Trafomatic RIAA network. Any good? - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th May 2017, 09:38 PM   #1
JordiMB is offline JordiMB  Spain
diyAudio Member
 
Join Date: Jul 2014
Default Trafomatic RIAA network. Any good?

While studying different RIAA deemphasis sistems (because learning is fun) I've found this phono stage that uses a different aproach:

6moons audio reviews: Trafomatic Audio Reference Phono One

The RIAA network is neither in the feedback path nor in the classic passive filter between stages. It's in the plate load. Maybe some of you were aware of it, but for me it's the first time I see something like this. Well, it makes sense, and it seems to work allright.

I've made a very quick simulation on LTSpice, using jfets instead of tubes, and with some tweaking of resistors and capacitors values I've obtained a decent result (not accurated, just promising). What it can be appealing is that you lose a lot less signal than with a passive filter.

Can it be a good alternative system, or has it been tried before and has it been rejected for not being good enough?

Last edited by JordiMB; 9th May 2017 at 09:39 PM. Reason: misspelling editing
  Reply With Quote
Old 9th May 2017, 10:27 PM   #2
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Cascais
Check out the last circuit in this thread

:: View topic - Pentode Phono

It is about the only way to build an entire phono preamp in a single stage. Having listened to a proto based on the idea i can attest to its viability. In fact it was remarkably good.

The idea is of course not new. Historic phono preamps have been built using frequency dependent loaded pentodes. If not mistaken one of Creek Audio's phono stages employed the same idea using transistors.
  Reply With Quote
Old 10th May 2017, 03:41 AM   #3
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
> nor in the classic passive filter between stages. It's in the plate load.

Electrically it is the same thing.

With triodes it is dubious because internal plate resistance is not known exactly. With pentodes the internal resistance is generally so much greater than the external DC resistor that we can work with resistor-based accuracy.
  Reply With Quote
Old 10th May 2017, 04:45 AM   #4
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Dht Rob built it and recommended it to me. So I'll build one...

Sent from my Nexus 6P using Tapatalk
  Reply With Quote
Old 10th May 2017, 06:52 AM   #5
JordiMB is offline JordiMB  Spain
diyAudio Member
 
Join Date: Jul 2014
Quote:
Originally Posted by PRR View Post
> nor in the classic passive filter between stages. It's in the plate load.

Electrically it is the same thing.

With triodes it is dubious because internal plate resistance is not known exactly. With pentodes the internal resistance is generally so much greater than the external DC resistor that we can work with resistor-based accuracy.
Interesting. That's the reason they used pentodes. Worth exploring, even you can use jfets or mosfets...

Last edited by JordiMB; 10th May 2017 at 06:56 AM.
  Reply With Quote
Old 10th May 2017, 07:24 AM   #6
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Cascais
Quote:
Originally Posted by PRR View Post
Electrically it is the same thing.
Is it? The frequency dependent load never allows full swing at high frequencies as it controls the gain. Overload performance cannot be equal.
  Reply With Quote
Old 10th May 2017, 09:33 AM   #7
JordiMB is offline JordiMB  Spain
diyAudio Member
 
Join Date: Jul 2014
From what I've seen in the simulation, you don't lose as much gain as with the classic passive filter. So maybe it's possible to make a phono preamp with only one gain stage. Interesting what analog_sa says: this kind of riaa network can prevent from overload at high frequencies, no?
  Reply With Quote
Old 11th May 2017, 12:55 PM   #8
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
If you use a voltage amplifier with low output impedance (e.g. a triode) then you need to add a series resistor to define the source impedance, then add the RIAA network.

If you use a transconductance amplifier with high output impedance (e.g. pentode or cascode) then you need to add a shunt resistor to define the source impedance, then add the RIAA network.

I can't see much difference between these two approaches. With the latter you may have to be more careful about PSRR because you probably want to take your final output voltage referenced to ground but the pentode version uses the supply rail as reference.
  Reply With Quote
Old 12th May 2017, 07:29 PM   #9
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Cascais
Another great example

Schematic riaa corrector
  Reply With Quote
Old 12th May 2017, 07:35 PM   #10
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Cascais
And another from forum member Wavebourn

Linearity
  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 network adjustment Sempati Tubes / Valves 33 30th April 2015 08:33 AM
RIAA Network Position payloadde Tubes / Valves 97 3rd October 2014 09:39 AM
Re- calculating RIAA network limono Tubes / Valves 12 11th July 2014 11:46 AM
RIAA Network Transfer Function BRSHiFi Software Tools 23 28th March 2012 02:09 PM
caps for RIAA network GAK Parts 2 8th February 2004 11:05 PM


New To Site? Need Help?

All times are GMT. The time now is 07:47 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki