Phono preamp without confusing RIAA stuff - Page 2 - 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 13th February 2010, 06:36 AM   #11
sled108 is offline sled108  United States
diyAudio Member
 
sled108's Avatar
 
Join Date: May 2008
Location: Deep in the Heart of North Jersey
Just go Here..And use what you have..

The Phonoclone and VSPS PCB Help Desk
  Reply With Quote
Old 17th February 2010, 03:39 PM   #12
PLB is offline PLB  United Kingdom
diyAudio Member
 
Join Date: Sep 2008
Location: The backbone of England
Hi PhantomBox,

Here in USA, we celebrated Presidents Day on Monday (didn't have to work that day) so I took the chance to check out the circuit of the "PAiA - RIAA phono preamp kit" and derived a mathematical model for it. This model defines its transfer function, which I then used to find the idealized component values, by equating its coefficients with those of the RIAA curve.
Are you still interested in using the "PAiA - RIAA phono preamp kit" if I were to provide you with the correct component values ?

Regards

Peter
  Reply With Quote
Old 17th February 2010, 05:19 PM   #13
diyAudio Member
 
Join Date: Jan 2008
Sure. I'm always open for ideas. More so if you took the time to check and optimise the RIAA phone preamp (thanx a lot). Can you send the values through the forum so anyone could use the info or do you need an email address?
  Reply With Quote
Old 18th February 2010, 06:17 AM   #14
PLB is offline PLB  United Kingdom
diyAudio Member
 
Join Date: Sep 2008
Location: The backbone of England
Hi PhantomBox,

No, I donít mind sharing these results with you and any other DIYAUDIO member.
Here are the changes, which I've referenced to the schematic you linked to in your first post ie, PAiA - RIAA Phono Preamp Kit

Change C3/C8 from 47uF to 220uF
Change C4/C9 from 1nF to 2.136nF
Change C5/C10 from 4.7nF to 6.247nF
Change R4/R8 from 68K to 38.02K

With these value changes entered into a Spice simulation I was able to verify the compliance of the response to within +/-0.05dB compared to the response of the RIAA standard.
The value of C4/C9 can be constructed by paralleling a 1.8nF with a 330pF, C5/C10 can be constructed by paralleling a 5.6nF with a 680pF and for R4/R8, a 38.3K can be used.
I suggest that you use +/-2% tolerance or better for the capacitors (except C3/C8) and for resistors, use +/-1%.
The value of C3/C8 has been made large so as to minimize the low frequency droop that would otherwise result with the original value of 47uF.
However, with a 100uF capacitor, a loss of only 0.15dB at 20Hz results, but of greater benefit would be the increased attenuation of unwanted signals caused by record warp. In other words, it will provide a better rumble filter.
As is common with this circuit topology there is an extra zero in the transfer function that is located at just over 212KHz. At 20KHz, the effect of this extra zero is quite minimal and for the circuit values Iíve given you above, a rise in the response of about 0.03dB is observed together with a phase change of 5 degrees. Hope all this helps.

Have fun.

Peter
  Reply With Quote
Old 18th February 2010, 12:33 PM   #15
diyAudio Member
 
Join Date: Jan 2008
Thanks Peter.
Since the capacitor values are a little hard to find (YV = a tough place) I will comment to you as soon as I have made out a supplier. Would C4/C9 work with 2 x 1nF in parallel and C5/C10 with 4.7nF + 1nF in parallel?
  Reply With Quote
Old 18th February 2010, 03:36 PM   #16
mlloyd1 is offline mlloyd1  United States
diyAudio Member
 
mlloyd1's Avatar
 
Join Date: Feb 2001
Location: illinois
i'd add 150pF to the 2x1nF

also, 4.7nF + 1.5nF is closer if you can find the 1.5nF

good luck,
mlloyd1
  Reply With Quote
Old 19th February 2010, 04:07 AM   #17
PLB is offline PLB  United Kingdom
diyAudio Member
 
Join Date: Sep 2008
Location: The backbone of England
Hi PhantomBox,

Iím not sure I understand your question, so I will give you two scenarios.

With reference to the attached Spice simulations, the blue curve shows the response if all of the component values are changed to the ones I posted, except C4/C9 and C5/C10, which I have made 1nF+1nF and 4.7nF+1nF respectively (as in your post).
The red curve shows no components having been changed except C4/C9 and C5/C10, which I have made 1nF+1nF and 4.7nF+1nF respectively.

These responses are error responses relative to the RIAA curve.

Regards

Peter
Attached Files
File Type: pdf PAiA topology RIAA 2.PDF (28.6 KB, 187 views)
  Reply With Quote
Old 5th November 2012, 10:53 AM   #18
diyAudio Member
 
Join Date: Nov 2012
I'm thinking about buying the PAiA RIAA kit, and change the component values as suggested by PLB.

But then I found this:
Circuits Online - Schakelingen - RIAA phono voorversterker

It's the same circuit as the PAiA RIA, but with the 1nF cap wired differently.
Could it be that PAiA have simply made a small error in their schematic?
Does the Circuits Online version match the RIAA standard more closely than the PAiA version?
  Reply With Quote
Old 5th November 2012, 07:37 PM   #19
diyAudio Member
 
Join Date: Nov 2012
Nahh, I guess it's just as bad as the PAiA version.

I'll try to get hold of the approximated component values. I'm thinking of something in the line of:

C4/C9 = 2000pF polystyrene || 130pF silver mica
C5/C10 = 6200pF polystyrene || 47pF silver mica
R4/R8 = some serial combination to get ~38ohm.

That should work, right?
  Reply With Quote
Old 15th March 2014, 07:47 PM   #20
diyAudio Member
 
Join Date: Mar 2014
Default Phono pream fuzzy sound

Hi guys,
I just finished my diy phono preamp based on the exactly same circuit. Haven't experiment with any moddifications yet but unfortunally I noticed this distortion problem expecially in the vocal region. Any suggestions what can be the reason for this ?
  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
Simple Single Supply Phono RIAA opamp preamp audiomodder Analogue Source 13 6th November 2012 04:15 PM
Noise on the RIAA phono preAmp diarav Chip Amps 3 23rd March 2007 05:27 AM
RIAA phono stage KevinTams Tubes / Valves 10 16th May 2005 01:05 PM
Tubed RIAA phono stage shif Analogue Source 7 30th June 2004 06:22 PM
RIAA phono preamp using single ECC83 DJG Tubes / Valves 19 29th March 2003 02:27 PM


New To Site? Need Help?

All times are GMT. The time now is 08:49 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