Unbalanced to balanced circuit: your opinion...please

[SFM-Ptgal]

Here it is:

http://www.fivefish.net/diy/balanced/default.htm

Will this fix the issues I have with the Harris Stereo 80 balanced inputs/consumer equipment consequent level and Z mismatches?

 

[littlejohn]

That's basically what the commercial products do. It ought to work fine. Commercially, in stereo, w power supply and gain controls, and nicely laid otu and boxed. $80 - $150 per. Henry Engineering makes the high end, Rolls and a coupleothers make the low. They'll fix the problems with the Gates.

 

[TomT]

I've used a TLO-72 in similar projects; have had better luck with that chip than with the 5532. Usually the 5532 wants to roll-off around 10 khz., the TLO-72 designs seem to have flatter response.

Note that you will have to build up a separate bi-polar supply; it doesn't have to be +/-18, can be dual 15 or even 12 volts. However, the lower voltage supplies limit the output level available before clipping occurs. With my TLO-72 designs this usually was around +18 dbm on a +/- 15 supply. Normally even 10 db of gain will be adequate to drive the inputs on these older consoles to a comfortable level from the typical hi-fi unbalanced level (nominally -10 db at 10K).

 

[SFM-Ptgal]

I've used a TLO-72 in similar projects; have had better luck with that chip than with the 5532. Usually the 5532 wants to roll-off around 10 khz., the TLO-72 designs seem to have flatter response.

Note that you will have to build up a separate bi-polar supply; it doesn't have to be +/-18, can be dual 15 or even 12 volts. However, the lower voltage supplies limit the output level available before clipping occurs. With my TLO-72 designs this usually was around +18 dbm on a +/- 15 supply. Normally even 10 db of gain will be adequate to drive the inputs on these older consoles to a comfortable level from the typical hi-fi unbalanced level (nominally -10 db at 10K).

I've been gloogling about the power supplies... I'm aware of the bp-ps... Thanks for reminding.
Regarding the TLO-72... If I place them on the circuit the remaining components can stay or should be replaced too? If not what values?

 

[OttoM]

I've used a TLO-72 in similar projects; have had better luck with that chip than with the 5532. Usually the 5532 wants to roll-off around 10 khz., the TLO-72 designs seem to have flatter response.

Note that you will have to build up a separate bi-polar supply; it doesn't have to be +/-18, can be dual 15 or even 12 volts. However, the lower voltage supplies limit the output level available before clipping occurs. With my TLO-72 designs this usually was around +18 dbm on a +/- 15 supply. Normally even 10 db of gain will be adequate to drive the inputs on these older consoles to a comfortable level from the typical hi-fi unbalanced level (nominally -10 db at 10K).

Also note the linked circuit is mono, so double the cost (and the construction time) for interfacing stereo gear to the Harris.

It's been said before (I think in threads originated by the OP) but unless you really are into rolling your own - it's a lot easier & cheaper to get a pre-made converter - yes, even if it's a Rolls or a cheap Nady dual DI box.

 

[SFM-Ptgal]

Easier yes, cheaper I don't think so. I can buit the circuits on a copper stripboard, with a single power supply I can feed several circuits...

I ask again: can I 5532 with the TLO-72 without changing the remainig components?

 

[TomT]

I have a diagram at the station--uses mostly 10 k resistors--I'll e-mail a copy to you tomorrow as a jpeg.

 

[SFM-Ptgal]

I have a diagram at the station--uses mostly 10 k resistors--I'll e-mail a copy to you tomorrow as a jpeg.

I don't know if it was you that a few months ago described that circuit in this forum. Having the diagram will be pretty much easy. Thanks for your help...

 

[radiorob2.0]

I've used a TLO-72 in similar projects; have had better luck with that chip than with the 5532. Usually the 5532 wants to roll-off around 10 khz., the TLO-72 designs seem to have flatter response.

Note that you will have to build up a separate bi-polar supply; it doesn't have to be +/-18, can be dual 15 or even 12 volts. However, the lower voltage supplies limit the output level available before clipping occurs. With my TLO-72 designs this usually was around +18 dbm on a +/- 15 supply. Normally even 10 db of gain will be adequate to drive the inputs on these older consoles to a comfortable level from the typical hi-fi unbalanced level (nominally -10 db at 10K).

Also note the linked circuit is mono, so double the cost (and the construction time) for interfacing stereo gear to the Harris.

It's been said before (I think in threads originated by the OP) but unless you really are into rolling your own - it's a lot easier & cheaper to get a pre-made converter - yes, even if it's a Rolls or a cheap Nady dual DI box.

For most applications, a D/I box will work. I've had good luck with this device: http://www.rdlnet.com/product.php?page=160

 

[gtomas]

Regarding the TLO-72... If I place them on the circuit the remaining components can stay or should be replaced too? If not what values?

If you're talking about the circuit in the first post, yes, you can replace 5532s with TL072s without changing the other components...

I don't particularly like the design of a circuit posted, but it will work. What I usually did is put two inverting op-amps in series, as the inverting op-amp arrangement is simpler (less components). Also I'd prefer to have higher input impedance (possibly lower output impedance as well) than the circuit shown, but that's just preference. Make sure you put some decoupling capacitors on your voltage regulators, the negative ones (79xx) are prone to oscillations.

I'm not sure what your problem is (I'm not familiar with the mentioned console) but you might get the same or better results with just a quality audio isolation (1:1) transformer. Also, there are integrated solutions for balanced drivers today offering higher performance (not sure you need it though) and reduced parts count, such as THAT 1646 or AD SSM2142.


Regards,
Goran Tomas

 

[TomT]

Goran...

This is an old Harris console, has transformer inputs, but I suspect he needs additional gain from the -10/ 10 k output on the consumer CD players. A lot of these older consoles were set up for +4 nominal levels on the inputs, from 600 ohm sources.

 

[SFM-Ptgal]

Goran...

This is an old Harris console, has transformer inputs, but I suspect he needs additional gain from the -10/ 10 k output on the consumer CD players. A lot of these older consoles were set up for +4 nominal levels on the inputs, from 600 ohm sources.

Yes and not only... Cd player, TT pre-amp, PC soundcard. Also need to match Z's because when I address one unbalanced device to a fader and In that fader there's already another device the EQ becomes completely messed. HF disappears...

 

[littlejohn]

There are strange paths in those old consoles if you try to feed unbalanced... all kinds of queeps and wheeblies can appear. Feed balanced at a good level and they do quite well.