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Old 7th September 2005, 11:49 PM   #1
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Default El84/6bq5/ecc83 + Ef86 = Dc Pp

There is a sketch in Bonavolta's website -- I converted to Multisim -- but am wondering about the shield connections on the EF86.

Tone controls model out pretty well.
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Old 17th September 2012, 04:58 PM   #2
fotios is offline fotios  Greece
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Quote:
Originally Posted by jackinnj View Post
There is a sketch in Bonavolta's website -- I converted to Multisim -- but am wondering about the shield connections on the EF86.

Tone controls model out pretty well.
Hello Jack
Have you managed to insert the SPICE model of EF86 into multisim database? Or this EF86 in your schematic is simply the schematic symbol?
I tried for 2 days any EF86 model offered on the web without success. Simulator shows each time an error and stops to run. Looking at the rest pentode models of multisim, in no one is used the "μ" (mu) parameter of tube while in all models i've downloaded there are equations related to it. Simulator shows two error messages per instance, either "unknown parameter" or "to many parameters". Have you any idea? I try to build a "1 Octave" (9 bands) L-C equalizer around an EF86. Using the 6F6 model in the place of EF86 the FFT AC analysis plot shows correct attenuation points, L-C band-pass filters are well calculated and each one shows a nice "cut" of -18dB max exactly at its center frequency.
Thanks for any help
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Last edited by fotios; 17th September 2012 at 05:11 PM.
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Old 19th September 2012, 07:40 AM   #3
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Shield connections go to chassis, normally. Or maybe you are asking about something else?

Last edited by costis_n; 19th September 2012 at 07:42 AM.
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Old 19th September 2012, 09:05 AM   #4
fotios is offline fotios  Greece
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Quote:
Originally Posted by costis_n View Post
Shield connections go to chassis, normally. Or maybe you are asking about something else?
Γεια σου Κωστη.
No, the issue is not related with circuit connections. It is probably an issue of incompatibility of SPICE equations and expressions. I think that all models i find on the web are compatible with LT-Spice which is Berkelay Spice simulator while this used by multisim is a simple SPICE simulator. There are different types of simulators. Τhe EDWinXP CAD-CAE software i use for PCB drawing includes a simulator named EDSpice which is also a Berkelay Spice simulator.
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Last edited by fotios; 19th September 2012 at 09:07 AM.
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Old 19th September 2012, 09:12 AM   #5
danzup is offline danzup  Romania
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Quote:
Originally Posted by jackinnj View Post
There is a sketch in Bonavolta's website -- I converted to Multisim -- but am wondering about the shield connections on the EF86.

Tone controls model out pretty well.
C3 connected wrong .
Shield connection to ground of course.
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Old 19th September 2012, 12:41 PM   #6
TheGimp is offline TheGimp  United States
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As treble is adjusted up, and bass is adjusted down, the input impedance of the tone circuit will decrease, particularly as frequency increases. Worst case around 240K at 20KHz.

It would be a good idea to add a buffer stage before the tone control.
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Old 19th September 2012, 03:43 PM   #7
fotios is offline fotios  Greece
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Oh! Sorry guys, i forgot to refer that i am not interested for the given Bonavolta's circuit reprinted by jackinnj. I simply was looking for a spice model of EF86 compatible with multisim. So my "Search" on diyAudio resulted in this thread. I saw the EF86 symbol used by jackinnj in this schematic and simply i asked he if has obtained a multisim compatible model.
In my own circuit i just use - to the present - the existing 6F6 pentode spice model connected as input pentode. Then i have connected a 9-band (1 octave) passive L-C equalizer circuit accross plate and cathode. It works just fine in simulator.
BTW, have any of you the EF86 multisim compatible model? Great thanks for any help
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Old 19th September 2012, 04:36 PM   #8
kevinkr is offline kevinkr  United States
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C3 is on the wrong side of R7 by way of clarification.

Consider a Baxandall based tone control with a CF in front of it to provide a constant input impedance. I expect the current implementation will be somewhat noisy, and good 2.5M pots may be a little hard to find.
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Old 19th September 2012, 08:26 PM   #9
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Doesn't this thing have WAY too much gain?

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Old 20th September 2012, 10:30 PM   #10
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I somehow fail to get the point with using models to figure out these (relatively) simple circuits. My most computerized tool is Photoshop and anode characteristics, and PSUD2.
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