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Thread: Tube amp build (s)

  1. #1
    Mentor JohnH's Avatar
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    Tube amp build (s)

    As doc pointed out that there is actually an amplifier section on this forum I thought I should start a build thread in the right place!

    First attempt at a tube amp build, but I'm assuming it won't be my last.

    The build is a 5E3, using mojotone wiring layout and instructions.

    The caps arrived yesterday, and I have resistors and a chassis in the post. I haven't ordered tubes, tube sockets or input jacks/misc hardware yet because I have to look through my stash to see what I already have - I definitely have 9 pin shields and sockets and a new 12AX7, and am pretty sure I have a 12AY7 too.

    I thought I'd try to keep track of the cost, just out of interest more than anything. I don't think any of us take up DIY because we are trying to save money, but it's still good to know what it comes to.

    So far - including postage - it's cost:

    $120 for the chassis
    $41 for tonnes of wire and resistors (lots more than I need, so hard to gauge actual cost there)
    $80 for capacitors

    #001 (LP-1S) [finished - co-runner up Nov 2018 GOTM]
    #002 (WL-1)
    #003 (MPL Megacaster - semi scratch build) [finished]
    #004 (ST-1 JR - Arachnoid Superhero build) [finished]
    #005 (LP jr)
    #006 (TL-1A)

    Junk shop acoustic refurbs (various)
    'The TGS Special'

  2. #2
    Mentor Marcel's Avatar
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    Yay !! ... Welcome to the club. The pain you go through now will wash away when your newly built amp barks at you for the first time... I know it did for me on my AC18W scratch amp build.

    Yeah, caps and resistors are pretty cheap when compared to tubes and transformers...

  3. #3
    GAStronomist DrNomis_44's Avatar
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    A total of $241.00 actually sounds quite reasonable, given that a vintage 5E3 in reasonably decent condition would maybe cost ten times that, as Marcel said, I would like to welcome you to the DIY guitar amp club, I hope you have lots of fun building your 5E3, and if you need help, we're all here for you.


    Which reminds me, I need to start doing some more work on my DIY Soldano SLO 50 amp head, I've decided that next year I will get back into doing some DIY electronics, because I have a few projects I'm itching to start working on, I'm done with futzing with my guitars.
    Last edited by DrNomis_44; 23-11-2020 at 03:00 PM.

  4. #4
    GAStronomist Simon Barden's Avatar
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    Just been looking at valve prices, and they've seem to have gone up considerably since the last time I looked, which was maybe two years ago. Got some of the new Electro-Harmonix 7502 valves on order. These are supposed to be a proper recreation of the original 7502 valves, not just low noise 12AX7s badged as them. We shall see if they make any difference to the performance of my new (used) Fender 68 Custom Reverb Deluxe, which is quiet (no mains hum), but I'm sure it could be a bit quieter on the hiss front. I'm not supposed to have it until my birthday on the 29th Nov, but I have had to do a bit of testing just to make sure it works. The trem/vib circuit needs adjusting as it is rather clicky with no guitar signal going through when turned on. Unfortunately, RoHS regs mean that the European amps have a solid state vibrato board added, as the CdS opto coupler on the US versions isn't allowed over here any more. I know Cadmium is pretty toxic, but there's been enough used in Ni-Cad batteries over the years that one small opto-coupler that isn't going to get thrown away wouldn't do much harm. Interesting to note that Fender still fit the valve that's part of the bypassed circuit!

  5. #5
    GAStronomist DrNomis_44's Avatar
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    I recently bought four 500g bargain grab bags of bits and pieces from my local Jaycar Electronics shop, they each cost me Au$9.99, anyway, once I got them home from the shops I opened them up and went through each bag's contents, in one of the bags I found a new and still in the box Electroharmonix EL34 tube/valve, which I might use to make a single-ended guitar amp like an AX84 High Octane next year, or, if I can buy a second Electroharmonix EL34 from Evatco, they might be matched well enough for use in my Soldano SLO 50 build.

    Click image for larger version. 

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    Brand new and still in it's box.


    I do understand that it's unlikely that two EH EL34 tubes in separate boxes will be closely matched enough for use in a guitar amp, unless I get lucky.
    Last edited by DrNomis_44; 23-11-2020 at 04:37 PM.

