TDA1387 continuous calibration dac

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You can get some bass improvement increasing the pin7 (Vref) capacitor. Try a few 3,300uF/6.3V in parallel.

I managed to fit a 4700uf in the case, and you are correct, the improvement was overwhelming!! It brought the same kind of accuracy in the top end to the bottom end, what a neat trick! The designers of the tda1387 themselves obviously didn't even know about it!
 
And here's my 4X TDA1387 with the output filter taken out, the iv resistors reduced to 120R and the output transformers installed.
Plenty of volume, no need for preamp, running it straight into power amp. Only been listening for a few hours, sound is excellent.

Hi lordearl,

What is brand & model of your transformer? Where did you get it? The specs you posted earlier seem impressive.
 
I managed to fit a 4700uf in the case, and you are correct, the improvement was overwhelming!! It brought the same kind of accuracy in the top end to the bottom end, what a neat trick! The designers of the tda1387 themselves obviously didn't even know about it!

The next step is to add lots and lots across the supply rails - from 10X to 100X what you have on the Vref pin...... But clearly you'll need a new much larger case for that :p
 
Hi lordearl,

What is brand & model of your transformer? Where did you get it? The specs you posted earlier seem impressive.

Hi mate, they're from a Taiwanese seller on fleabay, excellent quality and great pricing. The seller has some other well designed and interesting gear.
See item: 330435862267

The next step is to add lots and lots across the supply rails - from 10X to 100X what you have on the Vref pin...... But clearly you'll need a new much larger case for that :p

What sonic improvements do you notice when you make those changes?

Battery power supply is the best I can do given the space constraint!
 
More low frequency ambience retrieval is the thing I notice and the reason I spend so many hours soldering capacitor hexagons together :) It seems to lower the LF noise floor and as a result there's more information coming through in the lower frequencies. This is clearly noticeable even though my speakers have only 5.5inch bass/mids and I've no subwoofer at present. For speakers with better LF extension I'd guess the improvements would be even more apparent.
 
Parallel TDA1387s?
I'm just glancing at this thread -- w/o having read most of the posts since I last chimed in.
Years ago, I did try paralleling several TDA1545As ... and did not like the results.
Not sure what the "trick" is in getting a parallel arrangement to work.

Saw that Chinese "L1387A 8X 1969" headphone amp. Interesting. But the power consumption for a portable device is high with all those DAC ICs ... even one as frugal as TDA1387/1545A. My earlier argument was that this DAC should be in an iPhone-sized device ... LiPo battery and all.
 
Who's still manufacturing 1387s?

This DAC with 8 paralleled TDA1387s sounds just great to my ears ...
The label on the 1387 has Philips with the brand icon ... but TTBOMK, that IC was first released ~1994.
Did the Chinese find some new-old-stock stash of AUTHENTIC Philips chips ... or did Philips license some Chinese IC factory to re-manufacture ... or are they "facsimile" rip-offs? Not saying that's a bad thing ... who knows... with modern ('computer-controlled') production tolerances, a Chinese faker/duper may even improve on the original!
 
Check authenticity ...

BTW ... That 8xTDA1387 Taobao headphone amp is non-oversampling:

An externally hosted image should be here but it was not working when we last tested it.

:headbash::rolleyes:
YUCK! ;)

All the TDA1387s I've bought on Taobao haven't been new, rather recycled. Probably out of old 'Soundblaster' cards. I'd guess these are same. The price is right so I've stocked up on a few thousand :D
I've seen these chips on eBay for 10/$35USD. Even at $3.50ea, several thousand (if you're serious about your investment) is quite a sum.
I have several of these classic DACs in my parts bin, and I almost never use them. The IMPLEMENTATION is what's important. For my tastes, I can get a free sample TI PCM1792 to sound better .. with simple opamp swaps or cheap passive (R, C) upgrades/tweaks.

All that said ...
If you have a 'scope/spectrum analyzer, you can test how good they are compared to the genuine article (other 1387s of KNOWN vintage and/or TDA1545As from a few decades back).
YouTube has some how-to videos on how to perform these tests.
 
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According to the spec sheet this chip is only capable of 16bit resolution. With the USB CM6631 upgrade on E-Bay the DAC claims 24bit resolution at a 192k sample rate. I want to purchase this DAC and put it on the output of my computers optical port, without the USB upgrade. I have some 24bit 96k files that I would like to listen to with a DAC like this. Will this support 24bit audio and dither or just truncate it? Excuse me if this is a dumb question, I am just learning about DAC technologies. Thanks!
 
I reckon it'll just truncate any bits beyond 16. To do dither it'd need a DSP and AFAIK it doesn't have one.

In that case, does 24bit content sound good with this DAC? For some reason it never crossed my mind that a DAC would support 192k sample rates, but not 24 bit word length.
I also dont really know why a DAC chip (CS4272) would support 192k but the interface only goes up to 96k (Focusrite Saffire Pro 24DSP) but I digress.

When it comes to the optional USB "upgrades" offered, are they an expansion or do they replace the TDA1387 chip? Its not terribly clear on E-Bay or Cart 100. Does the CM6631 USB option have some DSP on it? It claims to add 24bit 192k support. Have you tried this option?

Sorry for all the questions. Again, I'm kinda new to this. Ive been an end user (audio engineer) for many years, but only recently got into DIY audio. I'm going to buy one regardless and play with modding it. :)
 
First, I can't see lots of questions as in any way a bad thing on here. If anything the apologies should come from the people claiming all kinds of stuff unsupported, not the questioners.

I can't think of a reason why 24bit should sound particularly bad just because its bottom 8 bits (which are mainly noise anyway) get lopped off. There's the potential for quantization distortion but it'll be at such a low level it can probably be ignored in practice. As for your question about sample rates - perhaps only going up to 96k is evidence its not using high speed USB - full speed (12Mbit/s) has a 96k limitation.

The upgrades are just to the digital front-end in my understanding, they change nothing about the D/A part, simply permitting more input options. About the CM6631 - I dunno. I don't think I have any hi-res filters above 96k myself, all my listening is to RBCD which I find fully satisfying.
 
The buss limitation makes a lot of sense as to why I can only run at 96k on the Focusrite Saffire. (Firewire, not USB, but same issue :) ) It's also a multi channel interface so it needs a lot of bandwidth when everything's cookin.

I ordered my L1387 8x off of Cart 100. I added the CM6631 USB option to try out. They said it will take about 10 days to build a 110v compatible unit. I threw in a couple "DIP-8 AD845JN" Op amps that I found for about $6 each on Cart 100. I hope they are genuine... They said "genuine" and were more than $1 so Im hoping for the best. (Its always concering when items have to be labeled "genuine" or "authentic")
Question: Can I just swap out these op amps without any other mods as soon as I get the unit, or do you suggest any mods first? Ive read that you can just swap them out and that will work but is that making the most of the op amps?

Thanks!
 
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