EL509 SE

[tinitus]

how about adding some form of integrated but mild and moderate compression and distortion control ?

[GeorgK]

Originally Posted by artosalo

The anode (to cathode) voltage is some 120 V, because there is R5 (22k) as cathode resistor. This means that the DC-voltage at the cathode is some 130 V.

Won't this exceed the maximum filament to cathode potential?

The idea with 2 levels of feedback is interesting, but isn't that potentially counterproductive in a SE guitar amp that is likely to be driven out of its linear range? Guess only listening can tell.

[artosalo]

Originally Posted by tinitus

how about adding some form of integrated but mild and moderate compression and distortion control ?

I do not know this.
Can you give an example of such circuit ?

Now the pentode goes distorted when the signal form guitar is at maximum.
And the distortion threshold can be adjusted to lower level by biasing the pentode a bit different way.

[artosalo]

Originally Posted by GeorgK

Won't this exceed the maximum filament to cathode potential?

The idea with 2 levels of feedback is interesting, but isn't that potentially counterproductive in a SE guitar amp that is likely to be driven out of its linear range? Guess only listening can tell.

The manufacturer has specified max. Ukh as +120 V...-150V.
Typically there is a lot of safety margin too. I am not concerned about this.

No, these two feedback loops are working fine together and both improve the linearity, alone and together.

I have used this system with Hifi-amplifiers and it seems to work with guitar amplifier as well.
If only the global NFB is used, then the overall stability of the amplifier could be a problem in some cases. In other words; the use of local NFB at the output tube makes a "good" amplifier easier to build.

[tinitus]

Originally Posted by artosalo

I do not know this.
Can you give an example of such circuit ?

a while ago I found this passive compressor curcuit
I dont know if its any good

distortion control I guess is only a matter of overdriving one gain stage
and I suppose it means one more attenuation pot
one to cranck up the gain, and one more after the overdriven tube, to attenuate it again

hmm, and maybe additional adjustment pot or switch, to bring the overdriven tube in a state where its easily overdriven

[GeorgK]

@tinitus: this is a simple diode limiter, I doubt this is of much use in a guitar amp.

[tinitus]

its probably not the most effective
but being less effective may not be a bad thing at all
anyway, its said that all compressors have flaws

but I guess we have to test it to know

[tinitus]

hi Arto, is this a country fellow man to you ?

Guitar Effects Projects - Richardo's Pages

and theres is a lttle bit here too

http://www.261.gr/limiters.html

dont if if its of any use to you

[artosalo]

Yes, he seems to be.

[tinitus]

Originally Posted by artosalo

I do not know this.
Can you give an example of such circuit ?

hey, found a sweet word for you....bass fuzzcaster