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Old 4th June 2005, 10:09 AM   #1
fergs1 is offline fergs1  Australia
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Default rjm 6dj8 phono section

greetings everyone. just wondering who has built the rjm 6dj8 phono and would like to share their views and experieces here.Ive looked at dozens of schems but I keep coming back to this one to build. It will be my first try at a valve phono and this one looks pretty simple and i like the fact that it uses 6dj8. also what output level could I expect running a mm at 0.5mv thru this stage. Also are there any particular things to whatch out for in building this circuit. Any help would be greaatly appreciated.
cheers fergs
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Old 4th June 2005, 11:12 AM   #2
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It seems everyone knows what rjm is...but I've never heard of it. Can you post the schematic or give a link?
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Old 4th June 2005, 01:35 PM   #3
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I haven't the foggiest idea what the rjm is, but the Bottlehead Seduction is built around the 6DJ8 too. Rigged out with CCS loads, the Seduction yields 40 dB of gain. The 6DJ8's mu is 33. That equates to 30.4 dB. Double that and deduct 20 dB. for the EQ network and, voila, there's 40 dB. If resistive loading is used, the net gain will be under 40 dB.

Boosting a 5 mV. MM cart. by 40 dB. yields 0.5 V. That will not be enough drive for many power amps. So, a line stage with a little gain is needed.

FWIW, 52 dB. of gain is needed to raise 5 mV. to 2 V., which is the O/P of a CDP.
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Old 4th June 2005, 02:21 PM   #4
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Quote:
Originally posted by Eli Duttman

Boosting a 5 mV. MM cart. by 40 dB. yields 0.5 V. That will not be enough drive for many power amps. So, a line stage with a little gain is needed.

FWIW, 52 dB. of gain is needed to raise 5 mV. to 2 V., which is the O/P of a CDP.
Don't know the circuit, but I'd be inclined to put at least a buffer between most phono stages and power amps...possibly with some amount of additional gain to insure flexibility for both cartridge and amplifier options for the future.
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Old 5th June 2005, 12:27 AM   #5
fergs1 is offline fergs1  Australia
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greetings everyone, here is the link to the rjm phono stage. i,m just curious about the gain. my amp is ideally driven with 700mv and if i can get close to 500mv out of this circuit then isn't it just a case of simply giving my power amp a little more grunt or is there something I am missing as to how a amp behaves when not properly loaded.volume is not an issue in my flat so i'm just wondering how important an extraa gain stage is. thanks for all your replies
cheers chris
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Old 5th June 2005, 02:02 AM   #6
fergs1 is offline fergs1  Australia
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Default try again

and again! cant seem to post the schem.lets see what happens
http://www.geocities.com/rjm003.geo/.../diy_pho3.html
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Old 5th June 2005, 02:03 AM   #7
fergs1 is offline fergs1  Australia
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ta daahh!
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Old 5th June 2005, 05:08 AM   #8
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This one is interesting to me but I've never heard it.

http://home.earthlink.net/~jeremyepstein/6c45riaa.html
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Old 9th June 2005, 08:34 AM   #9
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Default About RJM Phono

Hi Fergs,


The first image you attached is a Pre Phono from Nobu Shishido..

Do u have more info and a PSU for it?

Ciao,

Maurizio.
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Old 9th June 2005, 02:15 PM   #10
fergs1 is offline fergs1  Australia
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youl'll find the psu scem on the fi primer website.cheers chris
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