John, just to make sure I went ahead and measured my preamp's headroom. At 400Hz it was about 26dB, with respect to +4dB.
Hachidori Fukami Tape/Phono Preamplifier
- Thread starter Zeotrope
- Start date
That’s a good question. Maybe it’s a matter of experience and listening carefully. Who knows.
I’ve just had this discussion with Jonathan at Hachidori and an engineer at Revox (regarding the “new” Mk III machine’s 320-510 nW/m switch).
If the preamp is designed properly, and this is strictly in terms of playback, the strength of the record level does not make a difference. You simply turn up the gain for 320 vs 510, and vice-versa. The meters will respond according to the level, so if your meters read 0dB at peaks with 320 tape, they will look like the signal is clipping. If your preamp has different gain settings, in addition to the output level, then you will want to ensure they are adjusted accordingly.
Perhaps something got lost in translation.
The recording level (and therefore the tape head output) will have the direct bearing on SNR in some cases.
In solid state circuits, and also in tube circuits with tons of global feedback, that is not going to matter. But some of us eschew global feedback, and then your SNR is directly affected by the front tube own noise, and the magnitude of the signal applied to it.
What happens after that first tube is not important.
Last edited:
Nothing got lost in translation. The Hachidori is a tube design, and the other design is solid state. The record level of the tape does not make a difference for a well designed pre-amp.
If increasing gain by 4dB is making tube self noise audible, I would argue that is not a well designed amp. You can make a tube preamp silent without any feedback.
If you calibrate the tape preamp for 510 nWb tape and then play 320 nWb tapes, you have a couple of options:
1) do nothing on the tape preamp and turn the level of the line amp up 4 dB to get the same playback level. In this case, the level meters of the tape preamp and the modulometers of the line amp will read 4 dB low, but otherwise there will be no issues.
2) increase the playback levels on the tape preamp by 4 dB, in which case the volume control of the line amp can stay at the same setting. In this case, the meters will be recalibrated to read 0 dB at 320 nWb, and the modulometers in the line amp will read correctly as well.
Sonically, you shouldn’t hear much difference either way.
If increasing gain by 4dB is making tube self noise audible, I would argue that is not a well designed amp. You can make a tube preamp silent without any feedback.
If you calibrate the tape preamp for 510 nWb tape and then play 320 nWb tapes, you have a couple of options:
1) do nothing on the tape preamp and turn the level of the line amp up 4 dB to get the same playback level. In this case, the level meters of the tape preamp and the modulometers of the line amp will read 4 dB low, but otherwise there will be no issues.
2) increase the playback levels on the tape preamp by 4 dB, in which case the volume control of the line amp can stay at the same setting. In this case, the meters will be recalibrated to read 0 dB at 320 nWb, and the modulometers in the line amp will read correctly as well.
Sonically, you shouldn’t hear much difference either way.
Last edited:
Victor,
I've read of using +9 tape, e.g., SM900, but recording to it as if it were +6 stock. Any ruminations on this approach?
Different tape stocks have different distortion characteristics during saturation, so it is not just the level at which distortion rises that is important to consider. High output tapes allow a higher margin of safety during live recordings, whereas archive tapes do not need this as the peak level is already known. There is no point in pushing the limit when you are just copying tapes, unless the dynamic range of the recording is particularly wide. I find 320nWb to be more than enough in most situations, and in fact prefer 250nWb for Agfa 468.
I think this is good approach in general, and especially when using the VU meters, not the peak ones. But it is also the matter of how much of your music is in the above 0dB area. Random quick peaks is one thing, but if your piano "lives" there, then it is going to sound overloaded.
I have seen peaks in the +18dB area, and this is WAY, WAY too much.
My Studer A-820s are biased for SM900 and ATR Magnetics stock. The decks were aligned in preparation for live-to-2 track recording and stereo mixdown duty. Different producers and technicians have their preferred biases (lol) it would seem.
Are you using MRL 250 nWb/m ref fluxivity tape(s) to align your decks?
Similar threads
