Phase one
I bought this Bogen CHB100 at a yard sale last summer and it sat for months while as I was distracted by other projects.
This amp uses a voltage doubler and a quad of 7868 output tubes. The 7868 is similar in output to a 6L6 so with 4 it's close to 50 watts output.
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Phase two
I gutted the original point to point mic and tape deck preamp section and replaced the 6C4 phase splitter for a 12ax7 .
The I started off by trying a Train Wreck preamp circuit but it didn't sound good to me so I opted for something a little more conventional. I may have just implemented it incorrectly, obviously the Train Wreck amps sound good... The input of the 7868 is sensitive so I may have just hit the inputs too hard.
Here's how it looks now.
I may remove the third tube since i'm only using two and it sounds good.
This is the experimental stage so everything is just hanging out and sloppy right now.
I still need to fine tune the preamp, power tube bias and Negative feedback. ( Not to mention that the power and output transformers run in the same direction...)
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Phase 3
The last preamp circuit I was fooling with sounded ok but I tore everyhting out and rewired the amp with a Matchelss Chieftain type circuit. I really like how this circuit sounds. The Tone knobs are all independent of each other and are simple capacitor to ground circuits. The Treble control is fairly subtle but the bass and mid controls have a lot of affect. The two preamp tubes are tied together in parallel which gives this circuit it's distinct sound.
Now it's a just a matter of cleaning up the rats nest of wires and laying everything out on the circuit board. I didn't really use any of the circuit card for this circuit, I just floated the wires in the air like a jungle gym. I wasn't sure i'd like it and didn't want to commit to it until I tried it.
So far so good.
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Here are a few sound clips:
Clean strat
Special out of tune version with strat
Medium gain
Stratocater
High gain Strat
This starts out with the guitar volume on 3 and then turned up to 10
(I have a bypass cap on the guitars volume pot, hence the jangle at low volume)
High gain Humbucker
This is with a dimarzio distortion humbucker in the bridge
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