Atma-Sphere MP-1 preamplifier as tape head preamp: anyone with experience ?

adrianywu

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Nov 15, 2021
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I am currently using a DIY version of Allen Wright's RTP-3C preamp as tape head preamp for my Nagra TA. I built this more than 20 years ago as a phono preamp, and later modified it to serve as tapehead preamp. It is fully differential using constant current sinks, with a shunt regulated power supply, passive RIAA and an input stage that uses a FET/tube cascode to achieve a 70dB total gain. The differential input allows me to use an unshielded cable from the tape head, thus reducing capacitance, which is helpful as the playback head has a rather high inductance.
My friend is looking for a tape head preamp, but the RTP is no longer available in commercial form after Allen passed away. I just came across the Atma-Sphere MP-1 and it has a very similar philosophy. In fact, Ralph was one of the early or even original proponent of the balanced-differential approach. I am also very happy to note that tape head input is an option. I have never seen this preamp mentioned when people discussed tape head preamps. Does anyone have any experience with this preamp ?
Is the tape head input in addition to the phono input, or replaces the phono input ? How many EQs are available for switching ? How about adjustments to calibrate the EQ curve, and head loading ?
 

tima

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Does anyone have any experience with this preamp ?

I owned an MP-1 Mk III with phonostage and reviewed it for Soundstage. I did not use it with a tape machine.

It offers amazing OTL transparency - I loved it. Balanced phono input! Worked flawlessly with my MA-1 amps. The trick with the MP-1 is tube selection: 4 12AT7 and 5 6SN7 per channel. Along with the many NOS alternatives you want the quietest tubes you can manage.

Wrt your tape specific questions, send a note to @Atmasphere - Ralph is very helpful.

 

Gregadd

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I could be wrong but is not the tape selection just a line in, line out and not really suppose to do much?
 

adrianywu

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I could be wrong but is not the tape selection just a line in, line out and not really suppose to do much?
The tape head is a very low level signal in the same range as an MC cartridge, and also needs to have equalization.
 

Gregadd

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The tape head is a very low level signal in the same range as an MC cartridge, and also needs to have equalization.
Yeah thats what the tape needs to see
I guess the question is does the Mp 1 show it. I get it.
 

Atmasphere

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May 4, 2010
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Is the tape head input in addition to the phono input, or replaces the phono input ? How many EQs are available for switching ? How about adjustments to calibrate the EQ curve, and head loading ?
Its an additional input to the high gain section. There are usually two tape EQs; NAB and IEC2 are the most commonly requested. There are no adjustments as in playback you don't need to adjust the EQ; that's more on the record side of things. We've got no provision for head bump but so far its not been a problem. That can be controlled by loading the tape head.
 

microstrip

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I owned an MP-1 Mk III with phonostage and reviewed it for Soundstage. I did not use it with a tape machine.

It offers amazing OTL transparency - I loved it. Balanced phono input! Worked flawlessly with my MA-1 amps. The trick with the MP-1 is tube selection: 4 12AT7 and 5 6SN7 per channel. Along with the many NOS alternatives you want the quietest tubes you can manage.

Wrt your tape specific questions, send a note to @Atmasphere - Ralph is very helpful.


Ralph will probably chime-in, but the phono section of current version of the MP1 mkIII is different from the one you reviewed and I also owned. The old version was too noisy when used with a Studer original head - I tried it - but the current version using tubes in parallel in the input stage is much less noisier than the old version. Changing the equalization is a simple affair - it would be great if we could have a switch to keep both the phono RIAA and the NAB/IEC.
 

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