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

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Salas hotrodded blue DCB1 build
Salas hotrodded blue DCB1 build
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 22nd August 2015, 11:59 AM   #5101
max1979 is offline max1979  Italy
diyAudio Member
 
Join Date: Apr 2015
Quote:
Originally Posted by Salas View Post
P.S. Watch your power on/down system sequence as I see no relay in your build. What are those extra TO-220s for? Some post step down regulators for another circuit?
Yes, just a couple of 7812 and 7805 to feed an Arduino and the 12V trigger to startup the final amp (already developed) and a phono stage (designing).
The 5V will also be used for the input selector stage (relays based).

I just preferred to develop the audio section on another board: I have LDR attenuator, B1 buffer and mute relay there. Everything has to sit inside a 4cm height case, that's why you can see the 4 big caps lying down - now the PSU is less than 3cm including the 6mm spacers.
  Reply With Quote
Old 22nd August 2015, 12:15 PM   #5102
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
You got to allow higher CCS current so to feed those subsystems. Unless you are feeding those chip regs from the raw DC of the main reservoir capacitors.
  Reply With Quote
Old 22nd August 2015, 12:52 PM   #5103
max1979 is offline max1979  Italy
diyAudio Member
 
Join Date: Apr 2015
Quote:
Originally Posted by Salas View Post
You got to allow higher CCS current so to feed those subsystems. Unless you are feeding those chip regs from the raw DC of the main reservoir capacitors.
No no, I'm getting my current directly from the reservoir cap. I don't want to touch your baby
At the very beginning I designed a separate power supply, but I don't think that few hundreds of mA will create any real problem.

Anyway, later on I will increase the current at least to see if there is a real difference in sounds (I'm curious).
  Reply With Quote
Old 22nd August 2015, 01:05 PM   #5104
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
But with all those extra loads and/or hot rodding, the bridge diodes should be monitored for heat still.
  Reply With Quote
Old 22nd August 2015, 02:42 PM   #5105
max1979 is offline max1979  Italy
diyAudio Member
 
Join Date: Apr 2015
Quote:
Originally Posted by Salas View Post
But with all those extra loads and/or hot rodding, the bridge diodes should be monitored for heat still.
Good point, I'll monitor them.
  Reply With Quote
Old 23rd August 2015, 04:07 PM   #5106
max1979 is offline max1979  Italy
diyAudio Member
 
Join Date: Apr 2015
Ok, testing everything I have found something unexpected. If I don't apply any signal to the B1 buffer, the output DC voltage on one channel is 0V and on the other channel is 150mV. Sorry if you already covered this scenario in one of the previous page of this thread. Is it possible and acceptable? Something wrong in my implementation (bad solder joint, not well matched K170)?
Ok, we'd like to have 0V, but in real life what's an acceptable DC offset?
  Reply With Quote
Old 23rd August 2015, 04:30 PM   #5107
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
Properly selected k170 should give output offset less than -0.3mV
0V probably doesn't mean 0.0mVdc
150mVdc means something is broken.
__________________
regards Andrew T.
  Reply With Quote
Old 23rd August 2015, 05:59 PM   #5108
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
Max, how close did you originally match those four signal handling K170s? Maybe you mixed a non tested one with big idss difference during the assembly by mistake. No more than 5mV DC offset should be your goal. Many achieve +/- 1mV
  Reply With Quote
Old 23rd August 2015, 06:47 PM   #5109
max1979 is offline max1979  Italy
diyAudio Member
 
Join Date: Apr 2015
Guys, thank you for the precious advice.
Yes, the problem was the matching: I bought 2 couple of already matched K170 from ebay just to avoid to do extra work.
I didn't have so many spare k170 (just four) but I tested few combination of them and now I have something that works better: 2.8mV

Next time I will ask to someone in this forum to have a well matched set of 4 K170

Just a generic question regarding K170. Testing the ones I have here I have found better values in case of K170 with the same tag "K170 BL xx" in my case the "xx" was '3A'. Is there any meaning in this last two characters? I haven't found anything using google
  Reply With Quote
Old 23rd August 2015, 07:46 PM   #5110
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Salas hotrodded blue DCB1 build
Factory code xx. Probably batch. Not meaning something of practical value to the end user. Can you take a clear macro shot of a JFET you pulled and show it here? Genuine ones have some tell tale signs we could confirm or not.
  Reply With Quote

Reply


Salas hotrodded blue DCB1 buildHide 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
dcb1 buffer with shunt reg. merlin2069er Swap Meet 0 3rd August 2010 06:25 PM
F2 and DCB1 parts selection - please advice! DQ Pass Labs 6 25th November 2009 04:20 PM
Y B Blue - how blue LED improves the CD playback Peter Daniel Digital Source 176 25th September 2003 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 06:37 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