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Newly built clone ampeg B15 with 100watt output

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  • #1

    Newly built clone ampeg B15 with 100watt output

    Hi all

    Just finished a clone of the B15. Ive used a old chassis made for EL34. The 6L6's are very close together about 10mm apart. Is this going too be a problem ?
    Amp is working well no issues.Just concerned with the heat and these 6L6s being close together. Currently using a used set of mesa boogies.
    The amps output tx is out of a 100watt amp made for EL34. Would it be a better idea to use EL34
    Click image for larger version Name: ampeg_b15n_schematic.gif Views: 3 Size: 42.6 KB ID: 869367
    Would it be worth getting a fan?

    Im new to this building amp lark and don't really have the experience of you guys. want to confirm this before i spend my hard earned cash on new tubes

    Bassman
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  • #2
    Awesome.
    Using it for guitar or bass?
    It shouldn't be too much of a problem as long as the tubes are biased right, no high frequency oscillations causing them to work too hard.
    You could always add a fan if needed, if the tubes wear out faster than expected.

    I've seen alot of amps with output tubes sandwiched together like the SVT.

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    • #3
      Bass. I only do 4 strings. Ive fitted a variable bias from 20-30ma

      Comment

      • #4
        So it is essentially a B15 with 4 power tubes? What did you use for a rectifier?
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


        ​

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        • #5
          How is the chassis oriented, tubes standing up like a Marshall, or tubes hanging down like a Fender?
          It's weird, because it WAS working fine.....

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          • #6
            The tubes being 10mm apart should be fine with the caveat stated in post #5 by Randall (are they upright or hanging?). And I'll add, if upright the cabinet should be vented. Otherwise a fan is a good idea. I probably wouldn't try it in a guitar amp because they tend to run a higher idle current. This could make the amp run hot when it's just resting and no breathers in between notes. If the amp is working well, all is well. And I have a tad of envy. A 100W B15 is pretty cool
            "Take two placebos, works twice as well." Enzo

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

            "If you're not interested in opinions and the experience of others, why even start a thread?
            You can't just expect consent." Helmholtz

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            • #7
              One of the earliest Ampegs had 4 x EL37 side-by-each, standing upright in a power amp bolted to the cabinet floor. Somebody gave me the chassis from one, the wood had turned to dust & splinters. Separate preamp panel on an angled panel near the top. Some 10-15 years later they developed the flip top B15.
              This isn't the future I signed up for.

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              • #8
                Can you touch chassis, PT and other hardware around the power tubes without burning your fingers? A rule of thumb is, if you can touch without burning you're on the safe side. Is is a head or combo? In combos the speakers acts as cooling fans simply by moving air back and forth, heads obviously don't have these 'built in fans'.

                Builds such as this makes me wanna start new build projects. :-)
                In this forum everyone is entitled to my opinion.

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                • #9
                  Originally posted by überfuzz View Post
                  Can you touch chassis, PT and other hardware around the power tubes without burning your fingers? A rule of thumb is, if you can touch without burning you're on the safe side. Is is a head or combo? In combos the speakers acts as cooling fans simply by moving air back and forth, heads obviously don't have these 'built in fans'.

                  Builds such as this makes me wanna start new build projects. :-)
                  Fans are cheap!

                  Comment

                  • #10
                    Originally posted by olddawg View Post
                    Fans are cheap!
                    I don't think this thread is about €€€.
                    In this forum everyone is entitled to my opinion.

                    Comment

                    • #11
                      Maybe not, but if I questioned the heat, I'd rather spend the $ on the fan than the $$$$$$ for a tranny & tubes!

                      I say that having never installed a fan in an amp, as they've all been 20W and with LOTS of holes...

                      Justin
                      "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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                      • #12
                        The last fan I saw installed by (what I assume to be) an amateur was in the side of a Marshall cab blowing onto the power tubes and wired directly to the AC so it was on whenever the amp was plugged in. This is the wrong idea. You shouldn't blow air onto predominantly one power tube. I wired the fan to the switch, blocked up the top vent and about a third of the rear screen. That way it was sucking cool air across all the tubes more evenly and evacuating hot air from the amp. The implementation should get at least a little consideration. It's not just sticking a fan anywhere it'll fit and blowing it onto the tubes.
                        "Take two placebos, works twice as well." Enzo

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

                        "If you're not interested in opinions and the experience of others, why even start a thread?
                        You can't just expect consent." Helmholtz

                        Comment

                        • #13
                          I add a 12V PC power supply fan, the cheapest and most widely available type, and feed it with bridge rectified 6.3VAC which gives me some 8VDC .
                          The fan runs at a lower speed, does not properly "blow" but "move air" and keeps the chassis or inside of the cabinet a lot cooler than without.

                          No annoying noise and the slightest breeze is much better than any natural convection.

                          Don't straight point at the tubes unless they are at least 6 to 8 inches away, and anyway, being inside non heat conductive vacuum (what a thermos flask is, by the way) , I'm not actually cooling plates but the amp in general.
                          Juan Manuel Fahey

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                          • #14
                            Many thanks for the comments guys. Ive gone for a mains powered fan bolt at the end of the headshell blowing air across the chassis. Tha amp has not been gigged yet but its ready too
                            Click image for larger version Name: SAM_3316.JPG Views: 1 Size: 1.42 MB ID: 837206

                            Ive had the chassis and headshell + Iron knocking around my workshop. The whole thing has not cost more that £100 - $150 so am pleased. The most expensive part was the brass plate for the facier Got too get some tone labels for the front facier and a grille for the fan.

                            bassman
                            Ps it now has Chicken head knobs

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