Imageing, instrumental timbre, voices,detail

homeade looks, some distortion apparent if driven hard.

This is a great first project for someone who wants to build a great sounding piece of gear. Simple to put together, and would rate with preamps over $1000.00 easily in my view. All this for $200 or less depending on how much of a deluxe model you want. I slapped one together just for the hell of it after Audio Amatuer featured it in there mag. I used whatever parts I had on hand. I was floored when I hooked it up and first played Pink Floyds" The final cut".
I had been using a Dynaco pat5 bi-fet preamp with Jung power supply mods that I always thought sounded great. The BOZ blew it out the door. The soundstage ballooned in width depth and even height compared to the PAT5. I no longer had to strain to hear words and minute details within the music. The instruments sounded more real, and I finally understood what "palpable images" meant. It was if the performers were in my room. Bass is rounded, full, and detailed. On the last cut of "The final cut" by Pink Floyd. The vocalist, (Roger Waters?), sings:
At the moment that the breaks lock" A voice in the backround says: "Oh no!". That little phrase was always buryed back in the mix, barely discernable. When I played it for the first time with the Boz, I actually jumped back in the chair as it was exactly as if the singer stood 3 or 4 inches from my face and said "Oh no!" It was like a living breathing human being in front of me.
I then decided to do a rebuild with premium parts. I made some mistakes that I will let you in on if you are thinking of building the BOZ.
1. DO NOT USE THE TRANSFORMER SPECIFIED IN THE PARTS LIST.
I had an old Avel Lindberg 25+25 at 4 amps for my junkbox version. My deluxe used the specified 1/2 amp or so A.L.
The higher current version sounds better by a large margin. Why? I have no idea but it does.
2. My junkbox had only IRF510's so I used them first. When I got the specified IRF610's in, it did not sound as good and the stage shrunk. It has less distortion, but doesn't sound as good in the mids and bass as the IRF510.
3. My junkbox version used Carli Mylar film input and output caps sold by Madisound. Thats all I had on hand, and I used a 6uf input, and 15uf output. After changing to expensive Infinicaps, the magic was lost and it sounded dull.
I now use Carli 1uf input caps and Rifa 10uf output caps. Much, much better. I will try MIT's next, as they sound great in my Daniel project.
4. Try soft/fast recovery diodes in the power supply, sounds better than the specified ones.
5. To me, an expensive Caddock series drain resistor,(1000 ohm, 3w), sounds no better than my junkbox MOS 3w power resister.
6. Holcos sound very slightly better than the junk box Digikey 1% mf. in my first version.
7. Some owners are suggesting biasing the Mosfets at 30 ma. for a +/- 15 volt swing. To me it sounds much better biased at the 40 ma. Mr. Pass reccomends. These IRF's seem to preform better at higher current draw, and I plan on building a 120 volt regulated supply version, to bias the Mosfets at 60 or 80 ma. Higher power handling parts will be needed. Try it both ways and set it to your own ears. Its very easy to adjust the bias pot and measure the voltage across the 100 ohm source resistor. 40ma=4vdc across the resistor, and 30ma = 3vdc across it.
All in all, the BOZ is a joy to listen to. I prefer it easily over my CJ-PV10. The PV10 has a great phono amp though, so I keep it. Now if only Mr. Pass would publish a phono Zen style sibling project!
4.5 stars

Similar Products Used:

Dynaco tube & ss , nad, Curcio Daniel1, Curcio pas mods Vorhis last pas, Conrad Johnson PV10

Pass Laboratories Bride of Zen PreampI own and built this amp as well as its "improvement" the balanced version, using the highest and most expensive parts I could find. I had a lot of trouble with nervy highs. I tried matching the input impedence: to no avail. I have an old Krell KSL preamp that I used for comparison. Unexpectedly, the old Krell definitely sounded sweeter, more spacious, transparent, natural.
The Pass had somewhat more detail in the highs, but.... I can't listen to it for long. You can well imagine that I was extremely disappointed in my attempt to better my old Krell. The Krell is as ugly as sin but still sounds good.

Very detailed, huge 3-dimentional soundstage with great sense of space and top notch imaging. Excellent for the price.

System matching is important. You have to find the parts and build this thing yourself, some may think this is a weakness but I think it was a lot of fun.

I bought the BOZ board from Old Colony and used Holco,s, Bournes bias pots., a DACT CT-2 attenuator and the IRF610 and 510 Mosfets. I prefer the IRF510. I think the BOZ is about the best DIY solid state linestage available right now. It has a creamy, tubelike midrange and the soundstage has to experienced to be believed.

This is by no way the best pre-amp I have ever heard but it is amazingly good for $150. I think it may be system sensitive and so matching should be thought out before the project is started.

I also own a heavily modded Bottlehead, Foreplay linestage and though it is better than the BOZ I think it demonstrates how good the BOZ is that in the midrange the BOZ captures (some) of the tube magic.

All in all I highly recommend this project for anyone who wants a great sounding solid state pre-amp for cheap.