rjm 6dj8 phono section

fergs1 · 4th June 2005, 10:09 AM

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

SemperFi · 4th June 2005, 11:12 AM

It seems everyone knows what rjm is...but I've never heard of it. Can you post the schematic or give a link?

Eli Duttman · 4th June 2005, 01:35 PM

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.

pedroskova · 4th June 2005, 02:21 PM

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.

fergs1 · 5th June 2005, 12:27 AM

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

fergs1 · 5th June 2005, 02:02 AM

and again! cant seem to post the schem.lets see what happens
http://www.geocities.com/rjm003.geo/.../diy_pho3.html

fergs1 · 5th June 2005, 02:03 AM

ta daahh!

dshortt9 · 5th June 2005, 05:08 AM

This one is interesting to me but I've never heard it.

http://home.earthlink.net/~jeremyepstein/6c45riaa.html

Maurizio · 9th June 2005, 08:34 AM

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.

fergs1 · 9th June 2005, 02:15 PM

youl'll find the psu scem on the fi primer website.cheers chris

4th June 2005, 10:09 AM	#1
fergs1 diyAudio Member Join Date: Jan 2005 Location: melbourne	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

4th June 2005, 01:35 PM	#3
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	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. __________________ Eli D.

9th June 2005, 08:34 AM	#9
Maurizio diyAudio Member Join Date: Sep 2003 Location: Italy	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.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
My Pearl Phono Section	Algar_emi	Pass Labs	38	14th January 2010 06:06 PM
My new Aleph ONO Phono Section	Algar_emi	Pass Labs	115	28th October 2008 11:33 AM
Best Preamp phono section	metronman	Solid State	0	23rd September 2008 01:04 PM
Pearl Phono Section	neil_kaye	Analogue Source	0	12th January 2008 11:32 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

4th June 2005, 11:12 AM	#2
SemperFi diyAudio Member Join Date: Jan 2002 Location: nowhere	It seems everyone knows what rjm is...but I've never heard of it. Can you post the schematic or give a link?

5th June 2005, 02:03 AM	#7
fergs1 diyAudio Member Join Date: Jan 2005 Location: melbourne	ta daahh!

5th June 2005, 05:08 AM	#8
dshortt9 diyAudio Member Join Date: Apr 2001 Location: Milwaukee, Wisconsin	This one is interesting to me but I've never heard it. http://home.earthlink.net/~jeremyepstein/6c45riaa.html

9th June 2005, 02:15 PM	#10
fergs1 diyAudio Member Join Date: Jan 2005 Location: melbourne	youl'll find the psu scem on the fi primer website.cheers chris

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read