| lt cdr data |
| whaddya think? |
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| analog_sa |
Criticisms:
1. ECC82
2. ECC82
3. ECC82
4. Cathode follower
5. Cap coupled
6. Sand in PSU
7. It just can't compete with a good passive if gain or impedance matching is not an issue.
8. Not even the 'finest silver RCA' will help it |
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| Steve Eddy |
| quote: | Originally posted by lt cdr data
whaddya think? |
I'd just say don't let other peoples' prejudices discourage you or get you down. At the end of the day you're the one who has to be satisfied with it. And the only person who can tell you whether you've achieved that is you.
se |
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| bigwill |
| quote: | Originally posted by analog_sa
Criticisms:
6. Sand in PSU
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How on earth is that a bad thing? Anyway, tubes have more sand in them than solid state devices :clown: |
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| Giaime |
It's good. ;)
Said that, here's the things I would do:
1) ECC88 :D
2) sand regulator in the PSU. Trust me. :angel:
3) CCS under the tubes, throw away that led.
Practically that's my preamplifier, you can find detailed schematics on my site. |
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| Robski666 |
Hi
I would have to agree with Giaime on the led, other then that its all fairly arbitrary
Robert |
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| fdegrove |
Hi,
Yet another preamp that nobody really needs.
If you want to experiment and learn what valves are all about why waste the opportunity by throwing in all that semi-conductor trash?
I'm afraid I'll have to agree with Analog_SA's analysis.
Steve Eddy still hasn't caught up on tubes yet either so what else is new?:smash:
You want a preamp?
You want a little gain?
Reasonable output impedance?
Not too expensive?
Sound you won't believe was possible?
Get yourself a pair of 12B4A's and build Brett's little circuit, it's in the forum's archives and probably has been mentioned in the recent 12B4A thread by Mark Gulbrandsen.
Oh, pay attention to the PS.
Not a single circuit sounds better than its PS.
Thank us later, ;) |
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| Bryan |
| I'm with Frank on this one. 12B4A, simple and sweet ;) |
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| lt cdr data |
| the psu is actually tube rectified, but there was no tube rectifier on the drawing package :( |
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| dave dove |
are you building
or buying?
dave dove |
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| Miniwatt |
After reading all the promotional blabla about the Basie I'm quite disappointed when I see the circuit:mad:
ECC82 :dead:
But I'm sure there's people who are perfectly happy with it -until they know better:smash: |
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| fdegrove |
Hi,
For the Dutch/Flemish speaking only:
En dit is dan de ECC tweeentachtig,
onthoudt U dat dus goed
Want dat is van belang
wanneer U ernaar luisteren moet,
god allemachtig
Drs. F.
Cheers, ;) |
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| astouffer |
Hey analog_sa what is your idea of a good preamp? Don't even mention passive because "passive preamp" makes absolutely no sense. A passive preamp is a volume control, or for people with money to burn 100 holco resistors and a huge wafer switch. Whats wrong with a cathode follower? Whats wrong with cap coupled? Whats wrong with an LED for bias voltage? Merely dismissing everything without reason isn't the way to go.
Adam |
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| Giaime |
Hello Adam!
| quote: | Originally posted by astouffer
Hey analog_sa what is your idea of a good preamp? Don't even mention passive because "passive preamp" makes absolutely no sense. A passive preamp is a volume control, or for people with money to burn 100 holco resistors and a huge wafer switch. |
I agree absolutely. Useful ones are transformer based.
| quote: | Originally posted by astouffer
Whats wrong with a cathode follower? |
Poor linearity and poor Zout when poorly implemented.Please note that most CD players have a Zout of 10ohm or less, so a pre has to have low Zout. If not, it's completely useless or probably even bad.
| quote: | Originally posted by astouffer
Whats wrong with cap coupled? |
If it can be done without, why not? Capacitors are nonlinear.
| quote: | Originally posted by astouffer
Whats wrong with an LED for bias voltage? |
Naaah... to many nonlinearities. I don't trust sand ;) |
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| Gluca |
... I like LED's in the cathode? You DO NEED to be sure they are passing enough current to avoid non-linearities.
Can't remeber now properly, I think M. Jones showed somewhere the great performances cheap red led's can offer (not mentioning here his book).
Ciao
Gianluca |
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| Steve Eddy |
| quote: | Originally posted by Giaime
Poor linearity and poor Zout when poorly implemented. |
With that qualifier, you could say that about virtually everything.
| quote: | | Please note that most CD players have a Zout of 10ohm or less, so a pre has to have low Zout. |
Sure you didn't leave out a zero? Most CD players I've researched have had output impedances of 100 ohms and higher. Not 10 ohms and less.
se |
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| dave dove |
it's not a basie circuit
dave dove |
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| Johan Potgieter |
I will be very calm on this one, starting 2006 in a GOOD spirit (er - I mean of the mind!)
The anode load resistor is not given in the initial circuit, so one can hardly express an opinion regarding linearity etc. (LED bias does appear to be somewhat low, however, for an ECC82.) Then I am beginning to wonder exactly what all this criticism of an ECC82 per se is - excuse me, but it surely depends on the circuit?? It is as far as I know (which comes all of 50+ years) a good triode with a mu of about 18. The 12B4 is offered as an alternative - with a mu of 6.5! (at least according to the RCA Tube Manual). That will make a different pre-amplifier. I presume if someone uses an ECC82 he wants a gain of about 13, and likewise for all the other contenders in the marketplace, each according to their ability.
Regards. |
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| SY |
| quote: | Originally posted by Johan Potgieter
Then I am beginning to wonder exactly what all this criticism of an ECC82 per se is - excuse me, but it surely depends on the circuit?? |
Morgan Jones presented some measurements of what he called the "irreducible distortion" of a range of medium mu triodes in sufficient quantities to have statistical merit. These measurements were done with a current source load so that linearity is maximized. The ECC82s fared quite poorly compared with other similar tubes.
Happy New Year, Johan! |
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| Johan Potgieter |
Thanks SY, duly noted. I do not have that book - perhaps some tests of my own.
Same wishes to you! |
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