Using the AD844 as an I/V

Not saying the AMR sounded bad, in fact when we started it was a CAL CL-15 (PCM1702/PMD100) that was first listened to for two tracks. Then the AMR was put on and it comprehensively beat the CAL CL-15, at that time I thought the Cary will have it's work cut out if it were to stay with this, then it was put on and we were stunned that it was better than the AMR.

Cheers George
 
Yikes, George, I think you should have been a bit more ... diplomatic. :bomb:Why? I don't like glossing over the facts, I never said the AMR sounded bad, in fact after the CL-15 I thought nothing could be better it, till the Cary went on.

You better get your flame suit on! :firefite:Doesn't worry me, I have a thick skin

Regardless of your preferences, the size of the trouncing seems odd?
Can you say more about the session: source, data (rate, 16/24bit), setting of the Lightspeed ...All were RedBook 44.1 one or two were HDCD encoded RedBook which sounded even better again. The Lightspeed was the owner of the system and it was around 1/3 up from zero give or take for all 3 cdp played. Cheers george

Cheers,
Jeff
 
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They (all the cdp's) would see around 7kohm load with the 100kohm of the Halcro DM-78's added to the Lightspeed
The 100ohms output impedance of the AMR would have no trouble with this, as would the 68ohm of the CAL-CL15 as would the 100ohms of the Cary. All had around the same gain as the Lightspeed indicated for the cdp's with the same volume settings at around 10 o'clock knob position.

Cheers George
 
I have an idea that perhaps its incompatibility between the Halcros and the AMR. Halcro from what I know of it is an ultra-low distortion, ultra high-feedback design. The AMR being normal NOS puts out lots of out-of-band images between 22 - 44kHz. Perhaps this ultrasonic output upsets the Halcro and saps the dynamics.

Hi Abraxalito, Hi George,

John from ECdesign said something like that too. The NOS design and the DEM do not match with high switching amp or SMPS in poweramp.

Interesting proof of concept. George maybe anaother listening session with the same speakers and wires but with a Conrad Johnson 350 for curiosity... and the "poor" AMR77 owner?

BTW, i have a old Chord SMPS 1200 B (smps power supply style & 100k inputs) maybe I have to try the ad844 i/v with an I2s out from my Squeezebox... but haves some difficulties to check a good shematic around the tda1541 (DEM, I2S<), john 's thread is hard to follow... i'm just a hobbyst:D.

cheers
 
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Hang on you guys are reading too much into the AMR being beaten, as I said it sounded great, it also comprehesivly beat out the CAL CL-15 which is no slouch being PMD100, PCM1702 massive power suplies and a discrete direct coupled I/V and buffer. Look at the review and more so the measurments California Audio Labs CL-15 CD player | Stereophile.com
As for the Cary 303/200 AD844 (also direct coupled all the way) combo beating it, yes did, but I would own the AMR in a flash if priced much lower if I didn't have the Cary now. I point my finger at tubes and the associated coupling caps causing it, to be out done by the Cary.

Cheers George
 
I just say that the listing session was interesting and if you have the possibility to double it with an SS amp of a good quality too but no SMPS in it for checking the importance of NOS design // to the amp. BTW, it's not the subject of your thread but maybe interesting to understand the limit/no limit of the ad844 I/V design.

I have to test by myself cause your shematic seems simple to realise with veroboard and thanks for that...
Can I test it with a TDA 1541 with the sames values ?

cheers
 
TDA1541 resources from the thread:
(I'll be lookin' into this soon ...)

ad844_c-b_i-v_sch.gif

Pedja 1541 NOS AD844IV wBUFFER.png

I'm not sure what to set the current source at for the 1st hookup? 1/2 way?

Circuit to try after the AD844:
http://www.google.com/url?sa=t&rct=...RlHNoW8V3Xgq5Er4eTSsg&bvm=bv.1357700187,d.aGc

PS Hey Dirkwright, can you post that ad844 tina file? Thanks!
 
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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
 
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 :)eek: 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...
 
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:crying: : 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...
 
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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
 
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.
 
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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