Modern calibration, and old pre-recorded tapes
- Thread starter jviss
- Start date
evm1024
New member
With your 3440?
The short answer is Yes....
The long answer is:
1) A deck set for 355 nWb/m or 320 nWb/m will playback 250 nWb/m 3 dB lower than 0 VU and 185 nWb/m tapes 6 dB lower. You will have to make up that level and perhaps get an increase of noise.
2) Your 3440 most likely will not be able to calibrate to this level. I tried to calibrate a 3440 I had to 355 nWb/m and ran out of range in the adjustment pots.
3) to make it cal to this level will require some mods. It may be quite difficult to do.
I would suggest to cal to 250 nWb/m. This would allow for great headroom as well as allowing playback of older tapes with 3 dB more signal compared to 355 nWb/m.
Regards, Ethan
PS 320 nWb/m is a European standard that is not used here or on NAB machines. If I remember correctly.
The short answer is Yes....
The long answer is:
1) A deck set for 355 nWb/m or 320 nWb/m will playback 250 nWb/m 3 dB lower than 0 VU and 185 nWb/m tapes 6 dB lower. You will have to make up that level and perhaps get an increase of noise.
2) Your 3440 most likely will not be able to calibrate to this level. I tried to calibrate a 3440 I had to 355 nWb/m and ran out of range in the adjustment pots.
3) to make it cal to this level will require some mods. It may be quite difficult to do.
I would suggest to cal to 250 nWb/m. This would allow for great headroom as well as allowing playback of older tapes with 3 dB more signal compared to 355 nWb/m.
Regards, Ethan
PS 320 nWb/m is a European standard that is not used here or on NAB machines. If I remember correctly.
Interesting...more questions!
Thanks, Evan. That's interesting. I ask, because the tech to whom I entrusted my newly acquired 3440 (my first reel to reel deck) advised me that 320 nW/m was what was necessary for modern tapes, and that he sets many decks to that level. He didn't indicate that it would require mods to do.
I read the 3440 service manual, and for the life of me I can't find an absolute reference anywhere; that is, I can't determine what reference fluxivity is used for the calibration outlined in the service manual (by the way, is it safe to assume that the calibration voltages given are in units of VRMS?).
I searched around a bit, and everything I've found on RMGI SM-911 indicates it was designed for the 320 nW/m operating level. Indeed, this is the reference level specified for the measurements in their data sheet.
I've seen references to a higher, 500 or nW/m level referred to as European.
I don't see how it relates to equalization, if that's what you meant by the NAB comment.
On playback of older, lower-output tape recorded to a 180 or 200 nW/m operating level, do you think that simply turning up the volume downstream of the deck will result in an increase in noise? I can believe it; but I don't know the dynamic range of the playback amp in the deck.
Thanks, Evan. That's interesting. I ask, because the tech to whom I entrusted my newly acquired 3440 (my first reel to reel deck) advised me that 320 nW/m was what was necessary for modern tapes, and that he sets many decks to that level. He didn't indicate that it would require mods to do.
I read the 3440 service manual, and for the life of me I can't find an absolute reference anywhere; that is, I can't determine what reference fluxivity is used for the calibration outlined in the service manual (by the way, is it safe to assume that the calibration voltages given are in units of VRMS?).
I searched around a bit, and everything I've found on RMGI SM-911 indicates it was designed for the 320 nW/m operating level. Indeed, this is the reference level specified for the measurements in their data sheet.
I've seen references to a higher, 500 or nW/m level referred to as European.
I don't see how it relates to equalization, if that's what you meant by the NAB comment.
On playback of older, lower-output tape recorded to a 180 or 200 nW/m operating level, do you think that simply turning up the volume downstream of the deck will result in an increase in noise? I can believe it; but I don't know the dynamic range of the playback amp in the deck.
evm1024
New member
Here it the paper to read to get I good understanding of calibration tapes (I assume that you have read it but include it for those who have not)
http://home.comcast.net/~mrltapes/choo&u.pdf
The A-3440 is a quite old deck (I like them a lot) and was not designed for high output tapes of current design. The electronics in mine would allow some channels to adjust to 355 nWb/m but not all. Yours may allow all, who knows. In addition to the record level and playback levels you need more bias for higher output tapes. The bias amp may be overloaded trying to get to 355 nWb/m or saturate the record head. Also, the erase signal need to be greater as well to get a full erase. YMMV on your deck.
Yes the voltages are RMS. This deck predates Teac's standardization on 0VU = 1 V and uses -12 dB on the input and -8 dB on the output for 0 VU with a 0VU= 0.775 volt reference. It can be calibrated to -10 dBv = 0VU (with 0 VU = 1 V) which is more common today.
The test tape YTT-1003 and YTT-1004 are said to have a reference flux of 185 nWb/m at 400 Hz. THis tells us that the standard reference flux the A-3440 is calibrated to is 185 nWb/m. You can calibrate it to 250 wit the correct calibration tape.
