| Leolabs |
The overall view.Note that compare to earlier production,this one use a
"two-part" ATAPI drive as opposite to South Korea's DVS drive.
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| Leolabs |
The R-core transformer with 3 separate windings:2 for analog stages and 1 for the others.
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| Leolabs |
Sanyo's SF-HD65 laser pick-up unit,which can be found inside many cheap DVD players.
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| Leolabs |
The ATAPI board,which almost equivalent to a normal DVDROM without:
-Master/Slave/Cable Select jumper setting,
-Analog Audio Output,
-Digital Audio Output.
This one use a VOS chipset rather than the popular MTK chipset.
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| Leolabs |
The 'heart' of the machine:Analog Devices' Blackfin audio DSP.Note that
the adjacent Xilinx's FPGA.
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| Leolabs |
The SPDIF IN/OUT and DAC section.This CDP comes with digital inputs and putputs both on coaxial and optical,with AKM's AK4117 serves as input receiver and a AKM4103 as transmitter.
The DAC section employs a AD1955.
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| Leolabs |
The analog stages:OP275s as I/V converters and OPA2134s as low-pass filter/DC servo.Diamond buffers are also found at the final output stages.
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| Leolabs |
Power supply section:Standard adjustable linear regulators for the analog stages,low-dropout for the digital circuits and switching regulators for the ATAPI drive.
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| rfbrw |
| quote: | Originally posted by Leolabs
[B] Xilinx's FPGA.
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CPLD not FPGA. |
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| xaudiox |
| thanks for the pictures Leolabs! |
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| georgehifi |
Here is what Lars Viborg of LC AUDIO did to one, below is the pic, and he said it sounds stunning, even dacs at three times the RRP don't come close.
He instaled a LC Zapfilter MkII for the I/V and Output stage board with a Schoktty Shunt Regulated Powersupply board and Toroidal transformer.
And if you want to use it's own transport he put in a XO3 reclocking module and it's own XO Powersupply as well. Major surgery on this one.
I think just the output stage mods are enough and use it as a DAC only with a good transpot like Teac VRDS or alike. But then again a clocked internal transport like this could better the external clocked Teac VRDS?
Cheers George |
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| georgehifi |
Here is a pic of part of the output stage surgery.
Cheers George |
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| Extreme_Boky |
Just a suggestion,
The original analog stage uses simple bias solution to avoid a use of sound coupling / DC blocking capacitors. I personally never liked the sound of ZAP filter (too cold, washed-out / sterile). The original IC's are surface mount duals - perfect opportunity to try fast IC's from AD stable, or mellow sounding ones from BB. This will (again, from my experience) most definitely give better results than ZAP filter, for much less money!
Boky |
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| Leolabs |
| Thanks for the suggestions.FET or bipolar OPAMP???? |
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| georgehifi |
| quote: | Originally posted by Leolabs
Thanks for the suggestions.FET or bipolar OPAMP???? |
Has to be kept as fet input on both opamps, (as this is a direct coupled circuit from dac output to rca outputs), as bipolar input opamps in general tend to have more dc offset at their outputs an can cause the dc servo circuit to go out of it's nulling range and not null out the dc.
If I were going to do opamp subbing, I would dearly love to use the AD825 smd, but it's a single and I don't know if there is such a thing as a 2 x single smd opamp to dual smd opamp convertor board? Maybe Browndog?
In my experience the AD825 is the gun opamp the OPA627 is good also but doesn't have the slam of the AD825, and then I found that the Zapfilter II has even more slam but can on bad cd's sound a bit cold, but really makes up for it with good recorded material, but it's also more expensive way to go.
Cheers George |
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| Extreme_Boky |
| quote: | Originally posted by Leolabs
Thanks for the suggestions. ET or bipolar OPAMP???? |
Supply voltage is 24V - so AD8066 (my favourite) should work nicely. This IC requires very clean noise-free supply with proper PCB ground topology.
The second IC is half "DC servo", half diff-to-single-end gain stage (for discreet output) - I would try AD826 here. Alternative: LM4562 (different sound, also quite nice...)
Boky |
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| georgehifi |
Yes it does, the sound standard is a little warm (OP275) and also lacks a dynamics, it also needs more bass slam, this is compared to two other very good dacs. But it can be heard that it's very extended smooth/clean and distortionless, and low in "jitter" if I can identify what jitter sounds like.
