Hachidori Fukami Tape/Phono Preamplifier

[Foxbat]

The VU meters on my tape player are bypassed because I don't want the signal to go through them. I have adjustable step-up transformers at the input of my head-amp. I can select gain of 3db, 6db, 9db, 12db and 15db. I like adjusting gain using a transformer rather varying resistance. I use the adjustable gain of the step-up transformers to set the level I want with a particular tape. For example, for tapes recorded at 520nW/m I use 3db of gain. If I use any other setting, the head-amp will distort. With tapes that are recorded at 396nW/m (like Ed's), I use 6db of gain. The majority of tapes I have are recorded at 320nWb, so I use 9db of gain. Occasionally, I have a tape that sounds best at 12db of gain. For each of these gain settings, I use a different resistor to load the tape head.
If I decide to use a different tape head with a different output voltage, the adjustable step-up transformers can help make gain adjustments for the new tape head.

John, just to make sure I went ahead and measured my preamp's headroom. At 400Hz it was about 26dB, with respect to +4dB.

 

[JohnP]

John, just to make sure I went ahead and measured my preamp's headroom. At 400Hz it was about 26dB, with respect to +4dB.

Excellent, you obviously don’t have to worry about the level of tapes.

 

[Foxbat]

Not from the standpoint of overloading the preamp, but high levels overload the tape, and that is easy to hear.

Why don't people learn to do it in moderation?

 

[JohnP]

Not from the standpoint of overloading the preamp, but high levels overload the tape, and that is easy to hear.

Why don't people learn to do it in moderation?

That’s a good question. Maybe it’s a matter of experience and listening carefully. Who knows.

 

[Foxbat]

I think some producers take pride in the ungodly recording levels.

That... and the fact that most of them don't use PPM meters.

 

[Hxt1]

The VU meters on my tape player are bypassed because I don't want the signal to go through them. I have adjustable step-up transformers at the input of my head-amp. I can select gain of 3db, 6db, 9db, 12db and 15db. I like adjusting gain using a transformer rather varying resistance. I use the adjustable gain of the step-up transformers to set the level I want with a particular tape. For example, for tapes recorded at 520nW/m I use 3db of gain. If I use any other setting, the head-amp will distort. With tapes that are recorded at 396nW/m (like Ed's), I use 6db of gain. The majority of tapes I have are recorded at 320nWb, so I use 9db of gain. Occasionally, I have a tape that sounds best at 12db of gain. For each of these gain settings, I use a different resistor to load the tape head.
If I decide to use a different tape head with a different output voltage, the adjustable step-up transformers can help make gain adjustments for the new tape head.

Sounds like a brilliant setup.

 

[Zeotrope]

All tape playback amps/stages should have a calibration provision. Tapes can be recorded at many levels & it's not some are "hot", but some are recorded at 396nW/m (like mine) and I've seen some from Europe recorded at 520nW/m. One technically needs to calibrate the output level of the deck to that level so that the meters can actually read the tape level properly. If your deck is calibrated to 250 & you're playing a 396 tape, the needles will be buried in the red & you will think this tape is too hot, and you may get distortion.

Most early tapes were recorded at 250nW/m. Decca recorded their fantastic early SXLs in the late 50's early 60's, at 396nW/m NAB eq.

My sense, & I maybe wrong but I don't think most outboard tape amps include an accurate calibration stage. Maybe just a click onto a few set levels, which should likely suffice.

Ed

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.

 

[Foxbat]

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.

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.

 

[Zeotrope]

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.

 

[Foxbat]

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.

Please read carefully what I wrote, you are not getting it.