When calibrated for a higher reference flux you put more signal on tape. The tape is hotter. In order to play that hot tape back you need to reduce the gain of the playback amp so as to have a 0 VU in signal playback at 0 VU. This means that if you are calibrated for 355 nWb/m = 0 VU then a tape recorded at 185 nWb/m will playback 6 dB quieter. You will need to make up the 6 dB in the output control setting on the 3440. This is 6 more dB amplification of the noise generated by the Play EQ and Play Line amps. The gain structure will not be optimum (assuming it ever was) and may be the source of noise I wrote about.
Your deck was designed with Scotch 250 in mind which is a +6 tape like Ampex 456, BASF/RMGI 911 as well as +3 tapes of the time. It does not hurt to operate a tape at less than its designed reference flux. You do move the noise floor up 3 dB but you gain 3 dB in overhead (Running a +6 tape at +3).
THe reference to NAB EQ was an indication that only European machines (using IEC1 EQ) ever referenced 320 nWb/m cal tapes. Read about it in the above referenced paper.
Regards, Ethan
http://home.comcast.net/~mrltapes/choo&u.pdf
The A-3440 is a quite old deck (I like them a lot) and was not designed for high output tapes of current design. The electronics in mine would allow some channels to adjust to 355 nWb/m but not all. Yours may allow all, who knows. In addition to the record level and playback levels you need more bias for higher output tapes. The bias amp may be overloaded trying to get to 355 nWb/m or saturate the record head. Also, the erase signal need to be greater as well to get a full erase. YMMV on your deck.
Yes the voltages are RMS. This deck predates Teac's standardization on 0VU = 1 V and uses -12 dB on the input and -8 dB on the output for 0 VU with a 0VU= 0.775 volt reference. It can be calibrated to -10 dBv = 0VU (with 0 VU = 1 V) which is more common today.
The test tape YTT-1003 and YTT-1004 are said to have a reference flux of 185 nWb/m at 400 Hz. THis tells us that the standard reference flux the A-3440 is calibrated to is 185 nWb/m. You can calibrate it to 250 wit the correct calibration tape.
When calibrated for a higher reference flux you put more signal on tape. The tape is hotter. In order to play that hot tape back you need to reduce the gain of the playback amp so as to have a 0 VU in signal playback at 0 VU. This means that if you are calibrated for 355 nWb/m = 0 VU then a tape recorded at 185 nWb/m will playback 6 dB quieter. You will need to make up the 6 dB in the output control setting on the 3440. This is 6 more dB amplification of the noise generated by the Play EQ and Play Line amps. The gain structure will not be optimum (assuming it ever was) and may be the source of noise I wrote about.
Your deck was designed with Scotch 250 in mind which is a +6 tape like Ampex 456, BASF/RMGI 911 as well as +3 tapes of the time. It does not hurt to operate a tape at less than its designed reference flux. You do move the noise floor up 3 dB but you gain 3 dB in overhead (Running a +6 tape at +3).
THe reference to NAB EQ was an indication that only European machines (using IEC1 EQ) ever referenced 320 nWb/m cal tapes. Read about it in the above referenced paper.
Regards, Ethan
Thanks, Evan. I haven't read that paper, I will read it next! I appreciate your notes. I think I will try to get to the tech and have hims set it up at 250, for now, anyway, while I learn more about this (and gear-up with scope, signal generator and AC voltmeter).
Is this an externally adjustable, or switchable parameter for any decks?
Regards,
jv
Is this an externally adjustable, or switchable parameter for any decks?
Regards,
jv
More...
I wanted to follow up on this. First, Evan, thanks for sharing your knowledge, and your patience with me as I get up to speed on this topic.
I referred to an "absolute reference" before, and expressed m dismay at not finding a reference to the fluxivity in the service manual:
I had a long talk with Phil Paske, the sales manager at RMG, and an engineer who has been "at all three companies" (BASF, EMTEC, RMG, I guess). He recommended 250 nW/m as a good level to calibrate to (which, by the way, is exactly what Evan recommended (Nice!)). He said 320 was a non-standard level, and that for the higher levels he wasn't confident that the bias oscillator would be able to supply enough current, particularly to the erase head (which is also what Evan had mentioned). This is with regard to the SM-911 tape, which he thought would be a good tape for this machine. He was very kind and patient, and apparently a font of knowledge about recoding and tape.
So, Evan, thanks, right on the money.
I wanted to follow up on this. First, Evan, thanks for sharing your knowledge, and your patience with me as I get up to speed on this topic.
I referred to an "absolute reference" before, and expressed m dismay at not finding a reference to the fluxivity in the service manual:
On my ride home form the office it dawned on me! (Duh!) That there is an absolute reference to the operating level, and that is the level used to make the test tape! I guess Evan's comment about the test tape being an 185 nW/m is what led me to that realization. Sometimes it just takes a while to absorb stuff, eh?
I had a long talk with Phil Paske, the sales manager at RMG, and an engineer who has been "at all three companies" (BASF, EMTEC, RMG, I guess). He recommended 250 nW/m as a good level to calibrate to (which, by the way, is exactly what Evan recommended (Nice!)). He said 320 was a non-standard level, and that for the higher levels he wasn't confident that the bias oscillator would be able to supply enough current, particularly to the erase head (which is also what Evan had mentioned). This is with regard to the SM-911 tape, which he thought would be a good tape for this machine. He was very kind and patient, and apparently a font of knowledge about recoding and tape.
So, Evan, thanks, right on the money.