Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jordan86 on October 03, 2022, 03:56:39 pm

Title: 5V4 with 6L6 in push pull
Post by: jordan86 on October 03, 2022, 03:56:39 pm

Can a 5V4 power a 2x6L6 power amp section? Would be running about 330v on the plates. What other info/measurements might I need to calculate that?

Title: Re: 5V4 with 6L6 in push pull
Post by: shooter on October 03, 2022, 04:07:32 pm

here's the datasheet
5V4G (pocnet.net) (https://frank.pocnet.net/sheets/049/5/5V4G.pdf)


looks like it can handle 175mA into a cap or choke
I would expect a pair of 6L6's to draw around 120mA give or take a country mile, so looks like it should be good

Title: Re: 5V4 with 6L6 in push pull
Post by: PRR on October 03, 2022, 08:35:00 pm

Early Fender Bassman with 6L6-like 5881s sucked 250mA.

You really need to define your "2x6L6 power amp".

Title: Re: 5V4 with 6L6 in push pull
Post by: jordan86 on October 03, 2022, 08:48:42 pm

Yeah I am not sure how to calculate how close I am getting to the 5V4 limit of 175ma. What else should I factor in besides the plate current of the two 6L6’s?

Title: Re: 5V4 with 6L6 in push pull
Post by: shooter on October 04, 2022, 04:27:22 am

Quote

What else should I factor in besides the plate current of the two 6L6’s?

cathode current is a better measure of the tube since it includes both plate and G2 currents


you can get a sorta answer knowing plate voltage and OT primary impendence
I = E/R
so 330vdc / 5000(grabbed a number from air) = 66mA  +/- a country mile
since 66mA is at idle, no signal, expect it could swing to double for brief hard picking

Title: Re: 5V4 with 6L6 in push pull
Post by: pdf64 on October 04, 2022, 05:03:59 am

The valves can’t draw HT current from thin air, it has to come via the OT primary impedance. Cathode or fixed bias is also a significant thing, as cathode bias will reduce the HT voltage available for the anodes to swing.

Title: Re: 5V4 with 6L6 in push pull
Post by: PRR on October 04, 2022, 02:59:14 pm

Have you looked at the 6L6 (also 7027) datasheets for a condition like you plan to run?

Remember that push-pull is different from SE.

Title: Re: 5V4 with 6L6 in push pull
Post by: valvetones on October 16, 2022, 06:10:06 pm

FWIW my vibroverb is running a NOS RCA 5V4G and the tubes are running at 40mA each + the screen current + the current from 6 preamp tubes.

Been running fine for over a year now, and in my opinion it makes the amp sound better than a NOS GZ34.

It drops a tiny bit more voltage.

I love the 5V4 and in my experience it works great with 2 6L6GC and a ton of preamp tubes.

Title: Re: 5V4 with 6L6 in push pull
Post by: DummyLoad on October 17, 2022, 01:05:36 pm

Not really for push-pull making over 25-30W. See attached conditions, Yes, you can get it to work, however, in some conditions, you'd definitely be pushing over the tubes limits. Not something that I'd personally be comfortable doing with a 40-50W design. Just my 2cents.


--Pete

Title: Re: 5V4 with 6L6 in push pull
Post by: shooter on October 17, 2022, 01:19:34 pm

never overlook the power of really efficient speakers in large bunches for making a 25W amp SOUND like it's 50W to everyone on the room
 :icon_biggrin: