Newbie Going analog with a TEAC 80-8.

[Herm]

It sounds like things may getting better. I was wondering do you have dbx on this machine?

 

[samth3mancgp]

I do not have the DBX for this machine. I've read that some people say it is absolutely necessary and some people say that they get along just fine without it. I cant find a dx-8 module which goes with the 80-8, but I read that I can get some 2 channel dbx units with RCA i/o and it'll do the same thing.

What are your thoughts?

Do you think you know what I need to do to get channels 7 and 8 at decent levels? If it is a bias adustment could you explain to me what exactly happens when I adjust the bias? I don't know what it is haha.

 

[samth3mancgp]

So today I found this http://www.diamondcut.com/vforum/archive/index.php?t-2449.html I didn't realize how many adjustments could be made! I'm getting closer to having my machine setup correctly with the brand new reel of tape but I don't know how to perform these adjustments. I have my Owners manual and service manual for my 80-8, And the owners manual has instructions for some of these adjustments. I don't know if all the adjustments are necessary for my deck and I dont want to do something wrong.

 

[sweetbeats]

Go by the manual for your 80-8...I consider other resources like the one you linked as supplementary. Sometimes they have shortcuts to certain things or can expand your methodology as you advance, but your manual has everything you need to know for maintaining your 80-8 so don't let yourself get confused.

Do as I did and was advised: take it one step at a time and have fun.

Your manual, in addition to having all the info you need, is also generally well laid out step-wise for what needs to be done. And no, not EVERYTHING in the manual needs to be done. You've already done the most important thing and that's clean the tape path. The second most important is degaussing the tape path. Then comes mechanical alignment and then electronic alignment. I have the operations manual and schematics for the 80-8, but not the service manual so I can't really comment much further but put up specific questions here as you come to them. Lots of help here I believe.

Noise reduction: you want Type I dbx if you are going to use dbx noise reduction. You can get that in the Tascam DX-4D (with a simple mod that will allow it work without its "Control Cable"...many units have already been modded...you would need two of these since they are 4 channels each), dbx 150X (you would need 4 as they are 2 channels each) or the aforementioned DX-8. If you want the DX-8 just hold out for one. They come up on eBay every so often.

As far as whether or not you need it, only you can decide. Keep an open mind and don't be swayed by the absolutes of others. You might find you like it for some program types and not for others...maybe for all or none, but try your 80-8 without for a bit and see if the noise bothers you. If it does then you know what to do.

My 2p.

 

[samth3mancgp]

Ok it seems like I am on the right track. I opened up the manual again because I had not looked at it since I got the recorder and things are making more sense now. I adjusted input monitor level so it matches the input pot for all channels and I'm working on erase bias right now. (which fixed an erase problem I had with channel 2 ) But I stopped at channels 7 and 8 because I cannot get them to playback at the matching level that it was recorded, even when I adjust the playback levels to the Max level. I think I need to adjust the record bias, or record EQ to solve that one? I've heard that RMGI SM911 is similar enough to the Ampex 456 in specs that I wont need to do any adjustments for the RMGI. The only test recording I have done is 1khz test tones for testing record/play back levels and the erase bias. So I dont know how the RMGI really sounds yet.

Lastly, I don't think I can really do any mechanical alignment besides checking tape speed and wow and flutter using a multimeter to see changes in pitch during playback. I don't have an alignment tape But the electronic calibration that I am doing now is fixing a lot of the problems I had when I was messing around with the Ampex. Cleaning and de-gaussing made the most immediate and noticable difference though!

