Anyone on the tube forum ever heard a Bride Of Zen preamp?

[G]

I'm seriously considering building a BOZ preamp. A little change of pace. Something new. Just wondering if anyone on the tube forum has heard one or better yet used one to drive a tube amp? THe schematic is below. Simple class A mosfet gain stage. Should sound nice.

[G]

Never mind. Like anyone was going to reply anyway. I've been doing some thinking ( God it hurts! ) and I'm just going to go with a simple 5687 anode follower circuit. I do need some gain after all. Plus I will be getting a TubeDac kit from Scott Nixon in the future to go with my Cal Delta and from what I have read it inverts the signal at its output so an anode follower will work to get the correct phase to the speakers. I may try battery biasing the 5687. Any recommendations on which type of battery to use?

[G]

Here is the ultra simple circuit:

[powertriode]

I've never even heard of a Bride Of Zen preamp, let alone heard one, what is it???

[G]

Originally posted by powertriode
I've never even heard of a Bride Of Zen preamp, let alone heard one, what is it???

It is a single ended mosfet preamp designed by Nelson Pass to use with the Zen SE Mosfet amp that he also designed. Here is a link to both articles. The boards are still available through AudioXpress but there are things I don't like about Mosfets ( very high input capacitance )so I decided to stick with tubes.

http://www.passdiy.com/pdf/zenamp.pdf

http://www.passdiy.com/pdf/brideofzen.pdf.

The articles are an interesting read nonetheless. Cheers.

[Eli Duttman]

Gavin,

I agree with your reservations about MOSFET gate capacitance. The "solution" is pretty simple; buffer the FET. A 5687 cathode follower will not be overtaxed by the high gate capacitance.

You can play a euphonic voicing "game" with the CF. Use either NIMH cells or LEDs under the cathode for bias. The "bottom" of the grid leak resistor and the "top" of the load resistor tie to the "bottom" of the biasing parts stack. If the load resistor is less than Rp, the CF will generate some 2nd harmonic distortion. Use a pot. as the load resistor and "dial in" the voice of your choice.

FWIW, I'm scoping out a "melodious" near unity gain line stage for use with my neutral "muscle" amps, a H/K Cit. 2 and an AVA FET-Valve.

[G]

Originally posted by Eli Duttman
Gavin,

I agree with your reservations about MOSFET gate capacitance. The "solution" is pretty simple; buffer the FET. A 5687 cathode follower will not be overtaxed by the high gate capacitance.

You can play a euphonic voicing "game" with the CF. Use either NIMH cells or LEDs under the cathode for bias. The "bottom" of the grid leak resistor and the "top" of the load resistor tie to the "bottom" of the biasing parts stack. If the load resistor is less than Rp, the CF will generate some 2nd harmonic distortion. Use a pot. as the load resistor and "dial in" the voice of your choice.

FWIW, I'm scoping out a "melodious" near unity gain line stage for use with my neutral "muscle" amps, a H/K Cit. 2 and an AVA FET-Valve.

Hi Eli! I thought about doing something like that but then that defeats the whole purpose of building a SS circuit that exhibits the qualities that make tube amps so appealing. I thought about using a JFET as a source follower at the input to deal with the input capacitance of the mosfet. Then I would have to start laying out PCBs which is not my thing. Don't get me wrong I have done it and have layouts for different headphone amps that I have done but I don't enjoy it, which is supposed to be what this hobby is all about. I would rather just stick to tubes at this point. However if someone was going to build both the Zen and the BOZ to use together ( as was intended by Mr. Pass ) then I'm sure the resulting system would sound very nice indeed.

[Eli Duttman]

Gavin,

Your right about Nelson Pass; he KNOWS what music sounds like.

There is nothing wrong with the JFET buffer idea. Your local "Rat Shack" carries the MPF102 which will work. Assume the FET has no resistance and set the sum of the bias and load resistors for 7 mA. idle current. 6 V. of bias is enough to prevent clipping when the 2 V. O/P of a CDP is applied. You don't have to design a PCB. A small piece of perf board is more than adequate to hold the buffer circuitry. Use NP's PCB for everything else. BTW, don't forget a 1 KOhm CC stopper on the FET's gate. You should leave only enough of the gate lead to attach a hemostat to between the FET and the resistor's body, as the less wire available to be an antenna, the better. IMO, 63/37 eutectic SnPb solder with its low melting point is a good idea for soldering the FET/stopper connection. Use a temperature controlled soldering station or a LOW wattage pencil. Get in and get out quickly; it's NOT a state secret that heat is an ENEMY of semiconductor parts.

[24valveman]

Yes. The BOZ drives my Conrad Johnson to similar sound quality levels as CJ's own Pre

[leadbelly]

Originally posted by 24valveman
Yes. The BOZ drives my Conrad Johnson to similar sound quality levels as CJ's own Pre

Wow, it's great to get these definitive answers, even 5 years late