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Old 12th February 2013, 04:07 AM   #211
Eldam is offline Eldam  France
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thank you ALD,

yes i see that after and have to challenge it with the cen or sen discretes. thank you too for the link.
i have too a sort of jocko 's i/v stage variation in a chinese nos dac with 1865... but not happy with it (layout problem accordingto Abrax, low grade dac chip according to me).
Is the quality of i/v resistor important in these schems in relation to a full passive i/v shem with one resistor just after the dac chip?
Is there need to a little value resistor in serie to the input of ad844 for damping even with the low current output of the tda1541 ? (rhopoint wirewound or good surface mount?)
cheers
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Old 12th February 2013, 04:16 AM   #212
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Quote:
Originally Posted by Eldam View Post
Is the quality of i/v resistor important in these schems in relation to a full passive i/v shem with one resistor just after the dac chip?
I'm still using the cheapest thick film resistors for my I/V. Perhaps its important though and I've yet to notice. Certainly its way less important than good layout
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Old 12th February 2013, 12:36 PM   #213
Eldam is offline Eldam  France
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I am sure you are right. First the shem with active components, second layout (non comon impedance between actives parts=one complete supply by active component?), third resistors... something like that for the non specialist than i am. I am a sunday diyer, i play with caps and it's funny to hear that with to different electrolytic caps of the same voltage and value and esr... you can hear a different Q factor in the bass... but you right it's the cerise sur le gateau !

I would love to play with Tina, but the one i am able to understand the song or the long legs call Turner ( french humour ).

Why tubes can't be better in the treble like you said to me ? Can I understand that the discrete shem play better with higher voltage = less importance of the layout ? In another word : noise of the tubes in high is better than noise of transistor ?
I 'm loosing myself it's not the subject...
cheers...
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Old 12th February 2013, 01:13 PM   #214
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Originally Posted by georgehifi View Post
They (all the cdp's) would see around 7kohm load with the 100kohm of the Halcro DM-78's added to the Lightspeed
...
Hmmm, ya that's why I asked. I don't know the details of the tube output stage of the AMR but tubes sometimes have trouble with under 10k and may even want 20k.
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Old 12th February 2013, 01:17 PM   #215
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Originally Posted by abraxalito View Post
... Certainly its way less important than good layout
Eldam "...layout problem accordingto Abrax..."



I would love to see some of the layouts people are using ...



I have an ancient 844 i/v here somewhere, it's probably poorly designed ...
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Old 12th February 2013, 04:23 PM   #216
Eldam is offline Eldam  France
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Default layout

You are right too. For having lightly tweaked more than 20 cd players, i sometimes see that a good cap could be better and change more thing in final sound that just tweaking the powersupply of aop or change it. But "sometimes" is not "always" . It's difficult to me to understand when you must have local ground plane or not with at least a big ground plane at the otherside of the veroboard (with digital and i/v)... I read I read... sometimes i learn when i understand !

If i take my ad1865 board : ABrax is right; for example i input the spidf direct on the cs chip : better ; i leave the resistor of 75 ohms : even better (not good in theory); but it's just with my squeezebox spidf output (chinch and 100 homs between cold & hot pin !!!). And about layout i have to try I2S if i succeed to understand ho to use it with this board before going with a TDA1541 veroboard.
Last : if i move the caps with the layout not changed, it can sound more more greater ine with anothers fines chooses: just using FM cap or nichicon audio caps is not enough... at least for me and in a little perspective.

So the shematic & ingeenery first, the layout with the good components too. that's why i ask to John if he has more final sucess with the tda1543 module or the unfinish yet TDA1541. He said they could be very very near 3 years ago, and in another hand too much peopoe are waiting maybe too much from a "bad layout" with this chip. TDA1543 sometimes can sing too like anothers tda(1545) or the last Akai pcm56 cd player i kill by accident : great result with this last one : all the chips and aop supplied with the sames -/+ 5 V normal regs... may be better than a philips cd306.
So i talk i talk but soldering is the way to learn too for the hobbyst...

Last edited by Eldam; 12th February 2013 at 04:28 PM.
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Old 12th February 2013, 05:04 PM   #217
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Originally Posted by AudioLapDance View Post
Eldam "...layout problem accordingto Abrax..."



I would love to see some of the layouts people are using ...



I have an ancient 844 i/v here somewhere, it's probably poorly designed ...
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Old 12th February 2013, 08:00 PM   #218
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Quote:
Originally Posted by AudioLapDance View Post
Hmmm, ya that's why I asked. I don't know the details of the tube output stage of the AMR but tubes sometimes have trouble with under 10k and may even want 20k.
The AMR has 100ohm output impedance this should have no trouble right down to even 1kohm, and I maybe wrong but it may have a solid state output buffer and the tubes are just for I/V duties.
Even if the output buffer is tube they are specified by AMR at being 100ohm output so no trouble driving anything.

Cheers George
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Old 12th February 2013, 08:22 PM   #219
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Originally Posted by georgehifi View Post
The AMR has 100ohm output impedance this should have no trouble right down to even 1kohm, and I maybe wrong but it may have a solid state output buffer and the tubes are just for I/V duties.
Even if the output buffer is tube they are specified by AMR at being 100ohm output so no trouble driving anything.

Cheers George
OP is probably a cathode follower of some description.
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Old 12th February 2013, 11:09 PM   #220
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Just found this, yes it does look to me as, tube I/V then then tube L/P filter then tube output buffer, with a couple of massive coupling caps on the output and between the L/P filter and buffer. Doesn't look like there is a coupling cap between the I/V and L/P filter unless it's one of those electros?

Cheers George
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