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Review and Measurements of u-turn Pluto and ART DJPRE II Phono Preamps

SIY

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#41
The "classic" tube RIAA circuits were... not good. At least if you want objectively good performance. Insufficient open loop gain for good conformance to the RIAA curve and low distortion, heavy loading of the circuit by the RIAA network, high input capacitance.

The MC preamp I published at diyAudio ("His Master's Noise") used a D3a and ECC88-family tubes for gain, as well as a balanced input transformer. The MM stage I published in Linear Audio ("The Equal Opportunity") used ECC88-family for gain.
 
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#42
The "classic" tube RIAA circuits were... not good. At least if you want objectively good performance. Insufficient open loop gain for good conformance to the RIAA curve and low distortion, heavy loading of the circuit by the RIAA network, high input capacitance.

The MC preamp I published at diyAudio ("His Master's Noise") used a D3a and ECC88-family tubes for gain, as well as a balanced input transformer. The MM stage I published in Linear Audio ("The Equal Opportunity") used ECC88-family for gain.
 
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#43
Thanks again - I'll look for your MM design. What do you think of Hegeman's approach with EC83/12ax7 cascade feedback pair driving a passive RIAA filter?
 

SIY

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#44
Can you reference a schematic?
 

SIY

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#46
OK, the Citation; I've owned one and modified several. There are worse out there, but one can do much better these days. There's a lot of constraints in that design that wouldn't apply now.

Source impedance is relatively high, current source/sink capability of the output is severely limited, input capacitance is relatively high, and distortion is OK-not-great. Ditto noise. The need for lots of different switchable EQ curves is not a plus for reliability or noise.

A couple of 5534s will run rings around this.
 
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#47
OK, the Citation; I've owned one and modified several. There are worse out there, but one can do much better these days. There's a lot of constraints in that design that wouldn't apply now.

Source impedance is relatively high, current source/sink capability of the output is severely limited, input capacitance is relatively high, and distortion is OK-not-great. Ditto noise. The need for lots of different switchable EQ curves is not a plus for reliability or noise.

A couple of 5534s will run rings around this.
I've thought about making the bare RIAA circuit then using an "anode-follower" in the Hegeman fashion. It says a lot that a couple of 5534's can beat this - so assume objectively they would also be superior to most ARC and CJ designs.
 

SIY

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#48
There's nothing special about ARC and c-j. Other than the price and the hype. Something like the Self 5534 preamp will spectacularly outperform anything those companies made that I'm familiar with.
 
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#49
There's nothing special about ARC and c-j. Other than the price and the hype. Something like the Self 5534 preamp will spectacularly outperform anything those companies made that I'm familiar with.
:) - are there boards available for that preamp? - anything close in topology ?
 

SIY

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#50
Dunno, I can't see attachments there since deleting my registration, but he showed the circuits in his excellent book Small Signal Audio Design. I believe that the Precision Preamp from 20 years ago is basically the same.
 
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#51
Dunno, I can't see attachments there since deleting my registration, but he showed the circuits in his excellent book Small Signal Audio Design. I believe that the Precision Preamp from 20 years ago is basically the same.

Thank you very much for the info and your time - I assume its not just one opamp with loop RIAA feedback (?)
 

SIY

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#52
That's the core of it. His MC version has a discrete bipolar transistor input, and he uses a unity gain opamp as an output buffer. It's a very straightforward and competent design, thus no good for the fashion audio set. Great for the rest of us. ;)
 
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#53
That's the core of it. His MC version has a discrete bipolar transistor input, and he uses a unity gain opamp as an output buffer. It's a very straightforward and competent design, thus no good for the fashion audio set. Great for the rest of us. ;)

I think there was one (MM op amp) like that back in Audio Amateur Magazine - I have an early "Lounge Audio" phono stage which "sounds good"
 
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#59

thanks again - its kinda telling that a whole preamp can be bought from China including shipping vs what it cost to ship a little pack
from Australia to the US. IF it still works, I have an old switchable frequency VSP-Labs highpass filter and used to have the preamp
 

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#60
@amirm Running the ART on a 12V DC battery supply is a very popular mod in the diy community for this preamp. If you by chance still have the ART would love to see a test with the art powered by a battery. curious to see if that might do anything to the phase shift.
Thanks!
 
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