Metropoulos Forum

I have been wanting to build this amp since George came out with the kits, and now I finally got the chance!
Looks a bit messy now with the loose wires everywhere, but I think it will clean up when they get in the right positions.
Does anyone know where to get a JMP headbox for this amp? Who built the headboxes George used to ship with the kits?

Valvestorm has the JMP style headboxes in stock.

Thanks Danman! The cabs I have are more suited for plexi style builds.
Vegard, you got one of the last of these chassis/kits.
Not sure if Mojo made the original kit cabinets (I think they did). I did send this pic to andrew AT mojotone DOT com.
He said that they can build these cabs.

I have a question about the master volume in these amps. From 0-2+ , not much is really happening. From 2-5, its still okay to play it in the livingroom, then from 6 and up the beast really comes to life! Is this sweep normal?? This is with pre on 10. I want it to sweep more even.

VALVESTORM...

I bought a head box for a 100 Watt 1959 head that I built a few years ago, I think I ordered it from Mojo but it was actually made in St Louis by the guy who does the cabinets for Reason Amps. It was very nicely made.
It is the purple amp in this photo with my other two original 1974 Marshall 50 watt tops

Sounds about right. The MV on my build only increases volume between 0 and 5, after that it's just more gain really.

That's because volume pots are "audio taper" (A1M) rather than "linear taper" (B1M). It has everything to do with the way we hear. Your tones are linear (except for bass). If you take a pot (unwired) and measure across one of the outside lugs and the middle lug, you will get the resistance reading (since a pot is just a variable resistor). The lower the setting, the higher the resistance, until you get to zero, which then the resistance should be almost exactly whatever size pot you have (ex. 25k), and vice versa, at full open the resistance should measure almost zero. An audio taper will change very slightly until you reach about 80%, then it will increase all at once. A linear changes evenly. Easy way to tell is to take the pot to half, and measure. A linear will measure exactly half of your pot size (ex. 25k pot, reads 12.5k at half). An audio will read more like 19 at half.

Love this amp. I'm just getting back into making amps again and this will be my keeper I think. I say that about all my amps!