Re: [ARSCLIST] (dream) restoration phono preamp opinions wanted

[phillip holmes <insuranceman@xxxxxxxxxx>]

Sorry to spout off late.  Tubes can be just as quiet as transistors.  
I've heard noisy examples of both.  With classic tube stuff, you're 
going to have to replace the power supply caps.  They're crap.  The ESR 
of modern electrolytic caps are several orders of magnitude better than 
what was available back then.  As Tom points out, DC filaments are the 
way to go.  There were high end preamps back then that used DC on the 
filaments and choke regulation in the B+.  One of my favorites is the 
Harmon-Kardon Citation 1.  It has adjustable turnover and rolloff.  It's 
very quiet and the sound remains constant as the tubes age because of 
the judicious use of local/loop feedback.  The zero feedback stuff is 
BS--they'll always be prone to tube aging and noise.  If you have to 
rebuild one of these, they're very crammed with parts, so quite a chore 
to work on.  There are upgrade kits available for these that will 
replace the nasty electrolytic caps, the coupling caps and some other 
noisy parts.  A complete rebuild would take hours, but when you're done, 
it'd be world class.  I have one that'd covered in 20 years of dust.  
One of these days....  It uses stepped attenuators for tone controls.  I 
doubt anything like this, made as an audiophile product, would be 
affordable.  Just looking at the parts list, I'd bet it'd run at least $3k.
http://www.drtube.com/schematics/harmankardon/cit1.gif
http://www.quadesl.com/refurb/refurb_hkCitation1.html

Tom Fine wrote:
> This whole discussion is a little bit off. A power supply for a tube 
> preamp is easily built or obtained, and these days you can really 
> clean up the DC and send DC to the filaments to beat hum as low as 
> possible (usually inaudible unless there's something else wrong inside 
> the preamp or it was never a great design). For instance, PowerOne 
> used to make regulated supplies all the way up to 200VDC for a half 
> amp or so, plenty for a preamp. And they make plenty of 12V or 5V 
> adjustable to 6VDC supplies of different amps for the filaments. If 
> the supply needs more than 200V, you can always find an old Lambda 
> tube supply on eBay for south of a hundred bucks. Those things were 
> built like tanks and rarely need anything except a new rectifier tube.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "John Ross" <johnross@xxxxxxxxxxx>
> To: <ARSCLIST@xxxxxxxxxxxxxxxx>
> Sent: Wednesday, April 04, 2007 2:57 PM
> Subject: Re: [ARSCLIST] (dream) restoration phono preamp opinions wanted