DAC60 vs. Benchmark vs. PS Audio Link III

markC · « **Reply #80 on:** 26 Apr 2008, 03:36 am »

This is why I love this forum.. great info .
Just a thought; as a courtesy to Danny, (it is his circle afterall), should we start a new thread in the lab, perhaps? Danny?

Danny Richie · « **Reply #81 on:** 26 Apr 2008, 03:39 am »

I don't mind the discussion.

regal · « **Reply #82 on:** 26 Apr 2008, 03:39 am »

As far as the DAC-60 being hard on tubes, notice the mod I posted raises the plate and cathode resistors to 300 ohm. This lowers the bias current flowing thru the tubes. The stock 100 ohm resistors are much lower (higher current) than about any design I have seen.

pbrstreetgang · « **Reply #83 on:** 26 Apr 2008, 03:45 am »

And what designs are those, can ya give us a frame of reference? I love the help and discussions of the hard core DIY crowd but I like to quantify it before I go a chopping and soldering. Also since you allude to it being nearly 3X harder on tubes I am scratching my head with my 3K+ hr tubes testing near new. I would expect 10K hr tube being driven 3X as hard to be testing low at the 3K hr mark

regal · « **Reply #84 on:** 26 Apr 2008, 03:50 am »

Just search the internet for SRPP 6DJ8 there a lots of designs with this same tube stage. I'm not saying that the 100 ohms will shorten the tube life just that it could, no one can predict this sort of thing. It depends on how the tube was manufactured, some are more delicate.

markC · « **Reply #85 on:** 26 Apr 2008, 04:01 am »

Good of you to share your mods, Regal. Out of curiosity, have you done anything else besides the resistors and cathode bypass?

pbrstreetgang · « **Reply #86 on:** 26 Apr 2008, 04:02 am »

Thats fine there are many ways to implement a circuit and many compromises to be made at every different stage in design. Even cost no object pieces are subject to component values and implementation compromises. Its the nature of it, everything can be improved or implemented differently to suit different tastes or operational parameters.

regal · « **Reply #87 on:** 26 Apr 2008, 04:16 am »

Quote from: markC on 26 Apr 2008, 04:01 am

Good of you to share your mods, Regal. Out of curiosity, have you done anything else besides the resistors and cathode bypass?

I replaced the output caps with 5 uF paper-in-oils. I also have a choke to replace the CRC resistor but I am on the fence as to wether I should install it. It would be before the mofset so I am not sure it would help, also I know that if the choke isn't of the correct value it could screw up the B+ and add ripple. I have seen reports where the choke is a big improvement though.

pbrstreetgang · « **Reply #88 on:** 26 Apr 2008, 04:30 am »

Which PIO? I assume they were able to fit or did you go off to the side?

regal · « **Reply #89 on:** 26 Apr 2008, 04:57 am »

Off to the side, these are the $7 Sprague paper-in-oil caps from Nebraska surplus that get glowing reviews.

Make sure when you do any mod on this to leave it unplugged a few days so the caps discharge, the CRC caps hold voltage for a long time.

markC · « **Reply #90 on:** 26 Apr 2008, 02:40 pm »

The last mods I did were to change out the CRC caps and the 470 uf caps in the dac chip power supply. I hadn't used the dac in 5 days, (still plugged in but turned off). The 120 uf caps were holding 18V and I discharged them with a resistor. I replaced them with Nichicon 100 uf. I replaced the 47 uf electrolytics with Solen poly and the 470 uf with Blackgates. Sweetened up the top end. Next up is a Jensen 100 + 100 instead of the Nichicons and Multicap .1 uf to replace all the little blue 104 caps in the dac chip power supply.

regal · « **Reply #91 on:** 26 Apr 2008, 02:46 pm »

Do you have a supplier/part# for the Jenson cap ?

markC · « **Reply #92 on:** 26 Apr 2008, 02:56 pm »

Parts Connexion. #68081. Expensive little sucker though, $62.25. I just recieved it on Thurs. and measured it. Perfectly matched sections @ 117 uf per side. I'm going to try to get at it this afternoon.

regal · « **Reply #93 on:** 26 Apr 2008, 03:15 pm »

I take it that a single Jenson dual is replacing the two CRC 120 uF Silmic caps ?

markC · « **Reply #94 on:** 26 Apr 2008, 04:03 pm »

Yes, thats correct. Are you sure that they are Elna? There is no name on the caps and no listing that I can find anywhere for an Elna 120 uf cap.

regal · « **Reply #95 on:** 26 Apr 2008, 04:12 pm »

I assumed they were because the are brown with gold lettering, but now that I look closer I don't see a brand name.

Is this your cap ?

markC · « **Reply #96 on:** 26 Apr 2008, 09:48 pm »

Looks the same physically, but the colour is black with gold lettering running cross-wise instead of length-wise.

markC · « **Reply #97 on:** 27 Apr 2008, 02:15 pm »

Quote

http://www.audiocircle.com/image.php?id=14229

Here is a pic of my lastest mods completed just last night.

lpaudio2 · « **Reply #98 on:** 28 Apr 2008, 03:18 am »

Im about to get a dac-60. Very interested in this i/v resistor and filter mod. I cant actually read the stock schematic as it is not clear enough. Regal would you mind taking a picture of yours and adding some pointers (mabye with ms paint) as to what parts you swapped out and what went where? It would really help me out since I cant make sense out of the schematic you posted without seeing the original (Im not that tech inclined but I have done quite a few mods)

thanks!

regal · « **Reply #99 on:** 28 Apr 2008, 12:53 pm »

I'll take pictures but look at my previous posts its all expained.

I am upgrading the PCM1704's to the K version this weekend, I'll take pictures.