Baluns

pre65 · Post by **pre65** » Wed Apr 10, 2013 12:21 pm

I read that a "Balun" (balanced-unbalanced) is the device to convert unbalanced signals to balanced, and back again.

Is there any merit, on long interconnect runs (say 12 ft) between pre and power, or DAC and pre, of running it as a balanced line ?

If so, what sort of Balun should one be looking for ?

EDIT

Is something like this any good ?

http://www.ebay.co.uk/itm/Stereo-RCA-Au ... 35c028164f

OR

http://www.ebay.co.uk/itm/2-RCA-AUDIO-T ... 5631ae3128

pre65 · Post by **pre65** » Thu Jun 20, 2013 8:23 pm

So, nothing after two months.

Perhaps I should rephrase the question ?

It seems the phase splitter is the weak point in PP amps. As I only have one PP amp (the 832a) I wondered about converting the input signal to balanced, and then feeding each half into the single 12AT7 and thence to the 832a grids.

This would replace the "simple" phase splitter currently in use.

Thing is, what's a good way to create a balanced input ?

Paul Barker · Post by **Paul Barker** » Thu Jun 20, 2013 8:52 pm

If you buy them you can let us know?

I am suspicious of their bandwidth claims.

pre65 · Post by **pre65** » Thu Jun 20, 2013 9:15 pm

How about Fig 3a on this link ?

http://sound.westhost.com/project87.htm

Neal · Post by **Neal** » Thu Jun 20, 2013 9:30 pm

might help if you post the ct diagram again Phil or link to it.

Not sure how those devices in your OP work TBH, they seem to use a common mode choke for each channel but not being active in anyway I wonder how much signal loss they suffer...

pre65 · Post by **pre65** » Thu Jun 20, 2013 9:39 pm

The original post was for converting to balanced and back again for long cable runs, but I've moved it on to converting unbalanced to balanced on the input of a PP amp as in Steves EL84 PP amp at Owston.

The ESP PCB are $18 for the PSU and $15 for the converter + $12 post. So $45 in all plus components.

If the converter has gain then I might be able to do away with the 12AT7 input valve and go straight to the 832a grids (via cap of course).

Is my theory sound ?

JamesD · Post by **JamesD** » Thu Jun 20, 2013 11:15 pm

Phil,

That is just a balanced line driver - Something like the SSM2142 does it better and all within one chip. It takes single ended in and converts it to balanced line drive. Rapid have them at £4.55 each - add a couple of psu chips and you can build it yourself for a tenner...

James

pre65 · Post by **pre65** » Fri Jun 21, 2013 1:12 pm

Thanks James.

Something like this ?

http://www.waynekirkwood.com/forum/php/ ... f=12&t=474

JamesD · Post by **JamesD** » Fri Jun 21, 2013 2:55 pm

yes, exactly like that would work nicely.

James

pre65 · Post by **pre65** » Fri Jun 21, 2013 3:45 pm

JamesD wrote:Phil,

add a couple of psu chips

James

Where does one get +/- 18v PSU chips ?

I looked on e-bay but could only see Chinese +/- 15v PCB kits.

Mike H · Post by **Mike H** » Fri Jun 21, 2013 9:38 pm

Well you could contrive them using 15V ones with 3.3V Zeners in the ground terminal.

JamesD · Post by **JamesD** » Fri Jun 21, 2013 9:55 pm

Phil,

+/- 18V is the max supply voltage, they are very happy with +/-12V or +/- 15V and regulators for those voltages are plentiful.

J

Mike H · Post by **Mike H** » Sat Jun 22, 2013 7:52 pm

There you go then!

pre65 · Post by **pre65** » Mon Jul 01, 2013 12:02 pm

JamesD wrote:Phil,

Rapid have them at £4.55 each -
James

If you purchase 100 !

Now seriously looking at doing this mod.

I think I've (with DTB help) sussed out how to power this chip without buying any extra parts (that helps) so now looking for alternate suppliers.

pre65 · Post by **pre65** » Mon Jul 01, 2013 12:13 pm

Thicko question.

I'm going to use two DIP 8 sockets to mount the SSM2142P chips.

I thought I would mount the sockets on that PCB type with the copper strips, but don't know what it's called. Help.

EDIT.

Something like this ?

http://www.ebay.co.uk/itm/5x-New-PCB-St ... 1e6632640c

OR, even better ?

http://www.ebay.co.uk/itm/PC-PCB-VERO-S ... 23075881f3

*

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