Noisy 4 track Teacs?

[Bob Boyer]

Those of you who also own 3340s or 3440s - do you notice a fair amount of hiss coming from the machine? Not tape hiss - but hiss through your playback system when the volume is turned all the way up?

I'm noticing more than I would like on my 3440 and M50 mixer. A little of it is attributable to the mixer itself, but most of it comes from the tape deck, just turned on, in "play" mode and not pulling tape. This background hiss is coming through when bumping quiet material over to the computer...necessitating the use of white noise filtering software I'd rather not use to rid the recording of it.

This is not something a dbx unit would solve - since it's not coming from the tape, but the electronics themselves. Nakdoc suggested the ferrite heads may be some of the issue along with less than pristine circuit designs, but he suggested I poll everyone here to see what their experience is.

Thanks in advance for your comments and observations.

[Skywavebe]

Hi Bob,
Yes, I have heard complaints from people that they can hear amplifier noise when dealing with Teac and probably any other deck as well when extreme volumes are used. This is a case where the understanding of a Signal to Noise ratio is not understood and if one has an amplifier with enough gain they will hear some kind of noise from a DAT machine as well. Most of the time I get people that are using headphones that complain.
A signal to noise ratio is determined by a maximum signal to that of the least noise. Teac decks often read between 46 and 52 dB noise without any weighting circuit. Can there be improvement in the circuits- I have to say there sure could be. However we are dealing with a production line machine where it was to be sold for a certain purpose at a restricted cost.
Not the design match of a Studer at $14,000 a copy.
If you turn up a amplifier to full level and listen you hear what is really there not the attenuated audio as provided by the Pot. The next question you should ask is what would the audio sound like it I was to put some on-It would be ear shattering even with a modest sized amp.
This is what Signal to Noise Ratio kind of indicates. Therefore you do not run the deck with outputs at max and you do not set your computer inputs to microphone gain to see if there is any noise- of course there will be.
We could get into amplfier designs and component to use for such purposes but that is for future concerns and not what we are dealing with now.
dBx circuits do quiet down the noise when placed in use with no tape on with such an equipped deck. What happens is the dBx sees no signal from the heads and uses it decoder to indicate no signal which should lower it into the -80 dB area of noise. The other end of the dBx unit takes the loud signals to compress and make possible a +18 dB input signal. So you add headroom extension to the reduced noise floor and you get the 100 dB S/N ratio that the dBx is suppose to give you.
I have answered questions to people before when computer interfaces to tape deck was concerned and I often get this complaint. But some of the problem comes from wrong interface mismatches and the wrong type of connecting cables. Tape decks are not noise free- none of them are, it is something that one has to come to understand. Why do some have more noise than others? Probably because of specified outputs being different and some being balanced while others being unbalanced and with an output of -5 to -10 dBV or -10 dBu.
I don't know if this answers your concern but might shed some light on the subject.

[vinyldavid]

My M-50 is nearly silent...more silent than most mixers I've used.

My A3340S is fairly quiet, I haven't seriously listened to it's output in a couple years, I remember hearing some noise when I cranked it, but you have to remember these things are getting up in age, and were not super high end decks. They are what they are and I love them for it.

[Bob Boyer]

Sam & David,

Thanks for the feedback (pun intended). You pretty much confirmed my suspicions after talking with Nakdoc yesterday. One can get the noise levels down somewhat by replacing old capacitors and such with newer components - and for no more money than I have in these units, that may be worthwhile - but the noise is inherent. And yes, you don't notice it when an ensemble is cranking full tilt, especially since I'm driving the bejeezus out of the level on recording anyways with all the headroom that RMGI tapes have.

My curiousity comes from wanting to play around the edges a bit and gain some quietness for times when the volume level isn't so loud - which is a good bit of the time with acoustic music.

And I'm pretty impressed with the overall noise level of the M50. For a 30 plus year old mixer, it's very good. If all goes as planned, Tom's gonna go through it later this year and recap it, which will get it as close to new as possible without sacrificing the sound for which I bought it.

I was just wondering if it would be worth it to spend the money to do the same for the 3440. Given the excellent condition the deck is in, it doesn't sound like it from what you're saying. And from what you say, a dbx unit for the deck does sound like it's worthwhile so if anyone has one...

