Best cap to cathode tube bypass is …..

Katapum · 16th January 2006, 09:28 AM

Hi all,

I’d to know what is the best cap to cathode tube bypass. The 300B amp needs a 120uF/6.3Vcap.
I have in my place:

Panasonic FC
Rubycon YXF
Sanyo oscon
Elna RJH

Any comments or suggestions are very welcome (and sorry my English).

Katapum

DigitalJunkie · 16th January 2006, 09:35 AM

I dunno about the best,but I've heard the Oscon's are pretty good for cathode bypass duty.I havn't tried it myself though,yet.

6.3V ? are you sure about that? Seems low to me..

SY · 16th January 2006, 11:49 AM

Where in the circuit is this used?

andyjevans · 16th January 2006, 11:55 AM

You can get 100uF in motor run caps. Big, but good. I use ICW polypropylenes rated 160uF. Big but very good.

Katapum · 16th January 2006, 02:23 PM

Quote:

Where in the circuit is this used?

in input stage (not in 300B stage).

Quote:

You can get 100uF in motor run caps. Big, but good. I use ICW polypropylenes rated 160uF. Big but very good.

Amp has no room to big caps.

Katapum

summilux · 16th January 2006, 03:08 PM

Andy,

I've been thinking about using motor run caps for bypass. Were they noticeably better sonically than good elctrolytics (BG or other)?

Jonathan

SY · 16th January 2006, 05:21 PM

Why not lose the cathode bypass cap and bias up the input tube in some cleaner way?

Katapum · 16th January 2006, 07:47 PM

Hi,

Quote:

Why not lose the cathode bypass cap and bias up the input tube in some cleaner way?

Could you elaborate?
(Input tube is a triode; the amp has only two stages with no feedback.)

Katapum

SY · 16th January 2006, 07:49 PM

If you can sketch out the input stage, perhaps we can look at some alternatives.

Sorry, I just hate cathode bypass caps. Nasty things.

Giaime · 16th January 2006, 07:54 PM

If you can live whitout 3dB of gain, what's the problem? Just leave it out! Stuart, am I wrong? Does the first stage need to be fully redesigned? Just make up for the lost gain with a little increase in plate resistor (or tube change)...

16th January 2006, 09:28 AM	#1
Katapum diyAudio Member Join Date: Mar 2003 Location: Europe	Best cap to cathode tube bypass is ….. Hi all, I’d to know what is the best cap to cathode tube bypass. The 300B amp needs a 120uF/6.3Vcap. I have in my place: Panasonic FC Rubycon YXF Sanyo oscon Elna RJH Any comments or suggestions are very welcome (and sorry my English). Katapum

16th January 2006, 11:49 AM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Where in the circuit is this used? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

16th January 2006, 05:21 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Why not lose the cathode bypass cap and bias up the input tube in some cleaner way? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

16th January 2006, 07:49 PM	#9
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	If you can sketch out the input stage, perhaps we can look at some alternatives. Sorry, I just hate cathode bypass caps. Nasty things. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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16th January 2006, 09:35 AM	#2
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	I dunno about the best,but I've heard the Oscon's are pretty good for cathode bypass duty.I havn't tried it myself though,yet. 6.3V ? are you sure about that? Seems low to me..

16th January 2006, 11:55 AM	#4
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	You can get 100uF in motor run caps. Big, but good. I use ICW polypropylenes rated 160uF. Big but very good.

16th January 2006, 03:08 PM	#6
summilux diyAudio Member Join Date: Jul 2004 Location: ottawa	Andy, I've been thinking about using motor run caps for bypass. Were they noticeably better sonically than good elctrolytics (BG or other)? Jonathan

16th January 2006, 07:54 PM	#10
Giaime diyAudio Member Join Date: Oct 2004	If you can live whitout 3dB of gain, what's the problem? Just leave it out! Stuart, am I wrong? Does the first stage need to be fully redesigned? Just make up for the lost gain with a little increase in plate resistor (or tube change)...

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