RCD-971 tweaks

[Bill Fuss]

I just aquired a 971 and cant resist doing a few tweaks. I was thinking about replacing the output section with a Pass I/V stage, looking for input from you more experienced digital tweakers. I also thought about replacing the 63Ps with P-Ks but I'm not sure it would benefit the player sonically. You guys blow me away with your digital knowledge, I'm old and stuck in the analog world, but I'm trying to fight my way out. Any suggestions would be greatly appreciated.

[Guido Tent]

Originally posted by Bill Fuss
I just aquired a 971 and cant resist doing a few tweaks. I was thinking about replacing the output section with a Pass I/V stage, looking for input from you more experienced digital tweakers. I also thought about replacing the 63Ps with P-Ks but I'm not sure it would benefit the player sonically. You guys blow me away with your digital knowledge, I'm old and stuck in the analog world, but I'm trying to fight my way out. Any suggestions would be greatly appreciated.

Prior to replacing the J's, I'd suggest first to upgrade the clock and indeed the I/V stage.

best

Guido

[Bill Fuss]

Thanks for the advice Guido, I reclocked another Rotel that I have with your XO2, a 965BX discrete, but I tapped the onboard power supply for power. The outcome really didn't make sense, the analog output got more sterile sounding, but the digital output improved very noticably,really in the bottom octave. No offense intended but maybe the bitstream chips dont like your clocks or vise versa. Anyway that will be my first tweak. There isnt much room in there, Rotel packed it pretty tight.
Regards, Bill

[KP11520]

Hi Bill,

Do a search here, I remember Extreme_Boky and a few others, maybe Vynuhl Addict have modded these with nice results.

Take a look!

Regards//Keith

[Bill Fuss]

Hi Keith,
I've done a fair amount of searching,not done yet, and most of the threads discuss opamp rolling which could be a lot of fun. I also have an Adcom 700 DAC that also has the PMD100 that I can A-B with the 971 dig output. I've found the analog out of the 971 a lot airier with a lot more width and depth but it is very lean and aniemic compared to the Adcom. The 63 chips seem to be the better dac chip compared to the 1702s in the Adcom, I guess I'm looking for the ideal combination of weight and transparency. My experience with building the Pass Aleph P clone and falling in love with it has me leaning in that direction, ultra simple, no opamps, totally transparent. I've read a couple threads about the Pass I/V stage but really haven't read any direct comparisons from any converts.
Thanks, Bill

[Bill Fuss]

I went ahead and replaced the output stage with the NP I/V stage. Made some boards, wired them up and checked it all out.
Sounds fantastic but the output is so low I had to crank my pre all the way up. I only have 25mv out from a -10db test disc.
I have the Iout and BP0 of the PCM63s jumpered together running straight to the inputs on the board and picked up the ground near the chips. I've been over it again and again and everything checks out so I might just be dumber than I thought.
I built the boards using Promitheus' layout, I dont have the service manual, just info I gleaned from the forum. Do I need another gain stage or is there something I missed. I'm a newbie when it comes to digital innards.
Somebody straighten me out.
Bill