  6. #6
    Mentor JohnH's Avatar
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    Thanks guys, I'm looking forward to it. And good score on that tube, doc!

    I almost certainly have some power tubes in my collection, but I figure like you say there's unlikely to be a matched pair in there anywhere, so I'll have to buy those. The tubes and transformers are going to add a fair bit to the price, and hardware all adds up. Still it'll be interesting to see what it comes in at price wise.

    I'm hoping the power tubes can somehow be squeezed in as an xmas present, ha ha.

    Keen to see how you go on the SLO 50 - it's on my wish list for future builds
    #001 (LP-1S) [finished - co-runner up Nov 2018 GOTM]
    #002 (WL-1)
    #003 (MPL Megacaster - semi scratch build) [finished]
    #004 (ST-1 JR - Arachnoid Superhero build) [finished]
    #005 (LP jr)
    #006 (TL-1A)

    Junk shop acoustic refurbs (various)
    'The TGS Special'

  7. #7
    GAStronomist DrNomis_44's Avatar
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    Quote Originally Posted by JohnH View Post
    Thanks guys, I'm looking forward to it. And good score on that tube, doc!

    I almost certainly have some power tubes in my collection, but I figure like you say there's unlikely to be a matched pair in there anywhere, so I'll have to buy those. The tubes and transformers are going to add a fair bit to the price, and hardware all adds up. Still it'll be interesting to see what it comes in at price wise.

    I'm hoping the power tubes can somehow be squeezed in as an xmas present, ha ha.

    Keen to see how you go on the SLO 50 - it's on my wish list for future builds

    First item on my parts shopping-list is a new and properly-rated power transformer for my Soldano SLO 50 build, I've got a suitable one saved on my wishlist on my account with Evatco, it's going to cost me roughly about Au$200.00 or so, but I reckon it's worth it for the safety-factor alone, I don't really trust the insulation in the original power transformer I made for it.

  8. #8
    Mentor JohnH's Avatar
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    Quote Originally Posted by DrNomis_44 View Post
    First item on my parts shopping-list is a new and properly-rated power transformer for my Soldano SLO 50 build, I've got a suitable one saved on my wishlist on my account with Evatco, it's going to cost me roughly about Au$200.00 or so, but I reckon it's worth it for the safety-factor alone, I don't really trust the insulation in the original power transformer I made for it.
    You made your own?

    Transformers blow my mind to be honest - like capacitors, they seem magical. They definitely add to the cost of the build. I'd have to check again on my home computer, but I think the PT and OT together (plus postage) will be about $250
    #001 (LP-1S) [finished - co-runner up Nov 2018 GOTM]
    #002 (WL-1)
    #003 (MPL Megacaster - semi scratch build) [finished]
    #004 (ST-1 JR - Arachnoid Superhero build) [finished]
    #005 (LP jr)
    #006 (TL-1A)

    Junk shop acoustic refurbs (various)
    'The TGS Special'

  9. #9
    GAStronomist DrNomis_44's Avatar
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    Quote Originally Posted by JohnH View Post
    You made your own?

    Transformers blow my mind to be honest - like capacitors, they seem magical. They definitely add to the cost of the build. I'd have to check again on my home computer, but I think the PT and OT together (plus postage) will be about $250

    Yep, I took a power transformer from a defunct reel-to-reel tape recorder, pulled it apart so that I had a cardboard bobbin and a set of iron laminations left after removing all the windings out of it, then with the help of a small book called Design Your Own Coils And Transformers, I did some maths to work out how many turns of enameled copper wire I needed for the primary and secondary windings, then I re-wound the transformer according to my calculations, surprisingly it did work first time and the voltages were close to what I wanted.

  10. #10
    Mentor Marcel's Avatar
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    AU$250 incl postage for 2 transformers = BARGAIN.!!

    I had a customer come in with a Lexicon Signature 284 that wanted it modified from USA 120VAC to Aussie 240VAC... Transformer had to be custom made by Voltran in Melbourne... Cost AU$280 plus shipping, and then add my time to fit it (and get rid of some hum issues due dud 25yo caps)... But damn, it is a very nice sounding class A tube amp at the end...
    Last edited by Marcel; 24-11-2020 at 01:32 PM.

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