I restored a late 1960's Sherwood S-9500c a few years ago and recently found another that will receive the same treatment. Reviewing the service manual, schematic and original components in the amp, it seems I have a choice of using either 1500uF or 2700uF capacitors in the output stage.
The amplifier I restored has 1500uF caps and sounds very good. Would there be any benefits or drawbacks using 2700uF caps instead?
Attached is the service manual, Page 4 shows C290 (left channel) and C390 (right channel) as being either 1500uF or 2700uF. The schematic (last page) shows 2700uF.
The amplifier I restored has 1500uF caps and sounds very good. Would there be any benefits or drawbacks using 2700uF caps instead?
Attached is the service manual, Page 4 shows C290 (left channel) and C390 (right channel) as being either 1500uF or 2700uF. The schematic (last page) shows 2700uF.
If that is the output cap, I would say you even could use 4700uF.
Especially if your speakers are 4 Ohm.
1500uF seems to me too little.
Especially if your speakers are 4 Ohm.
1500uF seems to me too little.
Yes there's plenty of room and new caps are much smaller.
What would be the benefit of using more capacitance in the output stage?
What would be the benefit of using more capacitance in the output stage?
Last edited:
Assuming an 8 ohm load a 1500uF cap gives a -3db cutoff point of 14Hz, a 2700uF 8Hz and a 4700uF comes in at 4Hz
You may not notice much if any audible difference. The bigger cap will give more a thump on switch on and will pass very low frequency like rumble from vinyl sources. It also increase the output transistor current surge at switch on as the cap charges.
Fwiw the first amp I had used just 470uF and it sounded great. For smallish speakers your not going to tell much difference, for speakers with extended bass response you might on certain types of programme material.
2200uF and 2700uF would be fine but no point going bigger than that imo.
You may not notice much if any audible difference. The bigger cap will give more a thump on switch on and will pass very low frequency like rumble from vinyl sources. It also increase the output transistor current surge at switch on as the cap charges.
Fwiw the first amp I had used just 470uF and it sounded great. For smallish speakers your not going to tell much difference, for speakers with extended bass response you might on certain types of programme material.
2200uF and 2700uF would be fine but no point going bigger than that imo.
Thanks.
I already hear a "thump" when turning the amp on with the 1500uF caps, I normally switch the speaker selector to "off" before turning it on.
I already hear a "thump" when turning the amp on with the 1500uF caps, I normally switch the speaker selector to "off" before turning it on.
The switch on thump could be minimised (if not virtually eliminated) with a very simple speaker relay with a time delay of a few seconds. A highish value load resistor would need to be used to provide a charge path for the cap,