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-   -   E55L in triode as driver! (http://www.diyaudio.com/forums/tubes-valves/25479-e55l-triode-driver.html)

barossi 6th January 2004 01:12 PM

E55L in triode as driver!
 
Hello Tube-DIY-er's,

i wanna drive my 6c33 SE Amp with the famous E55L in triode modus with an interstage.
Like this:
Driver E55L, Output Tube 6c33.
I have got several interstage on stock: pairs LL1660/18mA
Tribute 1:1 20mA
Has anyone experiences with the E55L in triode modus with interstage. U, I?
Would 20mA adequate for the E55L because my interstages can't handle more than 20mA!

Thanks

Barossi

ThorstenL 6th January 2004 02:31 PM

Re: E55L in triode as driver!
 
Konnichiwa,

Quote:

Originally posted by barossi
Would 20mA adequate for the E55L because my interstages can't handle more than 20mA!

Yes. I find that High Transconductance Valves when driving Output Triodes sound much better at lower current than they do at high current, but of course, "better sound" is personal and subjective.

Sayonara

barossi 6th January 2004 02:47 PM

Re: Re: E55L in triode as driver!
 
Quote:

Originally posted by Kuei Yang Wang
Konnichiwa,



Yes. I find that High Transconductance Valves when driving Output Triodes sound much better at lower current than they do at high current, but of course, "better sound" is personal and subjective.

Sayonara

Hello Thorsten,

i count on you....thanks a lot!
o.k. i will try to fire the E55L with ~20mA, using the tribute interstage 1:1 and connect this to the grid of the 6c33!
How much Plate Voltage is your commendation for the E55L?
So i will connect the G2 to anode, G1 the real grid. But what to do with G3?
What's your opinion about that projekt? (E55L -- Interstage Tribute 1:1 5K, or LL1660/18mA---6C33 SE, 200V, 200mA)
Bias for the 6C33 like:

http://www.users.globalnet.co.uk/~va...s/SE108IT2.GIF


Have a nice day....

Barossi

fdegrove 6th January 2004 03:22 PM

Hi,

Quote:

But what to do with G3?
You need to ground it.

This may be of interest to you:

HIGH GM DRIVER PENTODES

Cheers,;)

ThorstenL 6th January 2004 03:50 PM

Re: Re: Re: E55L in triode as driver!
 
Konnichiwa,

Quote:

Originally posted by barossi

o.k. i will try to fire the E55L with ~20mA, using the tribute interstage 1:1 and connect this to the grid of the 6c33!
How much Plate Voltage is your commendation for the E55L?

I like to set the initial operating point for High Transconductance Valves fairly simple.

1) Set the anode dissipation to no more than 1/2 rated.
2) Set the Anode Voltage to about output Valve Bias *2.5
3) Check that your Bias is high enough to allow an input 3db higher than that neede to produce a voltage swing equal to the Bias of the Output Valve.

With your 6S33 Operating Point I get a Bias of 68V from the ANode curves I have. So the E55L Anode Voltage should be around 150V or a little higher at 155V to make using the curves easy. For that the Bias will be around 5V and the Anode dissipation 3W, well on the save side.

So actual +B is 160V plus 20mA * IT DCR, the cathode bias esistor should be 250 Ohm and ideally I'd provide a clean supply and use the "ultrapath" cathode bypass connection with a nice juicey big oil or film cap.

Anode impedance of the E55L looks a little above 1KOhm and gain around 30, so theoretical voltage swing before the bias is exceded is 300V P-P, that is well over 6db input overload margin, excellent.

So, I'd try 250 Ohm Cathode Resistor and 160V on the Anode for starters. Then move a little up and down with the Anode voltage by adjusting the regulator or droppwer resistor for the frontend and listen.

Quote:

Originally posted by barossi

So i will connect the G2 to anode, G1 the real grid. But what to do with G3?

Connect to the Anode of course.

Quote:

Originally posted by barossi

What's your opinion about that projekt? (E55L -- Interstage Tribute 1:1 5K, or LL1660/18mA---6C33 SE, 200V, 200mA)
Bias for the 6C33 like:
http://www.users.globalnet.co.uk/~va...s/SE108IT2.GIF

Sounds fine to me.

Sayonara

barossi 6th January 2004 04:32 PM

Re: Re: Re: Re: E55L in triode as driver!
 
Quote:

Originally posted by Kuei Yang Wang
Konnichiwa,



So actual +B is 160V plus 20mA * IT DCR, the cathode bias esistor should be 250 Ohm and ideally I'd provide a clean supply and use the "ultrapath" cathode bypass connection with a nice juicey big oil or film cap.

Sayonara



Hi,

what do you mean with "ultrapath" cathode bypass connection?
How large should the value be?

I have problems to understand how connect the getters of the E55L: The only think i know so far is G2 to anode! What about G1 and G3.

I will build tomorrow the driver stage using:

E55L in triode connection with ~160V at the anode.
Lundahl LL166o/18mA in connection ALT S with ratio 1:1,125.
Kathode R 250 Ohms, gives ~20mA, bypassed by a Oil-filled C.

Thanks a lot

Barossi

ThorstenL 6th January 2004 09:16 PM

Re: Re: Re: Re: Re: E55L in triode as driver!
 
Konnichiwa,

Quote:

Originally posted by barossi

what do you mean with "ultrapath" cathode bypass connection?
How large should the value be?

Look here:

http://www.electra-print.com/images/ultra2.jpg

Pretty much the same circuit, except E55L and 250 Ohm Cathode resistor and 160V +B.

Quote:

Originally posted by barossi

I have problems to understand how connect the getters of the E55L: The only think i know so far is G2 to anode! What about G1 and G3.

G1 remains the control grid. If you wish to triode connect ANY pentode, connect both G2 & G3 to anode, if G3 is freely available.

Sayonara

fdegrove 6th January 2004 09:53 PM

Hi,

Quote:

Connect to the Anode of course.
Sorry, I don't get this...

Shouldn't g2 be connected to the anode and g3 to the cathode or grounded in case fixed bias is used?

Cheers,;)

ThorstenL 6th January 2004 10:19 PM

Konnichiwa,

Quote:

Originally posted by fdegrove
Sorry, I don't get this...

Shouldn't g2 be connected to the anode and g3 to the cathode or grounded in case fixed bias is used?

Ever heard of triodes with a screen grid? The screen grid will alter the transfer function. To truely triode a pentode (even an EL34) connect G3 to anode, fixed bias or not.

Sayonara

fdegrove 6th January 2004 10:55 PM

Hi,

Quote:

Ever heard of triodes with a screen grid? The screen grid will alter the transfer function. To truely triode a pentode (even an EL34) connect G3 to anode, fixed bias or not.
While I do agree with you...

I just wondered why the Philips datasheets state Vg3 at 0V for a triode connected E55L.

As these datasheets don't provide operating curves for your suggested connections, I assume you draw the curves yourself and pick operating point from that?

Cheers, ;)


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