Q: Should the Express circuit have a 200K bleed resistor..

[rooster]

AFTER the Standby Switch? This would be in addition to the stacked 100Ks on the main supply cap(s).

The reason I ask is that I find that after playing the amp, and then placing it in Standby mode, if you continue to 'smack' the guitar strings, I still have a small amount of signal going to the speaker. It will eventually stop as the caps drain, but it can last more than a minute and it rather blows an otherwise good amp demo. This is a trait, for example, that typical Fender or Marshall amps do not display, a place where most of my customers hang out. Thoughts?

[frankdrebin]

use a volume,be it guitar or pedal its up to you.
Standby switch is total BS,useless.

[geetarpicker]

I have 2 original Express amps and they do not have this trait. I haven't timed it but the amp will not play very long at all when put in standby.

[rooster]

Ah, this is something unique to my build then, roger this and thanks, Glen. I did alter my power supply so this is on me, not Ken's design.

[Littlewyan]

How did you alter it? Higher capacitance?

[rp]

Brand of cap? Is that possible? We all use the same 2-3 brands so unlikely. You using something special - Nichicons? Panasonics?

[rooster]

Here's why I altered it, firstly: slight ghost notes at heavy loads. YMMV.

Here's how I altered it. The stock supply remains stock, however before it I added a 10 ohm 5 watt resistor and another 47uf cap. Both the original (40+40) caps and the added 47uf cap have bleed resistors at this point, the Standby switch has been moved to the 47uf cap, just before the 10 ohm resistor.

The amp sees the 10 ohm resistor as a divider between the 80if and the 47uf such that it is not looking at 127uf. It's a simple way to add 'storage' to the supply in an amp that might 'starve' a bit under load.

.....So, getting back to my initial post, At first I had simply moved the bleeder resistor(s) to the first cap. What I found was, in Standby mode, I could still hit the guitar strings and get low level audio from the speaker. Eventually it would stop, but a friend playing it was really bothered by it. My conclusion was that placing the three 20uf caps in Standby mode behaves differently than placing the three 20uf caps + the two 40uf (80uf) in Standby mode. Doh! So I have a bleeder before the Standby and immediately after it. I hope this explains things.