His Master's Noise: A Thoroughly Modern Tube Phono Preamp - Page 20

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.

25th November 2014

spinning wheel

diyAudio Member

Thx SY !

I have too many carts around here , usualy not happy with a couple hundred pf load . Is there another way to get the circuit more versatile for a large range of MM / MI carts ? I know there's some math involved here .. but would a sort of 1:1 or small ratio step up isolation transformer solve things for MM/MI ?
For MC's I have a pair of Lundahl LL9206 suts laying around here , also a pair of LL1676 Mic / line amourphe inp xfrs that may be usefull

THX
Paul

30th November 2014

spinning wheel

diyAudio Member

Excuse me SY , I have missed the other circuit meant for MM use . but all clear now

So here another thought of mine . suppose I would use the circuit with resistive 47K or 100K load at the input grid for MM carts ( I do realize the noise penalty ) , but using the 1:1 amorphous core input xfr ( thus with the resistive grid load across the primary ) ... will there still be a benefit due to the isolation from circuit ground ??

TIA
Paul

1st December 2014

Brinkman

diyAudio Member

You might want to consider going to the linear audio website and purchasing both articles pertaining to the Equal Opportunity phono preamplifier. I too was inching my way towards building the HMN (for MC duty) but also like the idea of having a preamp suitable for balanced operation of both MM and MC. Adding a SUT to the Equal Opportunity accomplishes this so I have thusly changed course.

1st March 2015

jackinnj

diyAudio Member

SY -- did you ever get around to trying the 6SL7 in this --

1st March 2015

On Hiatus

No, I'm piled deep in uncompleted projects.

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

8th March 2015

Tfan69

diyAudio Member

It is possible to adjust the HMN for use with MM cartridges without need to redesign in whole? maybe just using s different transformer at the input or just removing it and changing R1 to 47K?

8th March 2015

On Hiatus

That's been the most commonly asked question in this thread. The answer is sorta, but it's not a great option. You lose the advantage of balanced in (and thus common-mode rejection) and the input capacitance is quite high, a problem with many MMs. This is what led to the development of the Equal Opportunity preamp, optimized for MM. It was published in Linear Audio (volumes | Linear Audio) where the PCB files and layout are also hosted.

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

8th March 2015

Tfan69

diyAudio Member

thanks for your reply SY. The high capacitance is inherent to the D3a? because i was eager to use that tube...

8th March 2015

On Hiatus

Yes, any high mu triode will have correspondingly high Miller effect.

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

8th March 2015

Tfan69

diyAudio Member

I see.... thanks!!