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Oct 13, 2013 23:18:35 GMT
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 DSCF0704 by scaryoldcortina, on Flickr I've had this empty speaker cabinet in the garage for a while, and I thought it would be cool to mount an amp inside it. Not just any old amplifier but a proper valve amp. I looked at kits and thought about modifying something to suit but didnt get much further really. It isn't very big, I need a chassis that will fit in a 10" x 5" footprint.  DSCF0708 by scaryoldcortina, on Flickr I did collect some broken rubbish - a couple of 1950s/60s chassis, one transformerless "hot chassis" radio and the remains of a hifi amp with no valves in it. Unfortunatly I can't use the valves in the radio chassis as they are designed for a serial heater chain and the mains transformer from the other board is a 6.3v parallel heater type. I'm not prepared to build a transformerless amp to take advantage of the valves because that would entail connecting my guitar ground to the neutral side of the supply and I'm not that brave (*it isn't a good idea, really... possible exposure to mains if something else on the same ring goes wrong, and god help you if someone miswired a plug or extension cord!) Anyway, I bought a couple of valves on ebay, an ECC83 twin triode and an EL84 power tetrode. Between the two chassis and my component bag have the rest of the needed bits.  DSCF0711 by scaryoldcortina, on Flickr Can't buy or find a chassis the right size? When has that ever been a problem for me?  DSCF0712 by scaryoldcortina, on Flickr Holes cut for components and wires. I think that was the easiest bit, lol.  DSCF0719 by scaryoldcortina, on Flickr Took it home to wire up. Here, I'm about to install a 50/50uF 400v filter cap that is older than I am.  DSCF0720 by scaryoldcortina, on Flickr Other than the HT fuse and the dual pole mains switch, I'm wiring this to 1960s standards, I even found some red/black/green mains flex (PVC coated not fabric obv..)  DSCF0722 by scaryoldcortina, on Flickr I got this small tagboard and the two large carbon comp resistors from the radio chassis. It's almost ready to install here.  DSCF0723 by scaryoldcortina, on Flickr Almost done. PTP FTW!  DSCF0726 by scaryoldcortina, on Flickr Looks like this in the cabinet. Speaker was found in another (not as nice, and broken) cabinet.  DSCF0742 by scaryoldcortina, on Flickr Completed wiring. Works nicely too! The hum at the start of the video is because I forgot to tie the heater supply to ground. It's quiet now.  DSCF0745 by scaryoldcortina, on Flickr And here's my circuit diagram. |
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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Oct 13, 2013 23:26:08 GMT
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There's just no end to your talents  |
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Oct 14, 2013 14:58:56 GMT
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 DSCF0748 by scaryoldcortina, on Flickr Today I added a stereo jack socket "line in" to the amp - I put a 1k resistor on each of the stereo inputs then commoned them and ran a shielded wire to the input side of the volume control. This bypasses the first gain stage and gives a cleaner output than the instrument jack. The speaker jack disconnects the internal speaker in case I fancy running it through a 4x12 or something ;D  DSCF0749 by scaryoldcortina, on Flickr All that remains to do now is to tidy up and refinish the cabinet and it won't look out of place in the front room. |
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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Oct 14, 2013 21:32:59 GMT
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Loving the patina on that! More pleasing on the eye than a black box! I had a similar idea for an old Ferranti valve radio. I didn't go as far as a valve amp. Just transplanted the innards of an old 5w practice amp into it. Kept the old Bakelite on/off knob as I wanted it to look unmodified. The illuminated sliding tuning dials were kept too. The amp controls are on the back so it looks normal from the front.    I've spent many hours trying different guitars through it and the old case gives it a lovely sound. Admittedly, I've no experience of valves etc and was warned that you can get a savage shock off some of these old radios etc so I've shied away from meddling with them. |
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Oct 14, 2013 22:02:34 GMT
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The main risk with old radios and other valve gear is from the mains, followed by the smoothing capacitors (which can give you one hell of a whack) - once you have learnt a few simple safety precautions it's a load of fun!
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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Oct 15, 2013 11:52:38 GMT
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Great to see you out n about again creating stuff Andy.
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bstardchild
Club Retro Rides Member
Posts: 14,965
Club RR Member Number: 71
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Oct 15, 2013 20:54:01 GMT
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I haven't a clue what you are on about but I like what you started with and like what you ended up with so thanks for sharing.....
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Oct 16, 2013 22:55:17 GMT
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I haven't a clue what you are on about but I like what you started with and like what you ended up with so thanks for sharing..... It isn't the first time that's happened, is it?  Took it to practice tonight, it's surprisingly loud even on the 67 year old internal speaker. I think I might be fitting a triode/pentode switch to the power valve sometime soon. |
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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bstardchild
Club Retro Rides Member
Posts: 14,965
Club RR Member Number: 71
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Oct 16, 2013 22:59:35 GMT
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I haven't a clue what you are on about but I like what you started with and like what you ended up with so thanks for sharing..... It isn't the first time that's happened, is it? Err probably not but hey ho Took it to practice tonight, it's surprisingly loud even on the 67 year old internal speaker. I think I might be fitting a triode/pentode switch to the power valve sometime soon. Lost me after speaker  |
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Oct 17, 2013 10:18:30 GMT
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I meant "not the first time I've built something interesting out of 1950s scrap" rather than you not having a clue what I'm on about....
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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bstardchild
Club Retro Rides Member
Posts: 14,965
Club RR Member Number: 71
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Oct 17, 2013 10:21:29 GMT
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I meant "not the first time I've built something interesting out of 1950s scrap" rather than you not having a clue what I'm on about.... I knew what you meant but it was more fun to pretend I didn't  |
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Oct 17, 2013 20:10:08 GMT
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I knew you knew... I've come up with another circuit! I think I can build an amp with only one valve and a handful of other components. Might be my next project. Is there any interest in me showing some previous valve based messing around? I modified a marshall recently, and have pics. |
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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Oct 31, 2013 21:27:36 GMT
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 Hehehehehehehehehe! Look what I just won on ebay (for spares or not working) |
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To get a standard A40 this low, you'd have to dig a hole to put it in |
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I like valves. |
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jonw
Part of things
Can open a Mouse with a File
Posts: 768
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Love this!!! Valve amps and radios are the way to go. Love listning to mine.
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Suzuki SV650R The good
Triumph T20 The Bad
BMW G650GS The Ugly
Matchless G12CSR The Smokey
Toyota Hybrid One pint or Two?
Ingredients of this post
Spam
Drunken Rambling of author
Bad spelling
Drunken ramblings of inner voices
Occasional pointless comments
Vile beef trimming they won't even use in stock cubes
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does anyone else think toaster? Now you mention it, I won't be able to use it without feeling hungry! That would be a simply brilliant conversion! I've no idea how to go about it though! :-) |
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