But also no reason to. Increasing parts count for no actual gain in performance is not good engineering.
See, this is why I love this preamp. There's circuit elements in there to offend everybody.
See, this is why I love this preamp. There's circuit elements in there to offend everybody.
Who is offended?
Why don't you get rid of the tube, the heater supply and the plate supply and use the opamp as a unity gain buffer? Get rid of a lot of parts that way 😀
BTW, a with a bootstrapped (or non bootstrapped even) cascode the PSRR is significantly improved, so the HV regulator could be done away with in favour of just some stages of RC filtering after the power rectifier.
Nighty night.
Why don't you get rid of the tube, the heater supply and the plate supply and use the opamp as a unity gain buffer? Get rid of a lot of parts that way 😀
BTW, a with a bootstrapped (or non bootstrapped even) cascode the PSRR is significantly improved, so the HV regulator could be done away with in favour of just some stages of RC filtering after the power rectifier.
Nighty night.
Well, why not use bipolar transistors in your new Blameless design?
In essence, a non-bootstrapped cascode simply trades a solid state voltage regulator pass device for an inferior tube one- when it comes to keeping voltages and currents constant, solid state does a better job. That's why it's done this way. A bootstrapped CF will also work fine, though not gaining any performance in this application.
There are many ways to design a preamp. In this case, res ipsa loquitur. It's simple and the performance is... blameless.
In essence, a non-bootstrapped cascode simply trades a solid state voltage regulator pass device for an inferior tube one- when it comes to keeping voltages and currents constant, solid state does a better job. That's why it's done this way. A bootstrapped CF will also work fine, though not gaining any performance in this application.
There are many ways to design a preamp. In this case, res ipsa loquitur. It's simple and the performance is... blameless.
( SY... a nice way to sign off! Except that Gordy then chimes up... )
I've some experience with common-cathode designs but now want to build a CF. However it seems (from starting to read up on the subject) that CFs 'fall over' when driving a low impedance load? Why is that?
I have a load of 480 Ohms (actually 30 Ohm headphones through a 4:1 turns ratio, 16:1 Z ratio, transformer) and I would like to deliver about 6mA at 3V peak into the primary. I have a notion of using a 6H30 with a CCS in the cathode running at 30mA. This should have an o/p Z (pre transformer) of about 100 Ohms. So is this likely to 'fall over' or might it be OK?
It'll work after a fashion, but not be optimum. Think of it this way- if you put a 480R load on the plate, measured the distortion, then divided by the gain, what would the distortion be? In this case, higher than you might like. You need a lot more transconductance and mu than the 6H30 appears to give (judging from datasheets- I've never used one).
I'd be tempted to try a sweep tube in this application because of the perveance and low cost. Triode-connected 6JN6 with 100V on the plate and idling at 60mA...? As a pentode, the CF becomes a bit more complicated (you have to hold the cathode-screen voltage contstant), but the performance is excellent. 100V on that self-same 6JN6 would be where I'd start in the design process.
I'd be tempted to try a sweep tube in this application because of the perveance and low cost. Triode-connected 6JN6 with 100V on the plate and idling at 60mA...? As a pentode, the CF becomes a bit more complicated (you have to hold the cathode-screen voltage contstant), but the performance is excellent. 100V on that self-same 6JN6 would be where I'd start in the design process.
In a sense, yes, that's what a pentode is. Here, the lower input capacitance is serendipitous; the point of using a pentode is low impedance and extremely high feedback/low distortion with an unkind load.
Just use a 4CX1000A. 3000V on the plate and 250mA bias (that's what I'm running my two pairs at).
Imagine how linear that would be, only swinging 3mA peak into the load.
Imagine how linear that would be, only swinging 3mA peak into the load.
Why didn't you do that for your diff amp input on the Blameless? Are you wussing out in your old age?
Use a positronic tube. You're in Australia where everything is backward, so it should be easy to find. I think it's the -4CX1000. Takes heating air instead of cooling air.
No Audiophile clubs near where I live. Couldn't be bothered driving all the way the Melbourne or Sydney.
a map showing it how it actually is...
An externally hosted image should be here but it was not working when we last tested it.
You are right. Due to the mischievousness of a few, threads here often stray off topic. Lets us have the audacity to hope for change!
How effective is the screen at stoping RF stuff jumping over to the primary winding in that Jensen transformer?
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