Re: Question about grid behavior with triodes

On Sep 30, 5:07 am, Patrick Turner <i...@xxxxxxxxxxxxxxxxxx> wrote:
Eiron wrote:

Patrick Turner wrote:

Wessel Dirksen wrote:
Hello RAT friends,
......snip...
So putting 2V rms on the grid of a triode with a fixed bias of 2.4v
may not be such a good idea. Here's a circuit to experiment with -
http://members.lycos.co.uk/fiultra/BatteryT68bis.jpg

--
Eiron.

2Vrms = +/-2.8pkV, and grid current would flow in a tube with fixed bias
= -2.4V.

However, as its done in the above fiultra preamp stage, is OK because
the gain attenuater is before the
417A and probably quite low level output would be wanted, and therefore
applied input voltage
probably will be below 0.2Vrms. The bias of 2.4V suits having a healthy
huge 20mA bias current in the 417A
which is supposed to sound very well.

Patrick Turner.

Thanks for the input everyone. I would like an opinion about the
interstage connection for my 3 stage amp using 6CG7's and KT88's all
in triode:

The first 6CG7 stage is a CCS unbypassed grounded cathode stage
running at about 7mA with -1.9V bias. With a 2VRMS max input. The grid
leak resistor is 1M. I calculate the Zin at 100K, and Zout at 12K. It
has a gain of around 17. This is DC coupled to the next stage at about
100V.

The second 6CG7 stage is a positive PS long tail phase splitter and
driver for the power tubes. The Rl's are adjusted for balance. The
total current through Rk is about 17.5mA. with about -6V bias. Zin is
300K. Zout is 5K. The gain I calculate to be about 6. This is cap
coupled to the power tubes which are cathode biased now at about 70mA.

This sounds good to about 1/2 power. Then it sounds a wee bit thin,
not bad per se. So I'm thinking. The first stage would be +/- OK then.
But would there be alot of grid current driving the second stage? 1V x
17= 17V RMS with a tube biased at -6V? Have I created a monster? If so
what are my options?

Thanks so much,

Wessel

.

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