Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Oddvar on August 25, 2018, 07:34:22 am

Title: Dumble building
Post by: Oddvar on August 25, 2018, 07:34:22 am

Hi.  I am about to start building a Dumble type amp, and I was wondering if anyone here has some advice as to what transformer would be best suited?  It's 100w with 4 El34 tubes.

The build also has a transformer called Amigo, see pic, and I am a bit uncertain of what kind of transformer that is?  I need it to be 230v.

Title: Re: Dumble building
Post by: sluckey on August 25, 2018, 08:35:09 am

The transformer information is on the schematic. The PT is a Pacific 1052 TF130. It develops a B+ of 465VDC, has enough filament current for four EL34s and has a separate bias winding suitable for EL34s.

The Amigo is just a 12.6VAC filament transformer used to develop 12VDC to operate the relays.

Title: Re: Dumble building
Post by: Oddvar on August 25, 2018, 10:42:14 am

Thanks again Sluckey.

Title: Re: Dumble building
Post by: sluckey on August 25, 2018, 04:41:29 pm

You may be interested in the relay and relay power supply board that Hoffman sells. They are cheap and easy to use. The relays operate on 5 volts and can be supplied from the existing power transformer filament winding, thus eliminating the need for a separate "Amigo" transformer.

Title: Re: Dumble building
Post by: tubenit on August 25, 2018, 05:13:14 pm

Quote

You may be interested in the relay and relay power supply board that Hoffman sells. They are cheap and easy to use.

+1 !     

I think these relays are great and there is an abundance of information on using them (with pictures, schematics, layouts, etc.)  here:  https://el34world.com/Forum/index.php?topic=14348.0

Title: Re: Dumble building
Post by: Oddvar on August 26, 2018, 04:04:39 am

That was interesting.  This is my first build with these, so you think the Hoffman boards would be useful her? See pics.

Title: Re: Dumble building
Post by: sluckey on August 26, 2018, 04:32:19 am

Hoffman's relays will operate exactly the same as those relays. The boards don't look the same so you cannot use that relay board layout. You must be able to read and understand the schematic (which is a good idea for an amp of this complexity).

Title: Re: Dumble building
Post by: Oddvar on August 26, 2018, 05:41:31 am

You are right about the schematic reading off course, but I have a quite detailed layout for it, including explanatory  additional PDFs, so, with the clarifications on the filament transformer and the relays I think it will be doable.

Title: Re: Dumble building
Post by: Joel on August 28, 2018, 12:00:45 am

Hello Oddvar,

Would you mind posting your reference material?  I'm collecting info on D-style amps at the moment.  Thanks.

Title: Re: Dumble building
Post by: sluckey on August 28, 2018, 06:34:07 am

The schematic and layout are available at The Amp Garage in the Dumble Files forum.

Title: Re: Dumble building
Post by: Mike_J on August 28, 2018, 04:04:02 pm

I built the 124, HRM which is similar to 124 but with el34s instead of the 6L6s in the 124 and the Mike Hartman version of the Steel String Singer. Don't know how many amps you have constructed. If not many I would start out building the 124 because there are pictures that you can use so your wiring won't cause any problems for you. Like sluckey said I got all this information from the Garage Forum.