New tape pre-amp king!!

[Bruce B]

Stay tuned folks... I have a new tape pre showing up on my doorstep tomorrow.

Everytime I have heard this unit, it's the best tape sound around. It's a tube design with separate power supply. Super quiet with zero-feedback. Has the following features:

1- Level adjustments for each channel for NAB and IEC EQ

2- Head Loading adjustments to optimize HF response and compensate for cable length

3- HF tilt adjustment



Can't wait!

 

[rockitman]

what deck do you have with a wired out head to test this pre or do you connect this to an A80 somehow ?

 

[Bruce B]

what deck do you have with a wired out head to test this pre or do you connect this to an A80 somehow ?

I have 2 A80RC MkII that Ki has done for me. There is a nice clean switch on the back that can go from internal to external. Ki is da' man!

 

[JackD201]

Does the last word of the thread's title contain a clue Bruce?

 

[Bruce B]

Does the last word of the thread's title contain a clue Bruce?

Not a chance..... These were commissioned by me from a well known tube designer.

The tube compliment is NOS GE 12AT7 and JJ ECC99 gold pin in a fully balanced design.

As far as I know, only the designer and his distributor have one.

MSRP.... a cool $10k

 

[JackD201]

What a coincidence, my preamp uses the exact same tube complement except I use TFK 801s and JJ ecc99s (but only single ended). You should get a lot of voltage drive from those 99s...lots.

 

[microstrip]

I have 2 A80RC MkII that Ki has done for me. There is a nice clean switch on the back that can go from internal to external. Ki is da' man!

Bruce,
Did he connect the wires coming from the tape head directly to that switch?

 

[Curt Palme]

I have a challenge for the designers that I'll bet will make an audible difference to these preamps. A head by design is a balanced signal source, i.e. it does not have one side of the coil winding tied to chassis ground. Why then use RCA unbalanced connectors for the head? Why not use a mini XLR connector in a balanced configuration, and design the input of said esoteric preamp in a balanced configuration? I'll bet that would reduce any hum or other noise pickup measurably.

Just an idea.

 

[Bruce B]

Bruce,
Did he connect the wires coming from the tape head directly to that switch?

No..... he'll have to explain, but it looks like it came off a board under the machine.

 

[rockitman]

I have 2 A80RC MkII that Ki has done for me. There is a nice clean switch on the back that can go from internal to external. Ki is da' man!



View attachment 8563

Hmmm, if I were to get an A80, I could get that switch mod and use my King/Cello if necessary...Do the VU meters work when using the external electronics switch, not that it matter much, other than for aesthetics ?

 

[Bruce B]

Hmmm, if I were to get an A80, I could get that switch mod and use my King/Cello if necessary...Do the VU meters work when using the external electronics switch, not that it matter much, other than for aesthetics ?

No they don't.... I use my Fluke meter for calibration.

 

[rockitman]

No they don't.... I use my Fluke meter for calibration.

Okay, so that is how decks that don't have VU meter's get calibrated...I always wondered about that.

 

[Bruce B]

Okay, so that is how decks that don't have VU meter's get calibrated...I always wondered about that.

I use it to set the correct speed and voltage. I think it's a model 115

 

[Ki Choi]

I have a challenge for the designers that I'll bet will make an audible difference to these preamps. A head by design is a balanced signal source, i.e. it does not have one side of the coil winding tied to chassis ground. Why then use RCA unbalanced connectors for the head? Why not use a mini XLR connector in a balanced configuration, and design the input of said esoteric preamp in a balanced configuration? I'll bet that would reduce any hum or other noise pickup measurably.

Just an idea.

Well, Curt you are correct.

Although the RCAs in the photo look to be more common unbalanced preamp interface, the center pin and its outer "ground" are actually not tied to the headblock ground. It was a quick choice we made at the time more than a year ago to be ready for the "said last word" tape head preamp which is still good and maybe the best option to this day and was readily available at the time.

However, we are rectifying the situation by replacing the RCAs with XLR connectors by using a custom mounting plate made specially for Studer A80RCs and will be wired properly for "true differential input" configuration to the tape head preamp as the designer prescribed.

Use of differential input configuration for tape head preamp is indeed a good idea for maximum signal quality and rejecting any noise from the head to the connectors if you have a preamp that can make use of it but it's not new as far as I know. My Manley Tube Tape Head Preamp has the similar balanced head input configuration.

Ki

 

[Ki Choi]

I use it to set the correct speed and voltage. I think it's a model 115

We can actually experiment for ourselves instead of guessing but based on my experience, it is better to use an outboard analog AC millivoltmeter like this one:

http://www.tequipment.net/LeaderLMV-181A.asp in 2 channel version.

Although I have not tried the Fluke 115 multimeter, some of the issues of using digital meters for VU meter calibration or as a substitute are with frequency response in AC millivolt mode. It is very accurate up to about 1Khz but when you kick it up to ~16Khz and beyond, it could be way off or not respond at all in some models from overseas. Most of the analog AC millivoltmeters respond up to 1 Mhz with +/-1 to 3% accuracy.

Ki

 

[tony ky ma]

Today old equipment from surplus store is very cheap thank for the new digital equipment make that happen but they still working good for analog like H/P 400E AC voltmeter can measure down to 0.01 mv in a very wide frequency range
tony ma

 

[Bruce B]

It's HERE!!

 

[Bruce B]

Doshi Alaap Tape Preamplifier Mk II

 

[Bruce B]

Front and Back

 

[audioarcher]

Christmas in March. Bet it's gonna sound great. Congrats.