Simplistic NJFET RIAA

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Siberia

Siberia

Member
Joined 2011
Paid Member
Salas said:
He, he, TSSA will look very nice with such toroid metal jacket.
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Nah, I have them already and they are not metal, just semi-special.
 

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andyr

Member
Joined 2003
Siberia said:
Still we found SMPS regulated PSU deliver better in that particular application.
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Do I understand you correctly ... you are suggesting a regulated Switched Mode Power Supply is a good thing for a phono stage? :confused:

I'm afraid I have to strongly disagree with you. I bought a SMPS as an "easy" PS for use when I set up my phono modules - in normal operation, they get powered by SLAs. (Doing all the testing to set various operational parameters takes a while, so I found it was easier to have a mains-powered PS, to keep the voltage constant.)

Now, while I can read circuit voltages quite easily with the SMPS, when I start to measure the actual RIAA signal response (and set overall gain) ... the SMPS produces far too much hash on the signal to be able to measure it accurately.

I then built a double-regulated emitter-follower PS which is fed by the SMPS ... and I still got too much hash on the signal to make a good reading of the signal levels at the various frequencies.

So I use the SMPS for setting circuit parameters ... and then use batteries when I am measuring the phono stage output at various frequencies.

So, IME, an SMPS is a definite no-no for a phono stage.


Regards,

Andy
 
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andyr

Member
Joined 2003
Salas said:
@AndyR

Siberia refers to his class A MOSFET amplifier PSU. Switched mode on a phono is looking for trouble indeed.
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Thank you, Salas. But I find it "interesting" (actually, surprising is more like it! :) ) that Jim Hagerman's Bugle2 uses an external wall-wart SMPS to deliver 24v to the PCB. (I know because I recently modified a Bugle2 for a mate, to take out the fixed 100ohm res used as the load for 60dB LOMC use. I added a pair of parallel input RCAs for loading plugs ... and this necessitated putting the PCB in to a HiFi2000 metal box (instead of the plastic box the Bugle2 comes in).)


Regards,

Andy
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
andysr said:
Thank you, Salas. But I find it "interesting" (actually, surprising is more like it! :) ) that Jim Hagerman's Bugle2 uses an external wall-wart SMPS to deliver 24v to the PCB. (I know because I recently modified a Bugle2 for a mate, to take out the fixed 100ohm res used as the load for 60dB LOMC use. I added a pair of parallel input RCAs for loading plugs ... and this necessitated putting the PCB in to a HiFi2000 metal box (instead of the plastic box the Bugle2 comes in).)


Regards,

Andy
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To make an smps with low enough emissions beyond a silent rail in the first place so to house it in the same box even its something that Linn does after years of development and at a cost. I am not sure there are off the self units capable to do best in MC phono without any compromise, but I have not investigated. If it is about an amp I get the size & weight gains but on a phono it becomes moot to even risk a chance for EMI.
 
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