Noise Reduction for Reel to Reel

[naturephoto1]

I would appreciate your thoughts concerning the usage of noise reduction such as Dolby for your High End R2R tape machines both in terms for playback and for recording. Do you think it necessary or an asset? Also any thoughts or comments regarding the playback of Dolby B and other Dolby pre-recorded tapes with and/or without the usage of a Dolby or other playback (and record) unit.

Thanks for your comments and input.

Rich

 

[DonH50]

The decks I had came with Dolby B, C, and HX (IIRC); one had Dolby A. I used A and B now and then to reduce HF hiss, but frankly most of my recording was done without processing. I also had various combinations of dbx processors over the years. Sometimes that (dbx) seemed to help a lot, but most of the time it fouled up the dynamics and I eventually sold it all. Dolby A was used fairly often in the very limited amount of studio work I did.

For "fun" tapes made for myself, I usually used Dolby B as I felt it had minimal sonic impact and did a decent job of reducing hiss.

Playing back a Dolby-encoded tape without the post-processor always sounded pretty bad to me...

 

[ack]

I shelved my dbx 224 decades ago because of dynamic compression, and never used noise reduction since... still looks mint in its box.

 

[tony ky ma]

I would appreciate your thoughts concerning the usage of noise reduction such as Dolby for your High End R2R tape machines both in terms for playback and for recording. Do you think it necessary or an asset? Also any thoughts or comments regarding the playback of Dolby B and other Dolby pre-recorded tapes with and/or without the usage of a Dolby or other playback (and record) unit.

Thanks for your comments and input.

Rich

Hi Rich
You better have nothing in there because the system you have ( sensitive horns), listen to 15/ips recordings will provide the best analog sound with fully emotional and closer to the real sound, in ABX you will find it out very easily either to take a little bit of quiet or less of emotion like sound of digital, up to your favor
cheers
tony ma

 

[Tom B.]

Isn't it correct that any variant of Dolby NR is useless in playback unless the tape was originally recorded with that specific scheme? Or, does it afford some benefit when used with non-Dolby media?

Tom

 

[DonH50]

No benefit when not recorded with it...

 

[Steve Williams]

No benefit when not recorded with it...

Right on Don. I agree

 

[naturephoto1]

Guys thanks for the input. Tony I will keep your comments well in mind due to my Horn main speakers.

Do any of you use any noise reduction for your own recordings. And of course, what do any of you do with any pre-recorded Dolby B or otherwise recordings? Do you just play the tapes "naked", use any system for noise reduction, or just not play the tapes? Some pre-recorded tapes I believe are/were only recorded with Dolby.

Rich

 

[Gary D]

Guys thanks for the input. Tony I will keep your comments well in mind due to my Horn main speakers.

Do any of you use any noise reduction for your own recordings. And of course, what do any of you do with any pre-recorded Dolby B or otherwise recordings? Do you just play the tapes "naked", use any system for noise reduction, or just not play the tapes? Some pre-recorded tapes I believe are/were only recorded with Dolby.

Rich

Rich,
My experience has been to play the Dolby tapes without any external processing .If your playback system is good it will sound good.If you read on the net some don't like the Dolby encoded tapes because of the top & bottom end frequencies being chopped off.I find no evidence of that on our system.
Interesting side note note Ray Dolby started with Ampex in 1949 & worked on the 200 & 300 recorders.Ray was raised in the Bay Area and attended Sequoia High in Redwood City.Ampex was started in San Carlos then later moved to Redwood City.
Me and Rog grew up in San Carlos.Is it any wonder we have a room full of Ampex recorders

 

[mep]

I don't thnk that 15 ips 2 track tapes need any noise reduction boxes. And if the tapes weren't encoded with noise reduction, adding it after the fact is crazy.

 

[DonH50]

Actually, I agree with mep. Slower (7 1/2, 3 3/4 ips) four-tracks benefit from the added headroom; my 15/30 ips two-tracks did not use noise reduction (or very rarely). Faster, wider tracks allow greater bias and thus greater headroom and lower noise. Good tapes help, natch.

Dolby B and its ilk generally boost the highs during recording to get them further above the HF noise ("hiss") floor. So, to play back a Dolby B (etc.) recording on a non-Dolby deck all you usually need to do is turn down the treble a bit.

Anyone else used the ML-modified Studers?

I had a recording I used to demo to show why I dropped dbx. It had a slow kick-drum beat in the background with a quiet solo trumpet over it. You could hear the trumpet's long tones pulsing with the drum -- very unnatural.

 

[naturephoto1]

My Ampex Hybrid 440C/B R2R tape deck will playback 7 1/2 and 15 IPS and will play both 2 and 4 track tapes. Most professionally recorded tapes that my machine will play will be 7 1/2 IPS and many of the tapes are only available as 4 track and of course some were recorded with Dolby B.

I know that Roger has indicated with our upgraded reproduce cards that many of the 7 1/2 IPS 4 track tapes have really excellent sound. I believe that Roger has indicated Dolby B tapes sound quite good as well.

Rich

 

[DonH50]

The step in sound quality from 1/4" four-track at 7.5 ips to 1/2" or 1" two-track at 15 or 30 ips is large. That said, I have made many of the former that sounded great to me and my friends! If your deck does not have Dolby B and you get such tapes, listen and see what you think. My guess is you'll want to nudge the treble down a bit and that's all that you'll need to do to enjoy them.

This will sound strange coming from me, but don't let the technical details and specs interfere with your enjoyment of the music.

