Bride of Son of Zen heard shacking up with B&K ST-140...

[eLarson]

"It's alive!"

I finally tacked the components
of my BOSOZ together. It's been several
weekends of "a little here, a little
there."

So far its sounds fantastic, but hey, I
put it together. How else would I hear
it the first time?

The system right now is:
A Theta Data Basic II via AES/EBU link
to a Wadia 12. The balanced outs of the
Wadia feed the balanced-inputs of the
BOSOZ via 5' lengths of microphone cable
from the local Guitar Center ($14 each,
no muss, no fuss and with nice Neutrik
connectors to boot.)

The unbalanced outputs (Cardas GRFA
RCAs) of the BOSOZ feed my trusty B&K
ST-140 via Cardas Twinlink interconnects
that I had laying around. I have some
higher line Cardas cables (Cross) around
here somewhere, but to try them out
I'd have to turn the system off...

... and I DON'T WANT TO.

(For completeness' sake, the ST-140
drives a pair of Dunlavy SC-IIs.)

(Sorry, but I have no pictures. The
enclosure isn't, actually... it's a
maple cutting board with a cherry front
panel, but no side panels or even a rear
panel. Everything's sorta dunlopping
all over the shelf in a real squiddly-
diddley mess. That and I don't
have a digital camera.)

But I'm digging what I'm hearing so far.

Now to think about a more permanent home
for it while it breaks in. Oh, and I'll
want to solder up a couple of unbalanced
inputs, too, so I can listen to the
radio.

Back to the listening room!

Regards,
Erik Larson
proud matchmaker

[Taco]

And an other DIY pass-amplifier is born.

But is there a difference compared to a setup where the wadia is directly connected to the poweramp ?

[eLarson]

Originally posted by Taco
And an other DIY pass-amplifier is born.

But is there a difference compared to a setup where the wadia is directly connected to the poweramp ?

In theory there could be ... the Wadia puts out about a 4volt signal, way more than enough to clip my amplifier something awful. I could add in a bypass switch that would let me go

DAC ---> volume control ---> amp

so I could find out a little easier.

After letting my initial pride of completion stand down, I'm able to detect a broadband hiss that wasn't there prior to adding the zener/source-follower voltage stabilizer. (The hiss replaced a hum that reminded me of my old guitar amps.)

So, I'm definitely keeping the "regulator" and will bypass the zeners
to quiet them down.

Erik

[eLarson]

Here are a few construction details...

The theme of this project is reduce/reuse/recycle. All of the parts I had laying around the house with the exception of some Dale SN62 resistors I picked up at the local Active Electronics shop. (It closed for business before I could complete the project.) Other parts came from my previous DIY effort, the BOZ.

I implemented the circuit on a simple piece of perf board, so it is essentially wired point to point. I had initially thought about skipping the perf-board, too, but alas, I was so out of practice with respect to point-to-point wiring that I couldn't remember how best to keep the pieces from sliding 'round while trying to solder. :-/

(I got vastly better at that by the end.)

I used International Rectifier IRFD110 N-channel MOSFETS for the gain devices and also for the current sources that I felt compelled to try. Since this device will be tasked with converting single-ended sources to balanced outputs to my soon-to-be-started Aleph-X, I wanted to keep the amplitudes of the signal phases as close to each other as possible.

The raw supply starts with a massive (for this application) 300VA, 50x2 VAC transformer for Plitron. When I start thinking toward a more permanent installation, I'll be ordering something a little smaller.

The secondaries are rectified by a bridge of discrete IRF HEXFREDs, which is followed by a choke-input filter: a 1.5 Henry/56 ohm choke and a 10,000 uF ELNA Cerafine capacitor for positive and negative rails. These, too, will be replaced since the raw voltage is around 45 volts and the caps are rated at 50WVDC... a little too close for my taste. I mounted bleeder resistors directly to the capacitors' solder terminals in order to ensure I would always have a enough current draw to keep the voltage to 45 volts even if the BOSOZ circuit itself was left disconnected. (Managed that twice during test of intermediate phases of construction.)

