Milivoltmeter for audio work

[Fungus]

But I am curious what the specific process will be with the tape head measurements the OP is referring to?

Maybe tape head alignment...?

[Fungus]

Not You couldn't use a DMM to do it but it should have readout in DB like the 8060 and read AC flat up to whatever frequencies you are working with .

His Fluke 189 and 289 have dB readout up to 100kHz.

(as do many Brymens, etc.)

The 8060A is a fine multimeter in many ways but it doesn't have a bar graph.

[rob77]

But I am curious what the specific process will be with the tape head measurements the OP is referring to?

Maybe tape head alignment...?

most probably it is, but head alignment is frequency agnostic.. you can align the heads while playing a single tone. so i don't understand the fuss around the bandwidth of the meter. virtually any modern dmm has the bandwidth necessary to measure AC in the needed frequency range. ddm and/or scope is the only tools one need for such a task. 

[Fungus]

Maybe tape head alignment...?

most probably it is, but head alignment is frequency agnostic.. you can align the heads while playing a single tone.

Back in the day we used to just listen to it and tweak the screw.

[BeBuLamar]

Basically I use them to do level adjustments for the tape recorder. There are quite a good number of adjustments to be made. I do use my Fluke 189 and 289 but I just kind of wondering why those guys at tapeheads forum insist on an analog AC milivoltmeter. And if they are really needed some manufacturers should be making new ones but I really don't see new ones made. Buying used one how do you know if they are in calibration.

[Fungus]

I just kind of wondering why those guys at tapeheads forum insist on an analog AC milivoltmeter.

Analog readings are warmer than digital readings.

[david77]

Basically they're not needed anymore. It's nice to have one but not necessary. Your Flukes will give you good results.

I think most of the guys still playing around with magnetic tape are middle aged or outright old farts who are set in their way and use what they always used when the technology was current. I would include myself in that subset of people  .

Most of the cheaper DMM's in the early 80's where indeed not suitable for AC 20-150kHz. As I said today most half decent DMM's will easily work fine up to ~200kHz or so.

[BeBuLamar]

I am 67 and I do own a good number of cassette tape decks.

[Kleinstein]

Most of the cheaper DMM's in the early 80's where indeed not suitable for AC 20-150kHz. As I said today most half decent DMM's will easily work fine up to ~200kHz or so.

A tricky point with many of the analog RMS chips is that the bandwidth goes down with a reduces amplitude. So they may go to 200 kHz at full scale, but at 1% of FS the BW may not reach 10 kHz. So a small signal at the higher frequency is still not easy.

[david77]

No offence intended . I'm 40 and I own a good number of cassette decks. professional reel to reels and VHS recorders. So I do understand your predicament.

[david77]

Most of the cheaper DMM's in the early 80's where indeed not suitable for AC 20-150kHz. As I said today most half decent DMM's will easily work fine up to ~200kHz or so.

A tricky point with many of the analog RMS chips is that the bandwidth goes down with a reduces amplitude. So they may go to 200 kHz at full scale, but at 1% of FS the BW may not reach 10 kHz. So a small signal at the higher frequency is still not easy.

True. The 189 claims 1,5% accuracy at 10Hz - 20kHz in the 3V range. Easily good enough for aligning a tape deck and undoubtedly better than is easily achievable with an analog meter. Granted, the 8% accuracy at 20-100kHz sounds bad but in practice the only measurment in a tape deck where that would matter is measuring the AC bias. Something that is not usually done while aligning the deck.

[TimFox]

I just kind of wondering why those guys at tapeheads forum insist on an analog AC milivoltmeter.

Analog readings are warmer than digital readings.

When adjusting something to obtain a peak reading (such as head azimuth), an analog display is easier to follow than a digital display.  (This is also true when finding a null reading, as in a bridge.)

[BeBuLamar]

For peak reading I use an oscilloscope.

[TimFox]

I also use an analog CRO to find nulls on admittance bridges.  Instantaneous response.
However, when tuning or tweaking something for maximum voltage, the usual moving-needle meter can move quickly enough and can give better resolution near the maximum than on an oscilloscope.

[2N3055]

Most of the cheaper DMM's in the early 80's where indeed not suitable for AC 20-150kHz. As I said today most half decent DMM's will easily work fine up to ~200kHz or so.

A tricky point with many of the analog RMS chips is that the bandwidth goes down with a reduces amplitude. So they may go to 200 kHz at full scale, but at 1% of FS the BW may not reach 10 kHz. So a small signal at the higher frequency is still not easy.

True. The 189 claims 1,5% accuracy at 10Hz - 20kHz in the 3V range. Easily good enough for aligning a tape deck and undoubtedly better than is easily achievable with an analog meter. Granted, the 8% accuracy at 20-100kHz sounds bad but in practice the only measurment in a tape deck where that would matter is measuring the AC bias. Something that is not usually done while aligning the deck.

What he meant is that RMS conversion chip used in meters (mostly) have different bandwidth at 10%, 50% and 100% of the scale at the same range. That is common to all log/antilog RMS converters. S/D RMS converters (like  LTC1968, former Linear, now also part of Analog Devices) have linear frequency response independent of signal level. But unfortunately they are not used often...

[david77]

Ah I see. I did not know that.