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Old 28th September 2012, 07:42 PM   #1
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Default What phono preamp with Dynaco MKIII

Hello All,

I was wondering what phono pre to use if I were to build a pair of MKIII's...Would like it to be tube but I am not against solid state if I can get more amp for my money. Budget would be under $500.

Thanks much,
-david
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Old 28th September 2012, 08:13 PM   #2
20to20 is offline 20to20  United States
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Anything with at least 1.6V out if you want to reach full volume.
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Old 28th September 2012, 08:19 PM   #3
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Cool, anyone have favorites? how about phono stages with volume controls?
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Old 29th September 2012, 12:41 AM   #4
kevinkr is offline kevinkr  United States
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Take a look over in analog sources and do a search on phono stages..

The Salas Valve Itch would seem a particularly good match to your needs and is a known good performer.

I put up a detailed description of my most recent design the "Muscovite" but I suspect this design would probably be too complex and costly to meet your budget concerns.. (It wasn't that expensive to build but is complex and some parts may be expensive to get new - I benefited from a few key junk box parts.)

Eli has a re-interpretation of the classic RCA data book design with a mosfet follower on the output which would also be a good candidate IMO.

Any of these designs will drive a passive or TVC (check out Dave Slagle's TVC kits) with varying degrees of success.
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Old 29th September 2012, 04:23 AM   #5
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Quote:
Eli has a re-interpretation of the classic RCA data book design with a mosfet follower on the output which would also be a good candidate IMO.
Thanks for the "plug", Kevin.

I've uploaded the schematic. The project can easily be brought in under the stated $500. Contact member Jeff Yourison and get lots of info. about building it. Given that 1.6 V. number another poster mentioned, constant current source (CCS), instead of resistive, loading of the 2nd gain block, to maximize gain, is probably a good idea. Set the CCS in the 900 to 1000 μA. range.

BTW, the pentode I/P stage of the Dyna Mark III, with its approx. 470 KOhm I/P impedance, is a good candidate for use with a passive control setup. Keep the cables between the control(s) and monoblocks VERY short/low capacitance, as in unshielded and braided. Most of the time, a passive setup has to use 10 KOhm controls and that can be quite problematic. That 470 KOhm figure allows the use of a 50 KOhm control value, which quite a few designs can drive.
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Old 3rd October 2012, 05:16 PM   #6
Jaimo is offline Jaimo  Canada
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Default Mkiii phono mate

I use an Audio research SP8 with my mk iii clones and this works great!

Look at PAS3 derivatives - these will likely work well.
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Old 3rd October 2012, 05:33 PM   #7
BZed is offline BZed  United States
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I'm not sure that a phono amp only setup with passive VC would work that well. I think you'll need the gain of the post VC gain stage to drive the MKIII to full output. If you were driving with a CD player it would be OK in most cases. Due to the differences in phono cart. outputs and limited gain of the phono amps the extra gain will be very good to have availble.
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Old 3rd October 2012, 05:35 PM   #8
BZed is offline BZed  United States
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Quote:
Originally Posted by Jaimo View Post
I use an Audio research SP8 with my mk iii clones and this works great!

Look at PAS3 derivatives - these will likely work well.
PAS3 derivitives.... now thats funny. Of course they will, they were designed to.
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Old 4th October 2012, 01:26 AM   #9
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Quote:
I'm not sure that a phono amp only setup with passive VC would work that well.
That's precisely why I suggested CCS loading the 2nd gain block. A resistively loaded RCA setup yields approx. 45 dB. of net gain and that's not quite enough. CCS loading the 2nd gain block, along with buffering the O/P, will easily add 5+ additional dB. That should be sufficient to drive the Mk. 3 into clipping, when a loud passage is played back by a "typical", 5 mV., MM/MI, cartridge.
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