BC550 BC560 Very low noise RIAA - 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 3rd December 2006, 07:24 AM   #1
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Smile BC550 BC560 Very low noise RIAA

.

Hello, lineup here.

By paralleling low noise transistors, we can lower the noise further.
There is a formula for this. Number of parallel devices and dB lower noise.
But I do not remember.

This RIAA attached should give very good results
even though using only standard components.
4 transistors in parallel.
If course, with adjustments, you can parallel even more.
But the gain in low noise per added transistor
has largest value for the first 4 four.
(Each doubling of number of devices gives same noise improvement in dB)
-----------------

Discrete Op-Amp configuration.
It is using only BC550C BC560C transistors and +-15 Volt regulated.
The output stage works at ~ 9 mA push-pull Class A.

Some approximate data:

Gain at 1 kHz: +35dB, ( x 55 )
THD for 1 kHz, 10mV RMS input, 0.55V RMS output: 0.001%
RIAA curve, Using 1% film caps and 1% resistors: < +-0.20 dB

Max Output: > like 5-7 Volt RMS with distortion ~ 0.01%
Depending on the load.

A good and matching very low noise
regulated dual 15 volt supply is important!
For best results.

Enjoy!

( PS. If somebody would be kind design a nice fit PCB board,
this would make a nice low cost RIAA project for www.diyaudio.com members.
I know there are still plenty of turntables spinning, here and there.
I just don't have the tools to make a PCB myself. DS )

lineup
Attached Images
File Type: png bc550-560-superlownoise-riaa-v1.0.png (27.1 KB, 4459 views)
__________________
lineup
  Reply With Quote
Old 3rd December 2006, 07:35 AM   #2
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
It looks like the Elektor SUPA, decades ago. I made a board long time ago and called it QSX-001 Mark I and II. My design got 160-220 nV noise which is good for a medium level MC cartridge.

My very first QSM-001 http://home5.swipnet.se/~w-50674/hif.../qsxm2_old.jpg
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread ||
  Reply With Quote
Old 3rd December 2006, 08:22 AM   #3
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
Hey LU, I have a few of those, I bought for the class A buffer, but were told they sound too cold in that application, and my VSPS is lying open and semi dissasembled at my feet, as I am no longer happy with the sound, just too bass shy.

I looked at peranders's RIAA amps last night, but they seem terribly hardcore for someone more comfortable with things being only as complicated as they need to be.

Maybe I should spend a few minutes today to give a PCB a try...
We'll see what happens I guess. soo lazy and stoned allready and its not even 12 in the morning.
  Reply With Quote
Old 3rd December 2006, 08:30 AM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
I read a long time ago that adding the other half of the LTP doubles the noise (I don't know if that was +3db or +6db).

On that basis, removing the other half should make your circuit quieter and save half of those 550s and 560s.

Now, if it were single sided and single ended would it be quieter still?

BTW,
BC550c has a fairly high Cob for a small signal device. Eight of them is going to be quite a load.
__________________
regards Andrew T.
  Reply With Quote
Old 3rd December 2006, 09:17 AM   #5
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
Shouldn't there be another R like R17 on the other rail too?
  Reply With Quote
Old 3rd December 2006, 09:40 AM   #6
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
The formula for noise reduction is 20*LOG(SQR(N)) where N is the amount of transistors in parallel.

More than eight pairs aren't very useful for this. Better to get low noise JFET's of BJT's.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread ||
  Reply With Quote
Old 3rd December 2006, 09:52 AM   #7
diyAudio Member
 
Holger Barske's Avatar
 
Join Date: Jan 2001
Location: Ruhrgebiet
Quote:
If somebody would be kind design a nice fit PCB board...
I once did an "as compact as possible" pcb for that one.
RIAA caps are Wima FKP2, output cap is 2µ2 Wima - forgotten what type.
Attached Images
File Type: gif supra.gif (21.1 KB, 3613 views)
__________________
Best regards: Holger
www.holgerbarske.com - Deutschsprachiges Paradise-Support-Forum
  Reply With Quote
Old 3rd December 2006, 10:48 AM   #8
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
couldn't beat that layout if I tried
  Reply With Quote
Old 3rd December 2006, 12:37 PM   #9
diyAudio Member
 
Holger Barske's Avatar
 
Join Date: Jan 2001
Location: Ruhrgebiet
Thx Nordic.
Maybe there's some work to be done on it, some traces have very small clearance towards their neighbours. I am willing to do so if there's some interest.
__________________
Best regards: Holger
www.holgerbarske.com - Deutschsprachiges Paradise-Support-Forum
  Reply With Quote
Old 4th December 2006, 04:59 AM   #10
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
Wouldn't mind, especialy if you include board files.
  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
BC550 & 560's needed + 4558L Zero Cool Swap Meet 3 19th May 2007 07:00 PM
Noise on the RIAA phono preAmp diarav Chip Amps 3 23rd March 2007 05:27 AM
Who's measured the noise on their RIAA preamp? CeramicMan Analogue Source 20 19th February 2004 06:35 PM
try Pass preamp's with BC550!! tschrama Pass Labs 2 4th September 2001 08:37 AM


New To Site? Need Help?

All times are GMT. The time now is 04:27 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