Balanced Fet phono? - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

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 1st April 2006, 05:04 PM   #1
tubee is offline tubee  Netherlands
diyAudio Member
 
tubee's Avatar
 
Join Date: Jul 2004
Location: Netherlands
Default Balanced Fet phono?

I now have a tubed phono pre-amp, but am not completely satisfied by the sound. Very warm sounding, but also sometimes blurry around tones, and distorted compared to other sources due to a lesser harmonic distorsion, eg tuner and CD.
This could be because the phono is a single ended design (2 ECC83 halves with passive Riaa inbetween) The line amp is an 6N1P SRPP, the poweramp E88CC SRPP and cap coupled to two good old & big Hitachi TO-3 powerfets per channel.

All Power supplies are single and with a choke, only the fets have a balanced PS, so in all stages the second harmonic is emphasised, except in the last Fet-stage, wherein the uneven harmonics are amplified due to the balanced design. There is no overall feedback whatsover, only local feedback on some places, a decoupling cap over cathode resistor.

So now i have 3 "even" stages in my ampl. chain and 1 "uneven"

I am thinking of a balanced fet phono MC\MM phono stage to replace the tubed phono. This to combine "uneven harmonic" amplifier stages with "even harmonic stages" to reduce overall distorsion. Even harmonics are better to listen to, but it still is distorsion.

What do you here thinks of this?
__________________
Daisy Bell
  Reply With Quote
Old 22nd April 2006, 05:49 PM   #2
tubee is offline tubee  Netherlands
diyAudio Member
 
tubee's Avatar
 
Join Date: Jul 2004
Location: Netherlands
Well, has somebody a thought on this?
(combine single-ended stages with balanced ones, to reduce overall distorsion in an amplifying chain)
__________________
Daisy Bell
  Reply With Quote
Old 6th May 2006, 04:45 PM   #3
diyAudio Member
 
Join Date: Mar 2005
Location: Rimini
Dear friend,
this is the classic monotube preamp.
Some times ago there was a beautiful article on Audiophile written by Hiraga whrw you should understand how much difficult is build a phono pre with a single tube.
The distorsion is probably due to need to have maximun gain from tubes.Much gain mean much distorsion and consider tou throw gain with passive eq.Simply add another tube e retouch the gain in the stages.
You should have a fast confirmation of this removing the passive riaa eq and use a feedback riaa.
Ciao

cicero32
  Reply With Quote
Old 6th May 2006, 06:21 PM   #4
tubee is offline tubee  Netherlands
diyAudio Member
 
tubee's Avatar
 
Join Date: Jul 2004
Location: Netherlands
Ok thanks Cicero32. This is an other approuch to the theory. The designers of the phono stage had its reasons to choose a passive riaa. Will search out what reasons.
__________________
Daisy Bell
  Reply With Quote
Old 8th May 2006, 04:27 PM   #5
diyAudio Member
 
Join Date: Mar 2005
Location: Rimini
Dear tubee,
If you want use passive riaa it's better have a coumpound stage and not a single tube.The first stage must have high gain, high acceptance and low noise.All request are conflicting! In your design you should have 30- 35 dB in first stage and you throw it away with passive Riaa (-30dB).Try the feedback riaa, or feedback tout court. If pre sound better this is reason of your muddy sound and you can consider what configuration you want.
cascode or SRPP - passive RIAA - cascode or SRPP.
ciao cicero

P.S. I apologize for my poor english linguage
  Reply With Quote
Old 8th May 2006, 04:46 PM   #6
diyAudio Member
 
Audiofanatic's Avatar
 
Join Date: Oct 2002
Location: The Netherlands, Utrecht
Default Pass

Hi Tubee,


Why don't you try a Pearl stage.
This is one of the best Phono stage I've ever listen to for the $$$


Best regards,



Audiofanatic
__________________
Be nice to animals.
  Reply With Quote
Old 9th May 2006, 08:21 AM   #7
emw is offline emw  Germany
diyAudio Member
 
Join Date: Oct 2004
Look at the Borbelyaudio.com site.
Very very good balanced phono kit.
Best...EMW
  Reply With Quote
Old 9th May 2006, 06:32 PM   #8
diyAudio Member
 
Join Date: Mar 2005
Location: Rimini
In my opinion Borbely sound bad, too much feedback.
The tubee preamp sound bad cause it's a wrong design.
You should split Riaa passive network with another stage.
(and correct phasing).

cicero32
  Reply With Quote
Old 9th May 2006, 09:53 PM   #9
tubee is offline tubee  Netherlands
diyAudio Member
 
tubee's Avatar
 
Join Date: Jul 2004
Location: Netherlands
Hello all

Nice to have so much reactions!

The design-goals of the phono was to build it as simple as possible. They wanted a srpp first, but choosed a single stage. The first stage, 1st halve of ECC83 (Old Philips tubes) amplifies about 35dB, then a cap + resistor and one cap for RIAA (thats all!) and then 2nd halve which does about 25-30 dB to amplify the riaa loss. ( i fitted a decoupling cap over both cathode resistors to get some extra dB's, i have a Benz Gold with moderate output. The designer advised a cap for first stage only, a cap for 2nd stage only with low output carts.
I think i fitted Elna cerafines, not sure.

The line stage is SRPP, as the first stage of the hybrid poweramp. This is the reason why i don't want another srpp for the phono. A common cathode would be better i think, if this is possible for a phonostage.
Another fact: i have no feedback at all, not in phono, pre stage nor hybrid amp. I could try a small feedback in the phono stage and see what happens. Also a Sovtek 12AX7 could give some extra, but tried Haltron's no improvement, so the Sovtek won't either i think.
__________________
Daisy Bell
  Reply With Quote
Old 10th May 2006, 11:03 AM   #10
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
I think the problem with your existing phono stage is not that it is unbalanced or that it is valve or that it uses passive equalisation (I use all three of these things), the problem is the ECC83. ECC83 has high ra (typically about 80k or so) so it has to be included in the design of the passive RIAA. Trouble is, it forms a rather large proportion of the series resistance in the RIAA network but it varies. It is most likely that you have inaccurate RIAA and that is why it sounds lush.

It may also be that the RIAA stage is distorting due to inadequate HT voltage or poor gain structure, but without a diagram it's not possible to comment fully.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  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
balanced phono stage? ericpeters Analogue Source 21 6th July 2012 12:21 PM
Help - Balanced Pearl Phono Irakli Pass Labs 15 19th November 2007 04:22 AM
Minimalist balanced phono preamp? leadbelly Analogue Source 10 17th April 2005 08:08 PM
transducer's balanced phono amp peranders Analogue Source 0 15th February 2003 09:03 AM
Balanced Phono Stages reinhard Pass Labs 2 24th March 2002 04:46 AM


New To Site? Need Help?

All times are GMT. The time now is 11:05 PM.


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