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Old 29th April 2012, 03:45 AM   #171
popilin is offline popilin  Argentina
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For the brave who came up here, so you are not left with empty hands, I leave this version, not a big deal but has low output impedance
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Old 20th September 2012, 09:59 PM   #172
popilin is offline popilin  Argentina
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A line preamp is not a difficult matter, almost any bus leaves at home.

I think this brings interesting features, low distortion (0.04%), low noise, and output impedance in the order of 500 ohm.

The high voltage is a minor detail.
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Old 20th September 2012, 10:14 PM   #173
popilin is offline popilin  Argentina
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Here's version "civilized", for those lucky enough to have the 2SK170.
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Old 8th October 2012, 05:23 AM   #174
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Amazing findings with this deprecated vacuum tube.
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Old 8th October 2012, 07:36 PM   #175
popilin is offline popilin  Argentina
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Hi Dady
Nice to see you around here.
In view of the results obtained, I consider seriously this valve for my future designs.
Note that the circuit in post #172, #173, Vout = 6 Vpp, more than enough to drive most power amps IMHO.

If you use a more linear valve, the results must be better ?
I have eight NOS RCA 5687, so I made sims for it, the result was disappointing.
In the noise department, the 5687 is a winner because its high transconductance, however you can't go crazy with +B, Vkf = 100 V, distortion was acceptable.
An innocent potentiometer, can ruin your day !
When inserted the volume pot, all rotted, ofcourse noise, and especially the phase shift at high frequency.
A look at the datasheets clarify the situation

http://www.drtube.com/datasheets/ecc82-philips1969.pdf

http://www.drtube.com/datasheets/5687-ge1959.pdf

It's just my impression or interelectrode capacitances of ECC82/12AU7 are amazingly low ?

Maybe also consistently bad from sample to sample ?
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Old 8th October 2012, 08:22 PM   #176
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Quote:
Originally Posted by popilin View Post
Maybe also consistently bad from sample to sample ?
Some have less audible distortion. Please tell us what 12AU7's you were using.

jeff
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Old 8th October 2012, 10:06 PM   #177
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Is a simulation.
At the moment no vacuum tube there.
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Old 9th October 2012, 02:30 AM   #178
popilin is offline popilin  Argentina
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Quote:
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Maybe also consistently bad from sample to sample ?
It's just an irony about what someone said

sic "Later generation valves such as the ECC82 (also intented for use as a field scan oscillator) benefited from improved production techniques and distortion is extremely consistent from sample to sample: it is consistently poor."

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Some have less audible distortion. Please tell us what 12AU7's you were using.
As rightly points Dady, is just a simulation.
For those interested in simulations, they are made based on the mathematical model from Norman Koren, which in turn uses the curves of Mullard ECC82.

I have only some NOS Miniwatt, Tungsram...
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Old 9th October 2012, 07:13 AM   #179
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A 2SK170 cascoding another 2SK170, is there enough Vds for the bottom one? In cascoding general the top common gate one should provide at least 2x Vgs(off) than the bottom common source one.
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Old 9th October 2012, 03:24 PM   #180
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A 2SK170 cascoding another 2SK170, is there enough Vds for the bottom one? In cascoding general the top common gate one should provide at least 2x Vgs(off) than the bottom common source one.
Hi Salas

You honor me with your visit.
I totally agree with what you say, I also drew attention about that.

Probably the mathematical model that I have for 2SK170 is wrong.
Maybe RdsOn can help?
Toshiba does not mention RdsOn in its datasheet.
Putting a resistror, as in the previous circuit, the current is reduced too much, not to mention noise effects.

Possibly I'm saying nonsense, but remember that I'm just a TV repairman.
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Last edited by popilin; 9th October 2012 at 03:51 PM.
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