Rotel surround pre = crap.

[dorkus]

hi everyone,

just a general FYI. Rotel surround sound preamps sound like crap.

some of you may know that i started the Son of Dork project a while back, a purist yet flexible multichannel preamp to use with new formats (SACD/DVD-A) and integrate with a surround sound controller. work has gone in spurts and i'm not very far along so i decided in the mean time, i would upgrade my old Denon AVD-2000 surround sound controller, which doesn't even have DTS decoding.

so i got a used Rotel RSP-966, which has been recently replaced by the 1066 (has newer formats like DTS EX and Pro Logic II but otherwise identical). like the denon, it has a direct 5.1 channel analog input which i use for multichannel SACD. i was hoping it would sound at least as good as or better than the analog section (volume control) of the Denon. well, it sounds pretty disappointing to say the least.

before i even listened to it, i popped the hood to see what's inside. i could only really see the power supply and main audio boards, but the main board had all sorts of digital and analog circuits mingled together - Crystal DSP, AKM DACs, cheap JRC opamps, all clumped together into a fairly small area. it appears to be only a 2 layer board and the ground planes aren't all that big. the 5.1 channel inputs have to pass through all kinds of crap before even getting near the output jacks, where there are electrolytic coupling caps, more cheap opamps, and solid state mutes. yuck.

and the sound... worse than my old Denon that i paid $150 for used! the Denon actually has a much nicer layout internally, although it doesn't have anywhere near the switching capability of the Rotel so it's a little easier. also, the control flexibility of the Rotel sucks - you need a TV monitor to adjust anything more than volume, and it does not memorize separate level settings for each input like my Denon did. and it has non-defeatable tone controls! agh!

anyway, i thought i got a good deal on this thing ($699 mint used) but it turned out to be a hunk of $%^@! it doesn't even sound good for movies! Dolby Digital sounds marginally better than the old Denon in some aspects, worse in others (the Denon has a smoother, fuller sound, though with less detail). and DTS was not much better either.

anyway, this is totally unrelated to DIY except for the very loose connection to Son of Dork, but just needed to vent some frustration. this thing's going back on the used market pretty soon, hell, i think i'll build my own DD/DTS decoder as an add-on module to Son of Dork!

[mrfeedback]

.......but the specs say 20Hz-20kHz, 0.01% so it must be good.

Eric.

[dorkus]

right, what was i thinking.

[kirc]

I also have a Rotel (RA-970BX), sound quite good, but in comparison with DIY Zen V4 and BOZ sound like a crap. But most of integrated amp in 300$ rang sound even worst. So for small amount of money DIY is urgently.

best regards,
Leon

[BrianGT]

I have the same denon decoder that you have. I am content with it. I paid $150 off ubid about 5 years ago.

How do you propose to make your own DD/DTS decoder? I haven't been able to obtain the chips needed. I was considering integrating it into the pre-amp that I am building now. So far, all that I have for my pre-amp is a circuit with a pga2310 controlling the volume, and I ordered the display vfd from Noritake:

http://www.noritake-elec.com/7000.htm

I bought the GU140X32F-7002. It has sync serial, assync serial and parallel interfaces. You can order direct from Noritake for $96.

If you are looking for a beautiful display with a lot of features, check out the Noritake.

Datasheet posted at:
Datasheet

I am using a PIC18F452 microcontroller.

Let me know if you have find anyway to decode DTS. I would like to add this to my pre-amp project.

--
Brian

[Peter Daniel]

Denon surround receivers are highly regarded and supposedly sound very good.

[dorkus]

wow, that's a great looking VFD brian, thanx for the info. i will check it out for Son of Dork.

i'm not sure how i'll do the DD/DTS decoding. i said i would make it myself out-of-the-blue, sort of out of a mix of frustration with crappy/overpriced commercial products and pure DIY bravura. i would think we could get the same Crystal or Motorola DSP chips that the big boys use, but i'm not sure how the codec licensing works... i think not only the semiconductor manufacturers but equipment makers have to pay royalties to Dolby etc. are those the chips you've tried getting?

[dorkus]

Originally posted by Peter Daniel
Denon surround receivers are highly regarded and supposedly sound very good.

from the design of my old AVD-2000, i'd have to agree they are definitely above par. the circuit layout isn't purist but it's not all that bad either; i think Denon has a litlte more audiophile sensibility than most. you would think Rotel, with its pretensions to audiophile quality, would be at least as good, but the Denon unit is far superior in execution.

considering that $800 buys you a receiver with the latest decoding features, spiffy remote control, AND 5 channels of amplification to boot these days, i wish one of the big Japanese firms would make a decent quality surround sound preamp for around $1k. but i guess there isn't much market for that.

[BrianGT]

Yeah, it is the newest in VFDs that are out now. Look over the datasheet and check out all of the features that it has. My roommate has taken a class in Microcontroller design with the PIC18F452, and he will help me interface with it.

As for the DD/DTS chips, I e-mailed a couple of companies who provided chips (crystal and motorolla), and they wouldn't provide any chips for use, due to licensing issues. I was told that I had to pay large licensing fees in order to buy the chips. I just gave up with the effort. I considered taking the chips out of old broken equipment, and using them, but I haven't followed through with that.

How is your pre-amp progress going? (I guess this should be continued in the appropiate thread....)

--
Brian

[dorkus]

Son of Dork is on hold at the moment, been busy reviewing some equipment for the magazine i write for and tending to other things. but i hope to get back to prototyping more circuits soon, my work tends to come in spurts. the JFET buffer i built as a first step of the project is holding up very well though, it sounds great and has become my reference preamp of sorts.