Using DB25 to RCA to get TrueHD through old receiver

[craby]

Hi Guys,

I've previously posted about using my old Rotel RSX 965, and the help has been really appreciated (everything is sounding superb, and I've just got a DCX centre on the way to pair with the DCX's).

My question is this. I'm using a PS3, and I'm keen to swap up for an OPPO or a Cambridge 650BD (when I see some reviews of it). Now, my old receiver only does Dolby Digtal and Dolby Pro Logic, and as we know you can't get True HD or DTS Master through optical from the PS3.

The receiver has the ability to accept 5.1 via DB25 from external decoders, disabling the onboard decoders.

I'm thinking of getting the OPPO, and then connecting it to the receiver with a DB25 to RCA. I'll get the OPPO to do the decoding of True HD/DTS master, and then the receiver would only act as an Amp.

The amp puts out 75watts per channel, and drives the DCX's quite easily. I accept that I'll eventually be up for another receiver, but I intend to get the OPPO or 650BD for SACD and DVD-A anyway. I thought this might allow me to extend the life of the receiver a bit while I make that decision.

In the manual, it says this about the function:-

This button overrides all other inputs (both analog and digital) and

directly connects an external digital adaptor to the RSX-965’s

MASTER VOLUME control and outputs. This allows the RSX-965 to

remain the central controller for even the most advanced audio/

video systems and provides an upgrade path to future software

standards. When activated, all of the RSX-965’s inboard Dolby processing

is bypassed.

Does anyone have any experience in using this type of setup? Is it recommended or should I just hold off and get another receiver at some point later in the year (I've been hanging out for the Cambridge 650R reviews and it's just taking forever- sigh).

Thanks again.

craby

[craby]

Hi Guys,

Snappy update. I've found another post here that would suggest that this is a 'can do' situation. I'd still be interested in hearing from anyone who has gone down this path though.

regards,

craby

[kitflorida]

So I have the same issue that you have and am now looking at getting RCA to db25 cables. Are you happy with your results. I have a ROTEL and cant part as it still sounds so good. You had mentioned that you found another post that helped you. Can you share?>

[Mr_Gimlet]

It looks like a reasonably standard 6ch analogue output but into the Rotel through the DB25, it should be the same as running 3 RCA but with a different connection. craby, the text you quoted makes sense - because its an analogue signal, it will just go direct to the analogue outs rather than being redigitised

[craby]

Hello,

Thanks for the replies. In relation to the other post I found, I ended up finding several along the same lines after changing my search parameters, but here's one from this site:-

http://forum.blu-ray.com/audio-theory-discussion/91058-dolby-truehd-dts-hd-ma-old-receiver.html

But the main one was a post I found from 2004. A bloke in the US has the same receiver as I do, and decided he wanted to keep it, but wished to get the latest sound standards. He looked at buying a cable, but ended up just making one. In the manual for my receiver, it has the schematic for the layout. He said that he just cut a 3 cord RCA in half and the soldered it. That said, you can buy the cables already made up in the US for about $80AU.

It looks like what happens is when you press the 5.1ch button per my extract from the manual, the receiver basically just becomes an amp. The Oppo looks like a very capable unit, and I think that this will be a really good solution as opposed to coughing for a new receiver, when I could probably get away with keeping what I've got. I agree with you, it still sounds great after all these years, and drives the DCX very well.

I see that the Oppo BDP 83 can be bought directly from Oppo for less than $700 AU including postage, which is around $400 cheaper than buying them in Australia. I'll probably look to make a move shortly, and I'll post on how it goes.

regards,

[gat474]

You could contact International Dynamics in Melbourne as they were and still are the Rotel importers. I had had a couple of Rotel products over the years and recall that the DB25 plugs could be sourced from them. Alternatively if you could source the plug and the wiring diagram you could make up your own db25 to rca cable reasonably easily with three pairs of el cheapo rca's and one of the db25 plugs. The DB25 appears to be a reasonably common plug used in computing so there should be stacks of them around. International dynamics should be able to at least give you the wiring diagram for the applicaiton.

[craby]

Hi Guys,

I thought I'd post again to let you know how it all went. The OPPO BDP 83 turned up last week. I connected it using the stereo connections to the amplifier. When I hooked it up that way, the amp turned the internal DAC's off, and it behaved as a 2 channel stereo amplifier.

The sound was very impressive, and a significant improvement from the PS3. I was able to play an 320 bit rate MP3 of a song on the PS3 and then switch back and forth with a DVD audio version of it. Really noticeable, even to a lay person like me. Everything just sounded clearer and with more depth.

I hunted around for a DB25 to RCA cable, and also contacted international dynamics, but they couldn't help. In the end, I just fished an old null modem cable out of the cupboard and a handful of cheap RCA cables. I then fired up the soldering iron and got it sorted.

I plugged it all together tonight, and was even more impressed. When I select the 5.1ch option on the receiver, it just becomes an amplifier, and all I can adjust is the volume and tone controls. Dolby TrueHD is decoded in the Oppo, and then pumped out through the amp with ease. The demo blu ray disc that came with the OPPO has some great 2 channel and trueHD/DTS demo tracks, and it really gave me an opportunity to hear how well it all sounded. Even though my amp is only 75 watts per channel at 20-20khz, it's driving the three DCX fronts very easily. At higher volumes the sound starts to loose some of it's 'depth' (for want of a better word, it starts to sound a little hollow), but at normal levels it's very nice.

The bottom line is that by purchasing the Oppo and making the DB25 to RCA cable up, I've been able to extend the life of my old amplifier again.

Thanks again for everyones input.

regards,

[craby]

Hi Guys,

Just as an addendum entry, although I've noted that TrueHD and DTS master are superb through the DB25 via analogues on the BDP83, there's a definite hit (major hit really), on what appears to be the LFE channel on the sub when watching home theatre on blu ray or normal DVD. The difference between the analogue and the digital connections is chalk and cheese, with an almost complete absence of deep low end bass from the sub on the analogues. Even if I turn the sub up, there's no improvement, as it seems to be the player itself. I've increased the sub volume in the OPPO, but it didn't make any particular improvement i.e. I normally have my sub set to about 1/4 volume with 0db in the receiver. Even with it on max and the oppo up to +10DB, I wasn't getting good deep LFE bass. Master and Commander is my usual benchmark for deep hard bass, and it's noticeably missing. Unfortunately when I'm using the DB25, I can only adjust the volume and the tone controls, so the sub volume in the receiver is locked out.

The analogue DTS sound from the OPPO is vastly better than that coming from my old amp on the optical line, so it's a bit of a shame. I've read other forums where people have reported a similar problem, so hopefully there may be a fix coming out. I've emailed OPPO, but no reply so far.

regards,