 

[naturephoto1]

The step in sound quality from 1/4" four-track at 7.5 ips to 1/2" or 1" two-track at 15 or 30 ips is large. That said, I have made many of the former that sounded great to me and my friends! If your deck does not have Dolby B and you get such tapes, listen and see what you think. My guess is you'll want to nudge the treble down a bit and that's all that you'll need to do to enjoy them.

This will sound strange coming from me, but don't let the technical details and specs interfere with your enjoyment of the music.

Thanks Don.

At this point I will only have 2 Dolby B professionally recorded tapes- Seventh Sojourn by the Moody Blues and Blue Jays by Justin Hayward and John Lodge of the Moody Blues. Ultimately I may get more with time, but of course I will have to wait till I actually have the "new" upgraded Ampex 440C/B 1/4" R2R tape deck in hand toward the later part of the month to give them a listen. Hopefully you will be correct and/or I will have no problem. I also intend to compare the sound of these and other tapes particularly to my early UK vinyl pressings of these same recordings.

Rich

 

[Roger Dressler]

It is true that neither Dolby nor dbx should be used for playback unless the tape was recorded with the complementary encoder. These are companders.

B-type NR was designed for cassette or slow speed open reel, as in 3.75 ips, where HF noise dominates the noise spectrum. For 7.5 ips it does less.

I'm a little surprised that here at What's Best no one mentions the best NR out there, Dolby SR.

 

[c1ferrari]

Hi, Rich --

I would appreciate your thoughts concerning the usage of noise reduction such as Dolby for your High End R2R tape machines both in terms for playback and for recording. Do you think it necessary or an asset? Also any thoughts or comments regarding the playback of Dolby B and other Dolby pre-recorded tapes with and/or without the usage of a Dolby or other playback (and record) unit.

Thanks for your comments and input.

Rich

I have some 2-track tapes that appear to have been encoded with Dolby A or SR. I'll invest in a proper Dolby A/SR decoder.
I'm going to record with no NR @ 15/30 ips...hopefully, I'll be satisfied

 

[Roger Dressler]

I have some 2-track tapes that appear to have been encoded with Dolby A or SR. I'll invest in a proper Dolby A/SR decoder. I'm going to record with no NR @ 15/30 ips...hopefully, I'll be satisfied

If you do obtain an A/SR unit to play those tapes, you might consider making some of your recordings at 15 ips with SR unless you need to avoid that for interchange or other reasons. Just to see if you like the difference or not. The bass will be deeper and smoother than 30 ips as this moves head bumps and LF limit down an octave. And while you can use the "no NR" 30 ips tape as an artistic limiter as was fashionable in some circles, you wouldn't want to do that, would you? If not, you might like the extra headroom SR brings to the party.

Anyway, looking forward to hearing more!

 

[c1ferrari]

Nice to meet you, Roger --

If you do obtain an A/SR unit to play those tapes, you might consider making some of your recordings at 15 ips with SR unless you need to avoid that for interchange or other reasons. Just to see if you like the difference or not. The bass will be deeper and smoother than 30 ips as this moves head bumps and LF limit down an octave. And while you can use the "no NR" 30 ips tape as an artistic limiter as was fashionable in some circles, you wouldn't want to do that, would you? If not, you might like the extra headroom SR brings to the party.

Anyway, looking forward to hearing more!

Thanks for the informative reply If I were recording analog multitrack, I'd be more inclined to consider NR.
Probably, the most sophisticated recording I envisage is on location using Nagramaster EQ at 15.

 

[DonH50]

Pretty sure SR was not out when I last played with tapes (early 1980's); at least, none of my decks had it. I know I tried it later but by then my system was in storage (and I had sold all but my cheapie consumer R2R). For me it was B (C/HX) for consumer and A for pro'ish stuff. As I mentioned elsewhere, I had a full dbx system but eventually got rid of it because I just couldn't handle the pumping.

Roger, could you briefly describe SR? I know I could go look it up, but it'd be nice to get a capsule summary from the expert here in this thread, if you don't mind.

Thanks! - Don

 

[Roger Dressler]

Pretty sure SR was not out when I last played with tapes (early 1980's); at least, none of my decks had it.

No, it was not built in.

Roger, could you briefly describe SR? I know I could go look it up, but it'd be nice to get a capsule summary from the expert here in this thread, if you don't mind.

SR is like the other 2-way noise reduction systems that encode before the tape and decode after with the complementary process, thus restoring the signal and reducing the noise. What SR did was concentrate on achieving this with the least manipulation of the signal as possible. Noise is not audible all the time, so there's no need to "fix" it all the time. Yet a system like dbx (to take an extreme example) is dynamically adjusting the entire audio signal all the time. A-type NR divided the spectrum into 4 fixed bands to provide selectivity, and it gave 10 -15 dB NR. In order to increase the dynamic range improvement further, SR has more bands, but that means they can be more selective. Only when needed do they act.

One other interesting aspect of SR is the compression ratio. If you listen to the signal on the tape, you can hear significant differences between the various NR systems. So what? No one listens to that without decoding (Ok, except maybe B-type cassettes). But it is telling to listen to the compressed signal. If it has large changes in the signal, like when a transient occurs, that behavior has to track perfectly in the decoder in order to invert perfectly. But tape is not a perfect medium, and that affects how well the decoder tracks the encoder.

SR took the philosophy of ensuring the compressed signal was free of any obvious dynamic manipulations. It sounds compressed, but you do not hear rapid signal modulations. It's very smooth. By virtue of that, the decoder is not going to expose its operation.

There's a lot more going on besides just NR. Here's the Dolby paper in case you want to dive in.