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New amp project
http://rivercityamps.com/electraforum/viewtopic.php?f=40&t=5047		 Page 1 of 2
Author:  sandspur [ Sat Oct 23, 2010 4:01 pm ]
Post subject:  New amp project
Well, I not only have the archtop project going but an amp project as well. As some of you may remember from some another thread, I am planning to take an old 30's - 40's radio and replace the guts with a guitar amp. I took delivery of the "cabinet" today. I have posted pictures below.

This project will take quite a bit longer than the archtop project I have going, due to the sourcing of parts and most importantly - money. I'm planning on funding this project with the sale of some electronics I have around the house and no longer need.

For those who didn't see my previous posts, my plan is to take this 1936 Philco Model 660 and replace the guts with those of a Marshall 18W. I want to use the existing knobs and have the dial light up when you turn it on. I don't want any outward sign to proclaim that this is a guitar amp. This will mean that the jacks will need to be on the back. One of the reasons my wife has gone along with this (finally a project I don't need to hide and "spring" on her) is that this will look good in the house.

Anyway, first things first. I picked up the old radio today. I found it on Craigslist and drove about 70 miles away to pick it up. It was $40 and is in nice shape for a 74 year old. A little stain pen and Howard's restorer will do the trick.

Image

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Author:  Thorny [ Sun Oct 24, 2010 3:41 pm ]
Post subject:  Re: New amp project
Nice project! That should work well. I hope you can fit everything and still use the same knobs and all. Mine had LONG shafts and odd shapes for the radio knobs to push on. Not normal amp values, and normal pots woudn't work. I think you have the best idea though - make it look original as possible but function like an amp. Don't be surprised if you wind up having to do a bit of restructuring too as the speaker was very light weight compared to guitar amp speakers, so the cabinet area was not as sturdy as an amp cab.

Good Luck!
Author:  sandspur [ Sun Oct 31, 2010 11:43 am ]
Post subject:  Re: New amp project
Well I used some Howard's Restor-a-Finish and cleaned the radio up this weekend. It really looks nice now and the scratches and marks are gone. You can see below.

Thorny, you were right about the long shafts. I saw your comment and looked at the radio today. After much searching I have found the answer to this issue as well. They "extensions" are cheap and look like they'll do the trick. The site below is obviously for parts on these old radios.

One other thing of notice is the grill cloth on this old radio. I don't know if it is stock or not, but the pictures look odd as it has gold thread in no particular pattern run through the cloth. At first I thought it was just dirty.

Extensions (at bottom of page):
http://www.radiodaze.com/potentiometers.htm

Clean Radio:
Image
Author:  proendorser [ Sun Oct 31, 2010 4:12 pm ]
Post subject:  Re: New amp project
Sweet! How much does that behemoth weigh?? Are you going to be able to slide a 12" in there? I have a feeling the cabinet may rattle a bit with a 18watt Marshall in it. Thanks for photo documenting it, and looking forward to seeing it progress, Mike.
Author:  mortarman120gang11c [ Sun Oct 31, 2010 5:41 pm ]
Post subject:  Re: New amp project
This will be a rockin machine when complete. I like it look great. :up:
Author:  sandspur [ Sun Oct 31, 2010 6:40 pm ]
Post subject:  Re: New amp project
The weight is about 60+ pounds. It does currently have a 10 tube radio in it! You should see the size of the transformers. I'm going to have to re-purpose them if I can't find some old radio enthusiast who wants it. It currently has an 11" speaker (odd size right?) in it. I've measured and there is plenty of room for a 12" with a new baffle board.

I don't think vibration is going to be an issue. This is a VERY well made cabinet. I will do some bracing though just in case. I don't know how much of the back I want to cover though as I don't want to increase the bass response too much.

I don't know if I put this in an earlier post, but this thing sold for $187 in 1936, in the middle of the Great Depression.This equates to $2618 today. I think one of the strengths of the design is that the tube radio was on top weighing the cabinet down. Now this wouldn't be good for something you were dragging around to clubs constantly as it is bulky, but for my purposes it is great.

My amp is going to employ VVR. I need to be able to get some of that cranked sound at lower volumes in the house. I know it isn't going to be exactly the same, but I can't dime it all the time with the wife and kids around. It should be fun and I can't wait. I'm realistic though and know this will likely be around New Years at the earliest before I'm done.

Oh one thing about the choice of amp. I did say an 18 watt Marshall, but this will be of the lite variety, no trem channel on this one. There simply aren't enough knobs on the front for that.
Author:  slmguy [ Fri Nov 05, 2010 7:37 pm ]
Post subject:  Re: New amp project
Very nice! Great job and good luck.
Author:  0gre64 [ Wed Nov 10, 2010 8:02 am ]
Post subject:  Re: New amp project
What a great idea!

The finished product should be really cool.

I'm looking forward to it.
Author:  sandspur [ Wed Nov 10, 2010 8:48 am ]
Post subject:  Re: New amp project
I'm currently in the process of wiring the amp. I should have this done tomorrow and then it is time to work on the chassis. I will put some pics up when I finish the chassis. I have decided to partially close the back. That way I can easily remove it if needed.
Author:  Ldog [ Wed Nov 10, 2010 12:08 pm ]
Post subject:  Re: New amp project
I was looking around in a reclaimed material store and saw a cabinet similar to the one shown. It brought back the memory that there was one being reused as an amp. This one looked like it could hold 2 12" speakers. It too would be quite a conversation piece. Too bad I am electronically challenged.
Author:  sandspur [ Wed Nov 10, 2010 12:32 pm ]
Post subject:  Re: New amp project
You could always purchase an amp head and use it in this type of cabinet. I "think" I could fit 2 12" speakers but only want one in here. The head will have the ability to plug in to a separate cab if needed.
Author:  0gre64 [ Thu Nov 11, 2010 6:57 am ]
Post subject:  Re: New amp project
Too bad it's not deeper. It would make a great Leslie cabinet.
Author:  sandspur [ Thu Nov 11, 2010 7:01 am ]
Post subject:  Re: New amp project
I see Leslie cabinets range from 16" to 20+". It would be close on the smaller end but I bet it would fit depth wise. I think the width would be hard though. Still, there are larger antique radios than this one and it's a good idea.
Author:  sandspur [ Fri Nov 12, 2010 8:17 am ]
Post subject:  Re: New amp project
I received my speaker today and will work on the baffle this weekend. I took a closer look and noticed that they angled the existing baffle :wink: so this is one less thing I will need to do. Once I finish the baffle with the new speaker installed, I'll put up a picture.

By the way, the speaker I went with is a Mojotone British Series BV-30H. I haven't used this speaker before but have read many good things about it, especially in combination with a Marshall 18 watt. It is a Celestion copy rated at 30 watts.

I've also put together most of the amp, but still need to punch some more holes in the chassis. I'm contemplating putting the input jacks in the front of the chassis like normal and running "extensions" to the back of the old radio. This will allow me to remove the amp and repurpose it as a "normal" amp head in the future. I just don't like the idea of extensions.
Author:  Thorny [ Fri Nov 12, 2010 9:14 am ]
Post subject:  Re: New amp project
I have used that speaker before and it is an excellent speaker for the money.
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