universal chip pre-amp project - Page 11 - 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 December 2009, 03:26 AM   #101
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
OK,

Got it running and it passed the smoke test. Hooked it up to the LR system and listened for a while. Unfortunately the only pot I had was a cheap linear taper unit. With the volume cranked up a bit it sounds very nice. I look forward to a proper pot and more testing.
Click the image to open in full size.
  Reply With Quote
Old 7th December 2009, 11:51 AM   #102
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi CJ,
any and all wire pairs that are a flow and return should be twisted as pairs.
This reduces, massively, the loop area of the aerial/receiver that each flow return loop creates.
It also reduces the effectiveness of the aerial/receiver function since alternate turns of the twist cancel the EMI radiated or received.

Once you have the layout finalised and the transformer rotated to find minimum (null) radiated field you can reduce the length of each twisted pair to the minimum.
__________________
regards Andrew T.
  Reply With Quote
Old 7th December 2009, 01:12 PM   #103
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
Thank you,

Once I get it all stuffed in the chassis, I will clean up, twist and shorten the wire pairs. I ordered a nice Alps pot and still waiting for a couple small hardware bits.

I went with OPA2227P for starters. It will be interesting to start chip rolling once it is more complete.
  Reply With Quote
Old 7th December 2009, 03:15 PM   #104
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
Hi AndrewT,
this sentence "the transformer rotated to find minimum (null) radiated field" sounds intresting, what do you mean exactly?

Kr,
tent:wq

PS: still having some noise hearable.. any suggestio on the ground wiring for this amp?
PS2: any suggestion on how to connect directly some headphones on this amp (I'd like to add this as an option in my pre..)
  Reply With Quote
Old 7th December 2009, 03:22 PM   #105
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
Tent,

What transformer are you using? I have used Antek toroidals for my last 3 chipamp projects and they are dead silent. From the pics above, there are no twisted pairs and the test rig was dead silent. The PSU might also have something to do with it...proven design used by many folks by Carlos Felipe. The board I used was from chipamp.com.
  Reply With Quote
Old 7th December 2009, 04:07 PM   #106
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
An EI transformer radiates high magnetic fields in many directions.
A toroid transformer radiates a low magnetic field in many directions, but radiates a high magnetic field in a few directions.

If the toroid is installed such that one of these high field radiation peaks passes across a loop receiver then that will induce hum in the amplifier.

One can rotate the toroid to try to achieve a null in induced hum.

This can be done if the toroid has long flexible (stranded) twisted mains and output leads.
Once the Null position is found then the mains and secondary twisted leads can be shortened to the minimum.
__________________
regards Andrew T.
  Reply With Quote
Old 7th December 2009, 06:54 PM   #107
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
Hi,
ok, so you mean rotating it like I would do with a disc? I mean horizontally?
So, if it would be like a clock, being the primary and secondary wires the 12hours: could it be that, let's say at 4hours and at 8hours some high field radiation is coming out? and I should adjust this to make those, point out of my case, and not towards the pre-amp? wow, this would be a big news for me!
Anyway I'm using some no-name toroid.. do you think I should try with some better brand? I will try with the PSU from chipamp that cjkpkg is using since I have one of those lying around and will tell you if that is maybe doing some better.
But couldn't it be somehow because of the grounding that I should do better? I'm also kind of worried because the L and R channel grounds are "common"..

tent:wq
  Reply With Quote
Old 7th December 2009, 07:31 PM   #108
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
Quote:
Originally Posted by cjkpkg View Post
Thank you,

Once I get it all stuffed in the chassis, I will clean up, twist and shorten the wire pairs. I ordered a nice Alps pot and still waiting for a couple small hardware bits.

I went with OPA2227P for starters. It will be interesting to start chip rolling once it is more complete.
Where did you order your alps pot from ? i have been looking for a alps black beauty but can't find any

Looks good tho, any pictures of your chassis idea ?
  Reply With Quote
Old 7th December 2009, 09:21 PM   #109
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
I ordered THIS ONE. For the chassis, I am going with a Hammond box. Click the image to open in full size.
  Reply With Quote
Old 8th December 2009, 07:06 AM   #110
Atilla is offline Atilla  Norway
diyAudio Member
 
Join Date: Jul 2008
With toroids, you should have a lot less problems than with an EI traffo. Still, since no winding is absolutely perfect, if you do notice induced issues, simply rotating the trafo could help you out.

As AndrewT mentions, do keep the wires nice and tightly would around each other. And if you do need to cross signal and power lies in the chassis, do try to do that at 90 degrees angle to reduce any possibility of interference. Don't worry too much about your toroid, however, they can be a problem only when done really bad and yours seems to be alright just by its looks. Still, you do benefit from keeping it away from sensitive circuits.

You generally want to keep all wiring as short as possible in the selected chassis and layout. After you've got your layout set-up and tested, trim everything to its possible minimum.

You shouldn't have problems with a single PSU, given that it can handle the currents, but some channel decoupling with capacitors couldn't hurt.

If you can hear noise/hum/buzz with the input shorted, you should look for the possibility of induced signal from trafo/mains-wiring or better PSU filtering. If not, you're all good to go.

With an extra headphone output you might need to consider output resistors to target impedance/stability issues. With my headphone amp I did need output resistors to make it completely silent at high volumes and no signal and match the (in some cases) expected output impedance for an headphone amp. Now, I might have done something wrong in the layout, but it has been mentioned that some headphones are tested and specced at a certain, slightly higher, output impedance of the source. ( I was never too sure about that, so other people might have better input on this topic. It's a good chance I did something not entirely correct in my layout, I am not an expert yet, at any rate) If you don't need it hard-wired, you might put a switch for preamp/headphone output.

At any rate, with your hardware, you shouldn't come across big issues so go ahead, be cautious with the mains and tell us how it sounds like.

Oh, and don't forget - twisting L/R channel wires together is not beneficial. Twisting positive/negative wires is.

Last edited by Atilla; 8th December 2009 at 07:27 AM.
  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
Which Chip for first DIY project? systemerror909 Chip Amps 3 9th January 2006 05:32 AM
Project - Universal CD Controller? lgreen Car Audio 1 22nd September 2003 01:20 AM
new project - chip amp?? yuval Chip Amps 3 14th July 2003 01:47 AM
A new chip amp project JOE DIRT® Chip Amps 11 17th June 2003 02:56 PM


New To Site? Need Help?

All times are GMT. The time now is 05:54 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