My_Ref Fremen Edition - Beta build/Fine tuning - Page 28 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 18th April 2012, 10:49 PM   #271
squalor is offline squalor  United States
diyAudio Member
 
squalor's Avatar
 
Join Date: May 2005
Location: Redneck Riviera
Yes please ? The ceramic 22pF, the leg on the R3 side comes out pretty close to the BAV99 at D1
Must I populate C102, C202 ? I don't seem to have bought those. I need to find a fastener for the Aavid To-220 for R3. The slip-on Aavid To-220 sinks are for the LM317TG right ? and the LM337 does not need a sink ?
  Reply With Quote
Old 18th April 2012, 11:01 PM   #272
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally Posted by AndrewT View Post
The length of the leg of a leaded resistor makes a difference to the balance (output) of a bridge.

I don't know how well your calculations model trace resistances, but the resistance of 1cm of lead does affect the bridge balance.

That is working at DC. If you are working with AC, you then have the additional impedances of parasitics to make the "output" error even worse.

If you go back to post251 para3, you will see I have already confirmed that lead length makes a difference.
Wouldn't the resistor tolerances greatly exceed the trace tolerances? I will read that post again later, but could it be the way the trace run have more effect than the trace length themselves? This would be what I expect if a difference could actually be heard.
__________________
Hear the real thing!
  Reply With Quote
Old 18th April 2012, 11:02 PM   #273
Reality first!
diyAudio Member
 
ClaveFremen's Avatar
 
Join Date: May 2005
Location: Milan, Italy
Quote:
Originally Posted by squalor View Post
Yes please ? The ceramic 22pF, the leg on the R3 side comes out pretty close to the BAV99 at D1
Yes, but it's not a problem... they're on the same trace.

Do you have problem soldering those two components?

Quote:
Originally Posted by squalor View Post
Must I populate C102, C202 ? I don't seem to have bought those.
The initial Mouser code gone out of stock, maybe this is the problem.

I'm not using them, in fact it sounds better without.

Probably in the final version they will be omitted.

Quote:
Originally Posted by squalor View Post
I need to find a fastener for the Aavid To-220 for R3. The slip-on Aavid To-220 sinks are for the LM317TG right ? and the LM337 does not need a sink ?
I didn't shared with you the BOM?

The slip-on are not needed, I recommended them when I thought LM317 had problems but I was wrong.

You should also have two heatsinks that must be bolted with an M3 screw and bolt.

The hole in MP915 must be enlarged with a screwdriver to hold the M3 screw.
__________________
Dario
ClaveFremen "Bailando Salsa en el Sietch"
  Reply With Quote
Old 18th April 2012, 11:16 PM   #274
squalor is offline squalor  United States
diyAudio Member
 
squalor's Avatar
 
Join Date: May 2005
Location: Redneck Riviera
Yes, but it's not a problem... they're on the same trace. My bad, I did not realize that.

Do you have problem soldering those two components? no



The initial Mouser code gone out of stock, maybe this is the problem.

I'm not using them, in fact it sounds better without.

Probably in the final version they will be omitted. Great, I will omit the ones I don't have.



I didn't shared with you the BOM? Yes, I made a mistake

The slip-on are not needed, I recommended them when I thought LM317 had problems but I was wrong.

You should also have two heatsinks that must be bolted with an M3 screw and bolt.

The hole in MP915 must be enlarged with a screwdriver to hold the M3 screw. I had planned to dis-assemble a dead commercial amp for it's heatsinks, I should find some usable hardware too
  Reply With Quote
Old 18th April 2012, 11:28 PM   #275
KSTR is offline KSTR  Germany
diyAudio Member
 
KSTR's Avatar
 
Join Date: Jul 2007
Location: Central Berlin, Germany
Quote:
Originally Posted by AndrewT View Post
Howland and some parts of it's operation were discussed way back in the earlier Threads.
I raised that specific question and to my knowledge no one has posted a reply explaining what the difference does to the Howland Current Pump, nor confirming that anyone else has even measured whether their pump is set +ve or -ve.
MyRef_C with Ultimate BOM
Hi Andrew,

you might check this legendary app note on Howland current pumps : http://apex.cirrus.com/en/pubs/white...e_circuits.pdf

It details on mismatch by finite DC gain of the opamp as well as the frequency dependant mismatch coming from its output impedance characteristics.


