Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Passive Preamp (H.H. design) problem
Passive Preamp (H.H. design) problem
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 4th January 2004, 05:48 AM   #1
soneil is offline soneil  United States
diyAudio Member
Join Date: Jan 2004
Location: Michigan
Default Passive Preamp (H.H. design) problem

I've built of version of a passive preamp described here by HarryHaller. It works fine, except for the fact that when I turn the volume up it starts to distort quite a bit on the louder passages in the music.

Instead of the 2 series 22k resistors which he used for each, I've used a single 10k one, and I've also got a double-gang 100k pot instead of 2 single gang ones, which I got from Radio Shack. I'm using pretty cheap copper wire, and nearly six inches of it, so I'm sure that isnt helping. If I jumper over the 10k resistors the problem is not nearly as bad, though still present.

If anyone has any ideas on what might be going on, I'd like to hear it. This is only my second project, the first being a CMOY headphone amp. I've actually got one of these sitting inside the box with the passive preamp, along with a few inputs and outputs it makes for a pretty neat package, provided it would work correctly....
  Reply With Quote
Old 4th January 2004, 02:09 PM   #2
sreten is offline sreten  United Kingdom
Join Date: Nov 2003
Location: Brighton UK
diagram taken from planet10's post.

Can't see why it would distort at high volume settings,
unless you are driving a very low input impedance load,
as output impedance is only good with this arrangement
at low volume settings.

There are better arrangements of passive pre-amps for
driving lowish impedance loads, the original circuit :


Ouput impedance is lower at near full volume settings.

Attached Images
File Type: gif hhaller-passivepre.gif (3.1 KB, 341 views)
  Reply With Quote
Old 4th January 2004, 02:22 PM   #3
analog_sa is offline analog_sa  Europe
diyAudio Member
analog_sa's Avatar
Join Date: Aug 2002
Location: Cascais

What makes you think the passive is responsible for the distortion? Such a simple device, provided it is correctly wired and does not load excessively the source, simply cannot distort. Unless your source is a high Rp valve stage 10k should be a reasonable load. Something seems very wrong. Have you tried wiring the pot in the normal way?
  Reply With Quote
Old 6th January 2004, 07:42 PM   #4
soneil is offline soneil  United States
diyAudio Member
Join Date: Jan 2004
Location: Michigan
Ok, so upon looking at the circuit I built further, I realized that I had the wipers of the pot connected to the ground, and the legs connected to the outputs, instead of the other way around as is shown in the original design. That cleaned the sound up quite a bit, I'm not sure why really. Shouldn't the resistance be as, um, "clean" across the pot no matter which way you are running it?

Anyway, its still not as good as I would like it, and I plan on putting in the type of control shown on the link sreten gave. Thanks for that by the way.

As for input impedances and loads and stuff, I don't really know much about that. My input is my dvd player's audio out, and my output is going to my sterio reciever. I've looked around for reading material to learn about the sort of difficulties I might run into, to no avail. Any suggestions on books, or some more helpful links?

Thanks again!
  Reply With Quote


Passive Preamp (H.H. design) problemHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Passive Preamp Problem noway1 Solid State 0 15th December 2008 03:26 PM
Passive preamp? Skorpio Solid State 10 22nd May 2008 07:17 PM
passive preamp HOEK Solid State 7 28th March 2007 08:01 PM
My passive preamp?? jovan Solid State 1 27th February 2006 08:13 PM
how would i go about making a new passive preamp design Diederick Solid State 8 3rd December 2001 01:46 AM

New To Site? Need Help?

All times are GMT. The time now is 06:40 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio