harbinger one - offset trim

[luks999]

quick question:
i see the 250k trim combined with two 47k resistors in the harbinger. so in total 350j
the original uses a 47k and a 100k
in the forum vibe a 250k trimpot is used without any resistors

how does bigger resistance influence the sound?
im thinkin of omitting the 250k trimpot and go with the original values

[TGP39]

Even with the 250k trimmer, you can still get the original resistance you're after.

Steve.

[luks999]

thanks steve 
yeah? must be a 150k not 250k?

when i have 47k + 250k + 47k, its about 350k. or is just about the ratio, not the values?

thanks

[TGP39]

Don't forget that a 250k trimmer can be anywhere from 1 ohm to 250k.

Steve.

[luks999]

yeah i know. but the trim sets the resistance for both sides.
so original is 100k connected from base of the lamp driver to collector and 47k from base to ground

when i set up the resistance between c and b to 100k according to the harbinger schematic,  the resistance between base and ground would be 250k

what im sayin is you can only set one side to the vintage specs

[midwayfair]

"Vintage specs" don't change the operation in this case. It's just a voltage divider to bias that one transistor. The size of the trim pot doesn't really matter. It could probably be 500K or 50K as it's currently drawn and it wouldn't make much of a difference. If you want it to be the same as the vintage specs, use the same ratio between the legs. (Actually, don't. Bias it for optimal performance. That's the whole reason it's a trimpot and not fixed resistors.)

[luks999]

makes sense. thanks for the explanation jon