Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Zarrir on September 17, 2016, 12:15:23 am

Title: Upgrade from 18w to 36w Marshall Clone
Post by: Zarrir on September 17, 2016, 12:15:23 am
Hello there! I recently posted about chopping a tube amp project in order to obtain a power amp only layout. Now iīm curious to know what is the experts approach on how to extend a very well known project (like the Hoffman Stout bellow) by adding two more EL84s to double the wattage while keeping the basic tone. Anyone?
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: kagliostro on September 17, 2016, 06:14:35 am
I think you must consider a different PT and OT

the tone, to me, if you add one other pair of the same tubes will stay near the same

Franco


Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: Zarrir on September 17, 2016, 01:25:28 pm
Yep, definitely a AC30 type of transformers. But how about the schematics? Should i simply add the two new tubes in series with the other two? This is where my beginnerīs fears start.
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: sluckey on September 17, 2016, 01:46:49 pm
The output tubes will be parallel, not series. Look at Hoffman's AC-30 and just copy his schematic for the four output tubes. You will need a PT and OT suitable for the AC-30.
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: Zarrir on September 17, 2016, 03:03:02 pm
Awesome tip as usual Sluckey! Going there right now!
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: MakerDP on September 17, 2016, 07:13:19 pm
There are also 36-watt variants to be found on the 18watt.com forums.
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: labb on September 17, 2016, 10:18:54 pm
http://mhuss.com/18watt/schematics/36wTMB5.gif (http://mhuss.com/18watt/schematics/36wTMB5.gif)    Give this a go.
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: Zarrir on September 21, 2016, 08:39:18 pm
Super!! Is this one tested and confirmed, Labb?
Title: Re: Upgrade from 18w to 36w Marshall Clone
Post by: labb on September 21, 2016, 10:13:35 pm
should be. here is mhuss's site        http://mhuss.com/18watt/ (http://mhuss.com/18watt/)