I little blocking distortion never hurt anyone

[Gaz]

Does anyone like a little blocking distortion? Nothing crazy, but I kind of like the way an amp sounds when it's on the edge when turned up to full shred, like it's about to give up. It can also add some cool compression.

I've just been finding when I take all the appropriate steps to rid an amp of blocking (small coupling caps/bypass caps, grid stops, etc.), it sound a little sterile. I like to reduce grid stops on certain stages to design a little back in.

Anyone feel me on this?

[Cliff Schecht]

Moreso on the grid stopper issue. I sometimes will go smaller in size if I find an amp sounds dull and lifeless. Dropping the grid stopper value obviously increases the high-end frequency response and gives the amp more sparkle and/or bite. In really old amp designs that left off modern day upgrades/improvements I will tweak around with grid stopper values until I find a value that doesn't neuter the high-end.

With blocking distortion I am pretty careful to avoid it usually. I don't like so much blocking that the bias shifts too much and starts clipping the signal really hard but just a little bit doesn't always hurt and in some cases can actually add dynamics. By this I mean that when you play soft (low amplitude) the signal is nice and clean but when you dig in, the bias shifts enough to push one side of the wave further into clipping giving a nice asymmetrical clipping effect (which becomes symmetrical again at the PI but I digress here). But at some point the wave will start getting clipped so much that the blatty sounding distortion happens which is again why I typically try to avoid blocking completely. This is not a distortion mechanism that I would rely on in a design unless I was controlling it carefully (which is hard to do when tubes vary so much from one to another bias-wise).

[Gaz]

Nothing "blatty" Cliff, just a hint, "essence of blocking" if you will.

[Cliff Schecht]

"essence of blocking"

Eau de Blocking - by Gaz

[Gaz]

I actually had an idea to take it to the extreme, and add a switch that bypassed a large grid stop in front of a cathodyne. I'd call it "Disintegrate" or something hyperbolic like that

You know what I mean if you've ever had the (dis)pleasure of cranking an old Orange OR120 and listening to it just fall apart. It happens because of the lack of stopper on the cathodyne, the .47uf caps going to the EL34s, and when putting the FAC (variable coupling cap) on the largest setting. Some folks actually like this effect for nasty sludgy (see: novelty) tones! I wonder if just switching the grid stop would work though....

[David Root]

That's interesting about the cathodyne grid resistor, which is a good fix for that old Orange problem.

I'm putting together stuff for a "corksniffer's" 5E8A low power Twin build and I want to keep it as close to the original circuit as possible without blowing NOS tubes up. The usual recommendation for that grid resistor is "470K or so". That is big enough to take the frequency response down a good bit.

Anyone have a number that is more appropriate for a properly tweedy tone that won't come apart when cranked?

Of course there is more to this than just the cathodyne grid resistor. Maybe I'll start a separate thread on how to maintain "essential tweediness" while protecting old tubes and iron (OT in this case).

[TUBEDUDE]

If an amp is a little sterile due to coupling cap size, rather than compromise the protection afforded by a value change, i've lowered the feedback in the output. I still have the blat protection, but with a signal that breathes, as the added harmonics inject some life back into the signal.

[diagrammatiks]

it's not horrible in a 2 or 3 stage pre.