No input caps on Charlize - 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 11th August 2006, 06:20 PM   #1
Radian is offline Radian  Germany
diyAudio Member
 
Join Date: Jun 2004
Location: Wiesbaden
Default No input caps on Charlize

Hello folks,

I found this post from LeoK at the Klipsch forum.
He has build a Tripath amp without the input caps.
His amp is called the Waltham Integration. He send me the full schematic on request.
My question to the experienced amoung you is,
can this mod be done to the Charlize (TA2020)?

Here is his description of the mod:


Posted by leok ( A ) on May 03, 2002 at 02:40:20

I have designed, produced, and distributed (including a few sales) a small stereo amplifier based on the Tripath TA1101B. My design is taken directly from the Tripath application scematic in the TA1101 data sheet. I have made one very important change in the input, and learned a few things about which components should be optimized.
My application is driving Klipsch Forte, RB-5, and RF-7 loudspeakers. I generally use a fraction of a watt .. never more than two or three Watts. I have done some work with tubes: currently I have a design that uses KT66s, PP, triode, no feedback. The tube amp is nice, but the Tripath is very very nice.

The input:
see Tripath's TA1101B Data Sheet:
"Application/Test Circuit" at Tripath.com
There is a 2.2uF electrolytic (C1) on each input because the input amp is biased at something like 2.5V. That cap has a huge impact on the sound. To get rid of it:
Observe static electricity protection rules. Until this circuit is complete, the Tripath input is floating and very vulnerable.
1) Use a floating, non grounded, 12V power supply. They are readily available.
2) Isolate audio input ground from the 12V ground and connect it directly to the TA1101B-pin 14.
3) Connect the audio signal directly to the resistors: R1. Now the audio is connected differentially to the input amps.
4) Bypass the audio ground (now connected to pin 14) to the circuit 12V ground. I use a 22uF electrolytic and 0.1uF ceramic. + connects to the audio ground. This step limits common mode noise which otherwise totally swamps the input circuit.
5) Insert a 7 or 8 volt zener diode between the audio and 12V grounds, cathode to audio gnd, to protect the chip input, esp pin 14.
6) Put big rf beads on all power, input, and speaker wires (you really should do this anyway with this amp). A single bead for each +/- pair is fine .. that's 5 beads total.
That's it. it makes a BIG difference.
Other tips:
1) rf beads (I already said it, but it's important).
2) nice 1.5 amp torroid output inductors
3) nice (mylar or better) output caps. I use .22uF because my speakers
are 8 Ohms.
4) nice 2200 uF electrolytics for VDD1/2 instead of 180uF
  Reply With Quote
Old 11th August 2006, 06:45 PM   #2
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
This mod can be done to any of the Tripath chips that have access to the non inverting input pin of the input op amps. Just make sure your souce ground is completely floating. You will need good bypassing from the non inverting input to power ground otherwise you will get noise. Doing this will also have an effect the DC offset on the outputs.
__________________
Brian
  Reply With Quote
Old 11th August 2006, 06:52 PM   #3
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Quote:
Originally posted by BWRX
Doing this will also have an effect the DC offset on the outputs.
Yes it will. For the brave only.

A high qaulity film cap in that spot is a good idea.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 11th August 2006, 07:59 PM   #4
Radian is offline Radian  Germany
diyAudio Member
 
Join Date: Jun 2004
Location: Wiesbaden
Thanks guys,

Quote:
Yes it will. For the brave only.
Why do you think so? Is it brave to run the amp like that?
Leo sold a few of those amps and they seem to work fine.
I really would like to implement the mod on my bords for the TA2020.
I also want to run the chip with a clean external 5V supply. Do you think the sound would benefit enough to do it.
I would really appreciate it if you guys could take a look at my bord. Please tell me what you would do different.

Thanks, Klaus
Attached Images
File Type: gif ta2020--.gif (38.9 KB, 859 views)
  Reply With Quote
Old 15th January 2009, 02:54 PM   #5
diyAudio Member
 
Join Date: Jan 2004
Hi

I read somewhere to remove input caps you must connect the source ground to biascap pin.
The bias cap itself connect to GND.
Do I have to remove the bias cap or simply solder the ground source to the cap ?

thanks b4
  Reply With Quote
Old 16th January 2009, 08:25 AM   #6
diyAudio Member
 
Lostcause's Avatar
 
Join Date: Aug 2005
Location: NW UK
Hi Surya, you just need to connect the source ground to the pin or if that's too fiddly then the pin side of the bias cap.
DO NOT REMOVE THE BIAS CAP.
Also, you need to ensure that the source and the amp are running on seperate (isolated) power sources.
Generally this means that you must run one or the other off a battery.
  Reply With Quote
Old 16th January 2009, 11:50 PM   #7
diyAudio Member
 
Join Date: Jan 2004
Hi Lostcause,

Thanks for the info

Any tweak suggestion to improve this little amp ?

Surya
  Reply With Quote
Old 17th January 2009, 10:48 AM   #8
diyAudio Member
 
Lostcause's Avatar
 
Join Date: Aug 2005
Location: NW UK
No problem.

Not much to do with Charlize, she doesn't require much tweaking at all.
Direct coupling without input caps was the one mod that made a big difference to me.
If you dont have the air coils then that is a worthwhile mod... but I did change mine to toroids..... just my preference

Cheers
Lee
  Reply With Quote
Old 21st September 2012, 12:13 PM   #9
giulio is offline giulio  United Kingdom
diyAudio Member
 
Join Date: Dec 2004
Location: ???
Hi Radian,

thank you for the informative "How to".

I have used it to go capless on a Hifimediy T1 amp (TK2050 chip).

This is my experience:

1) The amp is dead silent, in the standard configuration with input cap.

2) I had some quite noticeable hum when I just connected audio ground to the bias pin without adding any cap (just the original ceramic cap). The hum went away if I disconnected the USB cable from my USB dac or the Ethernet cable from the PC driving it.

2) Paralleling, as you suggested, a 22uF cap with the original bias cap, reduced the hum level to barely (but still) audible. Would it go down further if I were to increase the cap to let's say 47uF?

3) I have not installed RF beads yet. Are they likely to reduce hum? If so what values do you suggest? Should they be in series with the various power and audio lines or should the relevant cables just go through them?

TIA
Giulio
  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
Charlize 2, no input caps, HISS Code Class D 4 3rd February 2008 06:09 PM
Can I remove the input caps? Nightpuma Tubes / Valves 17 12th April 2006 11:21 PM
Charlize input cap problem - Help! KT Class D 9 10th February 2006 03:22 PM
Input Caps on TDA7264 ThSpeakerDude88 Chip Amps 1 4th August 2005 02:44 AM
input caps in an Audible Illusions M3 funnyjoe Digital Source 0 24th October 2004 05:58 AM


New To Site? Need Help?

All times are GMT. The time now is 06:14 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