Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Quatro on March 09, 2013, 05:31:11 pm

Title: 5879 octal equivalent?
Post by: Quatro on March 09, 2013, 05:31:11 pm

Anyone out there know off the top of their head if there is an 8 pin tube or tubes that are equivalent or close in specs to the 5879?

thx

Title: Re: 5879 octal equivalent?
Post by: Backwoods Joe on March 09, 2013, 07:24:52 pm

The 6SJ7 is a Sharp-cutoff pentode but it has higher transconductance, plate disipation and heater current requirements. That seems to be the case when comparing the octals to the newer 9 pin tubes. The 6SJ7GT is the same tube in a glass envelope.

Title: Re: 5879 octal equivalent?
Post by: DummyLoad on March 09, 2013, 09:46:00 pm

6J7 is closer electrically to 5879 than 6SJ7.

6SJ7 and EF86 are close electrically.

6SH7 and 6AU6 are electrically same.

6J7/6SJ7/6SH7 are all octal except 6J7 has grid cap. i like 6J7, followed close by 6SJ7.

--pete

Title: Re: 5879 octal equivalent?
Post by: Quatro on March 09, 2013, 11:49:30 pm

thx gents.

Title: Re: 5879 octal equivalent?
Post by: HotBluePlates on March 10, 2013, 10:19:36 am

When comparing triodes, the figure of merit is mu. That's the key parameter you look at to see how one triode will behave when compared to another.

For pentodes, the figure of merit is transconductance (Gm). For pentodes, gain is pretty much Gm time load resistance.

So look for another pentode with a Gm similar to the 5879... at the same plate current. Cause Gm changes with plate current.

Title: Re: 5879 octal equivalent?
Post by: smackoj on March 10, 2013, 02:43:05 pm

<tubes are all octal except the 6J7 has 'grid cap'>  D-load

does that mean the tube has the small metal cap on top that the wire from the chassis attaches too?  are those always a 'grid' line going to the cap?

muhas gracias amigos.

 :icon_biggrin:

Title: Re: 5879 octal equivalent?
Post by: DummyLoad on March 10, 2013, 03:29:50 pm

Quote from: smackoj on March 10, 2013, 02:43:05 pm

<tubes are all octal except the 6J7 has 'grid cap'>  D-load

does that mean the tube has the small metal cap on top that the wire from the chassis attaches too?  are those always a 'grid' line going to the cap?

muhas gracias amigos.

 :icon_biggrin:

Si. In this case it is. Sometimes the cap is plate but mostly on power tubes. On preamp tubes it's a grid. Some older preamp tub es have a grid in base and a grid cap.

Title: Re: 5879 octal equivalent?
Post by: Backwoods Joe on March 11, 2013, 06:16:37 pm

DummyLoad, I've tried to find the cap that fits the 6J7 and all that i can find are made in China. Do you have a lead on some USA made caps. Also have you ever had issues with the caps coming off or getting loose?

Title: Re: 5879 octal equivalent?
Post by: DummyLoad on March 11, 2013, 10:48:06 pm

the pair i have i got at a ham swap meet. leeds radio 4 for a 7 bux.

http://leedsradio.com/parts-sockets.html (http://leedsradio.com/parts-sockets.html)

--pete