Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: frank57 on November 10, 2011, 03:07:23 pm

Title: What do these parts do in a Hiwatt tone stack?
Post by: frank57 on November 10, 2011, 03:07:23 pm

Are these caps in the Hiwatt tone stack there partly to reduce noise?
Is the 220k resistor between the 1n and 220p the same as a resistor across the treble pot,
effectively making it 110k?
The resistor across the mid pot is a low pass filter?

Are the two treble (I might be using the wrong term here) caps almost acting like a shelving filter?

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: Bierschinken on November 10, 2011, 03:23:42 pm

Hi there,

the 220k is not just like a parallel resistor to the treble Pot. - Well it is, but just for the "lower highs" (stupid term, sorry)
The highest frequencies tend to pass through the 220p and the pot while the lower frequencies within the "high-range" will pass through this 220k resistor. The frequency is dependent on the size of the treble-caps and the treblepot-setting.

And yes, the 1n across the midpot is some sort of lowpass.
It makes the midpot work in a lower frequency range and makes the treble-response not that interactive regarding the settings of treble and mid in comparison.

Best is to just build the circuit and hear the differences in values.
You quick will get a good clue how it works.

Cheers,
Swen

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: frank57 on November 11, 2011, 08:03:28 am

Would this work on pcb?

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: Bierschinken on November 11, 2011, 05:24:43 pm

Sure this would work.

Except for the fact that the 220k is connected to the wrong end of the 1n :)

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: frank57 on November 12, 2011, 10:17:19 am

Whoops!
So I would connect all 3 together there like so?

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: Bierschinken on November 12, 2011, 01:41:30 pm

yep  :thumbsup:

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: frank57 on November 14, 2011, 09:40:20 am

I gave it a try and did it help with the buzz issue this amp has?
Yes it did! It cut it down by quite a bit.
Is it because the treble pot is being cut down?
I didn't play on it so I'll try that next.

Title: Re: What do these parts do in a Hiwatt tone stack?
Post by: frank57 on November 16, 2011, 02:06:08 pm

Would this give me a Hiwatt tone stack?
I want to try one last idea on this amp.