50 Watt Plexi Kit Help!

[nostandardlife]

Hey Guys,

I am new to the forum AND to building amps. I've done some pedal and amp mods before and thought I would give a shot at building an amp. I choose the Metro Amp 50 watt Plexi and it has been fun to build. Until now... I am afraid I have reached the extent of my knowledge. Everything is assembled and I have tested the points. Everything seems a little high to me. When I turn the amp on and volume up I hear what I am playing. However, if I pluck too hard or turn the guitars volume up all the way I get a HORRIBLE loud digital sounding noise. ANy ideas? I recorded a video but I am not sure how to post that. I've attached some photos of my build and below is my voltage chart. Thanks for the help!

Voltage Chart PIN 1 PIN 2 PIN 3 PIN 4 PIN 5 PIN 6 PIN 7 PIN 8 PIN 9
VI 12AX7 157 0.99 3.5 3.5 212 1.7 3.6
V2 12AX7 167 1.07 3.6 3.6 298 168.4 3.6
V3 12AX7 227.1 41.3 3.5 3.5 222 41.3 3.5
V4 EL34 3.7 483 480 -44 484 3.6
V5 EL34 3.6 484 480 -44 484 3.6
bias -41.6 to -58.3
rectifier 332v dc

...and also, how do you add pics?

[neikeel]

Hey Guys,

I am new to the forum AND to building amps. I've done some pedal and amp mods before and thought I would give a shot at building an amp. I choose the Metro Amp 50 watt Plexi and it has been fun to build. Until now... I am afraid I have reached the extent of my knowledge. Everything is assembled and I have tested the points. Everything seems a little high to me. When I turn the amp on and volume up I hear what I am playing. However, if I pluck too hard or turn the guitars volume up all the way I get a HORRIBLE loud digital sounding noise. ANy ideas? I recorded a video but I am not sure how to post that. I've attached some photos of my build and below is my voltage chart. Thanks for the help!

Voltage Chart PIN 1 PIN 2 PIN 3 PIN 4 PIN 5 PIN 6 PIN 7 PIN 8 PIN 9
VI 12AX7 157 0.99 3.5 3.5 212 1.7 3.6
V2 12AX7 167 1.07 3.6 3.6 298 168.4 3.6
V3 12AX7 227.1 41.3 3.5 3.5 222 41.3 3.5
V4 EL34 3.7 483 480 -44 484 3.6
V5 EL34 3.6 484 480 -44 484 3.6
...and also, how do you add pics?

You need to reverse the polarity! (well maybe!) post some pictures through a hosting site (like photo bucket) if you post an [IMG} {/IMG] link to the web page your pics will appear here. The voltage chart looks pretty close to me. Likely reversed primary wires on the OT but post pics first.
bias -41.6 to -58.3
rectifier 332v dc

[nostandardlife]

Neikeel, thanks for the reply and assistance. Here is a link to the photobucket images.

http://s783.photobucket.com/user/nostan ... xi%20Build

Also, I'm using a Classic Tone (Magnetic Components) OT# 40-18025 and PT# 40-18054.

[danman]

Nothing unusual stands out to me and your wiring looks very neat and tidy. What Neikeel mentioned about reversing the OT primary wires at the power tube sockets may likely fix your problem. It is a common issue in new builds that employ NFB like this circuit does. One quick way of checking would be to unsolder the purple NFB wire from the impedance selector and leave it hanging without touching anything. Then fire the amp back up and see if it performs properly. If it does, then you know that you need to reverse the OT wires going to pin 3 on the tube sockets.

Have you also tried any different preamp tubes to eliminate them as a problem?

[nostandardlife]

You were right! I went back and look at the schematic for the OT. It listed the wire colors for the common drake OT with the classic tone OT colors. I had two of the primaries reversed! Thanks SO much for the help! The amp sounds great!

[danman]

Excellent! Glad it was an easy fix!