BoSoZ

[pjpoes]

Hey guys, I ordered a set of PCB's from Audioexpress for the BoSoZ preamplifier. First, does anyone know how these come, and how the quality is. Its my first attempt at a Pass diy project, and thought I would give it a shot. Does the Audioexpress come with anything other than the PCB's, such as a stuffing guide or parts list. If not I am sure I can find one either through Pass DIY or somewhere else. If you know it doesnt, or know it to be lousy, can you guys recomend a good source for the information.

As for parts, anyone have any recomendations on certain area's worth spending a little extra on. I figured good PS parts would be a good idea, I was gonna use Vishay Resistors, Panasonic, MKZ, or Nichicon capacitors probably (Elna if I can find them or need them), and a toirodal transformer. I have 4 small toirodal trannys from Parts Express, part of one of the buyouts. Its rated at 28v and is a CT style. I am yet to find uses for these, but they were cheap, so I figured they were worth atleast having around. Anyone know if this will work, or if the voltage is much too high. Is the VA value gonna be too low, I am guessing its somewhere around 150va or so, but that is just a guess based on size compared to others I know. For a volume control I was thinking about doing a discrete stepped attentuator, using the format I found on decible dungeon. Does this sound like a good plan, any better idea's?

For the case, Im gonna make people cringe. Ok, not really, I have a metal box I can put it in if I want, but I dont want to. I may need to because of noise, but I want to try something similar to the DNM idea. Not smoked plexiglass, Im gonna use wood, but the idea of a non-conductive case with a musical resonance to it. I just want to see if it works, it probably will look nice, will be pretty rigid, and I can make it myself. I'm thinking that solid wood and mounting RCA's wont be the easiest, so I will either get really long ones, or possibly use a piece of thinner plywood for the back panel. This may in the end become a hybrid of wood and metal. Im really concerned with the wood case not shielding the preamp cuircit enough, along with not being able to isolate the power supply from the preamp. Maybe I will mount the preamp powersupply in a metal case seperate from the preamp cuircit, either inside the main wooden box or seperate. Any thoughts on how sensitive this cuircit is to RFI and EMF, etc.

I have two preamps Im going to be testing this one against, a Perreaux SM6C modified with better resistors and caps, along with better RCA's, and a Musical Fidelity X-Pre upgraded with better internals, better tubes, and remounted onto a wooden board with a Noble Black Beauty volume control, and powered by a slightly modified X-PSU. Both of these sound very nice in there own right, but neither has left me completely satisified. Especially given the cost, the SM6 never lived up to its reputation over seas. We shall see if this Pass does it for me.

[hifimaker]

I seem to remember someone saying that the the slik screen is on the wrong side of the board from Old Colony. Double check parts placement and orientation before you start.

-David

[BobEllis]

Your transformers will work fine - they have a higher power rating than you need, but in diy overkill is a good thing, right?

I used Audioxpress boards for my A75 - and will echo the watch out for the silk screen comment. the traces will likely come up if you resolder them too many times.

If you find you need shielding in your wooden case, you can try some of the guitar suppliers like stewmac for shielding paint and foil - have your cake and eat it too.

[pjpoes]

thats so strange that they silkscreened them on the wrong side, and havent fixed it. I mean, they have been selling these for a while not right, you would have thought they would have redone them after the first batch, maybe these are just left from the first one?

What causes the solder pads to come lose, I hate when that happens? Does certain types of PCB manufacturing cause a lesser quality adhesion for the pads than others? The main reason I did it this way, which is silly, is that my Paypal account isnt working right now and they were the only place I could find that didnt take paypal.

I will likely use either copper foil, metal mesh, or the paint you had mentioned if shielding becomes an issue. Its my guess that, if wood truely does have an effect on the sound, that the baseplate is the most critical part. If I dampen the metal parts and isolate them from the base plate, I dont see them having negative effects on the sound, if infact they can. The only thing is that, having the case shielded still will reflect emissions from within the preamp itself back onto itself, which then doesnt really accomplish the idea of a non-conductive box.