Saying this I believe it can be achieved, with subbing the OP275 (known to be softish) and the OPA2134 for either better opamps, like my personal favorite the AD825, or to do the radical transplant of a Zapfilter MkII. The latter is extremly dynamic (unbelieveably so) and can sound cold on some sterile recordings, but I belive it's just staying true to the source.
Cheers George |
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| greierasul |
| I put LM6172 (remove OP275) in the I/V converter section and OPA2132P in summing section. I remove DCservo, I have only 5mV DC offset at the OPA2132P output. I remove all sections after OPA2132P. :D The sound ? stunning ! Another very important thing. Change the 47uF/85degree Samwha with Sanyo OS-CON SP or SH series in the digital section, near clock, C55 and C49 ..... In the I/V section I remove C33, C34.........in the summing section I remove C22 and C27 and I moved the negative feedback of the OPA2132 at the output (I remove discrete section and other filters). |
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| georgehifi |
| quote: | Originally posted by greierasul
I put LM6172 (remove OP275) in the I/V converter section and OPA2132P in summing section. I remove DCservo, I have only 5mV DC offset at the OPA2132P output. I remove all sections after OPA2132P. :D The sound ? stunning ! Another very important thing. Change the 47uF/85degree Samwha with Sanyo OS-CON SP or SH series in the digital section, near clock, C55 and C49 ..... |
OPA2132???? you mean OPA2134 I hope, I found the C55 it's an obvious one, but where is C49 can't find it anywhere on my circuit diagrams around the Xtal like you said?
I also belive this is going to be a killer dac just hope the transports up to it as well, after a clock upgrade?
Cheers George |
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| greierasul |
| NOOOOO, I put OPA2132P (so, P !). I must to looking at the schematic and I will tell you exactly what caps are ..... you can try LM4562 but you must to leave the opamp 2-3 weeks to work properly. |
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| georgehifi |
| quote: | Originally posted by greierasul
NOOOOO, I put OPA2132P (so, P !). |
Oh yes of course I forgot you removed the dc servo and now using a single insted of the double.
I still think if you use a AD825 in place of the OPA2132 as the output amp it will sound even better as I have compared the AD825 and OPA213X, and the AD825 has soooo much more slam and dynamics, you should give it a go. and it's dc offset is far lower out of 20 odd I have used not one was over +-1mV
Cheers George |
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| greierasul |
Nooo, OPA2132 it is a stereo opamp, like OPA2134. look: http://focus.ti.com/docs/prod/folde...t/opa2132.html.
I try LM4562 and other 6 opamps ...but it is very important to have a properly design of PCB, so it is better to use OPA2132 (P version if is posible). |
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| mlihl |
| Since it's an ATAPI drive, can I plug in any dvd rom drive when the HK transport in the 970 dies? |
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| greierasul |
| yes, I find 2 dvd-cdrom(writer) from 4 units tested wich work perfect. One old Teac cdwriter(8x), and Ricoh dvdwriter. Plextor Premium does not work without another firmware. |
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| Joe Rasmussen |
Here is an alternative internal view of HD970 and alternative upgrade:
1. Lower left hand side, the new clock power supply. The original M-Tron oscillator is still used. Why did the use 24.576MHz when this is a CD Player only. This is a DVD spec'd frequency 256 x 96KHz.
2. All post DAC circuitry has been disabled and no current drawn. We can now use the internal power supply before regulators. You can see the new output stage is powered from the input pins of the plus and negative IC Regs.
3. An entire new output stage using Passive Differential I/V (current canceling). This is kept Low Z and uses the FLTR 2.39V DAC pin to float it. The AC signal is very small and needs high gain and low noise. I use effectively a Moving Coil Phono circuit a la JLTi MC Phono, without EQ. No negative feedback. (See http://www.positive-feedback.com/Issue28/jlti_phono.htm). Minimal filtering - 50Khz single pole becoming 2-pole above 300KHz.
4. Replace plastic RCA output sockets with cryoed types. Signal single core wiring also cryoed.
5. Some SMD components fitted to lower back-EMF noise in the digital section.
6. Added a large bituminous loaded damping panel to Top Cover.
The end result? Very nice, a good and lively sound, even vibrant. Top end is quite good with plenty of nice detail. I would not describe as neither cold or warm but down the middle. Excellent bass IMO.
Joe R.
PS: George, it was two words?
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