SOZ unbalanced input wiring question

[moe29]

I would like to have balanced and unbalanced inputs
on the SOZ i will be constructing. I am using
Seungyun Lee's great wiring diagram to help illustrate
my question. Have a properly wired in the unbalanced
input? Thank you for your time and consideration. I
can follow directions, but am uncertain when i go it
on my own.

moe29

[halojoy]

I think you have made it totally RIGHT.
It will work.

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Is the input only 100-470 ohm?

What is used to drive this circuit.
I guess not an OP-amp output.

/halo - likes low input imp - but 100-470 ohms

[GRollins]

You might want to short the unused balanced input to ground.

Grey

[moe29]

thanks guys...

Grey, are you basically saying choose one or the other
(balanced or unbalanced) operation?

i'd like to build a BOSOZ and use it as a bal to unbal converter
to run the SOZ, but i'm not sure if i can wrap my head around
building a preamp like that. Proper wiring of balanced pots and
selectors is a bit scary. unfortunately i need a wiring diagram
like above, or i'm lost.

I like the simplicity of the SOZ, and coming from a -2A3
tube background an ~5W SOZ would easily match my
speakers. So i thought i'd give it a try.

[GRollins]

Oops, sorry. Didn't mean to be confusing.
If you intend to use the amp single-ended, ground the other phase of the balanced input. Your diagram has disappeared now that I'm in the reply thing, but I recall that you had the + pin of the balanced input hooked to the + of the RCA jack. In that case, short the - phase of the XLR jack to ground.
No, you don't <i>have</i> to, but it's better that way.
If you're going to use the balanced input, unshort the - phase. No further action needed. Do not short the RCA plug.

Grey

[GRollins]

Oh, one other thing...the SOZ doesn't do such a good job of being its own phase splitter. There's not enough resistance under the Sources for that. If you use it single-ended, you'll get a somewhat lop-sided output, with one side doing most of the work. Distortion will be somewhat higher as a result.
That's not to say that you shouldn't do it. Just be aware that it's not optimal.
A current source under the differential's tail will take care of the problem and increase the efficiency of the circuit in the bargain.

Grey

[moe29]

Thanks Grey!

when the heat sinks show up sometime in Feb.
i'll be able to start building this little beast


moe29
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...for a minute there, i lost myself
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[GRollins]

There's no need to fear the BOSOZ, by the way. The SOZ is the ideal warm-up (yes, pun intended) for a BOSOZ project. Same philosophy, same topology, same low parts count.
Okay, not quite as low a parts count, but still quite a simple project and a good mate for the SOZ. Reading schematics is like anything else--practice makes perfect.

Grey

[loren girsley]

Put the gate resistors at the gate of the mosfets for best stability. As show the wire can pickup RF noise the the gate resistor will not attenuate as well as having the RC filter at the mosfet gate (C being gate capacitance of the mosfet) This is important and most tube guru put the gate resistor right on the tube socket for the same reason.

There is really no point in driving this unbalanced as the amp is explictly designed for balance operation. I think some is working on a Aleph X type preamp that does conversion from single ended to balanced that is strongly rumoured to show up on the forum this week. I can't wait!

Loren

[moe29]

---------------------------------------------
Operating Son ofZen with a single-ended input will put some
second harmonic content in the output, possibly what you will desire.

In this regard, the amplifier adapts itself to the characteristic of
the source. You would expect symmetric distortion from a
balanced source, and you might similarly expect even harmonic
content from an unbalanced source (We aim to please).
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There is no arguing the point that the SOZ is designed for
balanced operation. I plan on running it from a unbalanced
source, and hopefully the carrot of better performance from
a bal. source will drive me to build BOSOZ. Kind of a built
in mod that will definently work.

Grey - you make it sound so simple!

"A current source under the differential's tail will take care of the
problem and increase the efficiency of the circuit in the bargain."

I read the article and looked at the schematic you drew up for
just that... but alas most of that is still flying way over my head!
I understand one needs to crawl before one walks. I'm gona
build SOZ just 'cause i think the circuit is cool - i don't care if it is
a space heater... and then after that, BOSOZ. I've built plenty of
tube kits (Audio Electronics, Electronic Tonalities) so i figure this
is kind of the next step. Finding this Forum has been fun, thanks
for everyones input... more to come.

moe29
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2+2=5
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