DAC60 vs. Benchmark vs. PS Audio Link III

JohnnyK · « **Reply #60 on:** 15 Apr 2008, 05:48 pm »

The Benchmark was one of the many DAC's that was in my DAC shoot-out. IMHO, the Benchmark sounded very similar to the DAC in my Aragon pre/pro. I can describe the sound as very boring and laid back. It did not have the extend high's and punchy bass of the modified DAC60 or the modified PS Audio. Not that there's anything wrong with that.

regal · « **Reply #61 on:** 21 Apr 2008, 01:57 pm »

Here is the circuit diagram for the DAC-50, the DAC-60 layout is identical with minor component changes.

You can see this DAC-50 was actually a much nicer DAC because the I/V and filter was optimized for the PCM63. With the DAC-60 they just slapped a PCM1704 in its place and raised the I/V. It is way too much load for the PCM1704 and this is why we hear the congestion/distortion in complex passages (high volume.) The PCM1704's internal diodes are clipping.

http://i299.photobucket.com/albums/mm294/regal55/dac-50.jpg

I plan on doing the mod this weekend.

Someone asked about the cathode bypass caps, they are added across R12 on this circuit. You have to add them first to increase the gain in order to fix the I/V for the PCM1704.

markC · « **Reply #62 on:** 22 Apr 2008, 01:43 am »

R12 and R10 I assume? Not to question your parts values, but where/how did you come up with them? I'll likely try it, as it is easily reversable and I'm pretty much done playing around with the mods on this dac. Thanks for your input/info.

regal · « **Reply #63 on:** 22 Apr 2008, 01:12 pm »

Yes R10 & R12 are the cathode resistors on the DAC-60.

I also noticed that R8 and R11 were deleted on the DAC-60, the filter is an absolute hack-job. It explains fully why Monachy kept using the DAC-50 and why many have said it sounds superior to the DAC-60.

As far as the I/V & Filter I posted it is a direct copy of the HAG/ChimeDAC (also PCM1704 + tube) which is highly regarded and sounds a lot better than the DAC-60, this is a big reason why. http://www.hagtech.com/pdf/chimeteardown.pdf

It is a 3rd order Bessel linear phase type with a slow roll-off, -3 dB around 32 kHz. The key is it has a lower load on the DAC output. But even with the cathode by-pass caps the Vout rms is about 6dB lower than before, but this shouldn’t be a problem for most amplifiers

Here is the parts list:

Caddock resistors 100 ohm - 445-1986-1-ND

MKP Film Cap 0.015 uF - BC2140-ND

MKP Film Cap 0.1 uF - BC2054-ND

TDK Shielded Inductor - 445-1986-1-ND

Silmic Cathode 1000 uF Bypass Caps - 604-1059-ND

330 ohm 1/4 W resistors R6,R10, R9,R12

rotarius · « **Reply #64 on:** 22 Apr 2008, 11:54 pm »

Quote from: regal on 21 Apr 2008, 01:57 pm

Here is the circuit diagram for the DAC-50, the DAC-60 layout is identical with minor component changes.

You can see this DAC-50 was actually a much nicer DAC because the I/V and filter was optimized for the PCM63. With the DAC-60 they just slapped a PCM1704 in its place and raised the I/V. It is way too much load for the PCM1704 and this is why we hear the congestion/distortion in complex passages (high volume.) The PCM1704's internal diodes are clipping.

http://i299.photobucket.com/albums/mm294/regal55/dac-50.jpg

I plan on doing the mod this weekend.

Someone asked about the cathode bypass caps, they are added across R12 on this circuit. You have to add them first to increase the gain in order to fix the I/V for the PCM1704.

My question is does the sonicraft mod address this issue?

regal · « **Reply #65 on:** 23 Apr 2008, 01:52 am »

markC · « **Reply #66 on:** 23 Apr 2008, 01:55 am »

Certainly not that I can see. From what I gleen from the Sonicraft mod, it beefs up power supply components and replaces inferior coupling caps, (much required IMO), but does not alter the circuit as does the suggested mod in the I/V / filter section.

markC · « **Reply #67 on:** 23 Apr 2008, 01:59 am »

Regal, how does the bypass C affect the load on the tubes? Would it not stress them somewhat, and does it trade minor distortion from the 1704 for distortion on the tube?

Danny Richie · « **Reply #68 on:** 23 Apr 2008, 04:31 am »

The stage 1 mod doesn't go there. The stage 1 mod is only $295. It address what does the most amount of good for the least amount of money.

