Is This Preamp Okay? - 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 2nd April 2011, 07:48 PM   #1
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Default Is This Preamp Okay?

What do you think of the attached preamp circuit? I usually don't like active preamps but mosfet amps tend to need them, and this circuit is from a commercial amp with build quality that I like to keep.

I know there may be many better solid state preamps in this forum. But I'm not looking for the best, just a "very good" one LOL. I want to know how this circuit may COMPARE with the "best" out there. Oh, I'm aware that you may ask for more detail about this circuit, but I believe that the experienced guy will "know" the quality from looking at the topology.

I'm using this preamp with the following amps:
Stochino ultra fast amp,
Mooly's amplifier,
JLH Mosfet 80W,
Bora's Sigma,
Goldmund Mimesis 3,

From your answers, I will decide if I better sell this preamp

Thanks
Attached Images
File Type: gif preamp.GIF (39.5 KB, 493 views)
  Reply With Quote
Old 2nd April 2011, 08:00 PM   #2
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
It looks like a very good preamp.
Complete and no shortcut in design.
__________________
lineup
  Reply With Quote
Old 2nd April 2011, 08:32 PM   #3
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Thanks Lineup. I'm happy to know that
  Reply With Quote
Old 10th April 2011, 08:31 PM   #4
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Well, what can I say? I hate to believe in my intuition (based on limited experience and other people opinions) that this preamp (as well as many other preamps) will not gonna work for my "ultimate" system.

If I sell the preamp I will probably get $150-200. If I use the casing for another preamp/buffer circuit, what will I do with the internal components??

My negative feelings towards preamps prevented me from even building the Blowtorch
  Reply With Quote
Old 10th April 2011, 08:47 PM   #5
diyAudio Member
 
Join Date: Apr 2003
Location: Eastern Pennsylvania
An interesting design, what with it's J-FET buffered bipolar input stage. Not an excessive amount of open-loop gain (for a feedback based transistor circuit) either. Perhaps, the main thing limiting it's sound quality may be that 100uF electrolytic output coupling capacitor, CL47. Before selling, you might try replacing it with a decent quality film cap. Unless your power-amp has an unusually low input resistance, line-stages usually don't need more than about 10uF of output coupling cap., and often, only a few microfarads will do.
__________________
Ken

Last edited by Ken Newton; 10th April 2011 at 08:49 PM.
  Reply With Quote
Old 10th April 2011, 09:01 PM   #6
diyAudio Member
 
aparatusonitus's Avatar
 
Join Date: Jan 2004
Location: Split, Croatia
Quote:
Originally Posted by Jay View Post
Well, what can I say? I hate to believe in my intuition (based on limited experience and other people opinions) that this preamp (as well as many other preamps) will not gonna work for my "ultimate" system.
Of course it ain't gonna work...it has to many transistors/fets/buffers in it.

Quote:
Originally Posted by Jay View Post
If I sell the preamp I will probably get $150-200. If I use the casing for another preamp/buffer circuit, what will I do with the internal components??
Use them to build something fare more simpler...like asymmetrical folded cascode/discrete AD797 with J-fet input.

Quote:
Originally Posted by Jay View Post
My negative feelings towards preamps prevented me from even building the Blowtorch
Then go for S&B TVC as I have
__________________
Non mai abbastanza...
  Reply With Quote
Old 10th April 2011, 09:26 PM   #7
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Thanks Ken.
I'm not even familiar with the used FET (M47F) and the bipolar (C2259). Currently (and temporarily) I use Black Gate N for the output cap. Of course pure film cap will be too big for 100uF. But if later I found it has potential, why not?

I'm planning to experiment with active speaker system later on, so I felt that I cannot try too many candidates for the preamp. Later the preamp will drive PLLXO and many kinds of active circuits (discrete opamps).

Yes sure Aparatusonitus,
I think you are right about it too complex I will check your preamp soon (never heard of it). Hopefully it is better than Aikido Chatode Follower in my system. Or may be the preamp designed by VladimirK.
  Reply With Quote
Old 11th April 2011, 02:24 AM   #8
Jay is offline Jay  Indonesia
diyAudio Member
 
Join Date: Feb 2003
Location: Jakarta
Default TVC

So TVC is Transformer Volume Control. But no thanks I don't want to invest so much money for improvement that I know not so critical. But I read that LDR is even better than TVC? I have very high quality ummm optocouplers (?) around.

The original idea/reason of having an active preamp is because many mosfet amplifiers really need them (such as the JLH 80W). Of course it would be a good idea to select mosfet amp that has suitably high input impedance (such as Mooly's amp).

My preference goes to a buffer with adjustable minimal gain, coupled with "perfect" power supply. Power supply is actually the key element here.
  Reply With Quote
Old 11th April 2011, 05:48 AM   #9
diyAudio Member
 
Join Date: Nov 2009
Location: Los Angeles
It's just a little odd to have a bias pot in a preamp though.

G
  Reply With Quote
Old 11th April 2011, 06:20 AM   #10
diyAudio Member
 
Join Date: Apr 2003
Location: Eastern Pennsylvania
Black Gate 'N' type bipolar E-lytics make excellent signal coupling caps. I utilize 4.7uF NX myself as an input coupling cap. on an diy amplifier project. The transparency is amazing, far better than I was getting with 10uF metalized film ClarityCaps.
__________________
Ken

Last edited by Ken Newton; 11th April 2011 at 06:22 AM.
  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
Running a tube preamp into a solid state preamp? Pckid212 Solid State 5 6th January 2013 10:12 PM
Tube Preamp Popping on Source Input Change (?) / 6DJ8 Preamp On Chip Amps MartyM Tubes / Valves 3 16th October 2008 04:52 AM
Guitar Preamp = MIC Preamp = other preamp ,,are they all same? Paswa Solid State 1 12th March 2008 05:16 PM
twisted pear Preamp/other suggestions for Preamp kit LukeDuke Chip Amps 1 1st February 2008 09:57 PM
Electret mic preamp - will phono preamp work? darthmullet Analogue Source 6 12th October 2007 07:32 AM


New To Site? Need Help?

All times are GMT. The time now is 01:14 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