Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Class D Switching Power Amplifiers and Power D/A conversion

TDA8954TH - XH-M252 board - anyone?
TDA8954TH - XH-M252 board - anyone?
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
Thread Tools Search this Thread
Old 8th December 2019, 09:35 AM   #51
FauxFrench is online now FauxFrench  France
diyAudio Member
Join Date: Dec 2017
Location: The mountains, calm and quiet.
The speaker protection circuit is designed with a simple relay that only connects or disconnects the speakers from the amplifier. No amplifier load when the relay disconnects the amplifier. That, I do not find good when a class D amplifier is started up without a load.
I short-circuited the relay contacts such that the speakers are also connected to the amplifier at start-up and shut-down. Then, the amplifier functioned well and all I hear in the speakers during start-up is a small "click". This type of protection circuits with a relay, I find mainly belongs to Class AB amplifiers without integrated diagnostic and protection functions. For this class D amplifier, I will probably disable the protection circuit.
Now the amplifier plays well with +/-24Vdc supply but even when the amplifier funtions well, the relay coil is not activated. I have a slightly high DC offset at one output (around 85mV) so I will try to make a compensation circuit later. 85mV should not influence the protection circuit.

Last edited by FauxFrench; 8th December 2019 at 09:37 AM.
  Reply With Quote
Old 8th December 2019, 09:28 PM   #52
dzwer is offline dzwer  Bulgaria
diyAudio Member
dzwer's Avatar
Join Date: Jun 2009
Location: Sofia
No, 85mV is too small DC offset to activate the protection.
There should be a 1k-1.5k resistor directly connected at the output filter, before the relay.
Examine the protection chip, if it is OK or not.
Nothing moves you like a hydropneumatic Citroen...
My Youtube channel with my concert recordings of Bulgarian bands: https://www.youtube.com/user/snejankoable/videos
  Reply With Quote
Old Yesterday, 08:27 AM   #53
FauxFrench is online now FauxFrench  France
diyAudio Member
Join Date: Dec 2017
Location: The mountains, calm and quiet.
You are right that as an engineer I should investigate and repair the problem. However as a pragmatic, I should realize it is a useless feature anyway and just bypass it. I chose half-way with a quick investigation.

The design values shown in the NEC datasheet are used without further thinking. That means for pin 8, 15K to Vcc and 56K from pin 8 to pin 7. 15K to pin 8 is for 45V positive rail supply. However, as the rail capacitors are rated to only 35V and Fig.6 of the datasheet is disregarded, 15K is a poor choice. With +/-18Vdc supply, I measure 2.8V on pin 8 of the C1237HA and it has to be minimum 3.0V. The Vcc-ON detection is invalid for lower range supply voltages which the TDA8954 can else operate with.
I stopped my investigation here but now you know where to look if also you have problems. I for a start continue with my relay by-pass and the amplifier part itself seems to work well (luckily). Later on, the C1237HA will be removed and perhaps also the relay, if not too much of a hassle.

If anyone is looking for an amplifier board that needs no modification, this board is not it. With some modification, I believe it can be turned into a very well sounding amplifier. If you aim for high power as promised for this board (more hundreds of Watt), I would rather go for an IRS2092 based board as the cooling abilities are better with external power FETs.

Last edited by FauxFrench; Yesterday at 08:32 AM.
  Reply With Quote


TDA8954TH - XH-M252 board - anyone?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
My Cambridge 500SE, needs an output board (to replace internal DAC Board) slbender Digital Source 1 11th July 2018 03:43 AM
Unknown Board DC12V TPA3116 amplifier board DIY L163-9 AUS Ben Class D 0 8th December 2016 05:05 AM
Wanted: LM1036 tone board (no ebay or aliexpress board) schdrag Swap Meet 0 2nd December 2016 07:47 PM
problem with tda8954th shahpoori Class D 2 22nd May 2016 06:52 PM
HIFI 700W Subwoofer Mono Amplifier Board By 10 Pairs 1943/5200 Amp Board For Subwoofe nelnar Solid State 2 21st July 2014 07:35 PM

New To Site? Need Help?

All times are GMT. The time now is 12:20 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio