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-   -   El84/6bq5/ecc83 + Ef86 = Dc Pp (http://www.diyaudio.com/forums/tubes-valves/63909-el84-6bq5-ecc83-ef86-dc-pp.html)

jackinnj 7th September 2005 11:49 PM

El84/6bq5/ecc83 + Ef86 = Dc Pp
 
2 Attachment(s)
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.

fotios 17th September 2012 04:58 PM

Quote:

Originally Posted by jackinnj (Post 718988)
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
Fotis

costis_n 19th September 2012 07:40 AM

Shield connections go to chassis, normally. Or maybe you are asking about something else?

fotios 19th September 2012 09:05 AM

Quote:

Originally Posted by costis_n (Post 3170546)
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.
Thanks
Φωτης

danzup 19th September 2012 09:12 AM

Quote:

Originally Posted by jackinnj (Post 718988)
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.

TheGimp 19th September 2012 12:41 PM

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.

fotios 19th September 2012 03:43 PM

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 :)

kevinkr 19th September 2012 04:36 PM

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.

planet10 19th September 2012 08:26 PM

Doesn't this thing have WAY too much gain?

dave

costis_n 20th September 2012 10:30 PM

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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