Regards,


Bob

[Skywavebe]

Hi Bob,
Yes, I know about the M50 mixer, it was my first one that I got to use and loved every part of it. Later on I have obtained a M520 and a M1516 to add to my studio.
The A3440 deck could be a good choice for recap and other improvements. But if you are going to change components it kind of goes without saying that the calibration will need to be gone through at the end.
The pull out cards make a parts change out much easier than on the A3340S and those types. Other things to consider is lower noise transistors, the use of low noise Metal Film resistors and if an Op Amp is involved to see if a direct replacement is possible in replacing the typical NJM4559 with something like a NE5532 or even something better than that.
All this trouble and cost might gain you a few dB in noise figures but on the whole you will probably not notice it too much except in the pocket book. I always wanted to see how a amplified send of the play signal would look like straight off the head- now with surface mount technology it is feasible to be able to mount a small board with a Op Amp directly behind the head to cut down on noise pickup. Once the signal is obtained in this way then the amplified low impedance signal after that is just adjusted as you need. This is not my original idea as it is kind of used in some Sony Video circuits where bandwidth is an issue in video. Let me know how your project works out.

[Nakdoc]

I was speculating that the higher source impedance in a ferrite play head might also result in more noise. Bob feels the 3440 has more hiss than his 3340. Did Teac design fairly noisy electronics knowing the tape hiss would mask it? If so, the Tascam dbx decks must have quieter electronics.
I suggested we freeze the 3440 in liquid nitrogen, but Bob wouldn't go for that.....silly man.

[Audiomayvin]

Hi Bob and Sam!
Having read many reviews of Reel to Reel machines in Studio Sound and based on my own experience, when one is playing a tape and hears hiss it is almost entirely tape hiss. A simple test- Play your acoustic music recording;take note of the hiss. Stop the tape(I believe that the 3340 or 3440 don't have playback preamp mute ccts.) and listen to the hiss. It will be alot less than the tape hiss-to the point that the preamp hiss alone is virtually inaudible. Of course, if you are going to turn up the volume the hiss will go up. But you would never listen to music at that level. (This whole thing doesn't work with cassette where the electronic hiss almost competes with the tape hiss.)
I don't see how changing caps will reduce hiss.
Going back to the Studio Sound tests, they tested the Revox B77 as well as some other semi-pro/high end home machines over the years and playback hiss has not really been much worse than that of the big machines(Studer, Ampex, etc.)
All the best,
Leon(The Audiomayvin, Montreal(514)739-5403)

[Skywavebe]

Good to hear from Leon again!
The other possibility is that when a deck is calibrated with worn heads where the frequency response is starting to go down, the answer is to increase the Play EQ to compensate for the loss. This is like turning up the high end in an equalizer. The hiss that most complain about is of a high frequency nature so that could be another possibility. It all depends on how much additional the hiss is from where it should be. We need numbers measured below the reference level setting to know what is going on.

[Bob Boyer]

Sam & Leon,

Thanks for the continuing input. I think what's about to happen is that I'm selling my Pioneer 1050 deck tomorrow and then I'll get the Revox tuner-preamp sold and that should give me enough funding to take both the M50 and the 3440 to Tom for recapping and whatever. Hopefully by then I'll also have completed the first cycle of archive recordings so I can afford a couple of weeks of downtime.

At that point, I suspect both of us will reference this thread and post some measurements on the deck and mixer as they currently are before proceeding with replacing old components like caps and such. Hopefully, those measurements will tell more of the story for everyone.

This place is such a great resource. Thanks, everyone.

Bob

[Nakdoc]

Sam & Leon,

Thanks for the continuing input. I think what's about to happen is that I'm selling my Pioneer 1050 deck tomorrow and then I'll get the Revox tuner-preamp sold and that should give me enough funding to take both the M50 and the 3440 to Tom for recapping and whatever. Hopefully by then I'll also have completed the first cycle of archive recordings so I can afford a couple of weeks of downtime.

At that point, I suspect both of us will reference this thread and post some measurements on the deck and mixer as they currently are before proceeding with replacing old components like caps and such. Hopefully, those measurements will tell more of the story for everyone.

This place is such a great resource. Thanks, everyone.

BobRecapping is a distortion reduction measure. I am concerned that noise reduction may be difficult. I would begin by replacing resistors in the first amplifier stages with low noise metal film. I would think that transistor or IC noise figures by themselves are well below the perceived hiss level. One mistake often cited by Yamaha as a noise contributor is the excess gain in the stages before attenuators. Perhaps the line input level amps could be altered to a lower gain. Comments?