DIY thoughts of the day

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Sat Oct 13, 2018 2:49 pm

Pics of the naked £3.43 Chinese Dac. Apart from the dac chip which I cant identify, there are only two 3 legged components. Rest are caps and resistors. P1 which is marked 662K is a 3.3V regulator . The other which is Q1 (Y1 on component) is probably a 0.3W Zener diode (see it on second pic).

Image

Image

Had to scrape some mask away to see what is underneath. May have a stab at tracing it all and see if any more power supplies can be attached
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Firebug1
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Re: DIY thoughts of the day

Unread post by Firebug1 » Sat Oct 13, 2018 4:31 pm

Sorry to say this Stu but your hifi looks like Dr. Frankensteins laboratory.... :shock:
Rega\Teac\NVA\SA Mantra30\ATH-A900X
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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Sat Oct 13, 2018 4:57 pm

Firebug1 wrote:
Sat Oct 13, 2018 4:31 pm
Sorry to say this Stu but your hifi looks like Dr. Frankensteins laboratory.... :shock:
Yes i know, wont be staying like that. Gonna build it in to something eventually. In a tidy fashion of course.
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_D_S_J_R_
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Re: DIY thoughts of the day

Unread post by _D_S_J_R_ » Tue Oct 16, 2018 9:10 am

My cheapo dac is different inside I think, but I can't currently post pics..

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Mon Nov 05, 2018 6:17 pm

No going back to output stage on the cdp now. Need to try some 1uf paper in oil coupling caps on the output. Shame the dac chip has 2.5V dc on it's output otherwise I wouldn't have a single coupling cap in the system :cry:

I got rid of two psu's when I ditched the active output stage but it seems this poor cdp may be breeding some more at some point :roll:
At the moment I have 3 psu's on the dac chip, one on the clock and the original Naim transformer doing all the purely digital stuff (laser, RF amplifier servo power drivers, front panel, RAM chip, processor/decoder).

People have told me not to bother trying to improve the psu on the digital side as everything already has its own LM317 reg already. Some one did try putting two ALW super regulators (opamp based with feedback) before all the local LM317's on the digital side and reported a tiny improvement. I wont be trying that approach (although i have some of those regs).

I think i will instead try adding more power supplies and give the processor/decoder its own and maybe the laser. If anything comes of that then possibly give the Ram chip and power drivers their own too. I dont think the display will look any better with its own psu :lol: but if everything else gets one then it will obviously end up with its own too. As these regs are 5V then the little LED mod can be done. Remove the voltage set resistor from the LM317 reg and replace with two green led's. Bingo- a whisker over 5V as well as lower noise and impedance. Not sure i will try any pre tracking regs with two LM317's. Then there are capacitance multipliers which can be put on the front.

All stuff i have done before on other things but playing about with regs is something that usually ended up with more complexity rather than my new less is more way of looking at things. Comparisons will have to be made and i will try lots of different approaches. But this is digital i am messing with now so who knows what the best musical choice will be. If there is no improvement then back to standard it will go.
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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Fri Nov 16, 2018 9:06 pm

Thinking about cdp's, transports and dac's. Keeping it simple (stupid) suggests to me that a cdp is the way to go rather than separate transport and dac. Very short i2s lines between decoder and dac chips, no sockets and cables, no reclocking, no spdif chips and associated bollox. Why have all that extra complex bollox ? Surely it must make the music worse.

The only drawback i can see for having it all in one box is noise from the high frequency digital part polluting the anologue part. Does not bother me too much though as i bypassed the 7 pole bessel filter in my naim. One good thing they did in my cdp is disable the spdif output of the decoder by means of the pic ram chip. Supposed to be a good thing sonically but there is no way i could insert a digital out facility even if i wanted one. I suppose the good thing about a stand alone dac is you can connect more than one digital source to it.
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Vinyl-ant
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Re: DIY thoughts of the day

Unread post by Vinyl-ant » Sat Nov 17, 2018 12:31 am

Get hold of an old Philips machine like a cd160 ect with a tda1541 in it for a couple of quid and you can go bonkers modding the heck out of it
A good one to play with is a cd471 as it has a large section down the right hand side that has nothing in it. You can fit loads of reg boards for separate psu's and reclocking and non oversampling mods can be done too.
As a learning aid these machines are great. Bullet proof cdm2 transport too. The boards in these are lovely and simple too, you can literally follow the circuit on the board and there is good component spacing. Only cramped areas are around the Dac pins. The smt decoupling caps for the Dac are shite but these can be left in place and bypassed with tantalums or nice ceramics.
For messing about on the cheap they are great
BTE designs type 2 lenco, Audio Technica AT1100 AT150sa, JBE series 3 mayware formula 4 shure M97xe (his), JVC QL-Y5F Audio Technica AT440 mlb (hers)
BTE designs type 1 mk2 passive pre, PASS F5 dual mono, modified Philips cd371, Metronome 'M' speakers, BTE designs balanced power supply, Benedict Audio hothead (mm) musical fidelity x-lps (mc) mac mini + beresford tc7510

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Sat Nov 17, 2018 9:04 am

Hey Ant. Messing about on the cheap - i like it :guiness;

Thats not a bad idea but my naim cd3.5 is already modded to within an inch of its life. I have further work to do in the digital section and i dont have an anologue stage as such anymore. This was a £1050 player when i bought it new in 1997 and now worth about £350 on ebay in stock form. Its been a long ride modding this (spanning 10 years) and i have become so attached to it now , its like my baby . Scared everytime i do a mod in case it goes pop and blows some unobtainable ic.

Would be nice to play with a 1541 equiped machine after all the hype that surrounds them. Something else to add to the to do list :roll:
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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Sat Dec 01, 2018 9:08 pm

Done a lot of circuit tracing in my cd3.5. Most things have their own lm317 reg apart from the front panel which share's a reg with the pic (ram chip) and two of the decoder's supply pins also share a reg. Also the laser supply has a pre reg which is the reg for one of the power drivers (TDA7073AT).

People i respect have said that nothing more can be done to this player on the digital side. Well you know me, i just cant help myself :grin: So, front panel will get it's own reg as well as putting in another for the combined servo and decoder chip so each supply pin has it's own reg. And why stop there i hear you cry. And why not a dedicated pre reg for the laser, god knows it deserves it with being the most vunerable part (very many vintage cdp's would be an expensive door stop if the laser gave up the ghost ).A few more transformers wouldn't go a miss either :guiness;

Dac chip already has 3 psu's and everything else shares the original psu (novutem 200va). How about one for the decoder and one for the two tda7073 power drivers. A crappy one for the front panel would take load and noise off the ram chip supply. Oh and maybe the laser desrves its own transformer as well. At this rate i will be surpassing some of the marantz cd63's found on the 2000 (yes two thousand) page modding thread on diyaudio. Half way through reading that epic :roll:
Last edited by karatestu on Sat Dec 01, 2018 9:16 pm, edited 1 time in total.
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Dr Bunsen Honeydew
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Re: DIY thoughts of the day

Unread post by Dr Bunsen Honeydew » Sat Dec 01, 2018 9:11 pm

More on chainsaw speakers please, that is the most entertaining part.

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