[JN] Top Cap

Johari Yip johariyip at singapore.com
Sun Feb 27 16:47:20 CST 2005

1/4" fuseholder, now why didn't i think of that...thanks everyone for helping out.


----- Original Message -----
From: "David Crittle" <david at retrovox.com.au>
To: sound at mailman.soundlist.org
Subject: Re: [JN] Top Cap
Date: Sun, 27 Feb 2005 14:42:47 +1100

> At 9:35 AM +0800 27/2/05, Johari Yip wrote:
> > Short of soldering the signal wire directly to the top of the 
> > 6J7G signal pentode, what other alternatives is there other than 
> > using those ceramic top caps? Anyone used other means in place of 
> > top caps?
> Dear Johari
> standard 3AG fuses have the same connection as 6J7G top cap: same 
> diameter (1/4" maybe?), similar metal-mounted-on glass-contact. You 
> can adapt any fuseholder fitting that works for you. For low signal 
> stages with top cap input grid, try shielded cable, and if 
> stability or parasitic oscillation is a problem mount a resistor 
> directly on the top cap  connector.  Here are some fuse holder 
> contacts that I've tried:
> http://www.retrovox.com.au/Images/P1130908.jpg
> http://www.retrovox.com.au/Images/P1130907.jpg
> http://www.retrovox.com.au/Images/P1130904.jpg
> Cut to shameless commercial plug: Shown in the last pic is Mullard 
> type M8091 / CV4044 single rectifier. MIl spec CV4000 series, 
> 10,000 hour life blah blah blah. Indirectly heated 6.3 volt. A pair 
> in CT full wave is good for 650+ volts @ 250+ mA. If the top caps 
> scare you the tubes can be mounted horizontally under the chassis 
> (with vent holes) enabling nice short anode leads direct to the 
> power transformer. For conventional mounting the anode leads form a 
> short path to the top of the transformer. I have waaaaaaaaaaay too 
> many of these. Email off-list for extraordinary pricing.
> -- David Crittle
> david at retrovox.com.au
> http://www.retrovox.com.au
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