Problem with T-amp Mods - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

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 5th August 2005, 06:41 AM   #1
kyban is offline kyban  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Walnut Creek, CA
Default Problem with T-amp Mods

First, let me thank everyone, but esp. Motherone, Roger, George, Panomaniac, and Panelhead for the detailed analysis and suggestions for modding.

This is my first electrical mod, so clearly at risk for a SNAFU.

I've done a test set up with the stock board in a simple rebox, to establish a baseline performance. I'm waiting on parts, esp. an Alps pot, so I'm using alligators instead of soldering the connections, as well as the stock pot. And therein lies the problem.

As shown in the picture, I've sliced into the pot, with the connections as labeled. I'm leaving the left three wires from the audio connection cut, as my understanding is these (left, right inputs, ground) are bypassed to the pot.

The problem is: on power up I get this sputtering, machine gun like sound.

A couple of additional facts:
1) I'm using a 12v regulated powersupply.
2) When I first wired it up, I spliced the input leads according to Motherone's listing of leads:

V = switch 12volt
out + = switch 12volt in
Ro = to volume from right channel
Lo = to volume from left channel
G = ground
Li = from volume control to amp left channel
Ri = from volume control to amp left channel.

When I did this, I got no sound out at all with power on, but actually a very faint output from my speaker with the power off (and the pot did work to attenuate the volume).

So: where did I miswire?

Thanks in advance,

Bob
Attached Images
File Type: jpg photo_080405_003.jpg (39.8 KB, 738 views)
  Reply With Quote
Old 5th August 2005, 07:48 PM   #2
diyAudio Member
 
audio1st's Avatar
 
Join Date: May 2005
Location: Foxton, CAMBS..
Hi, I don't know much but your first problem is you cut the ground wire between the cct and the pot,?
Also the 2 red wires to the pot are just the power swich, you can cut and join these together near the main board and switch at the supply(The alps will not have a connection for these. ) Good Luck...
  Reply With Quote
Old 5th August 2005, 08:18 PM   #3
kyban is offline kyban  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Walnut Creek, CA
Thanks.
Re: the ground, so just splice the ground from the inputs into this lead (once reconnected?).
  Reply With Quote
Old 6th August 2005, 06:22 PM   #4
diyAudio Member
 
audio1st's Avatar
 
Join Date: May 2005
Location: Foxton, CAMBS..
I have attatched a picture of one of my amps. I hope you can see how to connect the ALPS pot. A have soldered the the L, R and G pot wires to the bottom of the board. The G wire goes to the pot and the input grounds.
Good Luck Barry.
  Reply With Quote
Old 6th August 2005, 08:07 PM   #5
diyAudio Member
 
audio1st's Avatar
 
Join Date: May 2005
Location: Foxton, CAMBS..
Attachment I hope?
Attached Images
File Type: jpg sugar t amp 4.jpg (61.8 KB, 759 views)
  Reply With Quote
Old 7th August 2005, 07:34 AM   #6
diyAudio Member
 
Join Date: Apr 2003
Location: Seattle
If you're using a direct wired volume control (i.e. wiring from your input RCAs directly to the potentiometer), you don't need to worry about Ro/Lo. Those just attach to the 1/8" jack on the board.

To wire up an alps, with the shaft facing to the right and the pins facing you, it goes as follows:

Top pair: Ground
Middle Pair: Output
Bottom Pair: Input

If you're still having problems after this, please try to post a close-up picture of the board + alps.

Good luck!
  Reply With Quote
Old 8th August 2005, 06:22 PM   #7
kyban is offline kyban  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Walnut Creek, CA
Thanks.

I've put in the 2200uf output cap. That cleared up some high end grittiness and silibance.

Now onto the input caps.

Bob
  Reply With Quote
Old 8th August 2005, 06:39 PM   #8
diyAudio Member
 
Join Date: Apr 2003
Location: Seattle
Do you mean the PSU bypass cap? The onboard electrolytic (the one that sits between the 4 inductors) is just a bypass cap for the power rail.

Most people say it improves the bass by increasing it. 2200uF is fairly large -- did you manage to fit it comfortably onboard?
  Reply With Quote
Old 9th August 2005, 06:55 AM   #9
kyban is offline kyban  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Walnut Creek, CA
Yes, meant the PSU bypass. Mounted it on the bottom of the board for room.

No problem with bass from the beginning, as I'm used Def Tech towers with built in subs.
  Reply With Quote
Old 9th August 2005, 07:00 AM   #10
diyAudio Member
 
Join Date: Apr 2003
Location: Seattle
Ah, which Definitives? I've always meant to give 'em a listen.

Glad to hear the mods are moving along!
  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
Nad's mods Calamaro Solid State 8 13th July 2008 02:23 PM
Hafler XL280 mods gain/low frequency cutoff problem HaflerFreak Solid State 29 6th September 2007 11:55 PM
F1 Mods dude007 Pass Labs 2 23rd May 2006 06:50 PM
What is the problem with this amp? mods requested routhun Solid State 17 11th September 2005 04:39 PM
NSB mods - Do You know any I have not seen? Jared Multi-Way 3 8th July 2005 08:51 PM


New To Site? Need Help?

All times are GMT. The time now is 04:09 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