AudioSector-chip amp kits, dacs, chassis - Page 195 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Audio Sector

Audio Sector Kits & PC boards from AudioSector

Reply
 
Thread Tools Search this Thread
Old 25th October 2007, 02:01 PM   #1941
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Default Re: 2nd One

Quote:
Originally posted by rjkdivin
R7 and R9 are the correct ones to replace....correct Peter? I noticed you added the Caddock-spaced thru hole pads at R8 and R9, but not R7, and it threw me off a little.
Actually R8 and R9 are first to be replaced. Those are I/V resistors and if you check the traces underneath, they both connect with output coupling caps. In some setups using Caddocks here, in place of Rikens, may be beneficial (but may still require choosing different output caps).

Recently it's been brought to my attention that placing Caddock TF020 for R7 also improves things a bit, so you may try it as well (1k5)

All 3 Caddocks will fit in top layer, R7 needs pin properly formed.
Attached Images
File Type: jpg cad.jpg (99.3 KB, 1272 views)
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 25th October 2007, 02:12 PM   #1942
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Default Re: 2nd One

Quote:
Originally posted by rjkdivin
I'm planning to build two more boards without the PSU section, or at least without the inlet and transformer, and put them into the cases I built for my two NOS DACs, sharing one PSU switched between the two DACs in each case.

It looks like the PCB cut could be made to feed the second board from the first transformer secondary (so the PSU diodes, caps and inductors would be duplicated); or you could cut it right behind the inductors and make the connection at R1,2,3,4 (so none of the PSU would be duplicated). To switch the PSU between the two boards would require a 4PDT switch? Any suggestions?
I made a similar setup, in case both SPDIF and USB DACs are needed (and fed from common supply). I didn't want to go into switching I2S lines, not to compromise the performance.

The rectifiers and C1/C3 are common to both DACs, everything else is separate. The supply connections are done through pair of wires on each side, from the pads sideways to rectifiers (now you know what they were intended for

You may install 2PDT switches on each side to disconnect power from DAC on top.
Attached Images
File Type: jpg dual dac2.jpg (97.9 KB, 1412 views)
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 25th October 2007, 02:34 PM   #1943
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Peter where can one buy the RCA dual input blocks shown in the picture above?

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 25th October 2007, 02:46 PM   #1944
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
You may check with percyaudio.com , he seem to have an item like that in his catalog, although it's not clear if it's dual:

Cardas PC Mount: Ag/Rh plated, right angle or straight… $20.00 pr.

Or you can get it directly from me at $20/pair; I get them from Cardas.
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 28th October 2007, 02:49 PM   #1945
Frode is offline Frode  Norway
diyAudio Member
 
Join Date: May 2003
Location: Bergen
Default No sound

I just powered up my new LM3875 GC, but I get no sound, just hum. With 2x18V secondaries, I get just below 25V on pin 1 and -25V on pin 4 on both chips. Any ideas?

Frode

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 28th October 2007, 03:10 PM   #1946
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
You didn't install R1 (220R). Unless you put jumper there, there is no input signal connected.

With 100uf caps only (on amp board) you will be getting some hum. You still need to add bigger caps (like BG STD 1000uf) on rectifiers board (C1 and C2)
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 28th October 2007, 03:17 PM   #1947
Frode is offline Frode  Norway
diyAudio Member
 
Join Date: May 2003
Location: Bergen
Forgot the jumpers!

Frode
  Reply With Quote
Old 2nd November 2007, 04:02 AM   #1948
bfslm is offline bfslm  Brunei
diyAudio Member
 
Join Date: Oct 2007
Peter,

Very interesting in LM3875 but have some question before I mail you for order (DAC & amp).
My speaker is only 6ohm, 88Hz Sonus faber bookshelf
My taste of music: Jazz, pop. I'm not are rock fan,

Does LM3875 suitable for my speaker, do you suggest me to brigd/paranel or looking else ?

For DAC i'll contact you via email, for Amp i can order via audio sector, is it?

Many thanks for your advise
  Reply With Quote
Old 4th November 2007, 07:30 AM   #1949
bfslm is offline bfslm  Brunei
diyAudio Member
 
Join Date: Oct 2007
All,

Some concern on transformer need help.

For LM3875, should we use 2 transformer 160 VA mono block or 1 of 300 VA or 2 300 VA transformers, what option extract best performance from LM3875. For 6 ohm speaker, what Dc voltage workbest: 18, 20, 22, or 25 V DC. Becasuse i can customer make for trans. We use 220V AC in our country.

Many thanks

  Reply With Quote
Old 4th November 2007, 08:50 AM   #1950
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by bfslm
For LM3875, should we use 2 transformer 160 VA mono block or 1 of 300 VA or 2 300 VA transformers, what option extract best performance from LM3875. For 6 ohm speaker, what Dc voltage workbest: 18, 20, 22, or 25 V DC.
the chip can do upto 60W into your chosen load.
Using the normal factor, this requires a transformer with a VA rating of between 60VA and 120VA.
But small transformers have a high regulation value. This results in a high quiescent voltage making the chip run hotter than necessary and also results in the supply voltage sagging badly on longer duration transisents.
I think your suggestion of 160VA is probably about right for a single channel chipamp (monoblock).
If you can get a slightly bigger transformer cheaply then there is a small benefit in reduced regulation.

If you want two channels, then the transformer should be between 120VA and 240VA. Your 160VA would do just nicely for two channel as well. Two channel is more difficult to get hum free operation.

I recommend a supply voltage between 56Vdc(+-28V) and 70Vdc(+-35V) for 6ohm speaker and preferably at the lower end, particularly since the max output current is 4A to 6A when the chip is cold.

You need to identify your transformer and find out it's regulation, then you can decide which AC voltage you require to give your target DC voltage.
__________________
regards Andrew T.
  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 04:31 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