RCA BA-6A distortion during compression

[JMan]

Pins 2 & 3.

I don't see any reason you couldn't use a pad instead, provided it gives you the 600 ohm load. Unless I misread your second to last post, it seems you had a T pad in there at one point (makes sense). Any reason why you want to change it to an L pad? (I should say, I am fairly ignorant of the differences between all the different types of pads and attenuators, so this is a genuine question rather than a pointed "why would you do that")

 

[JohnRoberts]

Legacy (old) gear sometimes expects 600 ohm input/output terminations to operate properly as designed.

Modern gear not so much.

JR

 

[mrtnasty]

Pins 2 & 3.

I don't see any reason you couldn't use a pad instead, provided it gives you the 600 ohm load. Unless I misread your second to last post, it seems you had a T pad in there at one point (makes sense). Any reason why you want to change it to an L pad? (I should say, I am fairly ignorant of the differences between all the different types of pads and attenuators, so this is a genuine question rather than a pointed "why would you do that")

Thanks. I am also a bit ignorant but my understanding is that a T pad is for dropping level when connecting two pieces of transformer coupled gear, and an L pad is for dropping level after a piece of transformer coupled gear that is going to be fed into another piece of gear that doesn't provide a load, like the input of an audio interface.

 

[JMan]

Thanks. I am also a bit ignorant but my understanding is that a T pad is for dropping level when connecting two pieces of transformer coupled gear, and an L pad is for dropping level after a piece of transformer coupled gear that is going to be fed into another piece of gear that doesn't provide a load, like the input of an audio interface.

Ah, that makes sense. Now that I think about it, I guess a T pad would still give you a 600 ohm output so you'd still have to terminate it anyway.

 

[emrr]

You can use a 'T' so long as there's a load resistor after it to get it in the right operational curve, otherwise it doesn't attenuate as much as advertised on the tin. Review my previous posts.

This still seems possibly separate from the question of why you have distortion during compression. If it will output more level without distortion when the 6H6 is removed the problem is elsewhere. Could be the 6H6, could be a 6SK7, could be resistor value around the 6SK7's, could be the interstage transformer primary which can be checked with a multimeter to see if the DCR readings are symmetrical.....etc.....

 

[mrtnasty]

You can use a 'T' so long as there's a load resistor after it to get it in the right operational curve, otherwise it doesn't attenuate as much as advertised on the tin. Review my previous posts.

This still seems possibly separate from the question of why you have distortion during compression. If it will output more level without distortion when the 6H6 is removed the problem is elsewhere. Could be the 6H6, could be a 6SK7, could be resistor value around the 6SK7's, could be the interstage transformer primary which can be checked with a multimeter to see if the DCR readings are symmetrical.....etc.....

Ok thanks for the clarification. The distortion was just the clipping of my audio interface because the output of the Ba6a was too hot. Thanks!

 

[emrr]

680Ω resistor across 11-12 of P2, which should be same as XLR pins 2-3. Done. The stock 'T' will then attenuate 20dB at maximum. It won't without the correct load.

 

[mrtnasty]

680Ω resistor across 11-12 of P2, which should be same as XLR pins 2-3. Done. The stock 'T' will then attenuate 20dB at maximum. It won't without the correct load.

Done, thanks! And same goes for tube mic preamps like an ampex 601?

 

[emrr]

Done, thanks! And same goes for tube mic preamps like an ampex 601?

Preamps and other 'small signal' amps, depends. I look at response and affect on gain with different loads to determine what's best.

 

[mrtnasty]

Preamps and other 'small signal' amps, depends. I look at response and affect on gain with different loads to determine what's best.

Are you saying you always use a load resistor with small signal amps and just need to find the right value, or do you sometimes use them without a load resistor? How about with a BA2C?

 

[emrr]

I use many without, I use some with 620-680, I use others at all sorts of other optimized values.

 

[scott2000]

Preamps and other 'small signal' amps, depends. I look at response and affect on gain with different loads to determine what's best.

I'd buy that book ... well, should say if I could

 

[mrtnasty]

I use many without, I use some with 620-680, I use others at all sorts of other optimized values.

Thank you!