Best gain for input buffer

Hardware questions and issues with the FV-1

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Sweetalk
Posts: 141
Joined: Thu Oct 15, 2009 5:13 am

Best gain for input buffer

Post by Sweetalk »

Guys, I’m designing a new hardware and want to improve the SN ratio. To do this I need to feed the fv1 as hot as possible to maximize the dynamic range and here’s my question. Since the guitar signal is so variable in amplitude, what’s the best gain for the input stage feeding the fv1. I’m aware that there’s no RIGHT answer but hopefully some experience from you will lead me in the right direction. I don’t want to use a compandor (like the 570/571 used in many designs). Any thoughts?
smear
Posts: 39
Joined: Fri Jul 01, 2016 9:47 am

Post by smear »

For guitar, I feel like 3x or 4x input gain is best. You can go higher, but you're too likely to get clipping when using a high-output guitar.
Krali
Posts: 1
Joined: Mon Jan 28, 2019 6:43 am
Location: North Berhen,NJ

Re:

Post by Krali »

smear wrote: Mon May 21, 2018 9:59 am For guitar, I feel like 3x or 4x input gain is best. You can go higher, but you're too likely to get clipping when using a high-output guitar.
thank you!
igorp
Posts: 65
Joined: Tue May 19, 2015 6:10 am
Location: RU

Re: Best gain for input buffer

Post by igorp »

x4 gain will add +2 significant bits and may cause troubles with active pickups and strong attack.
You also may try kind of "Dolby" method, HPF before ADC and LPF after DAC (as on Small Clone done) and divide digital and analog power/grounds.
Sample rate of 48kHz may reduce some noise too.
mportnoy
Posts: 24
Joined: Fri Jan 25, 2019 8:06 am

Re: Best gain for input buffer

Post by mportnoy »

How sensitive are these IC's to regulator noise? Typically for ADC work I've always used some kind of local regulation, like an LM431 shunt or ADP3.3 LDO. I remember doing a project some years ago where we were able to get a 5dB improvement in ADC performance just because of regulator changes.
igorp
Posts: 65
Joined: Tue May 19, 2015 6:10 am
Location: RU

Re: Best gain for input buffer

Post by igorp »

we tested several power schemes, they did't slow down noise significantly.
And tried 4-th order LPF with 10kHz cut-off to output of the FV-1 to reduce noise. It's not helped too.

For all in one chip without balanced input ADC FV-1 still sounds cool and it's still a classic , i think, we've never get sound quality as AL3201 with balanced input and separate ADC
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