Guitar Amp Question!!!!! Adding Film Cap?

zxx123 · 20th March 2005, 01:06 PM

Many hifi DIYErs like to add Film Cap in decoupling electrolyte cap of PSU in order to lower impedence. Yes, it gives faster response of sound and more detail

However, how about guitar amp? Do you think of any benefit from adding film cap?

Thanks..

Giaime · 20th March 2005, 02:17 PM

If you mean an old tube guitar amp, you'll get more improvement by replacing the electrolitics capacitors. But wait! You will lose a part of that "vintage" warm compression, because with new capacitors the pwr supply would sag less. Many people has reported that when replacing old electrolitycs in guitar amp, there was an added detail and complexity in sound (just because hum seems to masque some armonics of the guitar).

If the amp has got fresh capacitors, remember that in tube amps there is significanty less current that comes out of the pwr supply than ss amps, so bypassing electros with small caps would have less effect. But why don't you try and report the results?

anatech · 20th March 2005, 05:13 PM

Now here's a good question. How did that old guitar amp sound when new? Do we want the "defective" sound or the manufacturer's intended sound? Since we are creating music, the worn out stuff can be considered an effect. It's all personal choice.
Replacing the caps to reduce hum brings the amp back to the original design and performance. Possibly a little better electronically, but still closer to new performance.
-Chris

zxx123 · 20th March 2005, 06:22 PM

i am not a vintage worshiper.
i will try and report here.

Enzo · 20th March 2005, 07:32 PM

Paralleling the filter caps with film caps is not done to affect sag, it is there to bypass higher frequency noise around the electrolytic. If you add them, probably only makes much difference on the first node. If it does anything it will reduce sizzle from power line crap.

I find that in guitar amps the sag comes mainly from the rectifier and resistance in the B+ chain. Also, the size of the power transformer makes a difference as the Rectified voltage will sag from transformer sag. A 20uf cap renewed I don't think is going to remove much sag from an amp.

New filters will reduce hum, but they can't do much about the voltage coming out of the xfmr.

Enzo · 20th March 2005, 07:34 PM

Oh goodness, the language police objected to my word for power line noise and garbage. I thought it was mild enough, sounds like the word "trap," but starts with a C. Sorry.

Giaime · 20th March 2005, 08:02 PM

Excuse me Enzo, I didn't explain it well. Caps affect the general dynamics and harmonics of the amp, not the "sag". Anyway for the sag you can change the rectifier type...

anatech · 20th March 2005, 08:53 PM

Hi Enzo,
Now that got me laughing! Thanks! Holy c**p!

-Chris

Giaime · 21st March 2005, 11:39 AM

Quote:

Originally posted by Enzo
sounds like the word "trap," but starts with a C.

Oh, we don't care. Same thing for me in another topic... and Chris remembers that.

pinkmouse · 21st March 2005, 12:06 PM

And that's quite enough of that sort of language!

20th March 2005, 01:06 PM	#1
zxx123 diyAudio Member Join Date: Aug 2003 Location: ca	Guitar Amp Question!!!!! Adding Film Cap? Many hifi DIYErs like to add Film Cap in decoupling electrolyte cap of PSU in order to lower impedence. Yes, it gives faster response of sound and more detail However, how about guitar amp? Do you think of any benefit from adding film cap? Thanks..

20th March 2005, 06:22 PM	#4
zxx123 diyAudio Member Join Date: Aug 2003 Location: ca	thanks.. i am not a vintage worshiper. i will try and report here.

21st March 2005, 12:06 PM	#10
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	And that's quite enough of that sort of language! __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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20th March 2005, 02:17 PM	#2
Giaime diyAudio Member Join Date: Oct 2004	If you mean an old tube guitar amp, you'll get more improvement by replacing the electrolitics capacitors. But wait! You will lose a part of that "vintage" warm compression, because with new capacitors the pwr supply would sag less. Many people has reported that when replacing old electrolitycs in guitar amp, there was an added detail and complexity in sound (just because hum seems to masque some armonics of the guitar). If the amp has got fresh capacitors, remember that in tube amps there is significanty less current that comes out of the pwr supply than ss amps, so bypassing electros with small caps would have less effect. But why don't you try and report the results?

20th March 2005, 05:13 PM	#3
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Now here's a good question. How did that old guitar amp sound when new? Do we want the "defective" sound or the manufacturer's intended sound? Since we are creating music, the worn out stuff can be considered an effect. It's all personal choice. Replacing the caps to reduce hum brings the amp back to the original design and performance. Possibly a little better electronically, but still closer to new performance. -Chris

20th March 2005, 07:32 PM	#5
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	Paralleling the filter caps with film caps is not done to affect sag, it is there to bypass higher frequency noise around the electrolytic. If you add them, probably only makes much difference on the first node. If it does anything it will reduce sizzle from power line crap. I find that in guitar amps the sag comes mainly from the rectifier and resistance in the B+ chain. Also, the size of the power transformer makes a difference as the Rectified voltage will sag from transformer sag. A 20uf cap renewed I don't think is going to remove much sag from an amp. New filters will reduce hum, but they can't do much about the voltage coming out of the xfmr.

20th March 2005, 07:34 PM	#6
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	Oh goodness, the language police objected to my word for power line noise and garbage. I thought it was mild enough, sounds like the word "trap," but starts with a C. Sorry.

20th March 2005, 08:02 PM	#7
Giaime diyAudio Member Join Date: Oct 2004	Excuse me Enzo, I didn't explain it well. Caps affect the general dynamics and harmonics of the amp, not the "sag". Anyway for the sag you can change the rectifier type...

20th March 2005, 08:53 PM	#8
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Enzo, Now that got me laughing! Thanks! Holy c**p! -Chris

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