Klemt Update!!!

Well, I must say, I’m very happy with the way the Klemt BS40 turned out.  It actually didn’t need much, other than the filter caps replaced and a few adjustments here and there.

I got rid of the rotting and oozing can cap, and replaced it with a JJ 32x32uf cap.  This is very much like what the amp originally looked like and is about  the same amount of filtering.  I didn’t want to go crazy with it.  I wanted it to sound and feel like it did originally,.  That’s always a toss up, “How Much filtering do I use?”  The tendency is to add alot more, but the results aren’t always better.  More filtering adds better bass response and often makes the power supply quieter, along with a faster/tighter response.  This is were the term “Stiff” comes into play, as with too much filtering, there’s less sag, sometimes making an amp too punchy.  The beauty of vintage amps was the electrical response to transients, giving in a little when you hit a big chord and compressing slightly.  All of that is a matter of taste, so I’m always treading the line of making the amp more responsive, while not going crazy with it, and losing the organic nature of a well designed tube amp.  It should be a joy to play, and respond to your pick attack with just the right amount of punch and just a little sag.

I don’t have an electrical background, so while what I’m trying to get across has a technical explanation, I’m trying to get across the nature of the sound.

New 1500 ohm 2 watt screen resistors mounted on the sockets.

One of the other housekeeping tasks was to install 2 watt screen resistors on the output tube sockets.  Normally, with an EL34 amp, I would use a 1k @ 5 watter there, but as this had little 1K 1/2 watters.  So I felt ok installing a beefy 2 watt 1.5K MO in it’s place.   I must say, this is one of the nicest sounding vintage amps I’ve had the pleasure of working on.  It doesn’t get super nasty, but is  more clean and punchy.  It has a real nice chime to it, clean tones sound wonderful and 3D.  Dimed, it breaks up nicely and gets real gainy if you crank the Presence control.  Speaking of which, the presence is almost more of a NFB control, than the traditional Presence Treble boost.  Roll it up and the volume increases a fair amount and it gets BRIGHT!.
Another thing that I played with was different settings of the voltage selector.  Unlike most amps from the UK, that have 110v/200v or 220v settings.  The Klemt has 110v/130v/200v/220v, making it possible to dial in for your own particular amount of wall juice.  I have anywhere from 118v-123v at my wall, so running at 10 gave me a heater of 5.7volts and a nice B+ of 424v.  At 130, the heaters are at 6.7v and the B+ jumped up to 480v, which is alittle higher than I normally like.  But after a resistor tweak, I had plenty of adjustment on the bias pot for either setting.  Also very forward thinking for the time, this circuit has an over all bias voltage pot and a balance between the two output tubes, along with 1 ohm resistors on the cathodes, making adjusting bias a snap.  Thanks Klemt!!  Anyway, I hope everyone enjoyed this little vintage ride as much as I did, maybe I’ll get some clips of it up before it goes home.

Thanks – Peace!

~ by mmandjk on September 14, 2012.