NE5534N limitations for balanced input

[delapoer]

6µ8 would align pretty well with typical sizing for a 22k input impedance in any case (my rule of thumb would be 10µ for 10k, i.e. RC = 100 ms or f3dB = 1.6 Hz).

I wouldn't say that the circuit is terribad, I mean, you can dial in a good amount of CMRR with the trim pot, and with shielded cable connections at line/pro level chances are nothing much would ever have happened, plus for really tough cases there still is the input transformer. So in practice it probably works well enough, it merely puts the electronically balanced input in a bit of a bad light.

Is the function of this cap purely for DC protection of the circuit? It seems that many active balanced inputs do not use this, could I just replace with a s/c? If I do need it would it be worth replacing (it is getting quite old) and if so, with what? I think I saw a Panasonic electrolytic recommended by Bill Whitlock somewhere.

 

[delapoer]

http://www.thatcorp.com/datashts/THAT_1200-Series_Datasheet.pdf

Tomchr on this forum does sell boards that allow you to add to any amplifier to give a balanced input. If you look at the data sheet you can see that, even with a 600Ohm inbalance you still get 70dB CMRR at 60Hz. Also works up to pro levels if you like your interconnects hot!

The THAT product range is excellent for home audio. But because it is used in 'pro' stuff hasn't been given the welcome it deserves. After all, why use well engineered chips when you can come up with some arm wavy theory like most high-end manufacturers do 🙂

Thanks for letting me know about the 1240 chip range, it is very interesting. Looking at the pin out and spec of the That 1240 it seems to me that it would be very easy to just replace the 5534 with a 1240 and at the same time eliminate all the resistors used for the bridge around it, and possibly the input caps, and clamping diodes as well.

Can you see any potential problems with doing this?

 

[billshurv]

I might keep the clamping diodes, but in principle that would work. You won't get the bootstrapping of the whitlock chips, but it will do the bal-unbal conversion well.

 

[delapoer]

I might keep the clamping diodes, but in principle that would work. You won't get the bootstrapping of the whitlock chips, but it will do the bal-unbal conversion well.

Are you referring to the That 1200?

 

[billshurv]

yes. The fact that you don't need a balanced source to get the CMRR makes it my go to part. I accept that, in domestic use you don't need that much CMRR!

 

[delapoer]

yes. The fact that you don't need a balanced source to get the CMRR makes it my go to part. I accept that, in domestic use you don't need that much CMRR!

I will check the pinout etc but it looks as though it would pretty much drop straight in. My sources are balanced (possibly not quite as "balanced" as I thought before starting this thread) at least they are differential and connected by XLR!

Do you have a favourite supplier of these in the UK? They are about £7.50 ea at Farnell and I need 8 or 10 of them.