Re: Line-out from speaker output

["IronMan Mike Curtis" <ironman@xxxxxxxxxxxxxxxxx>]

Actually, it's POWER SUPPLY caps that must be discharged.  And playing thru
the amp is NOT how to do it.  The safest way is to use a clip lead and
bleeder resistor.  If you don't know what this is, my advice is to let
someone who knows what they're doing fix the amp.  There can be lethal
voltages present, and I don't like funerals.

Speaker output is basically low voltage (P=E^2R, so even a 50 watt @ 8 ohm
or 100 watt @ 4 ohm amp has only around 20 volts present at full power).
Besides, the caps are DC shorted thru the transformer and speaker.  You will
not need to discharge these.

If you want to boost your amps input impedance, the simplest way is to build
an outboard box.  A simple op amp voltage follower will do the trick
http://www.ironmancurtis.com/Mmojo.txt .  Your crystal or ceramic mic will
sound VERY full.  Interestingly, I find that controlled magnetics and
controlled reluctance mics also have a fuller sound into an ultra high
impedance.

- ----- Original Message -----
From: "Hambone Hamilton" <harpmanx@xxxxxxxxxxx>
To: <gigs@xxxxxxxxxxxxxxx>; <harp-l@xxxxxxxxxx>
Sent: Wednesday, January 29, 2003 6:18 AM
Subject: Re: Line-out from speaker output


>
> Caps need to be discharged...the easy, safe was to do this is to plug it
in,
> turn it on, play through it, and have someone unplug it while you are
still
> playing, my tech says this is a safe way to do it...amp should be safe to
> work on then...but confirm this with a tech that you trust, G, I'm just
> passing along stuff I've heard.  Amps can kill you, in certain
> circumstances, it doesn't pay to screw around.
> Hambone
>
>
>
>
>
>
> >From: "G." <gigs@xxxxxxxxxxxxxxx>
> >Reply-To: "G." <gigs@xxxxxxxxxxxxxxx>
> >To: "harp-l" <harp-l@xxxxxxxxxx>
> >Subject: Re: Line-out from speaker output
> >Date: Wed, 29 Jan 2003 13:16:29 +1300
> >
> >
> >From:  Aki Karjalainen <akarjala@xxxx>
> >Date:  Tue Jan 28, 2003  4:10 pm
> >Subject:  Line-out from speaker output
> >
> >Just wanted to let you know I just added a line-out from the speaker
> >output to my Crate508. Instructions:
> >http://www.rru.com/~meo/Guitar/Amps/Kalamazoo/Mods/ezlo.html
> >
> >With Crate, you can just drill a hole in the plywood covering the
> >chassis and fit the jack there.
> >
> >After this you'll have two options from where to go the mixing board.
> >
> >Regards,
> >Aki
> >---------------
> >
> >Is this so you can use the built in LINE OUT for the Effects Loop Aki?
> >
> >I just scored a VC508 yesterday, very pleased about it.  Small, light,
> >loud,
> >nice tone.  :)
> >It already has a Sovtex EL84 power tube and I've ordered in a Sovtek
12AY7
> >pre
> >amp tube,  I think 12AU7 is a bit low for my tastes.
> >
> >I am looking for advice on increasing the impedance of the Input of my
> >Crate
> >VC508.   I use Crystal, Ceramic, CM & CR mics, is 5M a good impedance for
> >all of
> >these or is it worth looking into installing a switch and having two
> >impedance
> >settings depending on the mic?  If so what would the other value best be
> >set to?
> >
> >Can anyone give me some advice on rewiring this without eletrocuting
> >myself?
> >
> >G.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >--
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>
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