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

Ebay cheap TDA7498 boards
Ebay cheap TDA7498 boards
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 30th October 2017, 12:06 AM   #381
DreadPirate is offline DreadPirate  United States
diyAudio Member
 
DreadPirate's Avatar
 
Join Date: Jan 2006
Location: Athens, GA
I have been using this board (SW-HF20) now for a couple of months and am very pleased with the results. Detail and clarity are there, instruments and voices realistic. Good power to drive most small/medium sized moderate efficiency speakers at 24V supply at the default gain. I am running primarily on a set of Pioneer SP-BS22 with the Dennis Murphy mods (new Vifa tweeter and crossover). Mods to the board have been replacing the inputs caps to MKT 1822 2.2uF/63V (NOS from eBay vendor electronics-plus), the rail caps to Rubycon ZLH 470uF/35V (Digikey), and replacing the output caps with a 680nF value (mounted under board in pic) to better match the speaker impedance. The stock output filter is pretty much in line with the datasheet. Board was obtained from sanwulasers.org ($11 shipped). Very quiet, no buzz or hum at any volume. A very nice package overall, should make most happy.
Attached Images
File Type: jpg PA290291.jpg (751.2 KB, 492 views)

Last edited by DreadPirate; 30th October 2017 at 12:09 AM.
  Reply With Quote
Old 5th November 2017, 07:16 AM   #382
Ingborgbo is offline Ingborgbo  Sweden
diyAudio Member
 
Join Date: Aug 2017
Thanks for the advice, mr Pirate!
Would you please tell some more about your choice of output caps? I'll be using 8ohm speakers and I don't know how to match those caps.
Cheers
  Reply With Quote
Old 5th November 2017, 11:00 PM   #383
DreadPirate is offline DreadPirate  United States
diyAudio Member
 
DreadPirate's Avatar
 
Join Date: Jan 2006
Location: Athens, GA
Quote:
Originally Posted by Ingborgbo View Post
Thanks for the advice, mr Pirate!
Would you please tell some more about your choice of output caps? I'll be using 8ohm speakers and I don't know how to match those caps.
Cheers
Per the TDA7498 datasheet, the output cap C20 and C26 should be 470nF for 8 ohm speakers (680nF for 6 ohm) and on this module, that is what they are. I have verified that C18, C22, C24, and C28 are 220nF per the datasheet, the output caps are all in line with the test circuit in the datasheet. The resistors in the output filter are 10 ohm on the board and 8 ohm on the test circuit. 22uH inductors, same as test circuit. All in all, very close to the recommended output filter. With good input caps, very low esr rail caps, this unit sounds very nice.
  Reply With Quote
Old 6th November 2017, 11:06 AM   #384
Ingborgbo is offline Ingborgbo  Sweden
diyAudio Member
 
Join Date: Aug 2017
Thanks again!
  Reply With Quote
Old 9th November 2017, 10:31 PM   #385
sailormanbigd is offline sailormanbigd  United States
diyAudio Member
 
Join Date: Jan 2014
Location: New Port Richey, Fl
Default Hey pirate

What are the other two small boards on the right for? Not wired up yet. I am digging some mellow jazz with my stock blue sanwu board, wow stock sound is great. No listening fatigue like the other board I've tried. Mine is the board with 4x330uf 35V caps on both sides of heatsink i suppose they are input caps? Doesn't add up to what u say the test board calls for? You think it's worth upgrading to 470 d 4?
  Reply With Quote
Old 12th November 2017, 07:55 PM   #386
Kpt is offline Kpt
diyAudio Member
 
Join Date: Aug 2017
I have a couple questions about improving one of these boards(XH-M512 version):

The version of the board I have matches the datasheet output filter almost exactly for 6 ohm (which my speakers are) except for 33uH inductors instead of 22uH. How important is the 22 vs 33 uH? They're shielded SMT inductors with virtually no space next to the pads so it would quite hard to desolder and replace unless this plays a big factor in sound quality.

