RE: Working on early BOGEN JO/G/HO series amps (late 40s)

Posted by ivan_terrible (P) on October 18, 2020 at 23:25:17

In Reply to: Working on early BOGEN JO/G/HO series amps (late 40s) posted by ivan_terrible on February 20, 2019 at 11:56:17:

18 months later.
Time goes slowly during the pantomime "Sars-Covid 2020", so it have us plenty of time to do other things.

The H50 mixer amp is still going great.
It's a really fantastic guitar amp, probably because it has a lot of bass and mid range but not a lot of treble (clearly because of the tone controls and AF amp section).
A friend said it would be no good without a MASTER volume control, so one was added on the rear (which reduced noise and hiss by a quantum leap).

Just to be clear there, the original H50 didn't have such a thing, so the mixer volume was done at the input, then summing everything direct without any attenuation.

Here is the freq response tested 20hz-20khz of that rebuilt unit - complete with the higher HT we introduced when changing the amp to 230V using a NOS Parmeko transformer from the UK.

As you can see there's a +3dB boost to about 110hz.

At the top end it gives a HF drop of up to -5dB when tested from 10khz-20khz.

We also used the amp for testing a pile of Loctal 5B254M and 255M, as they are electrically identical to 807s (but a lot smaller).

I get the feeling this amp will go on another 70yrs they are so reliable.

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Follow Ups Full Thread

Topic - Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 11:56:17 02/20/19 (19)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 23:25:17 10/18/20 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 09:42:36 06/12/19 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 09:02:40 06/12/19 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 00:37:25 02/26/19 (2)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 22:18:50 03/29/19 (1)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 23:44:10 03/29/19 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 11:52:24 02/21/19 (8)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - Caucasian Blackplate 13:04:45 02/21/19 (7)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 17:49:23 02/21/19 (6)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - Caucasian Blackplate 17:59:14 02/21/19 (5)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 18:40:15 02/21/19 (4)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - Caucasian Blackplate 19:12:13 02/21/19 (3)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 19:40:30 02/21/19 (2)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - Caucasian Blackplate 19:55:49 02/21/19 (1)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 20:18:48 02/21/19 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 10:54:15 02/21/19 (2)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - Caucasian Blackplate 11:12:58 02/21/19 (1)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 09:15:05 06/12/19 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - Caucasian Blackplate 10:32:13 02/21/19 (0)

Follow Ups

RE: Working on early BOGEN JO/G/HO series amps (late 40s) - ivan_terrible 23:25:17 10/18/20 (0)

RE: Working on early BOGEN JO/G/HO series amps (late 40s)

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