• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

RH slayer

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Shoog

Shoog

Member
Joined 2002
SpreadSpectrum said:
Shoog,

I've only done one amp with a voltage-derived, parallel-fed output stage but I developed the linear current drive by simply driving a resistor with a linear voltage (p-channel source follower). This allowed a very simple feedback network with no caps and it presents a high impedance to the previous stage.

I blogged about the circuit here.

It probably isn't something that would work for a minimal-cost amp like this since it requires more voltage rails but is something to keep in mind as an option for these types of output stages.
Click to expand...
I think the FET driver approach is probably a step on from the pentode.

Overall what I wanted to achieve here was to use an obscure low voltage tube which because of its peculiarities is cheap as chips (a quad can be had for less than the price of a single EL84). I had proven that self splitter anti-triode configurations worked in a previous project. It was the discussion of SMPS and DC-DC boosters which made it all come together and suggest a viable budget project that anyone could easily build regardless of means.
As you will probably be aware there is no ground in this project which hasn't been furrowed many time over the last 5 years on these forums, but I think the combination of all aspects is novel enough to warrant some small attention as a contribution to furthering the work of others (including yourself).

Shoog
 
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DAK808

Member
Joined 2012
Shoog said:
My RH807 was a thing of a long time ago and has gone on to make different things since. It morphed into a Gary Pimm Tabor clone first, an amp I still have in storage and which is an excellent example of a Schaded amp design.

Shoog
Click to expand...

I don't understand how you got the data on the RH amp to make the comparison? The RH807 amp is a different circuit, 2 stage design i believe, than the rh84 which is just a single driver.
 
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DAK808

Member
Joined 2012
Shoog said:
The comparisons is of both mine and the RH84 in LTspice.

Shoog
Click to expand...

But, you don't have a RH84? How can you compare an imaginary amp against a real one? I would think that for a valid comparison you would be using real objects. I can not recall that you stated at the start of your blog that the RH84 was a simulation. If i missed that then my apologies for bringing this up. regards
 
Shoog

Shoog

Member
Joined 2002
DAK808 said:
But, you don't have a RH84? How can you compare an imaginary amp against a real one? I would think that for a valid comparison you would be using real objects. I can not recall that you stated at the start of your blog that the RH84 was a simulation. If i missed that then my apologies for bringing this up. regards
Click to expand...
You should be able to tell a lot about an amp by its FFT profile. If you believe in the magic of tube amps then that magic reveals itself in the FFT plot. Lots of higher order harmonics are generally what we strive to avoid and is why we run simulations to find out which designs produce them. However I have to admit that a static FFT plot cannot reproduce the effects of variable feedback with signal level which are inherent to a RH design.
But I have never claimed to have a RH84 in front of me for direct comparison.

Shoog
 
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