Parasound D/AC 1100 hd

[jamie]

I picked up a Parasound 1100 hd at a thrift shop and found this website searching for info about it, I guess I should have opened it because the manual on the Parasound website is wrong. According to the manual it has 2 PCM63's per channel operating a push-pull output stage. I saw it didn't have balanced outputs but figured the manual was correct.

Well it only has a single PCM63K per channel. It has an old high speed video opamp for the current conversion to voltage. I had bought it on the spot vagely remembering an Absolute sound article where they liked it as much as the TOL parasound and as much as any DAC at the time and I have always liked my friends Pass D1 which uses PCM63k's..

It is full of blackgate capacitors, I assume these are stock as it didn't look like anyone had opened it before. Sonically it is good in the midrange, bass a tad cloudy and the treble a bit harsh.

I ran RMAA (Asus STX) and it has a nice flat frequency plot and low distortion, but there is an unusual pattern with the noisefloor. It looks like rectifier noise and its harmonics (see picture). Not sure if this is from old rectifiers radiating their noise, lack of filtering from the old electrolytics caps, or poor PSRR capability with the old opamps. Or is it jitter? Anyone have experience refirbishing/upgrading these parasound DAC's have a suggestion where to start ?

[luvdunhill]

That's likely a measurement artifact. I would probably enjoy it as is or just sell it and find something else.

[Pars]

I would agree. Have you done a loopback RMAA measurement on your soundcard? Look at that and see how much of that is contributing to what you are seeing here. Sites like diyaudio.com would be useful as to where to go if you decide to stick with this DAC and upgrade it. Recapping the PSU caps, replacing the rectifiers with Shottky diodes, etc. might be a place to start. Redoing the output stage with something like a Pass D1 stage would also be a consideration.

[NekoAudio]

Yeah, I had the same issue when using an Audio Precision measurement device: when in loopback, there was 60Hz and harmonics. So it's somewhat normal to see this and you shouldn't feel that your sound card is bad or your setup is wrong.

If you really want to see the 1kHz harmonics, try manually/visually subtracting out what you see when there is no device under test and you are just doing loopback like Pars said.

[gurubhai]

When I ran RMAA tests on my Xonar STX, the THD results were quite poor at 44.1/48k frequencies but were excellent at 96k.

I am guessing that might be the issue here.

[The Monkey]

How much did you pay for the 1100?

[screaming oranges]

Btw, most excellent first post, Jamie! Shows class and an understanding of what this site is about. If you stick around though, you will see there's more to us than just that.

Edited March 4, 2012 by screaming oranges

[ecclesand]

If you want the balanced Parasound DACs, I believe you need to look into the D/AC-1500 and D/AC-1600. Those models have 2 PCM63 chips per channel. Also, I don't believe they came stock with Blackgates, but I could be wrong on that. Good find, though!

[The Monkey]

iirc the blackgates were stock.

[jamie]

How much did you pay for the 1100?

Sorry I have been late to respong (long week). It was $125, A good deal but immaterial as never sell it unless I find the balanced version to me these are sort of like collectors items in that really the 90's were sort of an interesting era quality digital audio it was pre-loudness war madness and I don't know I think one day I'll figure out how to hook it to my computer with out the spdif and all the c-mos before the pmd100-pcm63's , I've got an old Audiochemy DAC that I've owned for years also.

When I ran RMAA tests on my Xonar STX, the THD results were quite poor at 44.1/48k frequencies but were excellent at 96k.

I am guessing that might be the issue here.

I will check that. But here is a modern DAC same test setup. Its a NFB-12 with Wolfson 8741's. Now the noise floor is "nicer looking", I guess if Audio-gd does one thing right it is power supply, unfortunately look at how high the harmonic distortion is compared to the Parasound. I can't listen to the NFB-12. Just overwelhming harmonic distortion for my tastes (some may like it.) But I can't help but wonder if I could get the spikey noise floor of the Parasound improved that it would have a little smoother sound.

Thanks for the info on the Blackgates, they being stock may be the issue (age). I guess I can try to measure they capacitance left in each of them, maybe I will get lucky and its only one or two that need replaced.

[Pars]

If the Black Gates are just the standard series and in the PSU, I would just replace them with something Panasonic in the right form factor. Something like Panasonic FM if standard radial. You probably won't be able to chase down BGs, and if you could, pricing will likely be insane. I personally don't think they are that good anyhow, and are an 85°C cap anyhow, ve. 105°C for good Panasonics or Nichicons. You might also replace the PSU rectifiers with Shottky as well. I typically use 11DQ10s or 31DQ10s for higher current applications.