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FDP Forum / Amp Mods, Repairs, and Projects / Lately I've been reading all sorts of opinions on tubes amps .


LA , Calif

I try my best
Oct 22nd, 2016 04:08 PM   Edit   Profile  

Even watched some YT videos. I can't really say why other than it's a distraction from having to put our cat to sleep and all this political horror.

Some many opinions on how to build a tube amp.

I come here to ask a few questions.

1) if an amp just has 2 6V6's and 2 12A-X and a rectifier tube does it really matter what gauge and type of wire you use for heaters? I know 50's fender used cloth 18ga and routed to the edge of the chassis and later in the BF era they still used cloth 18ga yet routed it above the tube sockets. I did the 50's type and it works fine yet seems to have a longer path /more wire.

On David Allen amps he used solid core 22ga and 20ga for the power tube heaters and 22ga for the pre and PI 12ax-7 PVC and builds great amps.

I've used 22ga tinned stranded wire for all the leads on my SF champ build and that same wire for most of my AA964 build I got from AES rated 600 volt 221F insulation ,and a few solid core RS copper wire that as still on the preamp tube , maybe 22ga 300 volt ,since I made changes it was all RS solid core at first.

I do have some tinned copper Belden 18ga black and white rated @ 1000 volt @ 176*F PVC.

I thought maybe I might re due the heaters above the tubes if there is an advantage and use the 20ga from AES for the 12ax-7. Both twist well and hold their shape well. I'm not sure how hot a chassis gets inside in reguards to using the Belden 176* F PVC. The Allen and Weber PT and OT use smaller maybe 20ga tinned stranded wire for all the secondary's.

Then there are the fender style octal sockets and both AES and Hoffman sell the same ceramic type to fit the 1 " chassis hole yet the way the socket holder is crimped to the socket there are 4 tags that hit the chassis before the mount tabs so if you tighten then to tight they crack or chip the ceramic . On my champ build I used small thick lock washers so the tags don't hit the chassis . I need to look at the AA964 build same sockets to see if I added washers later one as I did on the champ . I never cranked the bolts real tight on either but found out the hard way on the AA964 that I did crack the rect socket so I had to replace it. I know the old fender original sockets were a hard brown bakelight that did not have these 4 insane tags and fit flush ,I should have seen this and at least filed off the 4 crimped tangs you don't need them yet the ceramic still juts out farther than the hold down so you do need the tangs. I see the ones Allen Amps uses are ceramic but don't have the tangs, they just have different socket female types they are 2 pin contact rather than slit circle to grab the tube pins.

Since my AA964 build is so crowded I though I would either buy of make a filter cap cover and board like larger SF and BF use . I just need to remove the eyelet board to drill the 4 mount holes and this would get the 4 filter caps and 3 droppers out of inside the chassis. I can't use a cap can like many Princetons/later Champs used and they cost to much. If I tried I would need to make a new eyelet board or alter the one I have and I just bought new F&T caps to replace the old Sprague.

I have looked at some builds others have posted here and it seems the heater leads over the top is the choice.

Any thought's would be great . It's not that my AA964 build does not work and it's dead quiet and has held up , it's more I want to re due it for a project and don't have money to burn.

I did send a photo of it to David Allen and he said it looks great because I asked what sort of boards and chassis he has and he does have one the same size as the MM bass amp chassis I used yet his is now aluminum and he said I would need to file the front holes a bit so I can use the MM bass amp face plate . I sort of like steel better. I also don't need three 9 pin sockets his chassis has yet I do like the way the output jacks come off the rear rather than under like I did mine . I did mine this way because the chassis is the same one SF Champs used and went with the fuse holder under and the speak jacks under and the fact that MM bass amps did not have a speaker jack or fuse holder. It just seemed the logical choice at the time.

(This message was last edited by catnineblue at 06:16 PM, Oct 22nd, 2016)

Contributing Member


Christian Slater
Oct 22nd, 2016 10:49 PM   Edit   Profile  

The tube sockets don't have to be super tight. Snug them down and use high-temp thread lock on the fasteners.

Solid-core wire is best for the heater supply because it's stiff. You want as little movement of the wires as possible, because any movement translates to noise in the circuit.

Here's a pretty good primer on

heater supply wiring.

Contributing Member

New Jersey

I'm back with the otters again
Oct 28th, 2016 01:24 PM   Edit   Profile  

Ya know...
I don't like using solid core wire under any circumstances other than in my house. This is because I'm a little paranoid about the wire fracturing from fatigue. It all comes down to what ever you feel most comfortable using. If your application allows you to solder the wires in place and they will remain totally static throughout your build process without being stressed when you do your final assembly or replace components then solid wires are fine. They also can be bent and arranged in a permanent fashion and keep the bends for a boutique hyper tidy result. On the other hand, my focus on my amp builds is repair-ability and dependability. I want to be able to replace sockets and other components without risking over fatiguing the solid core at joints. Maybe removing a solid core wire from a terminal lug is easier sometimes??? I can't say that solid is better than stranded but stranded wire isn't as prone to fatigue fractures.

I like using cloth covered wire when I can because its so easy to deal with. Push back insulation totally avoids the potential to nick the conductor creating a potential weak point.

As far as sockets are concerned, the key would be the alloy composition of the connector pins -- try to get a specification -- good luck. It comes down to reputation of the manufacturer and anecdotal whispers of other techs. Hey, maybe one manufacturer has solder lugs that are easier to attach wires to. Easy is good if it results in more consistently tidy solder joints.

FDP Forum / Amp Mods, Repairs, and Projects / Lately I've been reading all sorts of opinions on tubes amps .

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