Behringer T1952 TUBE WARMTH CIRCUIT

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ujszaszyistvan

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Joined
Oct 26, 2011
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The cheap Behringer T1952 is a well known "old song".  ;D
But apart from that I am curious about Your opinion...

The very first thing is: THE DEVICE DOES NOT WORK WHEN THE TUBES ARE REMOVED!

Can someone explain the strange cathode bias resistor and capacitor?
What does it do, how does it work?
I see the low voltage (48V, starved plate) of course...

Is there any advantage to modify the strange bias of this circuit to normal standards?

Look at the circuit below!
 

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Not that strange at all, methinks - the partially-bypassed cathode resistor setup is for having slightly different ac and dc working points.

Jakob E.
 
gyraf said:
Not that strange at all, methinks - the partially-bypassed cathode resistor setup is for having slightly different ac and dc working points.

Jakob E.

Thanks for Your reply, Jacob! :)

Is the partly bypassed section for a kind of high pass filter? (Cathode bypass capacitor has an effect to the frequency response)...

I wonder what would happen to change the cathode resistor to a standard 1.5k and playing with the plate resistor also...it is playing with the harmonics at different frequency range.
Anyway, it is a 48V starved plate low headroom circuit and playing with the plate resistor gives different headrooms and cliping...
We all know the cheap starved plate construction is there for creating harmonics and simulating the usual VARI MU distortion.
Is not it?
 
The tube is operated so far out of its normal regime that it is impossible to predict what it does now or will do if you change components. With a 240K plate load and a 48V supply the plate is probably at about 24 volts and the plate current is a meagre 100 micro amps.

Cheers

Ian
 
ruffrecords said:
The tube is operated so far out of its normal regime that it is impossible to predict what it does now or will do if you change components. With a 240K plate load and a 48V supply the plate is probably at about 24 volts and the plate current is a meagre 100 micro amps.

Cheers

Ian

Hello Ian :)

I played with starved tube things earlier with similar plate voltage and they worked with a lower headroom!
My goal was to create a well biased starved plate tube on purpose and I could make a distressor for certain things.
The plate resistor was a trimmer pot and playing with the resistance I could bias the  things to get a kind of symmetrical clipping/compression.

It was tasty for drums with an input level between -20dbm and -12dbm.
The distortion was musical for some instruments.
 

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