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Post by jj2106 on Mar 16, 2018 4:57:35 GMT -5
Hello,
In the respective manuals, I see that the maximum output level of the PT-100 is 4V RMS, whilst the input sensitivity of the A-150 / A-700 range is 1.2V (presumably RMS too).
This is more than a 10dB mismatch.
Isn't there a problem here? Should the volume control on the preamp be maintained @-10dB at the most?
Thanks all.
Jean-Jacques
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KeithL
Administrator 
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Post by KeithL on Mar 16, 2018 8:41:50 GMT -5
That really isn't an issue with modern equipment... and certainly not with ours. (And remember that you absolutely WANT the preamp to have some extra gain.) If the preamp wasn't able to deliver enough voltage to drive the amp to full power it would be a problem. (However, even though the preamp outputs on many receivers are rated to have a rather low output signal capability, most of them can deliver a bit more, and so have no trouble driving most of our power amps.) In general, the noise floor of an electronic device is related to its output level, so preamps with a very high output also sometimes have a somewhat high noise floor. If you pair such a preamp with a very sensitive amp you may end up with a tiny bit of background noise. This was sometimes an issue back in the days when it was difficult to design equipment to have a low noise floor. However, that isn't at all a problem with our BasX equipment (because it's all very quiet; so the noise floor simply is not a problem). It can also be a problem if the mismatch is so great that you literally end up "using the preamp with the volume control way down near the bottom". If that happens, you may not be able to control the volume as precisely as you like. Many old analog potentiometers also have a significant channel mismatch near the bottom of their range... which can be annoying. You won't have either of these issues with the digitally controlled analog ladder network volume control on the PT-100. Also, to be quite candid, even with older equipment, the mismatch between 1.2V and 4V is trivial, and useful for handling signals with a slightly lower than usual level. (I would be slightly concerned if the preamp was rated to deliver 10V and the amp was rated with a sensitivity of 0.1V ... but even that wouldn't necessarily suggest a problem with modern hardware.) Hello, In the respective manuals, I see that the maximum output level of the PT-100 is 4V RMS, whilst the input sensitivity of the A-150 / A-700 range is 1.2V (presumably RMS too). This is more than a 10dB mismatch. Isn't there a problem here? Should the volume control on the preamp be maintained @-10dB at the most? Thanks all. Jean-Jacques |
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Post by pedrocols on Mar 16, 2018 9:08:06 GMT -5
Don't quote me on it but I think that what is important is the input impedance of the amp.
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Post by jj2106 on Mar 17, 2018 3:15:27 GMT -5
Many thanks to both of you.
J-J
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Post by vcautokid on Mar 17, 2018 6:48:41 GMT -5
Allot of well designed components have generous headroom built in. Too much of a good thing clean is better than one that is not enough of good thing that is distorting at its limit before things get good on the input. While sure the output of some receivers are rather low, though not all. Take a mobile device like a smartphone and tablet, then it is very evident it is weak in the output department. I had a stereo receiver with a healthy Pre out gain stage, so meh, nothing to worry about. Any Emotiva Preamplifier output more than up to the task of getting it done. Which proves my adage, sometimes is never always. I just adjust according and figure next great thing to hear.
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Post by jj2106 on Mar 19, 2018 3:25:42 GMT -5
I will use the outputs of a PT-100 to drive the inputs of a MiniDSP, whose sensitivity is 2V.
Master volume will be controlled on the MiniDSP.
What is the position of volume control on the PT-100 which guarantees not to exceed 2V (not 4) on output?
Thanks very much.
Jean-Jacques
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KeithL
Administrator
Posts: 10,261
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Post by KeithL on Mar 19, 2018 8:56:55 GMT -5
The volume control determines GAIN and not output level. I'm not sure exactly what setting works out to 2V out with a 0 dB DIGITAL input signal... (which would be some specific level). However, with an analog input, the output depends on the input level, so there is no specific setting that will assure the output remains below a certain level. And, with a digital input, if you were to somehow limit the output level with a full-scale limit to a safe value, when you encountered a signal recorded at a lower level, you wouldn't be able to turn it all the way up. I will use the outputs of a PT-100 to drive the inputs of a MiniDSP, whose sensitivity is 2V. Master volume will be controlled on the MiniDSP. What is the position of volume control on the PT-100 which guarantees not to exceed 2V (not 4) on output? Thanks very much. Jean-Jacques |
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Post by jj2106 on Mar 19, 2018 12:17:26 GMT -5
You are obviously right, Keith. Sometimes I write before I think.
I will use 6dB attenuators and set volume to its maximum.
We'll see.
Thanks for your prompt answer.
Jean- Jacques
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Post by leonski on Mar 19, 2018 12:52:05 GMT -5
Don't quote me on it but I think that what is important is the input impedance of the amp. To a certain extent correct: But the RATIO of preout impedance and amp INput impedance is what counts. You could have a very high input impedance on the amp, say 50k ohms. Good, right? Not if the PRE has an outpu of say 20k ohms. (un real example alert) Good ratio>? 10:1 ? 20:1 ? Higher generally better until you reach some high level than it doesn;'t matter if it is higher still |
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