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

The Lounge A place to talk about almost anything but politics and religion.

John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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
Closed Thread
 
Thread Tools Search this Thread
Old 11th January 2013, 12:38 AM   #32501
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Quote:
Originally Posted by john curl View Post
Feedback resistors are CRITICAL. We have known this, for like, forever.
Up until recently I had adopted the money saving stance that Rf + Rg where the most critical positions and bought premium resistors only for those positions.

However, over the course of the last two years in an amplifier design I was working on I changed one by one all of the other resistors in the circuit from cheap industry standard metal films to Caddock TF020 or USF340 & some Caddock MK132s.

My conclusion from this process is that if we are aiming to achieve the best possible sound then every resistor is critical.

I changed the resistors over in what I guessed was order of importance and was surprised when I was getting towards the end of the process that I could clearly hear the effect of each swap.

Ascribing more importance to Rf + Rg also brings the temptation to increase the open loop gain to really cash in on the advantage - I tried this with TF020's & USF340's only in those two positions and the extra OLG brought an overall benefit to the sound. ( I increased the gain by changing the i/p stage load resistor to a CCS ).

However, towards the end of the process, with premium resistors in most positions, when I made this comparison again the amp clearly sounded better in the lower OLG mode.

p.s. I'm not claiming that caddock TF020s etc are the best resistors around - just that they sound much better industry standard resistors

Last edited by mikelm; 11th January 2013 at 12:45 AM.
 
Old 11th January 2013, 01:36 AM   #32502
fas42 is offline fas42  Australia
Banned
 
Join Date: Jun 2012
Location: NSW, Australia
Quote:
Originally Posted by mikelm View Post
My conclusion from this process is that if we are aiming to achieve the best possible sound then every resistor is critical.

I changed the resistors over in what I guessed was order of importance and was surprised when I was getting towards the end of the process that I could clearly hear the effect of each swap.
My suspicion is that the quality of manufacturing being significantly higher for the Caddock item is making the difference here; for example the termination of the resistive element to the lead would be substantially better, subtle non-linear behaviour here could have a significant impact on high frequency distortion, which the feedback network always finds more difficult to counteract.

Frank
 
Old 11th January 2013, 01:51 AM   #32503
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
does
Quote:
in an amplifier design... changed one by one... could clearly hear the effect of each swap...
mean you had 2 "blueprinted" amps (device matching, new R to <1% frequency response difference after swaps) transparent switching and a DBT protocol?

the "zeroth" condition for any of that testing is that you can make 2 amps that do sound alike - can't be distingushed in controlled DBT

Last edited by jcx; 11th January 2013 at 02:14 AM.
 
Old 11th January 2013, 07:11 AM   #32504
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Quote:
Originally Posted by fas42 View Post
My suspicion is that the quality of manufacturing being significantly higher for the Caddock item is making the difference here; for example the termination of the resistive element to the lead would be substantially better
Yes agreed and I suspect that the quality of the actual resistive substrate will also be an element in the mix.

But of these two options I suspect that the termination method may be the biggest culprit in cheap resistors.

Has anyone notice / tested that industry standard surface mount resistors sound / test better that their leaded counterparts ? with me this is only a theory at present.

Last edited by mikelm; 11th January 2013 at 07:15 AM.
 
Old 11th January 2013, 07:51 AM   #32505
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Quote:
Originally Posted by jcx View Post
does


mean you had 2 "blueprinted" amps (device matching, new R to <1% frequency response difference after swaps) transparent switching and a DBT protocol?

the "zeroth" condition for any of that testing is that you can make 2 amps that do sound alike - can't be distingushed in controlled DBT
Hi jcx,

No no no, I was not presenting the results of a formal scientific research like you might expect to find in a journal - just sharing informal findings & ideas in the way that is common in forums like this.

