Phono Preamp Question... - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, 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
Thread Tools Search this Thread
Old 22nd December 2014, 08:39 PM   #1
diyAudio Member
shredhead's Avatar
Join Date: Aug 2011
Location: NC
Question Phono Preamp Question...

Hi everybody,

I've been looking for simple schematics for a phono pre for a friend's setup and this one is about the least busy one I've found in the datasheet for the LM4562 opamp. I just don't understand the values that are circled in red. Are the resistors values supposed to be put in series with one another and that's why they have "+" signs? Are the cap values supposed to be put in parallel with one another and that's why they have "/" separating them? I've never seen this in a schematic yet.

It says that this is a passive design and seems fairly simple. Has anyone out there put this together and had success with it's curve being close to the RIAA standard?
Attached Images
File Type: png Phono Pre.png (32.3 KB, 421 views)
  Reply With Quote
Old 22nd December 2014, 08:55 PM   #2
SY is offline SY  United States
On Hiatus
SY's Avatar
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 2
Yes, you got it, the + means series, the \\ means parallel. You can use the RIAA calculator at to check the values for conformance.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
  Reply With Quote
Old 22nd December 2014, 09:46 PM   #3
Xoc1 is offline Xoc1  United Kingdom
diyAudio Member
Xoc1's Avatar
Join Date: Nov 2008
Location: Devon UK
The 5% spec for the capacitors seems wide given that the 500 pf is only 2.3% of the 22nf. This makes sense if you use 1% caps.
The circuit has gain to DC which could be a problem.
A 100R resistor on the output might help if it is connected to a lead.
  Reply With Quote
Old 30th December 2014, 11:39 AM   #4
reuben is offline reuben  United States
diyAudio Member
Join Date: Mar 2006
Location: on top of the hill where the reception is better
I built one and the equalization sounds spot on.

  Reply With Quote
Old 30th December 2014, 12:11 PM   #5
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
The tolerance of the resistors is just as important as the tolerance of the capacitors.

If one needs 2% tolerance, then all the RIAA components should be to this tolerance.

If one can "make do" with 5% tolerance then all the components can be 5%.
regards Andrew T.
Sent from my desktop computer using a keyboard
  Reply With Quote
Old 30th December 2014, 01:29 PM   #6
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
Not quite true. 5% tolerance on components may mean 10% tolerance on time constants. As high tolerance resistors are generally more easily available and cheaper than high tolerance capacitors there is a valid case for using, say, 1% resistors with 5% capacitors to get 6% accuracy. In addition, an RIAA network may use resistors to set the balance between LF and HF levels, while some capacitors may just set the transition frequency between these. Hence a cap value error may cause less change in response than a resistor error.
  Reply With Quote
Old 31st December 2014, 09:31 AM   #7
diyAudio Member
Join Date: Apr 2014
Location: Italy friuli
Default interferencies

But the poles and zeros of transfer fuction are more influenced by tollerace of components if a network is une for all ?
  Reply With Quote
Old 31st December 2014, 09:42 AM   #8
diyAudio Member
Join Date: Apr 2014
Location: Italy friuli
But what is the interferences from poles and zeros on the transfer function if values are affected by a large tolerance on resistors and caps ?
I think is possible to have a increase the precision of response dividing the poles one by one on its opamp . Is not best solution but is possible to use 5% tolerance components
  Reply With Quote
Old 31st December 2014, 11:36 AM   #9
Bonsai is offline Bonsai  Europe
diyAudio Member
Bonsai's Avatar
Join Date: Jul 2003
Location: Europe
Even with 1% resistors the non-conformance can be very high.

I think you need to parallel 1% caps and select the resistors for anything like accurate equalization - seems Self and a few others also came to this conclusion before I did.
bonsai and DIY here

Last edited by Bonsai; 31st December 2014 at 11:38 AM.
  Reply With Quote
Old 31st December 2014, 10:29 PM   #10
diyAudio Member
shredhead's Avatar
Join Date: Aug 2011
Location: NC
That's good news Reuben. I will probably order the parts I need for this project this weekend. I always use 1% R's and I'll go with 5% caps. I probably have enough film caps laying around to hit closer to the mark if it ends up being too far from what value it should be.

Thanks SY for that kabusa site reference to double check the values. I'll post up a frequency response for this circuit when it is finished.

Last edited by shredhead; 31st December 2014 at 10:36 PM.
  Reply With Quote


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
Phono Preamp PCB wanted - Transcendental Sound Grounded Grid Phono Preamp nathanjh13 Analogue Source 0 14th June 2012 10:19 AM
Noob Question: Phono Preamp Ducs Tubes / Valves 1 12th April 2012 01:54 AM
Question about phono preamp schematic jn2630 Tubes / Valves 11 3rd January 2008 01:36 AM
Art DjPreII Phono Preamp , some question about it thinker10 Analogue Source 4 23rd October 2007 01:01 AM
Phono preamp question ionutg Analogue Source 6 22nd February 2005 08:28 PM

New To Site? Need Help?

All times are GMT. The time now is 06:04 AM.

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