His Master's Noise: A Thoroughly Modern Tube Phono Preamp - Page 18

21st April 2010, 12:00 PM
SY On Hiatus Join Date: Oct 2002 Location: Chicagoland	His Master's Noise: A Thoroughly Modern Tube Phono Preamp After more than 25 years of faithful service, it seemed that it might be time to redo my phono system. After all, I like to think that I've picked up a few tricks in the intervening years... The old system consisted of a VPI HW17-II, a Linn Ittok LVII tonearm, and a Troika cartridge. The Troika was... Click here to read the entire article Last edited by Variac; 2nd April 2011 at 12:17 AM.

30th December 2013

Brinkman

diyAudio Member

Regarding my last post, after a little googling, I have discovered that the noise contribution of an RC network is dominated by the kTC of the capacitor. In the case of the Zobel network Jones recommends, a 500pF cap would introduce about 4uV of noise.

Perhaps the 6k8 input R in combination with the miller capacitance was satisfactory enough to tame the 8055x? Still curious if the circuit was tried with the Zobel network.

30th December 2013

On Hiatus

I left the network out because, with the cartridge I was using, the combo of 6k8 and the input tube's Miller ended up giving me nice looking square waves.

Any noise from the Zobel is shunted by the source impedance, so is somewhat smaller than the noise of the network alone. That's dropped another 20dB as well when it's input-referred.

"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

30th April 2014

6L6

diyAudio Moderator

I'm a bit unclear on the requirements for the input transformers ... I have a set of custom Electra-Prints made for the Denon DL-103, 40ohm input to 100ohm output. Two-wire primary, two-wire secondary. Can those be used?

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30th April 2014

On Hiatus

You'll have to tweak the RC network across the secondary. Do you have a square wave generator and a scope? If so, it's easy and I can walk you through it.

"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

30th April 2014

6L6

diyAudio Moderator

That's it? Awesome! I was concerned about the balanced wiring thing.

Yes, I have a generator and scope.

I'll order the boards from Jack right now.

30th April 2014

On Hiatus

You'll still want to run balanced in- the noise advantage is remarkable. All it takes is making up some cables (I used mike cable) and the right connectors (my prototype used DIN, my "nicer" build uses mini-XLR).

"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

30th April 2014

6L6

diyAudio Moderator

I fully intend to.

4th August 2014

Brinkman

diyAudio Member

What's the lowest rated voltage that would be okay for the output capacitors (C4)?
I have some 160V polystyrene foil capacitors I would like to use...

Thanks!

4th August 2014

On Hiatus

That should work- I like to assume that something will fail, so if the highest voltage present is 160V, the caps will survive.

"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

12th August 2014

Brinkman

diyAudio Member

SY-
I just noticed on some other threads that you have been using the Denon DL-103R cartridge. I had intended on using this same cart with HMN as it looks to have specs that would make it well-suited for the Sowter 8055 front end.

Can you tell us anything about your experiences using the DL103R in conjunction with HMN?

Thanks!