Tascam 38 Calibration

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fstrat76

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Please bear with me as I am new to this calibration and alignment stuff. I understand quite a bit of the info in the 38 manual.

I just started testing my deck.

According to the manual 0 on the meter = -10dB = .3V


I hooked up a 1kHz test tone and the source is .308 V. Looks good.

I hook that test tone source to track 1 of the 38 and select the input. 0 on the meter. Great.

I check the output of track 1 with input selected, but that reads .327 V, slightly higher than the .308 V of the source.

Now I record the test tone and play it back on the Sync head. I can see the meter below 0 and the voltage at the output reads .294 V.

I play it back using the Repro head and get an output slightly higher at .297 V.


However, my question is: What kind of tolerances are acceptable?


Thanks!
Mike
 
Mike, if you're like me you'll run yourself dizzy trying to get everything exact but the reality is that the swing from even 0.294V and 0.327V is less than 1dB on your deck's meters. So...is that important to you?

BUT...before you answer that, consider that typically Teac assumed you would have the outputs loaded with a 600Ohm load...that will slightly drop those output levels, so if you really want to get picky about it you would make a 'Y' cable so you can have the output of the deck connected to your mixer AND be able to check the voltage. A patchbay works really good for that two if you have a normaling jack from which you can "sniff" the signal (i.e. plug in a cable without breaking the input and output connection and have two outputs).

Also consider your meter. Unless it is a true RMS measuring meter with a bandwidth that covers the audio range (like 20Hz to 20kHz) then you are going to get inaccurate results outside of the 1kHz tone.

So think about loading your outputs when you are calibrating, and take a look at your meter and see what it can do for you.

To answer your question, I'd probably be inclined to advise that you try to get that first figure, the input monitoring level (the 0.327V), closer to your 0.308V input level, but do yourself a favor and don't be like me...call the 0.294V and 0.297V levels "good enough" because they probably are...less than 0.5dB as measured on your deck's meters. I'd sit there and try to get everything 0.300V all the way across and what you really want to be doing is capturing audio or mixing down or something, not listening to that @(#$^%* 1kHz tone and staring at the LCD on your DMM. :o:D

Good question. How else can we help, and would somebody else please weigh in on this because I don't trust what I'm telling the poor fella...
 
I agree with sweetbeats, I spent all Sunday getting my levels on my MS-16 to read exactly 316mv, that is what -10 is, I havent played a guitar or recorded anything in months. The important thing is to make sure all your other channels are just as close as the first one. Unlike tuning guitar strings, any small differences between levels and different tracks will not be heard. I do like to know my levels are right on but it takes a lot of time.
VP:eek:
 
Yeah, I hear you guys. I've had this thing a month now and have fixed and cleaned and tweaked and baked tapes and want to learn how to calibrate more etc, and I haven't recorded a darn reasonable thing on it yet except the test tone.

Then again, I'd like to make sure its in acceptable working order with acceptable tolerances. I purchased the Radio Shack meter that someone recommended in another thread here.

I was using an older baked tape on this first test. I just tried with a newer tape and got slightly higher levels in sync and repro, more like .300V. I get a brand new RMGI 911 tape this week and will try it again. I never thought about the load on the output, I'll give that a try also.

I realize there are more calibration things to do, meter cal, bias adjust and such, but I sure would like to get to some recording but want to make sure I'm "close".

So if my levels are the same (or close) between Sync playback and Repro playback, does this mean the heads are aligned?
 
Not sure if you want to use old baked tapes for this kind of work. I would think it to be counterproductive in this case. Buy a new tape and perform your tests again.
 
sweetbeats said:
Mike, if you're like me you'll run yourself dizzy trying to get everything exact but the reality is that the swing from even 0.294V and 0.327V is less than 1dB on your deck's meters. So...is that important to you?

BUT...before you answer that, consider that typically Teac assumed you would have the outputs loaded with a 600Ohm load...that will slightly drop those output levels, so if you really want to get picky about it you would make a 'Y' cable so you can have the output of the deck connected to your mixer AND be able to check the voltage. A patchbay works really good for that two if you have a normaling jack from which you can "sniff" the signal (i.e. plug in a cable without breaking the input and output connection and have two outputs).

