Preamp disappointment and passive mod??? - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

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
Reply
 
Thread Tools Search this Thread
Old 19th April 2011, 03:05 PM   #1
KanedaK is offline KanedaK  Belgium
diyAudio Member
 
Join Date: Feb 2011
Default Preamp disappointment and passive mod???

Hello everybody,

last week I updated the 30 years old crossovers in my speakers with new crossovers (for those who are familiar with it, the speakers are Klipsch LaScalas modded with Beyma cP25 tweeters and EV SM120A midrange horn lenses, old type AA networks replaced with new ALK).

After the few usual days spent being amazed with the greatly improved clarity these new crossovers bring, I'm now facing a problem I didn't expect to happen: there's something "weird" with the way treble sounds. That is, I can now hear something in my electronics isn't quite right. I've always been thinking they were up to the task but obviously something in the link isn't, something that was unnoticed with the old, more "rounded off" crossovers.

It's like the treble lacks purity and speed, like it's "dirty", and sometimes it feels like it's playing on its own.

So the first thing I tried today is to get rid of the preamplifier (a DIY Kaneda line stage) and connect the CD player output directly to the power amp (CD player has variable output).

I must say I'm totally bluffed / even with the CD player output level set at -39dB, wich is not supposed to sound good, it still sounds way better than with the preamp! treble is pure and extended, imaging follows exactly what's on the recording, sometimes very wide and enveloping, sometimes centered right between the speakers, bass is faster and punchier (but a bit less "warm" and "cuddly"), midrange is not grainy anymore (something I was afraid was coming from my power amp, but obviously not, this power amp is as clean and sweet as one can wish for)
...plus with the preamp there's always been some noise problem wich I already posted about in this forum.

so now i'm thinking: the gain stage in my preamp is AFTER the volume control. The latter is a stepped attenuator, 50K.
What if I just bypass the active stage from the signal, and connect the output of the attenuator directly to the output of the preamp? that way I could still use the input selector (4 inputs, relays, very handy) and use my preamp until I buy / build something better (maybe a passive, maybe a tube pre).
Now would this work? assuming for practical reasons I would leave the active gain stage and the PSU in the box, would this cause any problem to the sound and/or to the gain stage board? I don't wanna destroy the Kaneda line stage obviously, maybe someday I know better and I'm able to make it sound better, at the moment I just want an easy fix to make my system sound good.
I'm using mainly CD's and also FLAC files from my mac, and my speakers are 104dB sensitive so I don't need any gainstage in the preamp, I realise...

If for some reason it's not a good idea to just bypass the active gain stage in my preamp, could anybody recommand me a good quality and CHEAP passive preamp, possibly to be found second-hand? I'm on a low budget.

Power amp is technics SE-A5, input sensitivity/impedance 1V / 47Kohms

thanks!!

François
  Reply With Quote
Old 19th April 2011, 03:58 PM   #2
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
For CD output many times we need no gain=preamp.
If CD player and similar is the only sound source,
we can attach the signal direct to power amplifier.

A passive preamp can be very simple. A few resistors and one potentiometer, perhaps.
The less components, resistors, the better.
Few components keep the signal clean.
__________________
lineup
  Reply With Quote
Old 20th April 2011, 01:10 AM   #3
KanedaK is offline KanedaK  Belgium
diyAudio Member
 
Join Date: Feb 2011
Default tonight it got worse

I heard tonight for the first time some "distant thunder" noise trough the right channel

i'm afraid the caps might be bad and that's what causes the not-so-good sound, the noise and hum that I posted about a few weeks ago, and now this sound wich is, i guess, what people call "motorboating"?

i disconnected the preamp totally from the system to make sure the problem doesnt come from the amp but i don't hear any strange noise so far and it sounds great...

so i guess i'm in for a servicing of the preamp before I decide anything.
problem is those caps are HUGE and I don't know how much it's gonna cost me -i suspect the ones inside are cheap quality as I don't even see any label or anything printed on them... but they're the size of beer cans...
  Reply With Quote
Old 20th April 2011, 03:10 AM   #4
cbdb is offline cbdb  Canada
diyAudio Member
 
Join Date: Oct 2008
Location: Vancouver
Your pre amp has caps the size of beer cans??? Kind of unusual. What kind?
  Reply With Quote
Old 20th April 2011, 04:20 AM   #5
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
I've never needed or used a gain stage in my preamps. Whenever I've installed one, no matter how good I think it is, the result is too much gain and poorer sound. Admittedly I drive short cables into amps that have a flat input impedance. Read the gain staging article!
__________________
I may be barking up the wrong tree, but at least I'm barking!
  Reply With Quote
Old 20th April 2011, 11:30 AM   #6
KanedaK is offline KanedaK  Belgium
diyAudio Member
 
Join Date: Feb 2011
Quote:
Originally Posted by cbdb View Post
Your pre amp has caps the size of beer cans??? Kind of unusual. What kind?
The preamp is a Kaneda line stage.
The previous owner (who built the preamp) told me the filter caps are 169000uF total (2 caps), but I suspect he used cheap brand as there is nothing printed on the cans, no references, brandname, ratings, nothing wich is weird when you condider even the smallest caps have a whole litterature on them...

OTOH such big caps from a GOOD audiophile reliable brand must be quite expensive...
  Reply With Quote
Old 20th April 2011, 11:52 AM   #7
Itsmee is offline Itsmee  England
diyAudio Member
 
Itsmee's Avatar
 
Join Date: Feb 2009
You could cannibalize your Kaneda and make a Pass B1 (the DC coupled version), a couple of sets of jfets wouldn't cost much.
  Reply With Quote
Old 21st April 2011, 09:16 AM   #8
KanedaK is offline KanedaK  Belgium
diyAudio Member
 
Join Date: Feb 2011
Quote:
Originally Posted by Itsmee View Post
You could cannibalize your Kaneda and make a Pass B1 (the DC coupled version), a couple of sets of jfets wouldn't cost much.
Interesting indeed; I found a website selling pre-built B1 modules in Germany. Good quality parts and very cheap.
funny enough the same website sells high quality, pre-built PSU boards for... Kaneda linestages. with Roederstein and wima caps and 6x15000uF.

So I guess the best would be to get a Kaneda PSU, see how it makes my preamp sound; then if it's not to my liking (but performs as it should) I can sell it and try and build a Pass B1 kit.

What do you guys think?

Diy-Audio-World Onlineshop: a la Kaneda Preamp

Diy-Audio-World Onlineshop: B1 Fet Booster
  Reply With Quote
Old 21st April 2011, 09:41 AM   #9
Itsmee is offline Itsmee  England
diyAudio Member
 
Itsmee's Avatar
 
Join Date: Feb 2009
If you buy a B1 kit, I would go for the DCB1, boards are available from diyAudio member Teabag, you can buy the original from papa, available from the First Watt web site.
  Reply With Quote
Old 21st April 2011, 12:56 PM   #10
diyAudio Member
 
Join Date: Nov 2010
Forget the b1 kit and just make it entirely paasive as you suggested in your original thread.
  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
Passive cooling PSU mod Fuzzymuff Power Supplies 4 6th December 2009 12:50 PM
JBL Stadium Disappointment BlueWizard Multi-Way 29 11th July 2008 11:21 PM
T-amp stealth mod in passive biwiring Mr.Mekulic Class D 6 28th June 2006 08:25 PM
Newbie question: passive volume control mod for DAC Ichabod Analogue Source 0 4th November 2004 01:34 PM
Krell Disappointment,, mikeks Solid State 17 23rd October 2004 11:42 PM


New To Site? Need Help?

All times are GMT. The time now is 10:53 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