The voltage stabilizer mentioned in my previous post is much like the one in NP's article, except that I used a pair of 1N5366B 39V zeners instead of a stack
of smaller 9.1 V zeners. The source-followers are an IRF510 (positive side) and an IRF9510 (negative side). As mentioned in the previous post, I haven't installed bypass caps for the zeners yet. I had wanted to tack this one together quickly just to verify whether the hum would be banished. It has been, but there is now a low-level broadband hiss. I suppose I could also try a higher current through the zeners, but I'm not sure how much to begin with.
(Any suggestions? They are currently running at about 7 mA.)

The current sources are similar to those in the Pass A-75 article: a zener on the gates of the MOSFETs referenced to the negative supply rail. The drains of the current sources are tied together with a resistor who's leads bend upward to the source-pins of the gain devices. The current sources sink (er, well..) 25mA each.

The load resistors for the gain devices are 330ohm 2W resistors. Nothing fancy there, just generic "flame-proof" resistors. The drains of the gain devices sit at around 27volts. This puts it similar to the original BOSOZ with 60V rails, if memory serves. (My memory doesn't always serve, alas...)

That's about it for this morning. I'm going to sneak in a little more listening before going to work.

Tchau,
Erik

[mlloyd1]

sounds great- good job!

d@~n, Active closed?! Now, what's left?

mlloyd1
(who lives in Naperville and is bummed at the prospect of mail order and the local neighborhood "Radio Crap" (ugh!) stores for his parts

[eLarson]

Originally posted by mlloyd1
d@~n, Active closed?! Now, what's left?

mlloyd1
(who lives in Naperville and is bummed at the prospect of mail order and the local neighborhood "Radio Crap" (ugh!) stores for his parts

They only closed their retail location on Golf Road in Arlington Heights. (Or maybe it was Rolling Meadows? They all blend together around that area. *heh*) Future Electronics is still in business as AFAICT.

Resource Electronics still has a will-call window. I forget their new name at the moment...Something hyphenated... Epstein-Barr? No, that's not it... but something like that.

Also, there is Tri-State Electronics on 14 in Mount Prospect. I've gotten some stuff there in the past.

Hope that helps.

ObProg note: I installed a pair of single ended inputs over lunch. I'm still trying to gauge how radio sounds. WFMT and WNIJ sounded okay during brief listening ... any other Chicago-area stations that aren't grossly compressed?

Erik

[mlloyd1]

Thanks. Those are about the best ones. Can you get WDCB (90.9 College of DuPage) where you are? Good jazz ...

Originally posted by eLarson

...WFMT and WNIJ sounded okay during brief listening ... any other Chicago-area stations that aren't grossly compressed?

Erik

[grataku]

eLarson,
wait until you hear the X-bosoz! Just kidding, I finished it at 3am last night, I haven't tested it yet.
What gain are you running?
Now all you need is to lose your b&K and build a real amp!

Anyway, enjoy!

[eLarson]

ml - Yeah, I think I might be able to get 'DCB
now that they fixed their tower. (well, they fixed
awhile ago.) I'll give it a try. (yup... loud and
clear! sounds like a folk music show at the
moment.)

grataku - I hear ya, man. I think an Aleph-X
would be perfect for the speakers, room, etc.
I'm running it at what would be 10dB balanced
or 4 dB single-ended.

ObProgReport: After having been powered on for
a few days straight, things seem to have changed
a bit. Compared with day 1, it seems the mids
have really come into their own. I would have
almost sworn that they were a little shelved down
at first.

Instrumental images are nicely focused without having a 'cardboard cutout' edge around them.

Little incidental sounds (the announcer turning
pages of his copy as he reads, audience sounds in
a live recording such as Laurindo Almeida's
Outra Vez) are present and rendered a bit more
clearly than with the BOZ. Not any louder, just
more intelligible if you decide to try to listen for it.

eL