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Old 6th April 2003, 04:42 PM   #11
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<b>the anti-CF league is not based on facts.</b>

Bollocks.
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Old 6th April 2003, 05:36 PM   #12
SY is offline SY  United States
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Well-reasoned, Brett.

Anyway, Jay, the 12AT7 as a cathode follower will work OK as long as you're not doing anything weird with the load (like driving 50 foot high capacitance cables). A 6DJ8-type (there's a whole family of these) will work even better as a CF, being able to drive higher capacitances without loading down.
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Old 6th April 2003, 05:57 PM   #13
Jay is offline Jay  Indonesia
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So there is a pro and contra about Cathode Follower? Many don’t like CF (that’s the fact). I’ll call that a PHENOMENON. It coincidentally happened to me that from (only) a few amplifiers I know (I just realized now), CF designs are indeed “bad” sounding…

Hmmm… I think I will temporarily join the anti-CF league... For safety reason

Oh yeah, Frank, about the preamp, it was a line stage. This is I think a typical JADIS preamp, utilizing 12AU7/12AT7/12AX7. I wonder why they had survived…

Why should I avoid the paralleled triode? Like in SS, the effect is for tighter bass (beside longer tube life). In SS, there is no side effect to the mid, in tube it seems like there is a terrible trade-off… My option is then to parallel OR to inactivate half the tube. Sound-wise, which one is better?

BTW, SY, I’m not going with the CF. Is that badly-reasoned?
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Old 6th April 2003, 06:25 PM   #14
Morse is offline Morse  United States
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Hi Jay;

>>>....My option is then to parallel OR to inactivate half the tube....<<<

Why not share the valve between channels then, rather than just use half? That's assuming, of course, that you have enough current capability with just one triode section.

This is just the opinion of a hardcore audio cheapskate.....

All the best,
Morse
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Old 6th April 2003, 06:26 PM   #15
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Default NOT ALL CFS ARE CREATED EQUAL.

Hi,

Jay,

Do you mean something like this?

It's a buffered input (CF), followed by an anode follower using a 12AX7 RC coupled into another 12AU7A CF.

I don't know who thought this up but this one hell of a complicated way to make a simple line preamp.

The whole thing can be reduced to a single 12AU7A (or better) per channel.

Cheers,
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Old 6th April 2003, 07:04 PM   #16
SY is offline SY  United States
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Let's just say that there's an awfully large set of classic, highly regarded gear that uses a cathode follower. And that no-one has ever presented any measurable or audible evidence (beyond bald assertion) that CFs as a topology are inherently flawed for their intended application. Yes, you can do a bad CF design. That puts it in the same category as every other topology.

The acceptance or rejection of CFs is more of a sociological than electronic issue. If that's what's important to you, than by all means, don't use it.
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Old 7th April 2003, 02:20 AM   #17
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As for audible evidence, what exactly are you looking to be presented? Twice, once about 10 years ago, and again about 3, I built a number of CFs, switchable bypassed (level matched, good earthing and PSU) into two power amps or my ES headphone driver. The measurements between the two topologies was slight. The CF was plainly audible, some variations more than others. I've also tried a number of other times less formal experiments, into various loads, some variations including CCS as cathode loads. The best so far has been the Vacuumstate circuit I'm currently using, which drives my TVC a little better than some of the CC I've tried. Directly into, say, a high input Z poweramp, I would probably choose something else. I've built about 10 different linestages this year to try them out, before I reached this conclusion. Soon, I'd like to try some pentode CF's again, and some mu stages, and some Whites and even a Broskie, just to see. The experimentation can be fun.

There are classic designs out there that are well regarded amongst some people using CF's. In a commersial design, there is a requirement to be able to drive a wide range of poweramps, so some designers choose them. We are not so restricted in diy to the came commercial considerations. Having owned and/or used a number of commercial, 'well regarded' preamps, my feeling is, well regarded by whom?
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Old 7th April 2003, 09:24 AM   #18
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Jay,

I take it that your Aleph is hard to drive? If you don't want a CF, try a ECC99 anode follower, or, if this isn't enough gain, the before mentioned 6C45. I don't know why you'd need to complicate things with three stages...unless the Aleph is hard to drive and an insensitive beast.

An EC99 or 6SN7 as a VA and CF stage is simple, sounds fine, and will drive most amps. A simple circuit(even one using a CF) will generally sound better than a circuit with unneccesary additional stages.
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Old 7th April 2003, 02:34 PM   #19
Joel is offline Joel  United States
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Brett is siding with the Frank D. philosophy of DIY which is that any circuit that can be used in multiple applications is "bad". A "good" circuit is specialized to a single application.
I think that is bollocks.
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Old 7th April 2003, 02:44 PM   #20
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Quote:
Originally posted by Joel
Brett is siding with the Frank D. philosophy of DIY which is that any circuit that can be used in multiple applications is &quot;bad&quot;. A &quot;good&quot; circuit is specialized to a single application.
I think that is bollocks.
I have no idea where you got that from. It's not what I said nor what I meant.

You should write for politicians.
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