Balanced to unbalanced board

[kevin gilmore]

probably close to final  2.45 x 2.17 inch

 

Edited January 25, 2017 by kevin gilmore

[congo5]

nice, Very nice!

[sorenb]

9 hours ago, kevin gilmore said:

lm49830 is a chip amp

do you mean opa1632 and its clones, all of which require huge amounts of feedback and have all sorts of common mode dc issues

didn't you use lm49830 for the blackhole buffer?

[kevin gilmore]

that was not a buffer. that was a 60 watt + power amp done with semisouth as output devices.. It was pretty nice for a small chip amp.

Edited January 25, 2017 by kevin gilmore

[kevin gilmore]

transistors are 2sc3324 and 2sa1312

[Pars]

BL or GR?


Sent from my iPhone using Tapatalk

[kevin gilmore]

highest hfe, make sure to match hfe and vbe

 

[kevin gilmore]

deleted

Edited January 27, 2017 by kevin gilmore

[congo5]

Trying to figure out a way to make 6 boards manageable, would like some sockets but don't have any yet>

sockets for .030 pins with .100" spacing?

So the buffers clamp to 18ga wire with normal connectors

to take apart you have to work your way in.

one power connection

stereo in

balanced and buffered out,     pot could go between the white 3 pin connectors

[Pars]

Maybe some of these Amp receptacles? For 0.0252" pins

649-75915-304LF

That one is a 4 position. Are you trying to find a connector type to connect the buffers to the ubal->bal boards?

I actually think that Kevin should just put the buffers right on the ubal boards. They wouldn't add that much real estate, and if you didn't want to use them, you could just jumper them.

The Phoenix connectors seem to add a bit of real estate on small boards such as these though

Edited January 28, 2017 by Pars

[congo5]

10 minutes ago, Pars said:

I actually think that Kevin should just put the buffers right on the ubal boards.

they are on the smd version, plug in through hole solder  pins

and yes jumper them out, use em' or try other buffers, excellent!

thanks those connectors will work. if not here somewhere

Edited January 28, 2017 by congo5

[cspirou]

What's the gain on the ubal -> bal boards?

[kevin gilmore]

unbalanced to unbalanced, gain of 1

unbalanced to balanced, gain of 2

etc

you can adjust the gain by changing the 1300 ohm resistors, or the emitter resistors

up to 10x is possible with no increase in distortion

these days, I don't think there is any reason to add much gain

[cspirou]

For a preamp I have the following plan:

input -> (ubal/bal) -> digi.attenuator -> diamond buffer -> output

What value attenuation do I need to use?

[kevin gilmore]

the way the board is layed out currently its really input -> attenuator -> ubal/bal -> diamond buffer because there is only one set of servo's

and the attenuator is best at something like 10K

[sbelyo]

On 1/29/2017 at 3:18 PM, kevin gilmore said:

the way the board is layed out currently its really input -> attenuator -> ubal/bal -> diamond buffer because there is only one set of servo's

and the attenuator is best at something like 10K

If I wanted to make a preamp with these boards can I omit the attenuator and wire it like this?

For example:

 

[kevin gilmore]

for the input switch you want to ground the - input for SE inputs

don't need a switch on the output because you can do balanced and unbalanced at the same time

[sbelyo]

Got it...  So it's ok to omit the attenuator then?

[kevin gilmore]

sure as long as you don't mind the gain, or have a knob elsewhere

(or a dac with a volume control etc)

[sbelyo]

understood...  My DAC does have a digital volume control but I disable it.  So if this board increases the balanced gain and I feed it to an amp it's multiplied again by whatever gain the amp is at correct?

[kevin gilmore]

yes that is how it works

[sbelyo]

much thanks...  perhaps I will enable attenuation in the DAC when using this as part of a preamp

[fat joey]

On 2017/1/30 at 4:18 AM, kevin gilmore said:

the way the board is layed out currently its really input -> attenuator -> ubal/bal -> diamond buffer because there is only one set of servo's

and the attenuator is best at something like 10K

 

is this input + output board + attenuator also the same as here? Or put the attenuator in between the two boards?

https://www.head-case.org/forums/topic/12024-and-now-for-something-completely-different-part-3/?page=6#comment-724017

 

BTW, about these output boards, the orginal one and the newer one, could we wire them to output SE signals?

 

[recstar24]

Excuse my ignorance, but isn't this a good scenario where an opamp actually performs well? At minimum it's a more cost effective option. 

[kevin gilmore]

so I did something like that with an opa1632, everyone over at amb's picked on me, and in fact it sounded like shit. Then Ti released exactly the same thing.

Still sounds like shit. Lots and lots of feedback is why. This discrete thing is pure class A and current sources, and no feedback. except for dc servo sounds so much better

congo5 is testing the surface mount stuff, currently the output buffer blows up due to power over 15v, so will trim the current a bit, the surface mount transistors can only take 150mw. size vs power.  It will run just fine on 15v anyway

Edited February 4, 2017 by kevin gilmore