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Tube DIY Asylum: Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage by BBeck Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage posted by Thorsten on October 2, 2005 at 15:11:26:
Thorsten,Interesting!(But I can barely read your second posted schematic, BTW)
A question though: How much grid current are you measuring in the first grid? In a recent similar RIAA project a friend and I abandoned such low input tube biasing due to concerns about grid current flowing through the moving coils (of a MC cartridge in our case), creating a slight mechanical force and an electrical/magnetic imbalance. We used 4 parallel tubes (4HA5s we had on hand) but with a small Vgk bias of several tenths of a volt. Still we had significant grid current in the several microamp range. Granted, our application was for a MC that would generate roughly/typically 20 times less signal current than a MM cartridge. Even with a MM cartridge, if it is loaded by 47K and plays at 5mV rms "full blast", there is only about 0.1 microamp rms of signal current. DC grid current (with low frequency noise) could be an order of magnitude, or more, greater than this signal value. Any measurements/thoughts with the E810F (a great tube!)?
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Topic - Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 15:11:26 10/2/05 ( 23)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - pickle 12:34:04 10/4/05 ( 4)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 15:31:14 10/4/05 ( 3)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - pickle 07:17:07 10/5/05 ( 2)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 07:28:48 10/5/05 ( 1)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - pickle 14:48:36 10/5/05 ( 0)
Valve Substitutions - DON'T.... - Thorsten 07:18:45 10/4/05 ( 0)
Re: can i use D3a in the first stage? - papageno 00:19:14 10/4/05 ( 1)
- No, not enough transconductance (NT)... - Thorsten 06:44:01 10/4/05 ( 0)
Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Joao 22:58:21 10/2/05 ( 1)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 01:22:34 10/3/05 ( 0)
Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - tubelover@aol.com 21:42:01 10/2/05 ( 4)
- LCR Schematic - ecc83 01:29:37 10/3/05 ( 2)
- Re: LCR Schematic - Thorsten 05:45:42 10/3/05 ( 1)
- Re: LCR Schematic - ecc83 07:45:27 10/3/05 ( 0)
Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 01:19:35 10/3/05 ( 0)
Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - fred76 20:41:37 10/2/05 ( 0)
Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - BBeck 10/2/05 19:53:31 10/2/05 ( 5)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 01:16:54 10/3/05 ( 4)
- vernacular Stage - dhsettim 22:37:59 10/3/05 ( 0)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - BBeck 13:10:57 10/3/05 ( 2)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - Thorsten 13:37:11 10/3/05 ( 1)
- Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage - BBeck 13:51:27 10/3/05 ( 0)
Great work! Thanks T (nt) - Mike Spence 17:06:53 10/2/05 ( 0)