Re: A question I'm afraid to ask

Don't argue with him. He knows it all.


Dr Gang wrote:

The datasheet I've got says 400 Kilo Ohms when off for the 5C4 actually

"Jim" <askme@xxxxxxxxxxxxxxxxx> a écrit dans le message de news:
Dr Gang wrote:
Bingo, I'm building an amp inspired from the MkIV !

With an off-resistance of 50Mohms, I'm pretty confident very, very little
will leak.

I've NEVER heard it on my Mark III. And I'm pretty picky about that sort
of thing. The Mark III does a nice clean. I have to call B.S. on
Willie's comment, on the Mark III at least. There's a VTL5C4 before AND
after the gain stage. FOUR HUNDRED MEGS each. 75 ohms at 40 mA when

Do you suggest another scheme for switching ? So far, I've been
told about relays and JFET switching (the latter being IMO very
interesting). Now that I've ordered 19 LDRs at 6$ each, I expect this to
work. My Mesa Quad preamp is clean enough for me too.

"Lord Valve" <detritus@xxxxxxxxxxxxx> a écrit dans le message de news:

You're about to find out why Mesa Boogie amps leak trash
from the overdrive channel(s) into the clean channel(s).

Good luck with that.

Lord Valve

Dr Gang wrote:

Hi boys,

I'm working on my ultra versatile tube amp project and recently ordered
parts. Among them, there are some 19 Vactec optocouplers. According to
datasheet, the typical "off resistance" of a VTL5C1 is 50 MOhms while
"on resistance" is in the hundred ohms. The other optocouplers from the
VTL5CX serie offer smaller "off resistance" and higher "on resistance"
and I
can't see the point in wanting them for switching purpose. Still,
offer them and I'm wondering why.
Did I miss something ?

I'll have to submit a schematic to you soon about the switching section
the way, stay sharp ! :)