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Old 16th July 2003, 06:03 AM   #1
lgreen is offline lgreen  United States
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Default BSOZ Works! (but only 1/3 Done, pics included)

Hello again everyone. If you have read my posts you know I am building a Pass balanced preamplifier, "BSOZ." First, thanks to Nelson for the inspiration, and then thanks to all of you for answering my quesitons and hey, I even tried to answer some questions from people here on this topic, using what I learned so far.

This is my first DIY in about 15 years, and I have no workshop, minimal equipment (borrowed!), and no time to devote to this. I literally built this on weekends and nights on the kitchen table, with the soldering iron on the counter in front of the microwave. Well after a few months and a few sore backs from leaning over the counter to solder, I've got a power supply and a channel, something most of you can do in a weekend..... Anyway, tonight is the night I finally had the guts to hook up the channel to an actual stereo. Lacking an O-scope, I didn't know what would come out other than stuff measured from a DMM. Anyway, its playing now on my computer stereo, and it works, sweeet! Mono never sounded so good.

I don't know what ya'all think about posting pics when you are not done yet, but I have some so here they are. I believe that I am 1/3 done, in that built 1 PS and 1 Channel, I am going for dual mono and relay switching of inputs, so got 2/3 left to do, as well as the front panel. The back panel is done, but I have not yet installed all the connectors, and am screwing around with the screws I want to use (note the different types).

Pictures follow
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Old 16th July 2003, 06:09 AM   #2
lgreen is offline lgreen  United States
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Default Pic1

Here is a picture of (literally) the kitchen table and a test "board" that I used to test the power supply. The metal elbow actually contains an IEC AC socket connected to the wall. Looks like 119.7 volts across the plus and minus, just short of the 120 ideal required. Man am I lucky or what? Success. I used a Plitron transformer and soft recovery diodes rather than the 2 transformers stated in the project and a bridge. Check out the heatsinks, you can never have a sufficient amount of heat sinking, especially with the Pass projects. Note that I left space for 2 more caps, which I would add if it turned out that this worked.

Click the image to open in full size.
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Old 16th July 2003, 06:24 AM   #3
lgreen is offline lgreen  United States
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Default Pic2

Here is a picture of a channel and the PS in the chassis. The chassis I got on EBay is a Schroff 2U Multipac. Looks roomy now but I will be putting in a total of 2 power supplies, 2 transformers, and 2 channels of preamp, and also board for input relay switching and LED illumination. There will be a lot of LEDs. My space calcs indicate a minimum of free room at the end of the project.

Note I have added 2 caps to the PS, making it 4 total, this runs for quite a while after power is turned off. The PS heat sinks get too hot to touch after about 7 minutes, but hey, it seems to work and the sinks are standard as called for in the project....I think. You cannot see it from the picture but the heat sinks on the channel of preamp are too tall to fit into the case with the current standoffs. I need to replace them or get shorter standoffs. All heat sinks are bolted to the circuit boards from the bottom with 4-40 screws I tapped into the sinks. When this is done there should be minimal vibration.

Note the external ALPs dual pot for volume control. I have left in the other 3 pots, as I have not a clue as to the ideal values to substitute from them yet. I am going to try something special on the mechanics of the volume control, so you see it separated from the circuit, a typical no-no but perhaps not for long.

You also see part of my computer stereo, Revox "shelf" speakers and a B&O Beomaster 5000, and under the towel is a prized Nakamichi RX-505. 80's baby! Note also that I am wireless, via the Linksys AP.

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Old 16th July 2003, 06:37 AM   #4
lgreen is offline lgreen  United States
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Default Pic3

Here you see a view from the back. A few words about the back panel. I bought a set of vernier calipers and measured every hole, fitting, label and dimension to .001 of an inch, give or take. Turns out I measured pretty good and everything fits. Nice, but I don't look foward to doing the same thing for the front panel. The fittings are not all in and the ones there are not in perminantly, hey I'm still testing this out. As I said, I have no equipment, so this was sent out for drilling and labeling.

Also, please don't tell me that my differential outputs are really inputs! Ouch! I actually looked at this and I don't think so. The red covering is an EMI protector over the miniDIN 9 pin "expansion" connector. Gotta have something for "expansion" or "testing."

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Old 16th July 2003, 06:44 AM   #5
lgreen is offline lgreen  United States
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Default Pic 4

Here is another picture of the back panel, where I tried to get a close-up with my really bad digital camera. You can kind of see the "modified Nelson Pass BSOZ" entry and that 2 heat sinks look a little tall for inside the case. Connectors are Neutrik (differential) and Vampire (SE). Also 2 AC fuses.

It also says "No. 001 (2003)". Hopefully I will finish this project in 2003. As I said, its kitchen table all the way when the wife is agreeable and there is spare time.


[IMG]Click the image to open in full size. [/IMG]
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Old 16th July 2003, 06:56 AM   #6
lgreen is offline lgreen  United States
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Default OK, that's it so far

Well that's it so far. Thank you all of you who have posted messages for me, and obviously thank you to Nelson Pass. I hate to compete with the release of Zen V. 5 which happened earlier today. Hey, maybe I'll make an amp someday. As I said I will take a lot of time to do this, but its good to actually make progress and this is very interesting.

Please give me your comments good or bad, I can take it!

You will note a minimum amount of "audiophile" parts, I figured I wanted something working before I splurged for fancy caps or resistors, so I will wait. However, I am using silver solder and wire for the preamp sections, which is easy since its also pretty cheap (relative to the other components).

As with most people, the chassis looks much better in person than in the pics, and I hope to improve on the look in the future. In case you can't see it from the pictures, there are 4 outputs and 4 inputs. Outputs are 2 differential (balanced) and 2 single ended. Inputs are 2 differential and 2 single ended, no tape loop or phono. I have not designed my own PCB's and now that this is actually working, I don't know if I will. Perphaps for the input switching?

Thank you for your indulgence.
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Old 16th July 2003, 09:02 AM   #7
Taco is offline Taco  Netherlands
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Really a nice chasis, how did you make such nice holes for the XLR-connectors? Also the lettering is very beautifull. There is nothing wrong with your amp, good job!
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Old 16th July 2003, 08:55 PM   #8
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Good Job, it looks really neat.

I love the chassis, were did you get/buy it?
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Old 16th July 2003, 09:57 PM   #9
moe29 is offline moe29  United States
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lgreen,

Very nice work! You have nothing to apologize for - who cares
how long it takes to finish? Better to take your time and do it right
than slop it all together.

As far as not using expensive parts... They can always be
added later - as a natural upgrade path - if needed! I've been
so happy with my BZLS that it has remained stock, and i think it
sounds great

The one thing you might look at is adding another transformer
to your power supply, if you have room. I use two transformers
with one power supply board. Good luck!
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Old 16th July 2003, 10:47 PM   #10
JoeBob is offline JoeBob  Canada
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There is nothing wrong with taking your time, I just don't know how you do it. I usually can't wait until a project is finished.
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