Why do some Bogan amps sound so good as guitar amps? - diyAudio
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Old 15th June 2006, 01:56 PM   #1
amperex is offline amperex  United States
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Default Why do some Bogan amps sound so good as guitar amps?

Give me your ideas?
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Old 16th June 2006, 12:53 AM   #2
Enzo is offline Enzo  United States
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1. Because we built them ourselves.

2. Because once it is converted, it no longer IS a Bogen.

3. We take the power supply, chassis, and a few patrs of the Bogen, then proceed to build an actual guitar amp in its place.
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Old 18th June 2006, 03:41 PM   #3
amperex is offline amperex  United States
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Default No one seems to know this secret

One reason is the first preamp tube volume control configuration. It is unlike any guitar amp schematic I ever seen.
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Old 18th June 2006, 05:19 PM   #4
poobah is offline poobah  United States
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Because they use tubes.

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Old 20th June 2006, 12:28 AM   #5
Enzo is offline Enzo  United States
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Wiring the volume controls "backwards" like that is simply a way to make it cheap. If they wired them up conventionally, and tried to wire the wipers together, then turning one to zero will ground all of them. This way they don't. They might have had to use an additional mixing stage to recover lost signal.

I doubt the arrangement affects tone much, especially if it is up all the way.

A circuit is a circuit, doesn't much matter if you put it in a Bogen chassis or something else.
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Old 21st June 2006, 11:37 AM   #6
amperex is offline amperex  United States
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Default Errrrrrrrrrr..........

The first preamp 12AX7 grid is not connected to the volume control, just the signal input with a 1/2 meg grid leak resistor. This configuration produces a mild Marshall type overdrive sound at all volume levels. The volume pot is coupled to the tube plate via a coupling cap. The wiper goes to the next stage. The other end of the pot goes to ground.
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Old 22nd June 2006, 12:21 AM   #7
Enzo is offline Enzo  United States
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yes, I am looking at the drawing. Most guitar amps have the input going right to the grid and volume control after the first stage. So the only thing I see unusual about the volume control arrangement is the "backwards" aspect. The input is grid leak biased but that is a separate issue from the volume control. I don't doubt you can easily overdrive this mic input circuit.

You didn't specify a model, so if your pots are connected conventionally, then I don't know what you are referring to. The CHB series all are wired as I mention. The CHA20 has the more conventional wiring, possibly what you have?

The grid leak bias will be very low.
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Old 22nd June 2006, 11:46 AM   #8
amperex is offline amperex  United States
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CHB-20 is sweet with the PP 6V6GT tubes.

Another trick to sweeten up a boring guitar amp is replacing the poly coupling caps with ceramic caps. I just finished a Fender Champ 12 with these mods in the preamp tube sections.

Tube swapping is always different in every amp. The Champ 12 wanted a Sovtek 12AX7LPS to an Amperex 12AX7. A Sovtek 6L6WXT+ outperformed an RCA 6L6GC black plate in this amp- go figure.
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