CurtZHP

Re: Found an interesting problem with one of my recent builds
« Reply #20 on: January 14, 2021, 11:49:34 AM »
The point is that it's a very efficient, easy and cost effective way to attenuate low frequencies to increase headroom when you need it which is at high gain.

Imagine a signal that has a 100Hz component and a 1kHz component. The waveform would be the 1kHz superimposed over the 100Hz. When the 100Hz crests, the 1kHz is what will clip first because it's riding on top of the 100Hz. If you attenuate the 100Hz, the 1kHz is no longer riding on top of the 100Hz and so the chances of clipping decrease significantly.

A conventional mic pre applies low-cut after amplification and therefore cannot achieve the same benefit of increasing headroom by attenuating low frequencies. You only get that in these CFIA style amps that have the gain control network integrated into the input.

Meaning it's ok that the low cut only works at high gain. It would be great if it worked equally well at all gain settings but it is still useful.

In practice, I tend to apply a lot of gain at the mic pre to maximize noise performance of downstream outboard gear. Then I literally just move the mic closer or further away to get a good level. Otherwise, if the mic is really close, I don't think it sounds as good. Of course this strategy only works in a quiet room.

What I meant to say was, what's the point of having a HPF if it only works for a very narrow range of gain settings on the preamp, or just one gain setting.  Which is part of the reason why I'm looking at changing the gain circuit, taking a cue from your design so I get more practical use out of the HPF, and a more sensible range of gain settings.

Electrons don't read schematics.


abbey road d enfer

Re: Found an interesting problem with one of my recent builds
« Reply #21 on: January 14, 2021, 11:58:52 AM »
As you suggest, my present gain range of 19dB to 50dB is kind of useless for most applications.
That is surprizing. I found that 25 to 50 dB is the range I end up using the most. Actually if I had a preamp with a fixed gain of 35dB I could use it on 75% of the tracks.
Of course it depends on what you record and with what mics.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

CurtZHP

Re: Found an interesting problem with one of my recent builds
« Reply #22 on: January 14, 2021, 12:07:01 PM »
That is surprizing. I found that 25 to 50 dB is the range I end up using the most. Actually if I had a preamp with a fixed gain of 35dB I could use it on 75% of the tracks.
Of course it depends on what you record and with what mics.

I found that I never used the bottom two settings, and rarely used to top setting.  And at 50dB, it wasn't enough for the ribbon mic if I wanted to use that.
Electrons don't read schematics.

abbey road d enfer

Re: Found an interesting problem with one of my recent builds
« Reply #23 on: January 14, 2021, 12:21:30 PM »
I found that I never used the bottom two settings, and rarely used to top setting.  And at 50dB, it wasn't enough for the ribbon mic if I wanted to use that.
Yes, ribbon mics...mine are all active.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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