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Old 8th January 2013, 04:07 PM   #18961
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Default relay

Quote:
Originally Posted by 6h5c View Post
Alan,

The relay contacts are not connected in series with the signal, so there's no loss involved. Instead, they connect the outputs to GND when muting is active. You have to connect two 47ohm resistors in series with the ouputs though, you can't short the outputs hard to GND directly. But this was already the case in the original player (2x 100 ohms in series).

Ray
Thx ray,
Its not a problem to switch off the amp first, at the moment im
thinking of moving over to cfp dos over lme 49720ha/s anyway
thx alan
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Old 10th January 2013, 01:06 PM   #18962
Eldam is offline Eldam  France
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Hi, "bonne annéeeeeeeee"

Don't know if somebody try supercap as a battery before very low ESR cap like OSCON as supply before a DAC ?

It's hard to read every posts here from the beginning. I plan to feed a TDA1545a like that (Philips cd723) : main powersupply -> 4700 uf standard ca -> 0r7 -> 7805 reg with diode to adj (5,6 v) - 100 nf platic cap -> 0Rr5 (to make resistive output=passive supply) ->1500 uf (not low esr because better for sound after this type of reg; 1500 to flat impedance curve) -> SuperCap 0,5 F ( ripple killer? & as a batery) -> 0,1 uH Neosid -> smd very low esr cap (smd Panasonic SEPC : hope to be as good as larger SEPC Sanyo can type?) at the pins of the TDA 1545a... perhaps with 100 nf smd ceramic (or 10 nf ?)

Is it good, has it sense to make passive with active like simple 78xx reg ? I saw in a old CD42 (tda1540d) I have that Marantz use two normal 79xx in cascad to feed the tda540 and here all the caps value are small : 370 uf first then around 220 uf between the reg if my memory is not bad !

In fact I don't understand if these DAC need to see a linear voltage or better a stable curent and of course if caps be better than active stage for that (I don't spak about the continuous calibration Ir stage of the TDA1545a here)

Thank you in advance if someone has experiment a simple solution here because I' not a technician and d'ont want to go to a very or to pricy active stage to feed the DAC chip.

Eldam
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Old 10th January 2013, 04:52 PM   #18963
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I have 22,000uF -> LM317 -> BG NX/FK on each of my DAC pins, so 88,000uF total capacitance pre-reg. I think this is overkill. The DAC stays powered for about a minute after powering down. I think separate supplies are worthwhile but not so much capacitance is required.
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Old 10th January 2013, 05:29 PM   #18964
Eldam is offline Eldam  France
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Quote:
Originally Posted by Ben Hanke View Post
I have 22,000uF -> LM317 -> BG NX/FK on each of my DAC pins, so 88,000uF total capacitance pre-reg. I think this is overkill. The DAC stays powered for about a minute after powering down. I think separate supplies are worthwhile but not so much capacitance is required.
Hi, thanks for your reply,

What type of cap for the 22k uF ? Is the LM used for anothers active stage or only for the Dac chip ? In my Philips Cd723 the reg is not only used for the DAC that why i want to isolate the dac from the transformer with this Supercap as a battery, the personal cap for the DAC will be a low ESR like you. For what i Understand it's not the same if reg is only use for DAC or share its work with another circuit with the DAC..

I have just two 33 uf BG NX but sound harder IMHO than Sanyo OS-CON FS series for DACs (with TDA1545a & TDA1543).

Do you benchmark with big cap after you LM317 ? they seem (LM even L type) sound better if a "high" ESR cap is used at the output pin.

Do you try for example : big cap (low esr if not just after transformer) -> LM317 -> small cap (47 to 200 uf) or big cap (two are normal caps with high ESR) on LM pins -> BG NX/FX on DAC pins ?

I read that at the output of old regulators with modern caps (even of low grade) it's better if you use a little resistor (0R2 ?) in serie between the pin cap and ground (=the regs sounded better with old caps with high ESR, which I agree after hear tests on old Philips players : nichicon or philips caps).

Last edited by Eldam; 10th January 2013 at 05:41 PM.
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Old 10th January 2013, 08:06 PM   #18965
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Each DAC pin has its own dedicated transformer secondaries and diode bridge. DC is filtered by 22,000uF Mundorf AG. That feeds an LM317 board as per Martin Clark's tutorial 'Using 3-pin regulators off-piste' on Acoustica (sorry no link - replying from phone). They have small tantalum caps at the pins and green LEDs to set voltage. The regulated voltage is then fed direct to pin with BG 470uF local decoupling, NX series for digital and FK for analogue.
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Old 10th January 2013, 09:13 PM   #18966
Eldam is offline Eldam  France
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0,22 F for one rail and the little curent needs for the DAC, I can understand that you don't need Pi filter before your DAC...

Have to googling about Martin Clark's tutorial 'Using 3-pin regulators off-piste' on Acoustica.

I used to work with Philips Co136 or panasonic FM and basic nichicon but I have to try these Mundorf cap,

thank you Ben,

Anybody else please about gold cap / super cap emulating battery supply for low curent active device like DAC ? I don't find explicite answer here, or how to work with small inductance like neosid.

I'm looking for a small tweak here with caps and resistor... maybe small inductor (not a standalone transformer for DAC like Ben)

kind regards

Eldam
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Old 13th January 2013, 06:43 PM   #18967
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Quote:
Originally Posted by Fidelity Audio View Post
You can do the 63 without regulating and/or with regulating the servo driver psu, of course regualiting improves further. The one thing that needs sorting regardless is the psu. Disconnecting the tx for the +/- 10V is required and fit in the player a 2x 12V 30va - 50va tx to supply these rails. It makes a massive improvement. You can then run the regs at +/- 12V dc

Brent
Hi there, Brent or anyone, wich are the 3 pins for the 10V rails? I do have a TX to connect in there... U308 and U310? Need to keep u309 in and connect my new TX ground with the existing ground?

Thanks!
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Last edited by Malefoda; 13th January 2013 at 06:59 PM.
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Old 14th January 2013, 09:29 AM   #18968
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Hi Matthieu,

Yes, you have to make three connections to the board, U309 goes to the center tap of the new tranny, that is formed by connecting the two new windings in series. But I would use the ground point at U274 instead, this keeps the current path short.

Beware to keep the original tranny connected though, there's an extra 13.9V that runs to C854 for the display voltage, and it's used as power-on voltage through DN01...04. So you'll have to cut tracks somewhere between the fuses and D811...814 if you want to leave that intact, or take these four diodes out and fit an off-board rectifier somewhere.

If you don't mind that the new tranny feeds this extra stuff (I don't think it will do much harm), the easiest way to connect it is by taking out the fuses and use that as an insertion point. But I'd recommend to put some new fuses in... If one of the driver IC's ever burns out, a 50VA tranny can create a lot of damage!

Regards,

Ray
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Old 14th January 2013, 09:39 AM   #18969
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Hi Ray,
that's just neat, will use the fuse output to feed the player with fuse and handle some fuse holder so the player is safe

Thank you!
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Old 14th January 2013, 11:54 AM   #18970
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