Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: VintageRob on December 01, 2011, 05:39:15 pm
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Hi guys. Thought some of you might like to see my Deluxe Reverb build.
Although I have been involved in electronics all my life and even learnt some valve theory at school in the '70s this is the first amp build I have attempted. I studied many gutshots of vintage 60's DR's and basically copied the lead dress etc. from those (yay internet!)
I used ClassicTone transformers, F&T, Sozo and Mallory caps, and 1W carbon film resistors throughout.
I made a few mistakes along the way:
1. Destroyed a 1M volume pot by applying too much heat during soldering lug to the case (as I needed to replace it anyway I decided to install a switch pot so the bright cap can be switched in and out whilst retaining the original look).
2. Turned 6 feet of solid core heater wire into 6" of scrap by attempting to use an electric drill to make the twists nice and tight!
Other mods:
1. Unused AC outlet used as bias test points
2. Unused ground switch used to switch value of NFB resistor (will choose value once amp is up and running or may omit NFB altogether
3. I may also do the trem circuit removal mod if that proves to be useful, however getting the correct value pot that is switchable appears to be difficult.
Cabinet: As I dont' have access to any machine shop equipment I will probably have to forgo using finger joints to build the cabinet and go with butt joints reinforced with dowels. As it will be covered with tolex it won't be an issue.
While I wait for the remaining parts from Doug I will post a few pics of progress to date. If any of you experts can see any errors or have suggestions PLEASE let me know.
Cheers Rob
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290640.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290639.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290503.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290502.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290648.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290650.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290658.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290652.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290654.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290653.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290657.jpg)
(http://i294.photobucket.com/albums/mm105/vintagerob/P1290656.jpg)
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Looking good.
I'd suggest against grounding against pot bodies in the future, both for the reason you discovered (takes a bit of heat, huh!) and because integrating your tone and volume grounds into the preamp ground where they belong will likely give you less likely-hood of ground hum
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looks very nice. it's like opening an old fender and discovering it's still new :icon_biggrin:
oh and you didn't use those dreadful carbon comps to make it look even more vintage. good job!
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Nice work! First build, really??
You actually used the AC socket as the bias test point fixture. Creative thinking.... I like that.
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Very nice build! Like in the good ol'time!!
It seems you followed the classic grounding scheme, but pls never ever use pots as a ground bus :wink:.
I would be proud to build such a nice amp.
Best regards,
Danskman
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Two thumbs up from me :thumbsup: :thumbsup:
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I am surprised at the lack of love for grounding to the back of the pots. Doug suggests it, I usually do it. http://www.el34world.com/charts/grounds.htm (http://www.el34world.com/charts/grounds.htm)
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Nice! Looks entirely stellar to me. I assume you will get the heater wiring to the first two preamp tubes, otherwise you might have an issue with low volume. :icon_biggrin:
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I am surprised at the lack of love for grounding to the back of the pots. Doug suggests it, I usually do it. http://www.el34world.com/charts/grounds.htm (http://www.el34world.com/charts/grounds.htm)
I do it Doug's way too 90% of the time and all the amps have been free of noise associated with poor ground scheme. Though every time the topic of ground schemes comes up, the usual civility of this forum begins to degrade.
It's the hotbutton issue of the tube electronics world. :icon_biggrin:
j.
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Nice! Looks entirely stellar to me. I assume you will get the heater wiring to the first two preamp tubes, otherwise you might have an issue with low volume. :icon_biggrin:
Thanks for all the nice comments guys. Yeah as I said I ruined most of the heater wire that I had after the 'electric drill incident' :cussing: . Placed an order with Doug yesterday for the remaining parts need to complete the build then I will start thinking about a cabinet and speaker.
Thinking about a WGS speaker maybe a G12C or ET-65 if anyone has any experience of suggestions........
Cheers
Rob
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:bravo1:
Kagliostro
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Beautiful amp and nice work. :icon_biggrin:
Speakers...... humm.. how about an Eminence Legend 125. Or a Weber 12F150. The WGS option isn't a bad choice either. One could also consider the Alnico options. Depends on your type of sound and playing really.
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I am surprised at the lack of love for grounding to the back of the pots. Doug suggests it, I usually do it. http://www.el34world.com/charts/grounds.htm (http://www.el34world.com/charts/grounds.htm)
I do it Doug's way too 90% of the time and all the amps have been free of noise associated with poor ground scheme. Though every time the topic of ground schemes comes up, the usual civility of this forum begins to degrade.
It's the hotbutton issue of the tube electronics world. :icon_biggrin:
j.
I find it relatively easy to solder to the pot case if you remove the finish from the case with a dremel or a file prior to soldering. It removes the finish that impairs the solder adhesion.
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Very nice build! Like in the good ol'time!!
It seems you followed the classic grounding scheme, but pls never ever use pots as a ground bus :wink:.
I would be proud to build such a nice amp.
Best regards,
Danskman
I have used the pots for grounding and it works fine if you sand the backs. Usually I bend all the lugs that ground, forward and then 90 twist. Do this before adding any heat as they become brittle and can break after heat. Then I run bare copper wire from the inside of romex through the bent out lugs and make a loop on the end to bolt it to the chassis. It solders nicely. Then I have a ground strip for anything else I need to ground. Like grounding coming off the board, I run it to the chassis bottom and to the corner and up and bend it out to the copper rail. Makes for a nice clean look and keeps all my grounds straight and out of the way.