This other stuff and then some is all addressed in the stage 2 mod.

regal · « **Reply #69 on:** 23 Apr 2008, 12:35 pm »

Quote from: markC on 23 Apr 2008, 01:59 am

Regal, how does the bypass C affect the load on the tubes? Would it not stress them somewhat, and does it trade minor distortion from the 1704 for distortion on the tube?

Yes more tube distortion than before. But tube distortion is 100x better than silicone (DAC) distortion, and remember the DAC distortion is amplified 16 times by the gain stage. Also most all SRPP 6DJ8 preamps use a cathode bypass cap so it is an accepted design.

Here is a good read that explains the DAC-60 220 ohm design flaw:

http://www.dddac.de/pcm63/DAC_I-V_Resistor.htm

Gordy · « **Reply #70 on:** 23 Apr 2008, 07:01 pm »

I don't know if it's of useful quality but, here's a Chinese language schematic of the DAC 60... http://www.audiocircle.com/index.php?action=gallery;area=browse;album=847&pos=19

regal · « **Reply #71 on:** 25 Apr 2008, 02:55 pm »

I had tried NOS Tesla, Jan-Phillips, and Mullards in the DAC-60. But today I installed a pair of Amperex bugle boys and I am in awe, the difference is not subtle.

markC · « **Reply #72 on:** 25 Apr 2008, 09:57 pm »

Yea, I'm currently running 1968 Amperex orange globe logo's and they are by far the best I've tried yet. I even prefer them over a pair of early '60's Philips 6922 SQ's!
So far I've tried Sovtek 6922, Jan Philips 6922, Philips 6922 SQ and the Amperex orange globe 6dj8. One more I'd like to try, (no, I will try eventually), is the Aperex U.S white label 6922.

pbrstreetgang · « **Reply #73 on:** 25 Apr 2008, 10:22 pm »

Ditto on the orange globes and your findings about the phillips and Orange 6DJ8s. Old Eis are good but not like the oranges. Amperex whites I find are not worth the price premium over the oranges as there is little difference. A good all around compromise is the newer JAN Phillips green that can be had for $10 per.

markC · « **Reply #74 on:** 26 Apr 2008, 12:43 am »

Thanks for the tip on the whites, although I will disagree on the green jans. They are much better than the sovteks, but not even close to the oranges, especially in high freq. extension. Oranges are about $30-$40 bucks each and well worth it IMO. [Should we be disclosing this info on a public forum?]

pbrstreetgang · « **Reply #75 on:** 26 Apr 2008, 12:47 am »

Id like to know your source on the oranges for $40. They must be pulls. Tested matched ones from Andy are getting pricey. I did get a quad of PQ oranges recently for 130 shipped but the advertised match is not as close as Id like. Also the suggestion of the Jans had the disclaimer for a good all around tube and better than the new stuff I have tried.

markC · « **Reply #76 on:** 26 Apr 2008, 01:55 am »

Your right about the Jan comment-they are decent for the money, although I didn't think that I bashed them that hard.

The Oranges I speak of are not PQ's. Just regular 6dj8's.

pbrstreetgang · « **Reply #77 on:** 26 Apr 2008, 01:59 am »

I gottcha, I have the Orange 6DJ8s and they are a bit darker than the Amperex orange globe regular 6922s and the Amperex orange PQ 6922s with the gold pins. They are pretty close and do have that amperex house sound

Rasta · « **Reply #78 on:** 26 Apr 2008, 03:06 am »

Hey guys,

I'm using a Lite Dac-72 with the orange globes and a Shindo Montille amp - love it.

Can anyone comment on the rumor (can't find it now) that these dacs burn through tubes?

Best,
Rman

pbrstreetgang · « **Reply #79 on:** 26 Apr 2008, 03:27 am »

Heard the rumor and dont believe it. Ive had the same oranges in there for 6-7 months on 12+ hours a day and sometimes on constantly and they are testing very close to the level I recieved them in. Granted I dont have the super fancy accurate testers but its a good indicator. The key is to buy NOS from a very reliable source so they are not microphonic, and or used/low life. It pays in the long run. The "Deals" I have gotten off ebay have been dismal in terms of time before going microphonic or low testing (Also have other equipment that uses 6922 so its not a factor of the DAC 60 chewing through them)

Also arent those shindos uber pricey? Damn Id like to hear that