Dolby 361 noise reduction - more noise than tape

[Anderssvensson]

I bought a pair of Dolby 361 noise reduction units with cat 22 cards (Dolby A). Got them yesterday.. and I tried them out immediatly. They are really noisy! It's not noise reduction, it's noise increasing! Both units are equally noisy on the encoding, however the decoding is quiet.

I have attached an mp3 file. First there is an original digital 7 seconds sample unaltered, then the same sample with encoding directly to decoding back to the computer. Then there is the dolby tone, and then the noise only.

Do anyone have any idea why it is that noisy? Are both units bad, or am I, as a beginner to these units doing it wrong?

[Paul Gold]

Do you have a manual?

[Anderssvensson]

Originally Posted by Paul Gold

Do you have a manual?

No.. :( Is there any manual on dolby.com? I haven't found one for the 361..

[Paul Gold]

You should find a manual. It's from a time when manuals were complete and well written. I don't use mine that often. They are not that hard to set up but I always look at the manual to be sure I'm doing it correctly. It also has complete service documentation.

[Led]

They only either encode or decode, they don't do both at once, so wiring them the way you have won't work if I'm reading it correctly. What are you using them for, noise reduction or the exciter thing? For the exciter thing you only need to go through the encoder.

[Anderssvensson]

Originally Posted by Led

They only either encode or decode, they don't do both at once, so wiring them the way you have won't work if I'm reading it correctly. What are you using them for, noise reduction or the exciter thing? For the exciter thing you only need to go through the encoder.

Sorry for not giving you enough information.. :( The signal is monophonic, first I encode the signal in one unit, then decode it in the other unit without going to tape in between. So doing this in stereo, I would need four units.

However, maybe it's better focus on the encoding; that's where the noise is. Of all five colored buttons on the front, the "NR-in out" and the "REC" button is pressed in. Now the signal has increased treble, and it's quite compressed. The meter under the dolby tone button is pointing at the "NAB" point. I could change the levels at input level and output level, but no setting will decrease the noise.

It shouldn't be noisy, even if the units was made in 1973..? If it is this noisy, it's worthless to use it on tape.

Sounds like the noise I had from one of my condenser microphone when I burned it with the phantom power.. not really like pink noise.. more like a vinyl records dusty noise..

The strange thing is that both units are equally noisy.

[Mixermend]

I have a Dolby 361 manual in PDF format that I can send you if you wish?

Please send me an e-mail via my Web site with a 'real' e-mail address (it is a 5M file):

orchid-electronics.co.uk

I also have the vocal enhancer information - this entails a very simple modification to the Cat 22 module - and is easy to reverse if required.

[deda]

Originally Posted by Mixermend

I have a Dolby 361 manual in PDF format that I can send you if you wish?

Please send me an e-mail via my Web site with a 'real' e-mail address (it is a 5M file):

orchid-electronics.co.uk

I also have the vocal enhancer information - this entails a very simple modification to the Cat 22 module - and is easy to reverse if required.

Mixermend, ,,deda,, here wondering if I might get the 2 files mentioned above, the Dolby 361 manual in PDF. and the mod to the Cat 22 module. I will send an e-mail to you via your website as specified above.

Thanking you in advance for you consideration, regards ,,deda,,

[JohnRoberts]

Excuse me if I am stating the obvious, but it is the nature of encode/decode NR that the encode half is boosting up low level noise in the input signal. So listening to just the encoded signal may sound tinny and hissy. The decode process, restores this input noise back down to where it was, while at the same time reducing the noise from the tape process.

JR

[Number 6]

Can we just say a big 'THANKS!' to Mixermend for his gracious imparting of knowledge here?

[deda]

Originally Posted by Number 6

Can we just say a big 'THANKS!' to Mixermend for his gracious imparting of knowledge here?

A HUGE thanks to Mixermend for his help on this matter.

A HUGE thanks to all of you Geekslutz as well. You guys are always there with the answers.

HERE HERE to the entire Geekslutz Forum, the most important forum on Gearslutz. Without your help for information on gear no matter how obscure, information on how to maintain the gear and I mean every kind and of course the fixing of gear, sometimes in a single post, others by brainstorming over days but you will get it done and never let up. This I know is not a simple task at all and some fixs are like doing Brain Surgery over the internet but by god you get it done.

Thanks again to you all, regards ,,deda,,

[deda]

Originally Posted by Mixermend

I have a Dolby 361 manual in PDF format that I can send you if you wish?

Please send me an e-mail via my Web site with a 'real' e-mail address (it is a 5M file):

orchid-electronics.co.uk

I also have the vocal enhancer information - this entails a very simple modification to the Cat 22 module - and is easy to reverse if required.

Mixermend, I have tried to leave an email on your website for the above info but as I try to reach your conntact email address " info@orchid-electronics.co.uk " I keep being rerouted back to your home page. I've tried 10 times with the same results. Might I leave my email address to you via a Gearslutz PM?

Thanks again for your consideration, regards ,,deda,,

[Anderssvensson]

I found out one thing about my units. One has noise on the encode, and the decode is noiseless. But the other unit has noise on the encode And the decode. I didn't notice this before. So on the unit with noise on both encode and decode, I switched cards - and the noise on the decode was gone! (but the encode noise was still there, of course).
So now I know where the problem is. Gotta get new cards.

Originally Posted by JohnRoberts

Excuse me if I am stating the obvious, but it is the nature of encode/decode NR that the encode half is boosting up low level noise in the input signal. So listening to just the encoded signal may sound tinny and hissy.
JR

Yes, your absolutly right! Nothing wrong there I think.. the signal is "tinny" and "hissy", but with no signal at all it can't be tinny :( With no signal at all, there is just vinyl-dirty-like noise for me.

Big thanks to Mixermend for the 361 manual!!!!! This is great stuff!

[vengloop]

Does anyone know what is better, a cat 22 card or a telefunken telecom c4dm and how much would a 361-a with telecom c4dm cost?