Calvin Buffer for Paradise - Page 40 - diyAudio
Go Back   Home > Forums > Commercial Sector > Group Buys

Group Buys Members group buys

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 23rd November 2013, 04:39 PM   #391
atupi is offline atupi  Romania
diyAudio Member
 
Join Date: Oct 2010
Location: Bucharest
In the notes of building manual it written: "adjust with R5,R7 bias. If current is too low reduce resistors value ".
What is the targeted current to Q3,Q6 ?
  Reply With Quote
Old 23rd November 2013, 08:12 PM   #392
kumori is offline kumori  Europe
diyAudio Member
 
Join Date: Mar 2011
Quote:
Originally Posted by AndrewT View Post
Kumori,
your jFETs should work OK.
The highish Vp will result in a highish Id for the k170.
Expect Id to be 80% to 90% of Idss (about 7 to 8mA). This is very much higher than the 4mA given earlier in the Thread.
Using that predicted Id value, check your voltage drops across the various resistors.
It may be that you need to change some resistor values to get sensible output offset.
Thank you for your support Andrew.
I tried to get my head around the problem, but unfortunately it seems I lack the knowledge to do this on my own. Which resistors should i target and change to reduce the offset?

But, there is also good news, I made another buffer with the transistors from the group buy, they work right away with 8 mV offset and can be easyly trimmed to zero offset. Thank you for the matching work.

I wanted to ask how people power their buffers when it is not used with the paradise PSU. First I tried a TPA placid shunt regulator which worked, but with a loud hum that I could not get rid of. I tried different decoupling caps on the psu rails (220 uf elko, 10 uf elko, no cap) but the hum stayed. Then I used a LM317/37 regulator and it worked flawlessly with out hum.

Is there an obvious reason, why the Placid shunt results in a strong hum in this application?
I would probably try the buffer with a Salas regulator Did anyone try this already and can comment on how to decouple this properly? I thought about maybe a small elko or a small film cap with serial R? Any help appreciated.

By the way, the sound is excellent

Regards
Florian
  Reply With Quote
Old 24th November 2013, 12:31 PM   #393
CFT is online now CFT  United States
diyAudio Member
 
Join Date: Jul 2006
Location: Hong Kong
Anyone got a spare stereo set (or two) of pcb for sale?
__________________
SBT - Audial TDA1541A USB DAC - TVC - 26 dht preamp - Linkwitz Pluto2.1 / SET amps + field coils
  Reply With Quote
Old 25th November 2013, 11:34 AM   #394
atupi is offline atupi  Romania
diyAudio Member
 
Join Date: Oct 2010
Location: Bucharest
Quote:
Originally Posted by atupi View Post
In the notes of building manual it written: "adjust with R5,R7 bias. If current is too low reduce resistors value ".
What is the targeted current to Q3,Q6 ?
Can anyone answer to my question: wat is the desired current flowing into Q3,Q6 ?

Thanks!
  Reply With Quote
Old 26th November 2013, 08:21 AM   #395
Joschl is offline Joschl  Germany
diyAudio Member
 
Joschl's Avatar
 
Join Date: Dec 2005
Location: Ruhrgebiet
Hi atupi,
the current through the complete circuit is approximately 30 mA. Let's say 5 mA for the JFETs. So you need about 25 mA for the BJTs.
  Reply With Quote
Old 26th November 2013, 08:50 PM   #396
hesener is offline hesener  Germany
diyAudio Member
 
Join Date: Mar 2005
Location: Munich, Germany
Quote:
Originally Posted by atupi View Post
Can anyone answer to my question: wat is the desired current flowing into Q3,Q6 ?

Thanks!
Hi, the comments from Joschl are correct. R5 and R7 should be the values from the schematic. A few posts back Calvin explained the circuit in great detail, and there is a fine balance between R5, R6, and R1+R2 (and the same for the corresponding resistors in the other half). These resistors set the bias current, but also the amount of local feedback and thus the distortion behaviour, in conjunction with the characteristics of the selected transistors.

In short, don't change too much - if you want changes, you may want to simulate the circuit first, then try it out and measure the distortion, and see if you can get to the same magnitude Calvin did. Hope that helps.....
__________________
Paradise documents are here: Link list
  Reply With Quote
Old 10th June 2014, 07:41 PM   #397
diyAudio Member
 
Join Date: Jun 2004
Location: sheffield
Send a message via MSN to sq225917
Are there any boards left for these?
__________________
hoping to pick up some things.
  Reply With Quote
Old 10th June 2014, 08:01 PM   #398
diyAudio Member
 
Join Date: Jul 2013
You can have mine, unopened, unused pm me
  Reply With Quote
Old 13th July 2014, 05:25 PM   #399
flashgo is offline flashgo  United States
diyAudio Member
 
Join Date: Sep 2008
I'm looking for a pair of boards as well. Thanks!
  Reply With Quote
Old 13th July 2014, 05:29 PM   #400
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
I have 4 pairs of what was the first batch
__________________
...Shape the sound , Man!
  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
Paradise Builders Joachim Gerhard Analogue Source 3648 22nd October 2014 06:44 AM
MY PARADISE Bksabath Analogue Source 61 21st March 2013 10:59 AM
Diy Paradise! alexmoose Tubes / Valves 3 24th July 2006 04:37 AM
Ping Calvin moray james Planars & Exotics 7 20th September 2005 10:03 PM
Another way to paradise ? Bernhard Pass Labs 3 8th August 2003 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 04:10 PM.


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