Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: firemedic on May 17, 2011, 08:00:58 pm

Title: EL84/6V6 OTs
Post by: firemedic on May 17, 2011, 08:00:58 pm

Would an OT from a SE EL84 amp be safe to use with a 6V6? It looks like the load Zs are pretty similar, I guess I need to hear it from someone wiser.

Title: Re: EL84/6V6 OTs
Post by: jjasilli on May 17, 2011, 08:36:45 pm

Yes.

Title: Re: EL84/6V6 OTs
Post by: HotBluePlates on May 17, 2011, 08:37:45 pm

Yes.

EL84's and 6V6's generally output the same power into similar loads at similar plate voltages. The only significant difference between the tubes is the EL84's higher Gm, and corresponding lower bias voltage and input signal requirements.

Title: Re: EL84/6V6 OTs
Post by: firemedic on May 17, 2011, 09:25:26 pm

Okay, thanks. Datasheets are great but plain english is greater.

Title: Re: EL84/6V6 OTs
Post by: tubeswell on May 18, 2011, 03:59:41 am

Quote from: firemedic on May 17, 2011, 09:25:26 pm

Okay, thanks. Datasheets are great but plain english is greater.

gm = transconductance, or - how much plate current change there is for a given amount of grid voltage change - measured in mA/V (milli-Siemens, or 'mhos'). A tube with higher transconductance means that you'll be able to get a bigger swing on the plate for a given (input signal) grid swing.

Also, an EL84 doesn't take as much input signal to get into clipping as a 6V6.

Title: Re: EL84/6V6 OTs
Post by: firemedic on May 18, 2011, 09:15:28 am

That makes very good sense. You have all been very patient with my short attention span.
I'm on my way to pick up a 1962 Victor stereo that is apparently broken. It has stereo SE 6BQ5 outputs per the schematic. The tubes & parts alone should be worth the price, but hopefully the output section is salvageable as a whole. Any ideas are quite welcome.