Subject: Re: comments on using a MOSFET instead of JFET for audio compressor
Date: Sun, 19 Jan 2003 12:21:58 +0100
Organization: Wanadoo, l'internet avec France Telecom
NNTP-Posting-Date: 19 Jan 2003 11:15:19 GMT
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
I'm french sorry for my language
now look at that' corp dbx2150a for vca ans dbx2252 for rms
if you would i have schemas for multi bands vca 10 bands or model
simulatiion of dbx
"Tony Roe" a écrit dans le message de news:
> I need to build many ultra-low cost audio compressor/limiters, so I looked
> various designs from the internet (some commercial, some diy) using a JFET
> the control element as Rds(on) changes with gate voltage.
> But I needed better signal-to-noise than the classic designs (blame it on
> digital audio), and I didn't want any setup or component selection: with
> huge spread in gate threshold voltage, JFETs were out. A MOSFET looked
> might work, and in a hex inverter like the 74HC04 I would get 6
> channel MOSFETs, which I could parallel, or even use balanced signals
> to reduce even harmonic distortion. I could also use one of the MOSFETs to
> automatically bias the control voltage just below the gate threshold
> for consistent performance. I know I need to keep the unused supply pin
> somewhere near the average gate control voltage, partially modulate the
> voltage with the (buffered) signal, and do all the clever side-chain stuff
> But before I start, I would appreciate the benefits of the experience of
> so save me wasting a lot of time. So, when using a MOSFET as a variable
> Is a MOSFET less / same / more noisy than a JFET?
> Can the MOSFET handle less / same / more voltage signal for a given
> Do the same comments also apply to the MOSFETs in a hex inverter?
> Do some hex inverters work better than others (4049, 74HC4049)?
> Any other tips / traps come to mind?
> Tony (remove "_" from email address to reply)