High-end chipamp build project
Posted 24th January 2013 at 08:21 AM by abraxalito
Updated 15th February 2013 at 06:12 AM by abraxalito
Updated 15th February 2013 at 06:12 AM by abraxalito
Go here : Possibly the most frugal high-end sounding amp?
If you have comments, feedback, critique or improvements and don't want to put it on that thread, feel free to leave it in the comments here.
Here are the first measurements - the Nitro amp being fed by the Ozone DAC with a six-tone multiple, peak digital level -20dB. Peak output power around 100mW in an 8R speaker (connected for this test). It looks from this that the datasheet is a little pessimistic on THD, though here I'm measuring the TDA8566, not the 8561. No measurement graphs are presented in the 8566 DS and the 8561 only has plots for 2R and 4R loads, not 8R.
Schematic now added. BOM here : https://docs.google.com/spreadsheet/...Hc&usp=sharing
Additional schematic showing how to use TDA8566Q in place of TDA8561Q as the latter isn't available from Mouser. Mouser only has fewer than 300 TDA8566Q in stock so best to get in quick - I doubt they'll be getting more as this chip is going obsolete. The pins shown unconnected in the mod schematic aren't unconnected - it means they're connected the same way as for the TDA8561Q.
If you have comments, feedback, critique or improvements and don't want to put it on that thread, feel free to leave it in the comments here.
Here are the first measurements - the Nitro amp being fed by the Ozone DAC with a six-tone multiple, peak digital level -20dB. Peak output power around 100mW in an 8R speaker (connected for this test). It looks from this that the datasheet is a little pessimistic on THD, though here I'm measuring the TDA8566, not the 8561. No measurement graphs are presented in the 8566 DS and the 8561 only has plots for 2R and 4R loads, not 8R.
Schematic now added. BOM here : https://docs.google.com/spreadsheet/...Hc&usp=sharing
Additional schematic showing how to use TDA8566Q in place of TDA8561Q as the latter isn't available from Mouser. Mouser only has fewer than 300 TDA8566Q in stock so best to get in quick - I doubt they'll be getting more as this chip is going obsolete. The pins shown unconnected in the mod schematic aren't unconnected - it means they're connected the same way as for the TDA8561Q.
Total Comments 72
Comments
-
Yeah I'd recommend investigating some more of the Philips/NXP chips. I'm noticing a slight surge of interest in the STA540 (previously below the radar) but it looks to be a slightly lower specified version of the TDA8947 which gets a strong recommendation from me. Its biggest advantage is going to higher voltage (25V max) which allows it to be used with an output step down trafo to get better PSRR. Beyond that there's the TDA1521 which goes up to 42V but is current starved so a perfect chip to fit an output trafo to.Posted 27th August 2015 at 12:58 AM by abraxalito
-
Unfortunately my demo 7297 has stopped working. I'm really curious why. I'm hoping not because of the chip, since I'd like to make a commercial version (high end).
The 8947 and STA540 offer the ability for balanced outputs with single/balanced input. That's appealing. But I guess I'd have to make something with them to know if they can repeat the quality under similar conditions. Maybe I'll have to if the 7927 isn't proving to be robust enough!
But maybe a discrete is truly best, however as you may imagine I'd be starting nearly all over again.
All in all I think these little chips offer the DIY community bank-to-buck that can't be had otherwise. For at least twice as much you might have a pile of parts you call a Pass amp, screwed to a piece of plywood you found.Posted 3rd September 2015 at 03:01 AM by Destroyer OS
-
I agree the bang-for-the-buck for chipamps is pretty incredible. I'm coming to the conclusion that discrete OPS might indeed be best - in terms of solving the PSRR issue - looking at that now for my headphone amp. Then I hope to apply what I've learned to speaker amps....Posted 3rd September 2015 at 03:30 AM by abraxalito
-
what would be the consequences of bridging the inputs and outputs for mono?
or just have one channel unused?
in the context of been lifepo4 battery powered and been built in to a full range driver speaker cabinet
ive a lm1875 that showed some promise with very early testing but will need a lot of 3.3v cells and just gets more complicated and costly
thought it would be interesting comparison to the 8561q as it would be a much simpler option if its of comparable quality
thanks
nige
thx for posting your projectsPosted 12th January 2016 at 03:16 PM by nige2000
-
Interesting question - thanks. You can combine the outputs using capacitors (with a little bit of series R, say 0.22ohms). The capacitors are needed because the DC offset at the outputs can be rather high. I've done this on my TDA1521 amps (another blog post) and it worked fine. The 1521 needs this because its max current rating is rather low (2.2A) but for the TDA8566 this could never be an issue as its way higher.
So the advantage of paralleling would be to halve the supply impedance between the pins and the die inside. I have no idea what this impedance is but it could be significant. Having one channel unused means the external power supply is less stressed, also could give definite advantages. But you'll have twice the quiescent current - you can't shut down one channel independent of the other.
Batteries are a good option - aren't you the nige who's been using batteries on his DAC supplies and references?
I've made some more discoveries since posting this project - nowadays I'd use an input transformer to reduce the overall gain of the amp with the aim of increasing the input impedance. The 25kohm min spec is just too low, I like to aim for over 200kohm nowadays and this can be done with a step-down trafo at the input.Posted 13th January 2016 at 02:03 AM by abraxalito
-
right ok
looks like i need to try both single and paralleled then
thx for the method
shall report back when i get it tested
i have been using these batteries as capacitors with floating "run of the mill" regulated linear supplies to provide ps unobstructedly direct from the cells and in same manner as a voltage ref in soekris r2r dac
started out with desktop type computer audio ps mods and it looks like the disease is going to spread to everything from the wall socket to the speakers
so far it seems easier to get sq increase out of the computer mods than anywhere else in a digital audio setup
computers are a bit of an audio hell hole
i suppose everything can be improvedPosted 13th January 2016 at 12:00 PM by nige2000
-
Yes indeed, so much so that although I'm a digital music fan I don't use a computer to play my music. At least not a normal desktop - I'll either use a DVD player or a media player (on a TF card) I got from Taobao. The latter uses a Cortex M4 CPU so its a computer of sorts, a low power SoC.Posted 13th January 2016 at 03:15 PM by abraxalito
-
is there a simple way for western europe to order from taobao often seen stuff id like to tryPosted 13th January 2016 at 07:39 PM by nige2000
-
I've heard there are Taobao agents who will place the order for you, for a smallish fee. Guess try Googling for 'Taobao agent' and see what shows up.
I did a quick Yahoo and there's a website 'www.howtotao.com' which has reviews of agents. But it wouldn't load quick enough here....Posted 14th January 2016 at 01:02 AM by abraxalito
-
Sounds good
have you tried higher voltage than 19v?
or whats the upper limit?Posted 20th January 2016 at 05:55 PM by nige2000
-
Lol no need to answer that found out the hard way
On with version 2Posted 20th January 2016 at 06:52 PM by nige2000
-
I tried higher voltage - it has overvoltage protection but mine didn't blow up, just muted. Bring the voltage back down again and it's fine. That's automotive stuff for you, very rugged.Posted 21st January 2016 at 02:26 AM by abraxalito