Perhaps we have different ideas about what should or should not be presented here - personally I value any such anecdotal input from anyone who has some experience in a particular area - I don't need any kind of "proof" because I would always check out whatever it was for myself before took it on board anyway.

mike
 
Old 11th January 2013, 08:21 AM   #32506
john curl is offline john curl  United States
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Thanks for the input, Mikelm. I also use Caddock in the Blowtorch but with the precision power resistors in the power supply. Caddock is in fact another 'superior' manufacturer of resistors that we in hi end know about and use.
Your test procedures are similar to mine, in many ways. Don't let people discourage you. We don't have to answer to any 'stinkin referees'. '-) Just ourselves be true.
__________________
"Condemnation without Examination is Prejudice"
 
Old 11th January 2013, 08:30 AM   #32507
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
lots of guesswork going on here, SMD FTW! when results are presented even subjectively with some background info that can be taken for what it is, but above, you dont have any information, yet you are ascribing possible technical benefits without any substance at all.

what makes you think the terminations on something like a susumu or Vishay SMD is lower quality than caddock? the good industrial/instrumentation grade SMD will have been through much more rigorous testing than the leaded parts, because they have to do serious testing to account for board flex, flex from heating etc and these companies are massive, with massive resources.
 
Old 11th January 2013, 08:43 AM   #32508
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by fas42 View Post
The biggest reason, though, is that I know that my volume control makes a difference, I can hear it
Thanks for your honesty. I was reacting that way because your " I could not tolerate ... " seemed excessive to me. If your pot is not noisy when you move-it (dirty, tired or DC in) and not charged in excess (FET ?), i'm not sure the difference is SO obvious.

To be totally honest, on my side, the main reasons why we did this resistance array in 1970 was to have some argues during the audio shows, to provide some inputs to the marketing department and to get rid of some returns in the after sales service for noisy pots.

It is like changing all resistors in a preamp: Because you expect a positive change, you will feel a positive change. i'm no sure a blind test would correlate-it.

As far i'm concerned, i have so may things more effective i can change*before* in my system, mainly power supply side !

In recording studios, noisy pots are a real nightmare, the main cause of daily maintenance.
 
Old 11th January 2013, 10:02 AM   #32509
fas42 is offline fas42  Australia
Banned
 
Join Date: Jun 2012
Location: NSW, Australia
Quote:
Originally Posted by Esperado View Post
If your pot is not noisy when you move-it (dirty, tired or DC in) and not charged in excess (FET ?), i'm not sure the difference is SO obvious.

To be totally honest, on my side, the main reasons why we did this resistance array in 1970 was to have some argues during the audio shows, to provide some inputs to the marketing department and to get rid of some returns in the after sales service for noisy pots.

It is like changing all resistors in a preamp: Because you expect a positive change, you will feel a positive change. i'm no sure a blind test would correlate-it.

As far i'm concerned, i have so may things more effective i can change*before* in my system, mainly power supply side !

In recording studios, noisy pots are a real nightmare, the main cause of daily maintenance.
It's not the conventional noisiness of pots that I hear, rather a loss of treble sparkle. If I put on a recording with plenty of fine shimmer from cymbals, or violin solo on a top notch instrument, the loss of quality is obvious as the contact areas of the pot lose their integrity with time; this is why the Lightspeed attenuators and the like have a strong following, once you "tune" into this distortion artifact it sticks out like a sore thumb ...

Frank
 
Old 11th January 2013, 10:32 AM   #32510
Esperado is offline Esperado  France
Banned
 
Join Date: Jul 2011
Location: Portugal
Quote:
Originally Posted by fas42 View Post
It's not the conventional noisiness of pots that I hear, rather a loss of treble sparkle.
Funny, i would describe exactly the contrary. A pot sounds, for me, like a carbon resistor: It *add* sparkles, a little granular sound. With metal film resistor, the sound is more fluid, smooth. Since it can be very subtil, not an obvious difference.
For some instruments, mainly in low medium, like male voices or cello, or some bluesy electric guitars i prefer pots or carbon resistances as it adds a little 'body'.
The kind of things we use in various mike preamps, in studio, to add characters to some instruments.

Last edited by Esperado; 11th January 2013 at 10:35 AM.
 

Closed Thread


John Curl's Blowtorch preamplifier part IIHide 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


New To Site? Need Help?

All times are GMT. The time now is 04:40 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki