Go Back   Home > Forums > Commercial Sector > Manufacturers > Twisted Pear

Twisted Pear Superior quality electronic kits

Reply
 
Thread Tools Search this Thread
Old 2nd October 2009, 03:19 PM   #11
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
HI PD all good points.

And here is something I had thought about.

I am thinking I may make two versions.

A MC version with a op1632 front end. This cct would have basically close to 0R input impedance. It would really be an I/V stage. This of course would not be at all optimal for MM cartridges. But great for MC.

I can certainly go higher gain with the front end with the cct shown and with lower Rs, but I just have not tried that yet.

It is a trade off between being able to support both MM and MC on one board, or best performance for each MM and MC using two boards.

I think my inclination right now is the latter.
__________________
Less pulp more juice Twisted Pear Audio.

Last edited by Russ White; 2nd October 2009 at 03:24 PM.
  Reply With Quote
Old 2nd October 2009, 03:34 PM   #12
diyAudio Member
 
PigletsDad's Avatar
 
Join Date: Jul 2007
Location: South Worcestershire
One possible compromise that I have used (about 25 years ago!) is two frontends , and switch between them.

In my case, there were flat frequency response gain boards - from memory something like 20dB for MM, and 46dB for MC. The output of a switch went to the eq board; this had a passive 75us low pass, and the other time constants in the feedback loop of the second gain stage.

Another point - the design as shown is DC coupled. Depending on arm+cartridge and vinyl flatness, you can get some scary big subsonics. My own feeling is that you want at least one high pass time constant somehere; I went for about 10mS (16Hz -3dB) as it loses little audible, but is rolling off fairly well by the time you get to warp related stuff (harmonics of 0.5Hz). Some designs have multiple time constants; this trades phase shift for better supression of subsonic manure.
  Reply With Quote
Old 2nd October 2009, 03:43 PM   #13
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
PD,

Another excellent point on the high pass.

One way I had though about tackling this was to apply a symmetrical integrator (servo) with a relatively high corner. I was thinking 10-16hz.

This would have two advantages. It should remove any differential DC introduced at either the first or second stages due to input currents, part matching ,etc... and it would act as a high pass.

Any thoughts on this approach?
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 2nd October 2009, 04:01 PM   #14
diyAudio Member
 
PigletsDad's Avatar
 
Join Date: Jul 2007
Location: South Worcestershire
Should work, and avoids the need for large matched caps to protect CMRR at 50/60Hz.

As the gain at DC for an MC is very high (60dB), even normal input offsets of a few 100uV or so turn into worryingly large values unless you do something like it.

Never done it that way myself. I guess there are some issues to check in terms of startup behaviour and recovery from overload, but a short time constant should fix pretty much all ills.
  Reply With Quote
Old 2nd October 2009, 06:56 PM   #15
diyAudio Member
 
Join Date: Feb 2009
If MC gain is too daunting, perhaps consider an MM board with step up transformer. Myself, I'm pleased to see a balanced phono stage offered. I use an OC9 cartridge and would choose the MC board if available. Will this work from Placid supply?
  Reply With Quote
Old 2nd October 2009, 07:34 PM   #16
diyAudio Member
 
Holger Barske's Avatar
 
Join Date: Jan 2001
Location: Ruhrgebiet
Quote:
Will this work from Placid supply?
For sure.
__________________
Best regards: Holger
www.holgerbarske.com - Deutschsprachiges Paradise-Support-Forum
  Reply With Quote
Old 2nd October 2009, 07:48 PM   #17
krgaunt is offline krgaunt  United States
diyAudio Member
 
Join Date: Apr 2008
Default Retro to USB

I have a large vinyl record collection dating back to my first LP purchase in 1964. So I'd like a way to take the Retro output, digitize it (possibly through the ESS 9102 ADC), and then input it into my PC through the USB port. The combination of Retro and a good ADC, would most likely make a large improvement on the digitized recordings I've made with a cheap $99 USB digitizer that I currently have. Russ, any plans to go in this direction, or am I just being nuts?

RossG
  Reply With Quote
Old 3rd October 2009, 02:02 AM   #18
BrianL is offline BrianL  United States
diyAudio Member
 
Join Date: Mar 2002
Location: USA
Default op-amp choice

Russ,

Why not OPA211/2211 or OPA1611/1612? Very similar except the 161x has slightly different internal compensation and not as tight DC specs. Both are supposed to be excellent-sounding and quiet.
__________________
bel
  Reply With Quote
Old 3rd October 2009, 02:18 AM   #19
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Hi Brian,

Yes those are on the list to try out too.

I actually have some samples of the former, and wil get the latter too.

Cheers!
Russ
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 3rd October 2009, 02:20 AM   #20
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Quote:
Originally Posted by krgaunt View Post
I have a large vinyl record collection dating back to my first LP purchase in 1964. So I'd like a way to take the Retro output, digitize it (possibly through the ESS 9102 ADC), and then input it into my PC through the USB port. The combination of Retro and a good ADC, would most likely make a large improvement on the digitized recordings I've made with a cheap $99 USB digitizer that I currently have. Russ, any plans to go in this direction, or am I just being nuts?

RossG

The ES9102 is on the agenda. It will be its own module. It will would work just fine with this cct.
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
RIAA Phono Amp Design Sheldon Tubes / Valves 51 24th December 2007 06:45 PM
how build usb phono pre riaa tekton364 Analogue Source 2 28th September 2007 08:50 PM
WTB: RIAA Phono Stage mrdon Swap Meet 1 19th July 2007 04:00 AM
RIAA phono stage KevinTams Tubes / Valves 10 16th May 2005 01:05 PM
ls-37 MM/MC RIAA Phono Amp from diyclub.biz wuffer Tubes / Valves 2 13th November 2004 04:12 PM


New To Site? Need Help?

All times are GMT. The time now is 03:35 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2