The Amp Garage

YOu can mount the two 68K resistors on a Terminal Strip mounted to the chassis, wiring the junction of the two resistors to the V1 input grid, and the tail of each resistor back to your input jacks. You may have to re-wire the input jacks to ensure proper switching when the cable is plugged in to ea...

With 100K preceeding a 100uF cap in a simple 'Dumble-like" bias circuit with bias derived off a dedicated low VAC secondary winding, it would take about 47 seconds (5 RC time constants) for the cap to charge up to 99%. Fortunately, that resistance is typically 1 to 10K (the bias range resistor), an...

In addition to providing some additional filtering, the extra cap on the output bypasses the bias divider and insures that the power tube grids see the same ac impedance to ground regardless of where the bias pot is set. A little ripple in the bias supply shouldn't be a problem though, as a push-pu...

ChrisM wrote:Ya I understand that.

I am asking why some amps have this added filtering on the bias supplies output.

Good info on bias circuits:

http://www.el34world.com/charts/Biascircuits.htm

M Fowler wrote:Here is the info some one post a while back somewhere.

Looks like the lead channel is 98.6% Asteroid.

I use aluminum flashing from the hardware store. Stick it on with some 3M Super 77 spray adhesive. Some people use screen material, aluminum foil, or a full blown chassis lid, as well. 10ft of aluminum (aluminium, for you Brit's) flashing is cheap ($10, and often cheaper if you find a house being r...

dukeamps wrote:Hi, Just glue kitchen foil on the bottom of the head case and it will be ok.

Dukeamps

As often as I take my chassis out to tinker with the amp, I'd be tearing and having to replace that foil 3-4 times per year.

I stumbled across this and had to pass it along. Once out at the website click on the cliff jack phots for close ups of how this works. Mark http://www.tubedepot.com/gw-cl14427.html Novel idea. I like to ground my input jacks together with all 1st stage grounds (filter cap, V1 cathode, etc.) at a s...

M Fowler wrote:Teleguy I am not sure what your question is?

The Asteroid has a Heyboer PT specified and OT specified.

re: my original, opening post on this topic.

martin manning wrote:I don't think they're knocking the amp so much as the audiophule.

Agreed......it's not the item(s) in the commercial being ridiculed, but the individuals' rational for buying it.

That's funny - I've been thinking the same thing, but haven't got around to trying it. My main concern would be added noise. If you even think too hard about that area of the circuit it makes noise :shock: Shieded twisted pair to/from the pot outer terminals, and a dedicated shielded coax from pot ...

JD0x0 wrote:The lower the slope the more overall gain, bass and mids you get. so raising the treble cap will add upper mids and treble to compensate. (snip)...

EXACTLY what Marshall did when going from the 56K/250p to 33K/500p in the tone stack for lead amps.

If one wanted to have some control over the level of the TW Express OD/distortion, aside from the volume control, would replacing the 150K at the input to V3 with a series 50KL pot and 100K resistor, and using the pot wiper to feed the V3 grid (thus limiting the V3 input signal level similar to the ...

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