A3440 calibration to ampex 456

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evm1024

evm1024

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Hi,

I have a Teac A-3440 and I've been attempting to calibrate it with Ampex 456. Has anyone done this (I assume many). The problem that I am running into is that the playback cal adjustment will not adjust low enough to read -5 VU (I have a 200 nW/M^2 MRL, the MRL is 1 dB over 185 nw/M^2 and 456 should be 6 dB over so I need to under read by 5).

Most of the channels can reach -5 VU at the limit of their adjustments but not one. (only does -4) .

Any thoughts?

--Ethan
 
evm1024 said:
Hi,

I have a Teac A-3440 and I've been attempting to calibrate it with Ampex 456. Has anyone done this (I assume many). The problem that I am running into is that the playback cal adjustment will not adjust low enough to read -5 VU (I have a 200 nW/M^2 MRL, the MRL is 1 dB over 185 nw/M^2 and 456 should be 6 dB over so I need to under read by 5).

Most of the channels can reach -5 VU at the limit of their adjustments but not one. (only does -4) .

Any thoughts?

--Ethan
Click to expand...

My only suggestion is to make sure you have the right MRL cal tape. If you are down to the limit on the pots, there is something wrong. Call MRL and talk to an engineer. There are tons of cal tapes and each is different.
 
I'm afraid not!

456's MOL (maximum operating level) is +6, and it's STANDARD operating level is +3db over 185 = (0VU).

When using the 200nWb cal tape, you should be setting your playback response on the VU meter to "-2VU", for 456 "standard".

Therefore, when you hit the 456 tape at Standard operating level: (0VU), it's (+3db/185), and when you hit it at it's MOL: (+3VU), it's (+6db/185). When adjusted this way, anything that peaks over (+3VU) exceeds 456's MOL, and therefore produces distortion.

You should have proper range of adjustment to adjust to -2VU, using the 200nWb MRL tape, & shooting for 456-standard cal.

Hope that clears things up.;)
 
What your previous method denotes is actually calibrating for 499 tape.

That is,... targetting (-5VU) when using a 200nWb MRL tape.

So,... by your efforts, you've determined that the 3440's electronics don't have enough range to handle 499. Just as a "BTW" or FYI.

See my details about 456-cal, above!
 
456 Mol

Thanks, I was wondering if the +3 or +6 dB was max or operating. I was scanning everything I could read on this. So as you say the 3440 can be calibrated to 456 and 499 is just out of range for one of the 4 channels on this deck. Thanks.

I could make a feedback resistor change in the playback opamp to reduce the playback amp gain if I wanted to calibrate to 499 (I DO NOT want to...). I've not looked at the record range yet to know if it can handle the extended range. I would expect so but I will know more tonight.

Regards, Ethan
 
I did some searching of calibration info, and the data out there is misleading.

There's site after site that says (para) "you can operate 456 at +6db/185", (as if they're passing the same info around),... but other (non-web) info I have says +6db/185 is 456's MOL, & it's standard operating level is (0VU=)+3db/185. That's a significant difference in meaning, of the two relative statements!

If, F/I, 0VU = 250nW/m2 = (Tascam's R/R reference level), then that assumes a 0VU operating level average, with peaks no more than +3VU, to keep within 456's MOL. That's how your "typical" analog recorder is set up,... isn't it?

Yes.

You'd never want to run a tape at it's MOL as 0VU, because that wouln't allow for the natural fluctuations and peaks.

I admit, there's no clarification on the web based data on that. All the sites I saw said, "run 456 at +6db/185", and that's clearly wrong. Also, as evidenced by your 3440 not even being able to adjust that far!

The web is amazing, but it ain't all that!;)
 
Quantegy says...

I have some old specs for 465 and 499 that says that:

tape ref (nWb/m) 3% output dB 3% output nW/m

456 260 (+3dB) 12.3 dB 1040
499 320 (+6dB) 17.4 dB 2368

So if we ran 456 at:

185 nW/m we would have 15.3 dB headroom. (to 3%)
260 nW/m (+3) 12.3 dB
320 nW/m (+6) 9.3 dB

More confusing even yet. This makes me think that the +6 is correct...of course that is to 3% THD at 1kHz.

--Ethan
 
Aaaaaaaaagggggghhhhhhh!!!!!! Confusing!!!

...................;)
 
A small light

Looking a bit more I see that in the old days 9 or 10 dB of headroom was enough for most applications so running Quanetgy 456 at +6 dB and 9 dB headroom was (mostly) OK.

However, because digital must not be overdriven, 0 VU is 12 dB under (digital) saturation. So tape which can be overdriven and not sound too bad could exceed 9 dB (over 0 VU on a +6 tape) and thus drive digital into raw distortion. Of course this applies to ADD AAD recordings.

This is how one studio has described it as their operating procedures.

So having 12 dB overhead is playing it safe with analog and balistic VU meters.

Calibrating my a-3440 at 185+3 sounds good as that I may want to butn a cd master someday.

--Ethan
 
Yes!

Thank you for the good & enlightening research you've done!
........;)
 
A Reel Person said:
Troll on, dude. :)
Click to expand...

You sound like a broken (analog) record, Dave. Snap out of it and make some more of those stolen songs. Royalities, Dave




Posting and releasing songs written by someone else (copyrighted material) is a FEDERAL crime, Dave. I do hope you will own up to it and pay The Beatles their fair share.
 
A Reel Person said:
Trollboy!............. :)
Click to expand...

From Nowhere Radio's Website:

"Copyright notice. All material on nowhereradio.com is protected by copyright law and by international treaties. You may download this material and make reasonable number of copies of this material only for your own personal use. You may not otherwise reproduce, distribute, publicly perform, publicly display, or create derivative works of this material, unless authorized by the appropriate copyright owner(s)."

You see, Dave, you have violated the copyright laws and put nowhere radio in jeapordy. You are a low life weasle at best. Pay the royalties.
 
Thank you for the advice.

God bless you & have a nice day. :)
 
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