Navy Radio Tech Vet - Got Back into Guitar a Year Ago - Looking To Build 1st Amp

[Khristophorous]

Hi everyone. I'm new here, obviously. I got back into playing last year and its been like a reawakening. I'm disabled so I'm at home all the time. I didn't have any purpose or direction but on a whim I started playing again and it has brought me back from an early grave I think. For some reason I got it in my head that I *need* a tube amp and after guitar it has become something of an obsession this past month or so. However I can not afford to buy one outright. I figured given my schooling in electronics that I could save some money if I built it myself - plus it would be fun. Even the kits are pricey though so I thought that maybe I could source the parts myself over time, maybe even pick up some used parts. That is what brought me here. A lot of my internet wandering on the topic brought me here or DIYAudio again and again but the latter seemed more geared towards hifi rather than guitar amps. So I am here to learn from people who have made this sort of thing their main hobby. I hope I am in the right place. 

[EL34]

Welcome to the Hoffman Amps forum

There are many different boards on this forum for different topics.

The Tube Amp Building - Tweaks - Repairs board is where you can post amp questions.

That board is listed here.
https://el34world.com/Forum/index.php?board=13.0

Thanks,
Doug Hoffman

[shooter]

welcome aboard, petty officer dave here, sometimes, mostly....  you'll be ahead of the curve if you spend some quality time reading over active posts, past posts, achieved favorites as you refine "the amp in your head" to the realities of life and the fails n successes of those that sailed before you.   

[Khristophorous]

The forum that EL34 linked to above - is that where I can say "this is what I have in mind" and get some feedback? I'm not new to electronics by any stretch, but Ive never built anything from scratch before. Most of my real world experience after the Navy is mostly in TV repair. I was lucky enough to get into it before the switch to flat panels. All that being said I'm still not sure where to actually start. I know what tube and what configuration and a few other things I want in it but I'm not looking to design anything from the ground up. Ive already made the mistake of buying the wrong amp for restoration - its just not a good candidate to put the money into and still not have what I want. So I would like to have a design nailed before I start buying parts. 

[shooter]

is that where I can say "this is what I have in mind" and get some feedback


Yep

its just not a good candidate to put the money into

if you still have it, the main pieces, PT (power transformer) OT (output transformer), tubes, chassis, those are the 90% "cost parts" that are in virtually every tube amp, weather it sounds good or not.  It's also the best way to "re-voice" an amp to your ear.

[acheld]

Welcome aboard! 

I think a good place to start is to look at the "Project Links" located here:  https://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&thispage=PartsListIndex.htm&ORDER_ID=!ORDERID!.   These are all proven amp designs, and many of us are very familiar with them and can provide advice when needed.

These are NOT kits.   You do have to source your cabinet, chassis, speakers, etc.   Doug Hoffman, the sponsor of this website, has available all of the electric components in his store -- the parts list is to the left of the project details (and there is also a BOM within the project link itself).

This may help, or not, but you are in the right place for guitar amps.

[fdesalvo]

Thank you for your service and welcome aboard!

[Lectroid]

@Khristophorous,

Thank you for your service.  For my money, this is the best place to get good advice.  Some other sites I can recommend if you haven't found them already:

SchematicHeaven.com: vintage Fender, Marshall, Vox, Gibson, etc., etc, schematics. 
Also, a big schematics library is here (on the Hoffman Amps side.)

Valvewizard.uk is a great resource from a tube amp author, covers tube amp design concepts.

Other books? Richard Kuehnel and Bob Megantz are worth reading.  Megantz is more accessible, Kuehnel shows more math. YMMV.  Kuehnel has a site of helpful tube desigbn calculators at ampbooks.com.
 
Uncle Doug has a YouTube channel with more than a hundred well-done subject videos (20 min. to 1:30 long) on any tube-amp topic you can imagine. Very accessible information.

Rob Robinette's site is full of good information, too.  A little Fender-centric but lots of basic information and advice about vintage amps.

Definitely think about repurposing your donor amp; it might be an ideal first project.  Even 60 year old transformers can still be perfectly good.  (Hint: Uncle Doug has a video explaining how to test them.) 

And always remember to post a schematic with your question. Search for a thread discussing schematic drawing apps; I've see a couple here at least.  Ditto for more book suggestions.

Good luck, and welcome

[Khristophorous]

To Shooter and Lectroid - that "not a good candidate" is a Filmosound 185 (Part # 05311) - so there is no PT, as I'm sure you already know. However since I made that comment I think I have found a way to use most of it. I am going to rebuild it using this Danelectro Leader schematic as my general road map. I found a PT that will provide the needed AC for a 25Z6 to produce the HV and it also has a 6.3v winding for a 12AX(Y)7 preamp and 6SN7 PI. I'll be sticking with the 25L6 PP so I can reuse the OT and I found another smaller PT to provide the heater voltages for those and the 25Z6. Both of these PT are Antek. I am still learning so that is my general idea as of now and is of course subject to change. If need be I'll stick with the preamp and PI shown in the schematic but the transformers I found should still work. I have a 5E3 kit to assemble before I get into that though and I still have a lot relearning to do before I proceed with even that.

[DummyLoad]

In that schema, Lol @ copywrite.

--Pete