Edited for clarity.
This is bad HF PS design that looks like it can't be fixed (tiny vias). [Maybe with a lot of work ...]
Don't get the x4 board.
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PS Crap, now I see it comes with an aluminum case for $100 ! Hmm, even I'm thinking of getting one, removing the 3 1387s on the right, and then stacking them (a la 'Braxy) one-by-one and seeing if i like it ....
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I've been playing with the tda1387 board for a few weeks now and the sound is great, sweet treble and tight bass. Not major differences from the single TDA1545 board though.
Before I tried using it with output transformers, I checked the iv resistors with a multimeter and they are 460R. The seller said it uses 1.2k. Any ideas as to why it might read different? I'll need to get it quite accurate to reduce the iv resistance to use the gain stage transformers.....
Ah thanks, nice pic 
Looking at the 470Rs, one side looks to be connected to the ground plane. So they're shunt resistors I take it. Which you definitely don't want - they're going to reduce the output level from the DAC if they're in circuit. Suggest removing them and you could wire the 'raw' DAC output, via a coupling capacitor, to the edge connector. Then you can put your trafo in the sensible place you already mentioned - between that connector and the output RCA.
Looking at the 470Rs, one side looks to be connected to the ground plane. So they're shunt resistors I take it. Which you definitely don't want - they're going to reduce the output level from the DAC if they're in circuit. Suggest removing them and you could wire the 'raw' DAC output, via a coupling capacitor, to the edge connector. Then you can put your trafo in the sensible place you already mentioned - between that connector and the output RCA.
Yes you are spot on - one side is connected to ground. So basically they've set the circuit up as follows; the DAC chip -> IV resistor -> shunt resistor -> os con capacitors (2) -> output terminals.
So I've already reduced the iv resistors from 1.2k to 120R, all we need to do now is simply snip out the 470R shunt resistors, correct?
So I've already reduced the iv resistors from 1.2k to 120R, all we need to do now is simply snip out the 470R shunt resistors, correct?
I agree - these DACs are very forgiving (not that I have any experience of those other two). The sound is very addictive - you'll be moving on to massive cap arrays to improve bass definition real soon...
Speaking of cap arrays, here's my latest DAC PSU (for initial testing of the Aune card on my blog). Its a series-parallel array of 100F EDLCs. Since each cap is only rated to 2.7V I need to put two in series - the yellow wires are to the balancing circuit attempting to head-off any overvoltage on each.
Speaking of cap arrays, here's my latest DAC PSU (for initial testing of the Aune card on my blog). Its a series-parallel array of 100F EDLCs. Since each cap is only rated to 2.7V I need to put two in series - the yellow wires are to the balancing circuit attempting to head-off any overvoltage on each.
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Far out Abraxalito, that is incredible. Is it with the express aim of tightening up the bass? What other sonic benefits does it give?
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.
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.
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Actually the most enjoyable sonic benefits are the increased ambience noticeable at the lower frequencies. It gives a more impressive impression of spaciousness, more 'you are there' feeling. Tighter bass I haven't noticed (not to say it isn't there) just my attention gets drawn to the LF spaciousness.
So the trafo mod is definitely a winner then? Looks like a very clean, simple build. Good stuff.
Incidentally there's now an octal 1387 DAC on Taobao - http://item.taobao.com/item.htm?spm=a230r.1.14.33.Jib45t&id=42524269798&ns=1&abbucket=13#detail
So the trafo mod is definitely a winner then?
Looks like a very clean, simple build. Good stuff.Incidentally there's now an octal 1387 DAC on Taobao - http://item.taobao.com/item.htm?spm=a230r.1.14.33.Jib45t&id=42524269798&ns=1&abbucket=13#detail
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Yep the trafo mod has been burning in for the last eight hours or so and definitely the key improvement in the mids, a bit more relaxed....closer to how the perfect treble of the 1545/1387 sounds.
So now...how to improve the bass? Knowing that there isn't much space in the case for a behemoth capacitor pyramid like yours Abraxalito!
So now...how to improve the bass? Knowing that there isn't much space in the case for a behemoth capacitor pyramid like yours Abraxalito!
ok great, i've got a bit of space between the edge of the board and the case of the chassis so can fit a few capacitors in there. How many thousand uF do you prefer to use?
Another thing I notice is that there's a loud pop sound which always starts when I press play on JRIVER. It's always only at the start, never during playback. What's the best way of stopping it?
Another thing I notice is that there's a loud pop sound which always starts when I press play on JRIVER. It's always only at the start, never during playback. What's the best way of stopping it?
Well I just use as many as I can fit close enough. The DAC I was listening to most of the summer has about 6 TDA1387s paralleled up and each one had a hexacap of 61 * 3,300uF on pin7. Maybe that's overkill. The newer DAC I've been working on will have fewer (19 * 3,300uF per chip, 4 chips) due to space constraints.
I don't use a computer as source so I'm out of my depth in answering this question about JRIVER.
I don't use a computer as source so I'm out of my depth in answering this question about JRIVER.
Insane!
The one I have in there at the moment is 22uF.
Might try 100uF to start and see if there's any diffference!
Do you bypass them with film caps or similar?
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