XPOST Dumb KT-2A (or any +4dBu gear) level question

[Blue Jinn]

Kinda dumb question here, but I believe the KT-2A is designed for "pro" level +4dBu in and out. Is there really a problem using it on "prosumer" -10dBm signal path, or should I bring the level up on the input and back down on the output.? I've had advice that it's fine either way, but would work better bringing the level up, as the compression is dictated by "how hard you hit it." (The level amp would probably have a lower output impedance too.) Looking for opinions/advice.

TIA.

 

[sweetbeats]

Well…if I’m understanding correctly, if the device is one of those types where you have to drive the input to push the signal level to the threshold in order to achieve gain reduction, I think you just need to try it with your unbalanced -10 source. Remember, the -10dBv is just a nominal reference. Depending on the device it may still have significant headroom and drive far above -10dBv. It just depends on the device. And you have to use your ears to hear when you are clipping the output amp of the source, and keep in mind clipping may be occurring before you can hear it, depending on the program content or whatever. So I’d try it…no reason you can’t do that. And then if you’re straining to get the amount of g/r you want, then I’d bump the source signal. Yes…many modern devices don’t do well with a 600R input impedance.

 

[ecc83]

Well…if I’m understanding correctly, if the device is one of those types where you have to drive the input to push the signal level to the threshold in order to achieve gain reduction, I think you just need to try it with your unbalanced -10 source. Remember, the -10dBv is just a nominal reference. Depending on the device it may still have significant headroom and drive far above -10dBv. It just depends on the device. And you have to use your ears to hear when you are clipping the output amp of the source, and keep in mind clipping may be occurring before you can hear it, depending on the program content or whatever. So I’d try it…no reason you can’t do that. And then if you’re straining to get the amount of g/r you want, then I’d bump the source signal. Yes…many modern devices don’t do well with a 600R input impedance.

I gave my 2pen'oth about this question in The Rack earlier today but I must confess I did not spot that arcane "600 Ohms" input impedance!
Yes, that is going to bother quite a bit of gear and if nothing else, reduce a -10dBV source even further. I would use a pair of NE5532 sections in parallel (10R sharing resistors on the output) and configure the amp for about 12dB of gain, could even make it adjustable. The 5532 can drive 600R but that is about its limit and distortion will be a bit higher. The LM4562 can drive 600R per section. There are of course other high current op amps used for headphone drive but are likely to be more expensive than the venerable NE5532.

Dave.

 

[Blue Jinn]

Thanks Dave. I have a line

I gave my 2pen'oth about this question in The Rack earlier today but I must confess I did not spot that arcane "600 Ohms" input impedance!
Yes, that is going to bother quite a bit of gear and if nothing else, reduce a -10dBV source even further. I would use a pair of NE5532 sections in parallel (10R sharing resistors on the output) and configure the amp for about 12dB of gain, could even make it adjustable. The 5532 can drive 600R but that is about its limit and distortion will be a bit higher. The LM4562 can drive 600R per section. There are of course other high current op amps used for headphone drive but are likely to be more expensive than the venerable NE5532.

Dave.

Thanks Dave I have an active line level adjuster (actually two of them....) but one is pin 3 hot... I have it wired up without that just yet and ran some signal through it. I'll give it a go both ways.