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 2009, 09:53 PM   #881
puma2 is offline puma2  Sweden
diyAudio Member
 
Join Date: Sep 2009
Peter Daniel, one of your LM3875-kits got a new home this weekend in my fathers old Pioneer SX-400L chassi.

http://img197.imageshack.us/img197/2888/dsc00172gu.jpg

It required a little bit of modification though, but hey, the sound is great considering the use of some 20 year old equipment.

Thanks for this thread. Greetings from Sweden.
  Reply With Quote
Old 1st November 2009, 03:44 AM   #882
GregH2 is offline GregH2  Australia
diyAudio Member
 
GregH2's Avatar
 
Join Date: Oct 2009
Hi Peter,

Thanks for the link.

I'm interested to know if there is any particular reason (either scientific or subjective) for your choice of 0.75W ratings for 22k resistors? For example, are larger power resistors more stable or less inductive or something? Or do you just think they sound better?

I would have thought a 0.25W rating would have been enough for this purpose (though I'm pretty ignorant to this stuff), and I'm just interested to hear your thoughts. I would like to design my own gainclone circuit one day and am trying to learn everything I can.

Thanks,

Greg.
  Reply With Quote
Old 2nd November 2009, 02:44 PM   #883
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
It's not the actual wattage of resistors that I'm after but I like that particular brand of resistors in that application (Caddock MK132). If you check my regular kits you will notice that I'm using 0.5W resistors there; 0.25W rating will work fine as well.
__________________
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 3rd November 2009, 08:31 AM   #884
GregH2 is offline GregH2  Australia
diyAudio Member
 
GregH2's Avatar
 
Join Date: Oct 2009
Thanks Peter.

One more question, judging by your photos, when you use an external PSU, you are not grounding the chassis of your amplifier (only the PSU chassis). Is that correct?

Thanks,

Greg.
  Reply With Quote
Old 3rd November 2009, 10:13 PM   #885
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
I connect PS enclosure to Earth ground. Additionally, you can run a separate ground wire from PS enclosure to amp enclosure.

This way, everything is properly grounded.

Amplifier's output ground connects to chassis through CL60 thermistor.
__________________
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 5th November 2009, 07:49 PM   #886
puma2 is offline puma2  Sweden
diyAudio Member
 
Join Date: Sep 2009
I have a little problem. Today after playing for approximately an hour my left speaker started to sound really bad.

After disconnecting the speakers I measured the DC offset, the left channel had DC ratings at -22,7 V, while the right channel was as normal.

The voltage from the rectifier is 25 V.

Now my plan is to remove the amp board from the chassis and check everything again. I would really appreciate it if someone has an idea of what could be wrong.
  Reply With Quote
Old 5th November 2009, 08:28 PM   #887
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
Has anyone found that really low impedance on their pot is way way better than 25k or more?
I love impedance around 8k. The sound is so much more alive.
Uriah
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 5th November 2009, 09:30 PM   #888
diyAudio Member
 
LucasAdamson's Avatar
 
Join Date: Feb 2009
Quote:
Originally Posted by udailey View Post
Has anyone found that really low impedance on their pot is way way better than 25k or more?
I love impedance around 8k. The sound is so much more alive.
Uriah
I use a 10k stepped attenuator on my lm3875, and I find that with a line level input, I have to keep in on the bottom two or three steps of the 22 available. Above that it begins to distort.

When my Pass Labs B1 buffer is built, however, I hope that these problems will be over. I plan on using a 25k or 47k pot with the buffer, so that it brings it within a more practical range.

It sounds good with the 10k attenuator, but I have nothing to compare it to, and can't imagine why a small pot would sound any better than a larger one, as any given volume will require exactly the same degree of attenuation with any device. The only difference is the range of resistance on offer.
__________________
Lucas

Last edited by LucasAdamson; 5th November 2009 at 09:32 PM. Reason: Spelling corrections
  Reply With Quote
Old 5th November 2009, 10:41 PM   #889
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
With higher impedance I get a more muffled sound. The lower the impedance the livelier the sound. The pot along with your cables capacitance creates a filter so we can lose part of the music depending on that. I built a pot with LDRs and had made it so i could change impedance at will, during music, but not change volume much. The change is definitely there. Better with lower. Then I built the DCB1 buffer and used that same pot on it and since its a buffer I could get away with wild impedances without sending my amp oscillating away. I ran it from 400k down to 600R and liked the range in 600R-4.7k best. Makes you want to move! So crisp and clear.
I think if you use that 10k attenuator but try a little fix it might do well for you. Try getting a few different values of resistors. Like 500R, 1kR, 2k, 5k, 10k. Take each one individually and put it parallel to your shunt resistors you will find a value that allows you much more rotation on the pot so you can bring the volume up in smaller steps. When you say distort I am not sure if the sound just gets bad or if you mean that it gets loud really fast and sounds poor when its that loud. If its to loud to fast that fix might do it.
Just a suggestion that I have tried and it worked for me to get more range out of my pot having an amp with lots of gain and super sensitive speakers.
Uriah
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  Reply With Quote
Old 6th November 2009, 11:36 AM   #890
diyAudio Member
 
LucasAdamson's Avatar
 
Join Date: Feb 2009
Hi Uriah,

The gain is too high when feeding a line level signal into my gainclone, owing to too high a voltage. These amps aren't line level input, nor even close, so attenuation is definitely in order, even for top volume level I find, or else they will distort. The buffer I'm making right now should help, but I'm not exactly sure how, to be honest. It won't amplify the signal, but what I really need is to reduce the voltage from line level to something closer to the amp's ideal input.

Lucas
__________________
Lucas
  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
Commercial complete Gainclone kit for a beginner? gychang Chip Amps 365 4th October 2011 08:19 AM


New To Site? Need Help?

All times are GMT. The time now is 05:02 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