His Master's Noise: A Thoroughly Modern Tube Phono Preamp - Page 15

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.

5th November 2012

PET240

diyAudio Member

Gday Sy,

Still haven't heard from Mr Gregory, will email again to be sure, anyway, asa thought, had you looked at the 6N2P tube? If the D3a is all over the shop, not sure the sound or ease of use, im sure you would know by looking at it.
Also, if I wanted to get a balanced output, what's the process here?

Thanks,

Drew.

5th November 2012

On Hiatus

Easiest way to get a balanced output is to use a transformer. Otherwise, you're looking at adding another stage. IMO, balanced brings nothing to the table between preamp and power amp for home installations.

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

20th February 2013

luvdunhill

diyAudio Member

Many, if not all phono preamps for MC have switchable loading resistors. I'm curious, is that not needed in your opinion, or is there something about the design that makes this unnecessary?

20th February 2013

On Hiatus

My experience with low output MC is that they tend to be very noncritical of loading. If you do want to play with that, do it on the primary side of the input transformer.

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

22nd February 2013

gortnipper

diyAudio Member

I just inherited a nicely built up HMN that a a late friend of mine did last year before he passed.

He built it up with Jensen JT-44K-DX transformers, but he did not add the Jensen recommended Zobel after the secondary.

https://www.jensen-transformers.com/datashts/44kdx.pdf

Now, I have these same transformers in a standalone SUT I have used for years with various carts (with varying degrees of success), and it uses the recommended implementation.

In the HMN w/o the Zobel , the sound is very bright and the bass is very thin in comparison - which is consistent with what I have read should be the case in this type of standalone implantations of the JT-44K-DX w/o it.

Do you forsee any issues in adding this immediately after the tx secondary in the HMN?

22nd February 2013

On Hiatus

No, I don't see an issue- if you want to be thorough, load the transformer with the proposed Zobel and ~100pF in parallel, then drive it with a square wave from a source impedance equal to the DCR of your cartridge at 0.1mV or so (a resistor voltage divider is your friend here!). See what the square wave looks like.

While you're at it, double check that the EQ components are all correct.

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

23rd February 2013

gortnipper

diyAudio Member

"While you're at it, double check that the EQ components are all correct."

This may be beyond my nascent abilities. See the attached pics that show a break in the traces on the board adjacent to C7. From the wiring coming from the output end of the board, it looks like the two boards on the end of the chassis have been inserted into this break point.

I will have to figure out what these are for.

Any ideas?

23rd February 2013

gortnipper

diyAudio Member

OK, so the photos I attached earlier didnt show up. You can see them here - Flickr: gortnipper's Photostream

6th April 2013

SMOTH

diyAudio Member

Hey there...

I'm a bit new to this of thing... I've read the article several time and I love the sounds of this project! I'm just wondering if I could build this for a mm cartridge, and skip the need for a step up transformer? If that would indeed work, would I have to make any further modifications? Apologies if this is a rudimentary question, and thanks in advance for any advice.

7th April 2013

On Hiatus

Two caveats: first, you obviously lose the advantages of the balanced input. Second, the input capacitance is quite high, which some MM cartridges tolerate and some don't.

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