Also consider your meter. Unless it is a true RMS measuring meter with a bandwidth that covers the audio range (like 20Hz to 20kHz) then you are going to get inaccurate results outside of the 1kHz tone.

So think about loading your outputs when you are calibrating, and take a look at your meter and see what it can do for you.

To answer your question, I'd probably be inclined to advise that you try to get that first figure, the input monitoring level (the 0.327V), closer to your 0.308V input level, but do yourself a favor and don't be like me...call the 0.294V and 0.297V levels "good enough" because they probably are...less than 0.5dB as measured on your deck's meters. I'd sit there and try to get everything 0.300V all the way across and what you really want to be doing is capturing audio or mixing down or something, not listening to that @(#$^%* 1kHz tone and staring at the LCD on your DMM. :o:D

Good question. How else can we help, and would somebody else please weigh in on this because I don't trust what I'm telling the poor fella...
Click to expand...

Good point about an accurate RMS meter. I read 2 times this weekend on the net that Tascam meters are not accurate at signals other than 1K. So I did a test. At 16K my meters on the MS-16 read exactly 0db. On my brand new Tenma digital multimeter it reads 310, according to the formula for db's: db=20logV1/V2, that is only .166 of a db. That seems pretty accurate to me. I take alot of what I read on the net with a grain of salt. Some people like to badmouth Tascam. I think they are the high end studio snobs. If it were'nt for Tascam with their "semipro" machines I wouldnt have all the goodies I have now.
VP;)
 
It is true though...the Tascam meter ballistics are off as you proceed into the HF region and that is my personal experience measuring input levels with a good true RMS meter...the Teac meters tend to be over-sensitive as you get past 16k...they are pretty good everywhere else AFAIC...certainly not just at 1k :rolleyes:. Give me a break.
 
My only thought is that this is why I bought an old HP AC voltmeter with a meter and needle and a mirrored scale reading in both dB and volts. I hate reading those voltage numbers off a DMM, though I do it when I have two meters hooked up, say, one minding audio levels and the other checking bias or erase output and I don't want to keep swapping and repatching. Much more intuitive on the old meter.

Oh, and having lots of room on patchbays to multiple stuff is essential to sanity when working on these machines.

Just my two cents.

Cheers,

Otto
 
Victory Pete said:
I take alot of what I read on the net with a grain of salt. Some people like to badmouth Tascam. I think they are the high end studio snobs. If it were'nt for Tascam with their "semipro" machines I wouldnt have all the goodies I have now.
VP;)
Click to expand...

Nothing wrong with Tascam. Mackie suffers some of the same abuse, because their gear is cheap, durable, works pretty well and sells a bunch. Usually the abuse is at the hands of people who are trying to sell you much more expensive stuff.

Good musicianship and smart recording practices can get good results from that semi-pro gear, and they just don't want anyone to know that. And what if people found out they could get a decent recording more simply on a tape machine without having to throw in all those plug-ins and stuff? Bad for business. :)

Cheers,

Otto
 
ofajen said:
Nothing wrong with Tascam. Mackie suffers some of the same abuse, because their gear is cheap, durable, works pretty well and sells a bunch. Usually the abuse is at the hands of people who are trying to sell you much more expensive stuff.

Good musicianship and smart recording practices can get good results from that semi-pro gear, and they just don't want anyone to know that. And what if people found out they could get a decent recording more simply on a tape machine without having to throw in all those plug-ins and stuff? Bad for business. :)

Cheers,

Otto
Click to expand...

No wonder why I am so defensive! I have had a Mackie 32-8 for 15 years!
VP:eek:
 
ofajen said:
My only thought is that this is why I bought an old HP AC voltmeter with a meter and needle and a mirrored scale reading in both dB and volts. I hate reading those voltage numbers off a DMM, though I do it when I have two meters hooked up, say, one minding audio levels and the other checking bias or erase output and I don't want to keep swapping and repatching. Much more intuitive on the old meter.

Oh, and having lots of room on patchbays to multiple stuff is essential to sanity when working on these machines.

Just my two cents.

Cheers,

Otto
Click to expand...

I have a bunch of old HP meters, The one I am using right now is the 3400A. It is easier to watch a needle, DMM's jump all over.
 
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