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Thread: British 5E3 in a Vox cabinet

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    British 5E3 in a Vox cabinet

    Hi to everyone. Have really enjoyed reading posts on these forums for some time, especially on the legendary 5E3. A unique amp with a unique sound. I have been working on my own version of this amp for several months now so thought I should share it with other knowledgeable dudes! I have chosen to build my british 5E3 in an old Vox transistor amp cabinet (Escort lead 50 I think). I think it has a nice vintage look to it. I'm afraid it has a solid state rectifier at the mo as I couldn't find a suitable type to power a 5Y3 tube. I dont think the sound suffers much because of this but purists might disagree! It uses PM 6V6's (Chinese I think) at the mo but will be trying others in future. The speaker is a good old reliable Celestion which adds to the british flavour I think. The chassis is the original steel job that came with the amp but suitably bent and drilled to take the tubes, trafos etc. Please check out the pics. It is still work in progress so will update on future activity. Thanks.Click image for larger version. 

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    Old Timer soundguruman's Avatar
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    I am building Marshall 2204 in a Hot Rod Deluxe Cab, I had the same inspirations.

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    Last edited by soundguruman; 05-22-2014 at 09:10 PM.

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    Bent Member Chuck H's Avatar
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    Seems like a great re use of an otherwise useless cabinet. And very nicely done too. I love those large pad eyelets.

    I can think of two solutions for your rectifier issue if you're interested in adding that element to the amp. One is to use a separate 5V transformer. Not too expensive and you certainly have room. The other is to use a big resistor just after the diode rectifier to simulate the power supply sag of a rectifier tube. Something like 150R to 220R at 50W should do it. If your Vp is hi-ish for a 5E3 either of these solutions could get you closer to the vintage spec (and sound) in that regard.

    Welcome to the forum.

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    Quote Originally Posted by Chuck H View Post
    Seems like a great re use of an otherwise useless cabinet. And very nicely done too. I love those large pad eyelets.

    I can think of two solutions for your rectifier issue if you're interested in adding that element to the amp. One is to use a separate 5V transformer. Not too expensive and you certainly have room. The other is to use a big resistor just after the diode rectifier to simulate the power supply sag of a rectifier tube. Something like 150R to 220R at 50W should do it. If your Vp is hi-ish for a 5E3 either of these solutions could get you closer to the vintage spec (and sound) in that regard.

    Welcome to the forum.
    Thanks very much for that and all other replies so far. As regards the fitting of an extra 5V trafo, I think I would rather wait until a suitable one turns up before taking the 5Y3 plunge as it were. In the meantime, I am quite happy making little tweaks to try and improve the core sound. I have the wrong type pots fitted at the mo (linear type) and these need swapping for log in order to get a more gradual change in loudness on both channels. The control panel also needs labelling. One thing I have noted which was a bit of a puzzle is the rather low B+ volts from the SS rectifier. The power trafo secondary supplies about 248V ac and after rectifying I measure 315V dc at the first smoothing cap. This results in about 310V dc at the 6V6 anodes(plates). Is this about right or is something wrong and is 310V high enough for a 5E3 output stage? Any comments welcome.

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    Does it SOUND good to YOU? Sure, it might be a bit low for a clone, but, who do you wanna sound like, you or everyone else? As long as it doesn't blow up or sound bad to YOU, anything goes in my book! I'm not trying to dissuade you from trying to get closer or anything, and always use tweaking as a learning exercise, but SOUND comes first in my book.

    You might be the only person running 6V6s (non GTA) within their maximum ratings. So that might be the only accurate representation of how they SHOULD sound! (Tongue in cheek there, no rants about exceeding values, etc. I do it all the time too...) Some NOS 6V6G or GT should last forever in there.

    Justin

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    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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    A nice looking amp. Where did you get the tag board from?

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    Bent Member Chuck H's Avatar
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    I looked at your pics and I think I see what looks like a "rectifier" part, rather than the more typical rectifier found in guitar amps which would be constructed from individual diodes. So I can't tell if your rectifier is a full wave or bridge type. I'll guess it's a full wave by your voltages. You can probably gain about 25V by changing to a bridge rectifier. At these lower voltages the amp might become too loose and lack dynamics if you added power supply sag, so I'd skip that. IMHO 6V6's sound especially good below 350Vp. If you like the tone don't change the transformer. Maybe experiment with the rectifier just because you can without much trouble.

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    Quote Originally Posted by Chuck H View Post
    I looked at your pics and I think I see what looks like a "rectifier" part, rather than the more typical rectifier found in guitar amps which would be constructed from individual diodes. So I can't tell if your rectifier is a full wave or bridge type. I'll guess it's a full wave by your voltages. You can probably gain about 25V by changing to a bridge rectifier. At these lower voltages the amp might become too loose and lack dynamics if you added power supply sag, so I'd skip that. IMHO 6V6's sound especially good below 350Vp. If you like the tone don't change the transformer. Maybe experiment with the rectifier just because you can without much trouble.
    I seem to have sparked a bit more interest after my comments about the low B+ supply. First off, regarding the rectifier, it is in fact a bridge in there already. Quite small I know but seems to do the job. I am quite pleased with the sound at this time so probably would not be too wise to make drastic changes. One tweek which did improve things was changing the first coupling cap on the bright channel for a 0.022uF. I used a nice NOS Wima in there and it has certainly tamed much of the boomy bass which the 5E3 is known to suffer from. I have tried to use vintage parts where I can for this build so its vintage caps and carbon comp resistors all the way! A bit of extra smoothing in the power supply will be coming soon as I've only got 10uF in the main B+ position at the mo.
    Regarding the tag board, thanks for the compliment but I could not say where it comes from. It was just one I had in the spares box which I had picked up from somewhere.

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    Bent Member Chuck H's Avatar
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    The lower volts aren't a problem for tone as long as the rest of the circuit is tweaked around that aspect of the circuit. Decreasing the value of the first filter was a good start. The lower volts will likely present less apparent treble dynamics, making the amp seem dull. Add farty bass and it's a problem. Try decreasing the value of the HV rail preamp resistor (schematic shows 22k). Increasing preamp volts closer (or even above) stock specs can liven things up if you feel the need. And do increase the main power supply filter/reservoir cap. Go a little higher than stock, like 68uf or even 100uf. This will give the bottom end a little more clarity and authority.

    Just some useful stuff when an amp has low-ish B+. At your discretion of course.

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    Just a quick update. Thanks for all the replies so far. I have been working on the amp this week. New work done is
    a)Labels for control panel (good old dymo tape strikes again!) see attached pic.
    b)Extra filtering for main B+ supply - now 20uF.
    c)Volume pots changed to log type - now improved control of output sound.
    I must admit I am surprised at how loud the amp is when cranked up - it really shakes the windows at its meagre 12 watts or whatever! I am pretty happy with it for now anyway so will probably leave it over the summer and then try some more tweaks later.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Senior Member CharlieP's Avatar
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    Quote Originally Posted by soundguruman View Post
    I am building Marshall 2204 in a Hot Rod Deluxe Cab, I had the same inspirations.

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    Good way to fix a HRDx!

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    CharlieP
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