My "audiophile" LM3886 approach - Page 105 - 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 6th October 2005, 05:04 PM   #1041
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Default Re: Re: PDFs for single side PCB

Quote:
Originally posted by rudi




it sounds as if you are retiring now that you are in heaven

Heh! Me retire! Never!

Actually I am just sharing the wealth.

Cheers!
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 6th October 2005, 05:06 PM   #1042
diyAudio Member
 
Join Date: Dec 2004
Location: gran sasso
Russ, Rudi,

I think what Rudi wanted to say originally with "less noise" was to have a better PSRR. So, given that You are in the fiddling mood, maybe it could be tried as well to fit in, instead of the resistor feed, an another CCS.. Because of the higher dissipation, You could do it with an LM317 as a first approach, or a more elaborated LED-BJT CCS?
[On top of the zeners, to be clear]
It's just an idea, and I am not even sure, because Mauro has good points about the simple Zener shunt.
Maybe you even have tried it already? At least it would clarify if Rudi had some valid point in the better PS separation?

Ciao, George
  Reply With Quote
Old 6th October 2005, 05:10 PM   #1043
diyAudio Member
 
Join Date: Dec 2002
Location: Houston
Default Active Current Source

Quote:
Originally posted by Russ White
Rudi,

I think you hit on something.

Increasing the supply voltage of the LM318 also increases its slew rate. I was reading the datasheet to see what sane values would be and decided to perform some experiments.

I actually like the shunt regulators better than the LM78xx/LM79xx as they are actually more quiet(noise wise, if you use a good quiet resistor) and let less AC ripple through to the LM318 (check it with a scope, if you have good zeners you will see there is less ripple).

So what I did, was I took two 18V zeners and popped em in, and then biased the LM318 class A with 7ma with an adjustable current source. I also tried a resistor for kick(3.3K as suggested) but the current source is better.

All I have to say is wow.

This amp has always been excellent, but now I think I am in heaven.



This is on my REV C monoblocs with no other mods at all.

Now keep in mind I have a 300Va toroid on each channel, so my supplies are stiff and clean.

Cheers!
Russ
Russ,
I have biased an opamp before using a pair of 2SK170's and a reisistor. How did you impliment it?
Going to the 18 volt zeners sounds like it should be my ticket also. Less heat off the 1K resistors to boot.

George
  Reply With Quote
Old 6th October 2005, 05:17 PM   #1044
VT67 is offline VT67  Belgium
diyAudio Member
 
VT67's Avatar
 
Join Date: Jun 2004
Location: Belgium
Quote:
Heh! Me retire! Never!
My thought exactly. You will keep on designing amp's and PCB's even after you're death. You're just way to impassioned, AND WE LOVE IT

Regards
  Reply With Quote
Old 6th October 2005, 05:20 PM   #1045
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Default Re: Active Current Source

Quote:
Originally posted by Panelhead


Russ,
I have biased an opamp before using a pair of 2SK170's and a reisistor. How did you impliment it?
Going to the 18 volt zeners sounds like it should be my ticket also. Less heat off the 1K resistors to boot.

George

Hi George,

I used LM334, but there may be even better constant current sources, but i have had exceelent results with those.

Cheers!
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 6th October 2005, 06:31 PM   #1046
diyAudio Member
 
Join Date: Apr 2002
Default Some other mods

Good to hear that the Rev C gets better by the day (or is that by the hour?)

Some other mods that are worth considering include:

1. Discrete diodes, hi-speed, soft recovery of course. These normally result in a lower noise floor when replacing diode bridges

2. 100R in series with 330nF caps as snubbers across the diodes. Same effect as 1.

3. Double regulation for the 318's power supplies? This requires more work, but could be worthwhile based on experiences with NAIM pre-amps

4. Speaking of NAIM, I have always had excellent results from using oversized toroids to provide power supply. I know that Rudi is using relatively small transformers (20VA I think) and it would be easy enough to determine if using say a 100VA makes a worthwhile difference. I would expect it to result in further big improvements in bass resolution.

5. Now that the power supply voltage is at a decent level, it may be worth trying the 318 replacements (627, etc) again, as perhaps these made no difference in the past vs 318 because they were not receiving sufficient juice....

Thats about it from me for now. Anyone else with some ideas on pushing the boundaries?

Ryan
  Reply With Quote
Old 6th October 2005, 06:40 PM   #1047
diyAudio Member
 
Join Date: Jul 2004
Location: .
Ryan

it seems that i will have to re-design the current board so we can incorporate all the changes.

the digital is now going to used as a driver for the new subs using HIVI D10.8 in 80L boxes

cheers
Rudi
  Reply With Quote
Old 6th October 2005, 06:42 PM   #1048
diyAudio Member
 
BrianDonegan's Avatar
 
Join Date: Dec 2004
Location: TPA HQ
these are worth a shot, but remember that the noise floor of the RevC is already very very low. Better then -120dB I believe, so lowering to PS noise floor may be a more esoteric mod.
__________________
Twisted Pear Audio
  Reply With Quote
Old 6th October 2005, 07:14 PM   #1049
Byrd is offline Byrd  South Africa
diyAudio Member
 
Join Date: Dec 2003
Location: Cape Town, South Africa
Send a message via MSN to Byrd
i was going to say Russ. 300VA . I know we like overkill here but ehm - what level would be reasonable overkill
__________________
Ross Saunders
  Reply With Quote
Old 6th October 2005, 07:17 PM   #1050
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Quote:
Originally posted by Byrd
i was going to say Russ. 300VA . I know we like overkill here but ehm - what level would be reasonable overkill

I know, I was orirginally using them for stereo amps, but I had two, so I said what the heck.
__________________
Less pulp more juice Twisted Pear Audio.
  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



New To Site? Need Help?

All times are GMT. The time now is 07:43 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