the wires sticking up like soar thumbs in some of the connections. They are antennas.

[axeman]

Thanks MarshallGeek, I'll try rerouting the NF wire like you recommended, and as far as the Fizz mica cap, 100pf is what Eddie used on his amp. I don't think that's a problem.

Omn, I'm going to move the ct for the heaters and send it straight to ground.


Thanks

[Omn]

Omn, I'm going to move the ct for the heaters and send it straight to ground.

Not sure that will do anything for the sound..., mingling more with the power trace than the sound trace.

There was a great thread earlier where Rockstah took someone (can not remember who) through some intense tweakings with an excellent result. You might find some good things there. I tried searching for it but gave up...
Here you have a nice 12xxx http://forum.metroamp.com/viewtopic.php?f=16&t=22611" onclick="window.open(this.href);return false;

[axeman]

Thanks OMN. It sounds a little bit better.

[wdelaney72]

The ground from your AC in needs it's own isolated lug. I use one of the Metro single hole ground lugs and mount it under the PT mounting bracket for the AC ground.

[axeman]

Thanks wdelaney72. I'm going reroute the ground.

[itsonlyadam]

So wait, did the issue ever get resolved? I like your style axeman, not doing the whole low voltage option. Im considering building a 12xxx just the same way (with the standard SPDT stand-by switch as opposed to the VH aficionado 3P3T "Rudolph's Red-nose" switch). So I'd love to hear that this issue was/is resolved.

[axeman]

Thanks buddy. (itsonlyadam) The amp sounds better, but I believe what I have now, as far is tone, is not it's true tone. So what I did today is dismantle the beast and ordered some wire, power transformer plate and some Sozo cap's from Fido ( that guy is to COOL) so I can start over again. Any way here's a clip of what it sounds like .

http://www.youtube.com/watch?v=VuYFqLtY ... annel_page" onclick="window.open(this.href);return false;

[Fido]

So what I did today is dismantle the beast and ordered some wire, power transformer plate and some Sozo cap's from Fido ( that guy is to COOL) so I can start over again. Any way here's a clip of what it sounds like .

http://www.youtube.com/watch?v=VuYFqLtY ... annel_page" onclick="window.open(this.href);return false;

Hey bro, thanx for the props...you rock as well. When will you post an updated clip of the re-tweaked amp?

[demonufo]

There was a great thread earlier where Rockstah took someone (can not remember who) through some intense tweakings with an excellent result. You might find some good things there. I tried searching for it but gave up...
Here you have a nice 12xxx http://forum.metroamp.com/viewtopic.php?f=16&t=22611" onclick="window.open(this.href);return false;

Ah, that would be this one then. Absolutely the most essential guide for anybody serious about tweaking one of these. I'm not suggesting that you should absolutely follow every detail to the letter, but at least you can hear the results of everything, and decide what is for you.
http://forum.metroamp.com/viewtopic.php ... g+rockstah" onclick="window.open(this.href);return false;