This is a bit more complicated since it is a grid driven, pentode with all the
bias supplies.
I was thinking of runing the tubes as you do 4-400A or 813s in grounded grid
operation.
I suspect the tube will perform ok but not sure of it.
73
Bill wa4lav
________________________________________
From: Máximo EA1DDO_HK1H [ea1ddo@hotmail.com]
Sent: Monday, February 27, 2012 11:44 AM
To: Fuqua, Bill L; amps@contesting.com
Subject: RE: [Amps] 4 x Glass Glowing tubes
Hi Bill,
GU81M grounded grid...
What you think about this one;
http://www.ua1cbm.ru/images_doc/2008/pa_ex8a_hifi/HiFi_Contester_EX8A_image001.gif
Thanks
73, Maximo
> From: wlfuqu00@uky.edu
> To: ea1ddo@hotmail.com; amps@contesting.com
> Date: Mon, 27 Feb 2012 06:14:20 -0500
> Subject: RE: [Amps] 4 x Glass Glowing tubes
>
> The GU81 may be a good choice.
> It should be stable in grounded grid operation with all the grids grounded
> unlike the 833. Check out the G1 to plate capacitance. It is very low which
> also
> means that the cathode to plate capacitance is low in GG operation.
> It looks like an 833 as well.
> The question is if it will operate safely as a trioded conneted pentode.
> Some tetrodes and pentodes do not but most glass envelope ones do.
> Just about all the 4- series do except the 4-65.
> 73
> Bill wa4lav
> ________________________________________
> From: Máximo EA1DDO_HK1H [ea1ddo@hotmail.com]
> Sent: Monday, February 27, 2012 5:37 AM
> To: Fuqua, Bill L; amps@contesting.com
> Subject: RE: [Amps] 4 x Glass Glowing tubes
>
> Hi all, Bill,
>
> Yes, Bill is right.
> I am not looking for just watts. I don´t want a closed box with ceramic tubes
> inside (I already own one).
> What I would like to get is a beauty looking amp with good/high quality
> audio, based on glass tubes.
>
> Let me change the question.
>
> What tubes do you recomend to me to build a 14 MHz monoband amp from these;
> GU48/833A, GU81M or GU5B?
>
> GU5b (triode) is powerfull, cheap and AB2 class quality, the only issue is
> the blower/noise they need. http://tubedata.tubes.se/sheets/018/g/GU5B.pdf
> GU81M, tetrode, are cheap, and I guess has quality as well, no blower (or
> small one), but tetrode needs more power supplies
> http://tubedata.tubes.se/sheets/018/g/GU81M.pdf
> GU48/833A, (triode), are cheap, B class, unstable?
> http://tubedata.tubes.se/sheets/018/g/GU48.pdf
>
> It could be just monoband amp, for 14 MHz, may be I can add 7 MHz later on.
> Thinking in 4 tubes to get blowing glass enough and power between 4 to 10 Kw).
>
> Any other glass tube?
> Any recomendation?
>
>
> Thank you very much
>
> 73, Maximo
>
>
>
>
>
>
> > From: wlfuqu00@uky.edu
> > To: hsu4qro@gmail.com; ea1ddo@hotmail.com
> > CC: amps@contesting.com
> > Date: Mon, 27 Feb 2012 03:03:03 -0500
> > Subject: RE: [Amps] 833A/GU-48 x4 Amp support
> >
> > I believe he wants 4 glowing plates. Larger the better.
> > 4x 250th would work but a bit expensive compared to the Russan 833.
> > I once ran 2x 250th in grounded grid driven by a pair of 6146Bs on 20
> > meters.
> > So 4 should work.
> >
> > 73
> > Bill wa4lav
> >
> > Subject: Re: [Amps] 833A/GU-48 x4 Amp support
> >
> > I don't think 833A is a good option.As it have long electrode and bad
> > freqence response. I'm afraid it can not work in 20m in 4X
> > parallel(self-oscillation).
> > 3CX3000A7/F7 is better. But if you use ACOM2000A as driver, it will over
> > drive easily.The drivering power is 400W (max) for 3CX3000A7/F7. or you can
> > use low/ medium Mu triode
> > in GG like 3CX3000A1/3CX2500A3..., they need more driving power. Just my
> > thought.
> > 73!Hsu
> >
> > -----原始邮件-----
> > From: Máximo EA1DDO_HK1H
> > Sent: Sunday, February 26, 2012 6:00 AM
> > To: amps@contesting.com
> > Subject: [Amps] 833A/GU-48 x4 Amp support
> >
> >
> >
> > Hi all,
> >
> > I am not an amps expert but I am thinking to build an amplifier using 4 x
> > GU-48.
> > I guess GU-48 is equivalent to 833A, not sur if all specs are same.
> >
> > This is trying to get an amp "looking beauty" and good audio quality, it is
> > not looking for extremely high power. I already have an amplifier (Acom
> > 2000A) i can use as driver.
> > Something like this, but HF;
> > http://www.luxurylaunches.com/entry_images/0511/17/Audio-Power-Labs-833TNT-tube-amplifier-1.jpg
> >
> > Gates BC-1g is an example too; http://w5ami.net/bc-1t/833.glow2.jpg
> >
> > It could be monoband amplifier for 20m, perhaps 40m too.
> >
> > I thought in GU5b and GU-81M before, but I guess GU-48 is better because
> > needs no specific blower and is triode (easier to build).
> >
> > Please, Any of you have sperience with this kind of amplifier?
> > Any squematic?
> > Recomendations?
> >
> >
> > Thank you very much
> >
> > 73, Maximo - EA1DDO
> >
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
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