However, in the MyRef this is all of little consequence because of the tight feedback wrapped around the pump. Even when the pump's output Z drops to, say, 100Ohms this still results in very little additional output on the 318 on top of what is required by the current transfer function alone because this 100Ohms is effectivly in parallel to the speaker and hardly dominating its impedance.

Note that the biggest mismatch will probably come from the effective output impedance (also vs. frequency) of the 318 which spoils any precision matching of the 22K/47k R's.

Last edited by KSTR; 18th April 2012 at 11:35 PM.
  Reply With Quote
Old 18th April 2012, 11:41 PM   #276
Reality first!
diyAudio Member
 
ClaveFremen's Avatar
 
Join Date: May 2005
Location: Milan, Italy
Quote:
Originally Posted by KSTR View Post
However, in the MyRef this is all of little consequence because of the tight feedback wrapped around the pump.
...
Note that the biggest mismatch will probably come from the effective output impedance (also vs. frequency) of the 318 which spoils any precision matching of the 22K/47k R's.
Thanks for you great post!
__________________
Dario
ClaveFremen "Bailando Salsa en el Sietch"
  Reply With Quote
Old 18th April 2012, 11:59 PM   #277
KSTR is offline KSTR  Germany
diyAudio Member
 
KSTR's Avatar
 
Join Date: Jul 2007
Location: Central Berlin, Germany
To avoid misunderstanding, I mean good matching (to at least 1%) is still required.

-----:----

Maybe Andrew can find his notes since I'm not exactly clear what he did to circuit to make his matching test.
  Reply With Quote
Old 19th April 2012, 09:22 AM   #278
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
When I posted we were part of a group buy using Uriah's hand matched resistors.

The Group Buyers knew they were getting matched resistors. That is because the Howland papers that we had seen up till then all specified accurate matching of the resistors ratios for proper operation of the pump.

I tried to find how resistor tolerance affected those critical ratios. Then asked the question. Does it affect the sound?


I will go and read your new link.
__________________
regards Andrew T.
  Reply With Quote
Old 19th April 2012, 09:24 AM   #279
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by soongsc View Post
Wouldn't the resistor tolerances greatly exceed the trace tolerances? I will read that post again later, but could it be the way the trace run have more effect than the trace length themselves? This would be what I expect if a difference could actually be heard.
Have you ever investigated the tolerances around a bridge circuit and how small the errors need to be to yield a good "output" that is believable?
Have you built a bridge?
Have you measured a bridge?
__________________
regards Andrew T.
  Reply With Quote
Old 19th April 2012, 02:34 PM   #280
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally Posted by AndrewT View Post
Have you ever investigated the tolerances around a bridge circuit and how small the errors need to be to yield a good "output" that is believable?
Have you built a bridge?
Have you measured a bridge?
I agree tolerances are important, but it seems that resistor tolerances are greater than trace tolerances provided that you don't use VERY accurate meters to hand pick. I don't think these meters even measure other "additional impedances of parasitics" you mention. Additionally, cables used for measurements have these "additional impedances of parasitics" of their own that effect the measurements too.

To answer your question about bridges, that was done some 30 years or so ago.

But I'd also like your opinion on "Have you ever investigated the tolerances around a bridge circuit and how small the errors need to be beyond which YOU feel that further reduced errors are not audibly of concern?" As you can see this can be subjective.
__________________
Hear the real thing!
  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
My_Ref Fremen Edition - need help on PCB evaluation ClaveFremen Chip Amps 450 23rd October 2013 03:38 PM
fine tuning of tapered TL...can i do this??? mondogenerator Multi-Way 6 8th December 2009 05:05 PM
F3 fine tuning ZUM911 Pass Labs 5 31st January 2008 09:14 PM
Orion fine tuning PT914 Multi-Way 6 14th February 2005 09:11 PM


New To Site? Need Help?

All times are GMT. The time now is 12:14 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