Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: KimboDb on August 17, 2017, 06:24:24 pm
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So, I populated the board and notice on the schematic calls for a .0033uf cap wired to one tab of the reverb pot that's wasn't on the parts list order sheet. Also does it matter were the Nixon .1uf/630 cap goes. The other .1uf/630v caps are the Mallory ones. Also the schematic calls for 5 22uf 500v but the order comes with 3 FT and 2 100uf/350v FT caps. Any help will be appreciated. also there are 2 extra 120p silver mica caps what are those for
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The Hoffman AB763 amp is not a single amp. It is a whole family of amps and there are subtle differences. Look at all the documentation for the "two" channel AB763 and I think it may clear up most of these questions.
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So, I populated the board and notice on the schematic calls for a .0033uf cap wired to one tab of the reverb pot that's wasn't on the parts list order sheet. Also does it matter were the Nixon .1uf/630 cap goes. The other .1uf/630v caps are the Mallory ones. Also the schematic calls for 5 22uf 500v but the order comes with 3 FT and 2 100uf/350v FT caps. Any help will be appreciated. also there are 2 extra 120p silver mica caps what are those for
KimboDB,
I was confused by the capacitor order for that circuit as well. Doug pointed me to his technical information page that indicated popular configurations of the caps. I believe the two 100uF caps are in series.
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Thank you. Found the caps page. Also populated and soldered the board. Thanks again everyone.
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The AB763 is several different reverb amps
All the way from Deluxe reverb to Twin reverb
And the bandmaster reverb head also
Different models will have a different value cap or other part in the same location
Power supply caps can be done any way you want them
All parallel or the 100/350v in series, it does not matter
The BOM says the 120p caps are optional bright switch caps
You can use a .0022 in the reverb section if that is what you have
I updated the BOM to match the schematic as a .0033
I updated 5 x 22uf filter caps
Added 4 rca plugs for the reverb cable
http://el34world.com/Hoffman/files/Hoffman_AB763_1_BOM.pdf (http://el34world.com/Hoffman/files/Hoffman_AB763_1_BOM.pdf)
You will have to hit refresh on your browser or it may still load the old version
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Mr. EL34, what difference will the .0033uf be from the .022uf for the reverb cap in operation if any i.e. affect to sound. For a super reverb type ab763 or like your super vibrolux from the project page, can i used the 100uf caps since thats what i got. i plan on following your caps option #2 using the terminal lug board and 2 resistors and both the 100uf cap. Thanks ahead of time for the responds
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Mr. EL34, what difference will the .0033uf be from the .022uf for the reverb cap in operation if any i.e. affect to sound.
I'm not Mr. EL34, but I can answer your question.
Using .0022 instead of .0033 with have a very little effect of shaving a slightly lower frequency coming from the reverb return signal.
Not very noticeable at all, especially due to the fact that the reverb signal will be mixed back in with the 'dry' signal
If you really mean using .022 (as I highlighted in red in your question), that will allow a lot more lower frequencies to pass than either the .0022 or .0033
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Thanks Silvergun!