Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Shack on May 13, 2019, 04:43:25 pm

Title: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: Shack on May 13, 2019, 04:43:25 pm

Subject says it all.....the new Marshall  series and others are doing it.....some others use EL84 or 6V6.........I just want to know what they are doing to get the amps lower watts , and also how the builders make the 5 or 1 watt settings.....can anyone shed light on it for me?

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: shooter on May 13, 2019, 05:46:22 pm

I searched this string on web and got way more than I wanna read

Quote

variable power switching tube amps

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: kagliostro on May 13, 2019, 09:25:54 pm

Some amp use a VVR, other a control on the cathode of the PI, other has a lower voltage intake on the PS to have low B+, other has a lower power alternative set of the Power Tube, some has circuit able to go from PP to SE, may be also MV or PPIMV


Franco

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: PRR on May 13, 2019, 11:05:31 pm

EL34 and 6L6 are not so very different. It is no trick to build an amp which will take either (or both), no change.

If it is big bottles or peanut bottles, there are many ways.

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: kagliostro on May 14, 2019, 12:29:00 am

Look to the PI and PPIMV/MIX here

https://el34world.com/charts/Schematics/files/Egnater/Egnater_rebel_20.pdf (https://el34world.com/charts/Schematics/files/Egnater/Egnater_rebel_20.pdf)

Franco

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: d95err on May 14, 2019, 12:34:48 am

I think those 20W EL34 amps simply use a transformer with lower voltage.

For the 5W mode, they probably switch to single-ended operation.

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: JB on May 14, 2019, 12:43:05 am

The new Marshall’s are switching power transformer secondary taps.

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: kagliostro on May 14, 2019, 12:45:49 am

Traynor dark horse example that uses different tubes for Power section

(https://i.imgur.com/tSF4ib1.jpg)

and also look to this Ampmaker Kit for the B+ switch

(https://i.imgur.com/vhBNVd5.jpg)

Franco

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: d95err on May 14, 2019, 02:40:00 am

Quote from: JB on May 14, 2019, 12:43:05 am

The new Marshall’s are switching power transformer secondary taps.

Does that mean they run with very low preamp voltages (especially in the 5W mode)?

Or do they use a separate preamp winding?

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: kagliostro on May 14, 2019, 02:59:25 am

Here you can see how they do it on the Mesa Boogie Lonestar Special

Note the PS section and PA section

(https://i.imgur.com/JMcaPyW.jpg)

(https://i.imgur.com/up6e2rN.jpg)

(https://i.imgur.com/EACpdsu.jpg)

(https://i.imgur.com/7NnKpxz.jpg)

(https://i.imgur.com/EzjkfUs.jpg)

(https://i.imgur.com/w5z9SHG.jpg)

Franco

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: JB on May 14, 2019, 01:42:48 pm

Quote from: d95err on May 14, 2019, 02:40:00 am

Quote from: JB on May 14, 2019, 12:43:05 am

The new Marshall’s are switching power transformer secondary taps.

Does that mean they run with very low preamp voltages (especially in the 5W mode)?

Or do they use a separate preamp winding?

In the Superlead version they're running the preamp on typical Superlead voltages but the PI/PA are lowered in 5W mode.  It's cathode biased and they're running the EL34's at way less than in a real Superlead, even in 20W mode.

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: Shack on May 16, 2019, 05:51:01 pm

interesting.....I just see it is a big thing these days to use 30/10/1 watt amps, and wondered how we could accomplish that

Title: Re: 20 watt/5 watt amps with EL34 or 6L6, how are companies doing that?
Post by: Shack on May 16, 2019, 05:53:40 pm

I think that lower plate voltage gives you lower power with these tubes I belieave......and PP/SE or triode mode gets you lower.....but to design such amp has me boggled