 

[samth3mancgp]

Ok, I think I fixed the problem with channels 7 and 8 by adjusting the record level. But I am now adjusting the record bias.. which i think is a very important part. I am unsure of what to do. The manual says "set up a signal generator. the frequency is 10khz. the level should be 0 VU on the INPUT setting. (I can get the input level to 0 VU on every channel except channel 1 for some reason?) Start the machine and record the signal, and switch to MONITOR (playback) mode on the INPUT SELECT. Raise the bias level until the VU meter rises, peaks out as high as it will go, and starts to fall back. Reduce this peak reading by 3dB"

then next it says "If the meter goes off the scale, adjust the front panel input level control to keep the reading on the scale. What is important here is not the zero dB. It is the reduction of the peak by precisely 3dB.If you have moved your input pot to keep your reading on the scale, The next adjustment (record level) will correct your input reference.

Besides the channel 1 not input monitoring at 0 VU (and it does monitor 1khz like it said in the manual at 0 VU, but not 10khz ), I am fine getting everything ready util the adjustment. I'm not really sure what I am watching for. The part about the VU meter rising isnt very specific. If i move the VU adjustment pot in one direction it makes the VU meter rise up until it is clipping like mad, and the other direction makes it decrease in volume. Could somebody clear this up for me? and are the "Volume Units" the same as dB? or will I have to somehow measure the dB reduction? After bias is just record level (which i will have to do again after doing the bias i guess) and the record EQ adjust.

 

[sweetbeats]

Mechanical alignment: manipulation of adjustable components in the tape path to ensure that the tape travels steadily across the centerline of the heads and to ensure the tape does not buckle or curl at its edges or otherwise become physically distorted or stressed. This may involve djustment of reel tables, tension arms and guides. It may also include adjustment of the brake tensions, tape tension and pinch roller pressure. Those last three are not always essential unless you are having problems. The important thing here is that a test tape is not needed for the mechanical alignment points mentioned above.

Bias adjust: 456 and SM911 are indeed considered bias compatible, but that doesn't mean the deck has been properly biased or biased at all for that tape type...and it is a comon rule of thumb to bias whenever introducing a new tape type to the deck even if it is considered bias compatible. Also, I bet your manual says to bias with a higher frequency tonethan 1kHz...usually 10kHz... :???:

You are going to need a calibration tape.

You should check your record eq and then check the bias again for your channel 7 and 8 problem, but first you need to calibrate the repro level and meters...follow the steps in the manual.

 

[samth3mancgp]

I already fixed the reproduce levels. And the record level for 7 and 8 was the problem for why i couldnt get it playing back right. Sorry I must have made a typo. I am using 10khz for the bias adjustment. I am just not 100% on what to look for on the bias adjustment because the manual is confusing for that one. All of the small problems I had while messing around with 456 before i got the RMGI were fixed after cleaning and d-mag and some erase and level adjustments. The bias ad record EQ and checking the record level again is all that's left for me. the manual does not include anything about head alignment and adjustments, which I found odd.

 

[samth3mancgp]

So while I was waiting for a reply today I decided to try and figure out bias adjustment for myself and I found this. http://www.digitalprosound.com/Htm/TechStuff/2000/Oct/Analog101P3_3.htm

It seemed to shed more light on what bias is and why It is needed. What I am looking for it the minimum distortion level correct? and the record EQ adjustments are made to compensate for the fact that the bias adjustment made for some lack in frequency response. I still don't exactly know what exactly adjusting the bias is doing electronically or physically to the oxide on the tape, but I guess that the adjustment becomes apparent when using low frequencies. I will do the 40hz test letting only 40hz through my EQ so I can hear this change in distortion level.

But this is still unlike what the owners manual says to do. is the dropping of precisely 3dB the "optimized over-bias" on the 80-8 calculated as the difference in test A (40hz) and test B (20khz)?

 

[samth3mancgp]

Bump. I don't know if there are forum rules or something that I am not aware of. I'm trying to find an answer to this question. Should I make a new thread about it?

 

[cjacek]

I think you're doing fine. You're following the service manual so that's good. I'd personally do the 3db over-bias method, as laid out in your manual.

You do have the service manual but it doesn't specify anything on head alignment, azimuth? Is this correct? I'm surprised that it doesn't.

First off, any head aligning is done with a proper test tape so don't touch anything now. There's also the case of only aligning heads which show to have uniform / even ware or are re-lapped / new.

 

[Victory Pete]

Lots of good advice being shared here. Keep it up.
VP

 

[samth3mancgp]

Thanks guys! The owners manual only had instructions for electronic adjustment. I got the service manual out and it does have instructions for everything from tape tension to head alignment and brakes oh my.

So the 3dB method is what I should do I guess. But i'm not really sure what i'm supposed to be doing. I get the 10khz frequency recording, and I go into tape monitor mode and move the bias adjust around.

"adjust bias level until the VU meter rises, peaks out as high as it will go (is this all the way to the right or clipping on the VU?) and then starts to fall back. (I'm not noticing this)."

If Volume units are the same as dB adjusting down 3dB from that point should be easy I just look at the VU meter. below that it says that I should keep the reading on the scale. So is it a point where the sound peaks out on the VU, or is it supposed to go all the way to the right and clip?

 

[cjacek]

No, it's not supposed to clip. Your input signal is set too high.

The needle should be around average level and no more. You're just trying to align the oxide particles for best quality. Completely reduce bias (to the left I believe) and then slowly (while the input signal is playing) increase it (the bias pot to the right) until it peaks (keep going) and then watch it go down 3db. Stop. You've set your bias. Your needle should be just working enough so that you see what's going on and not more, so keep it lower.

 

[samth3mancgp]

Sounds good, I'll try it right now

I have a feeling this new tape is going to sound great with it all setup properly on the electronic side of things. I think the heads are in good shape and are aligned well. when I switch between sync and tape monitor I get the same great sound and now that erase bias has been adjusted, all channels erase just fine

The test tape is used to make sure heads are in alignment and the levels are set right for playback? So that the tapes can be played on other machines with little trouble. And I've heard that recording test tones at the beginning of tracking tapes and master tapes help If they might be played back on other machines.

 

[cjacek]

There is a slightly different / add on method, that you can also try. It's from Steve Albini, the original post escapes me now, but here it is:

1) Set an oscillator to a medium frequency, like 1000 Hz at a nominal recording level and monitor the recorded signal with a VU meter.
2) Reduce the bias level until the signal drops precipitously, then increase it until the meter just peaks. If you overshoot, back it down a little bit until you are just below the peak level.
3) Set the oscillator to a low frequency, say 30 Hz and monitor the recorded signal with headphones. You will hear the low frequency tone modulating the noise and distortion components. Try to separate these in your attentions.
4) while listening to the tone being recorded, adjust the bias until the modulating noise is at a minimum.

It's a way to set correct bias for any tape deck. It's basically like dialing in a clean FM radio signal.

 

[cjacek]

The test tape is used to make sure heads are in alignment and the levels are set right for playback?

Yes, in a nutshell, that's correct.

Also, remember to take your time and, as was previously mentioned, you don't need to do absolutely everything from your service manual.

If and when you get a test tape, here's a cool way to find if the heads are aligned: http://www.analogrules.com/azimuth1.html

 

[samth3mancgp]

I just tried it with a few channels and I start with it turned all the way down (where I don't get any input signal) then I turn it up. I keep turning the adjustment waiting to see the needle drop the 3dB but it does not drop
even if I turn it up all the way

It does seem to stop at a certain point and not want to go any farther though. Is it automatically dropping 3dB or do I make that adjustment after it reaches the peak?

That other method seems similar to the article I had a link to in an earlier post. except the low frequency was done first.

Thanks for the help. I must be missing something really simple for this adjustment.

 

[cjacek]

Prior to adjusting bias, did you do anything to those channels?

OK, when the peak hits, where does it hit and what happens when you keep turning?

 

[samth3mancgp]

I adjusted playback levels for both sync and playback, input monitor level, record level, and erase bias.

When It peaks it just stays there about halfway up on the VU meter, but If it keep going it will climb a little bit more until the adjustment wont turn anymore.