the McMartin 'ma20' amplifiers have the 'Z5U' Dielectric.
as they work and sound, as well as they do,
i've been apprehensive to change anything.
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That's fine John, how about a blind shootout SY tells Belle Helene from 2 Buck Chuck and you tell the difference between Dale RN55C and naked Vishays. No peeking.
John, I don't want to discuss sonic reasons here, I only want to mention that music - here the music as amplified signal - is really the dynamic condition
I will try out the BF but I my feeling tells me that the SK170 is the JFet for my circuit ...
What Dales you have in mind and what about the Caddock 132?
Currently I don't use the cascode even with the SK170 but I have to experiment with it as well and compare the circuits.
Can I contact you by PM for some questions out of topic?
Joao, I think that I understand what you want, but I cannot answer your questions here, because of the 'extra commentary' that almost always comes from people who do not think that questions like these are 'important'. Of course, you can PM me on specific issues. In truth, I have never found any 'dynamic' differences in fets. Resistors perhaps.
However, it is still almost impossible for me to say something about them here, except FACTS. For the record I have used Caddock power resistors and I like them. We have found a particular version of the Dale resistor to be pretty good, but I don't know its exact number. All that I was told is that it is non-magnetic. This is usually a very good thing, but not always necessary. For example, the end caps on the Roderstein Resista resistors have a slight magnetic attraction, probably nickel plating on the end caps, and it doesn't make much difference, in fact, they are a very good resistor at any price. Unfortunately, they don't make them anymore, and that is why we are switching to Dale for our less critical resistors.
Getting back to jfets, it is important to take care about voltage and leakage issues, especially at very high impedances, because then. a carbon resistor just might show its 'excess' noise due to the voltage drop generated across it by the current needed to supply the 'leaking' jfet.
However, it is still almost impossible for me to say something about them here, except FACTS. For the record I have used Caddock power resistors and I like them. We have found a particular version of the Dale resistor to be pretty good, but I don't know its exact number. All that I was told is that it is non-magnetic. This is usually a very good thing, but not always necessary. For example, the end caps on the Roderstein Resista resistors have a slight magnetic attraction, probably nickel plating on the end caps, and it doesn't make much difference, in fact, they are a very good resistor at any price. Unfortunately, they don't make them anymore, and that is why we are switching to Dale for our less critical resistors.
Getting back to jfets, it is important to take care about voltage and leakage issues, especially at very high impedances, because then. a carbon resistor just might show its 'excess' noise due to the voltage drop generated across it by the current needed to supply the 'leaking' jfet.
There's two aspects to this: technical superiority and audible superiority. You can appreciate that it depends on very many things whether any technical superiority translates into audible superiority.
But technically a parallel (I guess that means shunt) regulator is superior, for at least one reason: in a shunt reg topology, the return current (or ground current) circulates locally between the load and the shunt. That means it is much less critical to ground current loop contamination, or ground currents from one stage ending up causing distorted signals in another stage's ground traces thus causing signal distortion.
That makes sense?
jan didden
Thanks for the reply. I'm trying to understand what exactly you mean by this statement.
What happens in the case of the series regulator: does the return current circulates somewhere else than locally ? I'll try to post a schematic later to clarify the issue.
In a series reg, the return current goes back to a capicitor at the reg output. That means it goes through some traces or wire. This same wire or trace will carry return current from other stages or other parts of the (pre) amp. So there is coupling between stages through the voltage induced on the return leg, and that induced voltage is generally distorted, but also can be seen as part of the input signal.
In a shunt reg, the return current doesn't go back to the supply but is part of the shunt current which varies with the load current.
Yes a schematic would be nice ;-)
jan didden
Maybe, but if you use a series reg AFTER the shunt reg, that's a giant step backwards.
jan didden
I believe we were talking about a conceptual diagram to illustrate the conceptual difference between series and shunt. After that it's just engineering
.jan didden
Look at Fig 5 and it's description: Electronics Tips: Shunt Regulator
Now try to picture the VARYING current due to a VARYING load like an audio amp. Then do the same with a series reg.
jan didden
Now try to picture the VARYING current due to a VARYING load like an audio amp. Then do the same with a series reg.
jan didden
Not when the series regulator following the shunt one is a capacitance multiplier – not as far as supply ripple is the issue. With class A amps, the extra inner impedance of the capacitance multiplier is a lesser issue than ripple value. Now, shunt regulators have benefits other than including the return in the regulating chain.
CTC Blowtorch is, I believe, Class A, therefore no varying load for the regulator.
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