Metropoulos Forum

Put together a 50 watt build using the layout below. The output is very low and "weak" sounding. The voltages are:
V 1 2 3 4 5 6 7 8
v1 248 0 3 214 0 2
v2 167 0 1 286 167 168
v3 216 23 37 209 24 37

That has been my experience with JCM800 design. Thin at low volume. You'll have to read about the tweaks people do to thicken their sound at lower volumes. I think the Tone Lizard had some stuff about it.

I seem to remember the the Kevin Oconner book talked specificaly about the JCM800 style master volume design and it acted as a high pass or low pass filter with the volume rolled down.

Key would be to crank the amp! Or to play at low volume, check into an attenuator or PPIMV and use the preamp master volume and attenuator/PPIMV in tandem.

Mike

Worse than that. This thing has no soul at all. Hisses bad with the volume turned up. Something is definetly wrong with the build. I have goone over the board twice and verified all the components. As a starting point anyone have a pic of the cliff jack wiring.

Did you use shielded wiring at the input jacks, etc. Once I converted a plexi build over to a JCM800 style when I was in a Slash kick. I had some issues, but I had to sort out the tone one step at a time and I got some noise at high preamp gain levels.

Mike

I will record a sound clip. It's pretty bad.

Are the tubes good? Do you have an extra set to try? Try to post some pics. The guys here are really good at spotting things.

Tried different tubes. It sounds like an old transistor radio. Going to do a sound clip and a few pics.

Memphis wrote:Tried different tubes. It sounds like an old transistor radio. Going to do a sound clip and a few pics.

O I see, it sounds bad, like something is wrong with the build, not trying to get cranked Marshall tones at bedroom levels. If you can post pics, there are guys here with really good eyes that might spot something.

Mike

A couple pics. All help is appreciated.

Ok, so I made the changes from the following post I found. The next issue is with V1 voltages

http://forum.metroamp.com/viewtopic.php ... k&start=15

1 2 3 4 5 6 7 8
309 0 3 214 0 2

Seems a little high according to the kit instruction voltage chart.

So I made the necessary changes. Now the LO input jack produces nothing. The HI works "ok" . If I remove the ground from the jacks the lo input will work but obvious hum etc.. This thing is driving me crazy. I must have checked it over a hundred times.