Monarch

• 12au7 input driver
• Interstage Transformer for a SE amp driving A Push-Pull amp
• AB2 Push-Pull U/L fixed Bias, using 2 KT77's
• Tubes: 12au7, El84, (2)kt77
• Tag board Layout

Finished

As the schematic shows, you can use a range of power-tubes in the amp. Of course which tube you use will effect the output power of the amp, but also change the colorization of the amp too. I've found that in this amp kt77's sounded the best for my liking. Also running kt88/6550/kt120 will lower your B+ by 20~30volts, so remeasure your B+ when changeing from any of the other tubes to one of these before setting your bias.

Output measured into an 8 ohm resistive load with a .7vac rms 1k input sin wave (don't take these numbers as gospel, was using a cheap meter to take these readings, wasn't done on a scope.)

Tube	Power RMS
6l6gc	47 Watts
el34	67 Watts
kt77	67 Watts
kt120	78 Watts

Transformers:

Power - Fender Twin Reverb

Choke - weber 5-8H @ 200ma

Interstage - Hammond mfg 124A

Output - Hammond mfg 1650R

these samples where record with two Shure 57's set up to ambient mic the room plus a kick drum mic and a line from the main mixer with the vocal mics into a sony Mini-Disk Recorder.
I was just using a bellari MP105 round sound tub mic preamp, for the bass on these, to feed the power amp. The cabs are a kustom 2x15 with altec 421's and a JCA 4x12 loaded with eminence alpha 12.
Sample 1 (NOS large bottle 6CA7 Power Tubes)
Sample 2 (NOS large bottle 6CA7 Power Tubes)
Sample 3 (Svetlana 6550 Power Tubes)

Pictures taken from gig's

Pictures of the test bed amp, so not pretty and was rewired a couple of times so is a little messy but it's very quiet and hardly any noise floor

Copyright 2011 Bryan James please do not repost on other web sites without permission. Feel free to link to this page. I just ask that I be notified.