Secondly all of the yellow film caps do match for the correct values on output filter and input caps. Would replacing these with brand name film caps or increasing the input capacitance make any improvements?
  Reply With Quote
Old 14th November 2017, 12:08 AM   #387
df audio is offline df audio  Canada
diyAudio Member
 
df audio's Avatar
 
Join Date: May 2014
I've had my Sanwu 7498 for around a month and it suddenly failed with no output. Power supply voltages looked good (as far as I could probe without taking off the heatsink) and the solder joints seemed solid. I noticed that the heatsink failed to warm up like it used to, even though the amp had been powered up for a while.

Removing the heatsink was extremely difficult and in the process the chip was pulled up and I broke a couple of the traces on the board. Fixing those to the best of my ability and resoldering the chip didn't work, despite seeing proper voltages at the inputs to the chip.

Maybe 24V was too much for the 7498 and this tiny heatsink - the heatsink was quite hot when the amp was idling without anything playing (when it worked). Anyways, my amp is now toast.

Last edited by df audio; 14th November 2017 at 12:12 AM.
  Reply With Quote
Old 14th November 2017, 06:12 PM   #388
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
Quote:
Originally Posted by df audio View Post
Removing the heatsink was extremely difficult and in the process the chip was pulled up and I broke a couple of the traces on the board. Fixing those to the best of my ability and resoldering the chip didn't work, despite seeing proper voltages at the inputs to the chip.
Well, I wouldn't exactly expect it to work after that ordeal because it was defect in the first place afterall.

Quote:
Originally Posted by df audio View Post
Maybe 24V was too much for the 7498 and this tiny heatsink - the heatsink was quite hot when the amp was idling without anything playing (when it worked). Anyways, my amp is now toast.
The amp got a thermal shutdown/protection, that should not be the cause. The TDA7498 can be used up to 39V (not recommended though unless you are using high impedance speakers) and got a over-voltage protection at 42V, so that's not the problem either. What kills most of these amps is if you cross-connect the output/speaker wires or short them to + or -/gnd.

If your amp gets too hot and the heatsink is glued on, in most cases it's better to leave that be and instead of changing the heatsink, add a small fan.
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 15th November 2017, 02:10 AM   #389
df audio is offline df audio  Canada
diyAudio Member
 
df audio's Avatar
 
Join Date: May 2014
I treated this as PCB rework practice, and didn't really have high expectations... but it was worth a try. The speaker cables were attached securely and shouldn't have touched anything without me knowing. I checked the speakers (16 ohm Pioneer SX-7) and those aren't shorted.

The chip is dead though, so that's that. Sometimes, these things just happen and you have no idea why. I've been itching to do some design work again and this might push me to design a new amp this winter break. Still have some plans for a full-digital Class D sitting in a notebook somewhere
  Reply With Quote
Old 28th November 2017, 08:38 AM   #390
broadways is offline broadways
diyAudio Member
 
Join Date: Oct 2016
Just to inform others...

The tda7498 amp(with the single 35v cap design) not only kills FM reception in my house but in the vicinity also. When this amp is switched on, android phones in the other room no longer catch FM signal. In the neighbours house, their FM reception gives lot of static noise.

: evil :
  Reply With Quote

Reply


Ebay cheap TDA7498 boardsHide 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
Tons of class D boards on eBay here. EBBCO Parts 0 8th September 2012 12:17 AM
some help on TDA7293 boards off Ebay sardonx Chip Amps 40 25th March 2012 09:29 AM
DIY Gene on eBay - Aleph 5 boards monarodan Pass Labs 114 28th August 2008 06:09 PM
Regulator boards (on ebay) Nathan A. Swap Meet 0 2nd June 2006 11:28 PM
briangt boards+caddocks -- ebay jeff2747 Swap Meet 0 28th February 2005 06:46 PM


New To Site? Need Help?

All times are GMT. The time now is 08:25 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki