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5F10 Harvard, Cathode bias, Point-2-Point. and thank you.

Discussion in 'Shock Brother's DIY Amps' started by bigguy12321, Apr 10, 2018.

  1. bigguy12321

    bigguy12321 Tele-Meister

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    Hey @debrad ,

    Just saw this. Glad you made it out ok. I like the re-build/re-purpose route also.

    Isn't it amazing when you look into those old P2P wired radios and amps how quiet they were even though there are wires everywhere?

    That amp will serve you well for a long time... Unless you're like me and want to build and use another right away.

    Most, if not all of the 5E3 mods on Robs page will work on this circuit if you want to mod in the future.

    Any chance of a sound clip?

    a
     
  2. debrad

    debrad TDPRI Member

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    Thanks @bigguy12321!

    What makes it even MORE amazing is that I have new components and a fraction of the wiring and yet I think my build is probably more noisy than the original rat's nest EVER was! I'm stoked to have been able to make something work but I think it's going to take me a little bit of tweaking to tidy up my wiring so that it doesn't induce any hum or contain nasty ground loops.

    I haven't had much time to really play around with it...especially at HEALTHY volume levels...so I can't say for sure but I get the sense this thing will stay pretty clean right up to full volume so I might swap out the 6AT6 preamp tube for a 6AV6 I bought at the same time just to see if it gives me some earlier breakup. That was actually my original plan but I did all my tube socket wiring with the 6AT6 in there just in case I wound up breaking something.

    Like you, I got a lot of help from @robrob directly AND his amazing web site...wouldn't have been able to do ANY of this without either (I followed his lead specifically when adding my FX Loop and Negative Feedback mods). I was also chatting with Anthony from At Mars and he was a great resource as well; in fact, he was the one who suggested I go with the 5F10 Harvard circuit when I was trying to figure out what to do with the original Filmosound.

    Anyway, now that the amp APPEARS to be running properly, I'll try to clean up this bit of hum, adjust the bias a little cooler (Anthony's calculations put me closer to 14 watts dissipated from each tube which he thinks might be a little too much), test drive the 6AV6 tubes, and then see if I can share an audio clip or two...

    - brad -
     
    robrob likes this.
  3. debrad

    debrad TDPRI Member

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    Well, I still haven't really had the chance to test drive this thing because my wife was upstairs watching TV when I snuck down to play but, OMG, I might have spoken too soon when I said I'd probably need the 6AV6 preamp tube to get more drive out of this thing!

    Up until tonight I've been running all of my tests with a Strat but tonight I plugged in the Telecaster and immediately noticed a huge difference...the amp jumps from 0 to LOUD and then I've got overdrive starting around 4 on the volume know (even though I'm playing light and dialing the guitar's volume back to keep from driving my wife and my neighbour's nuts!). I did crank it full tilt but, again, I was plain light and REALLY dialing back on the volume know. Flicking the negative feedback on gave me a notable volume cut and a cleaner tone but I'm sure it would still be pretty dirty if I banged it hard...especially at max volume.

    After a little of that; I swapped the 6AT6 for my 6AV6 and I *THINK* there was more gain and a little sweeter tone but I got the sense the tube might be a little sensitive or "microphonic" but I don't have enough experience with that to really tell. Truth be told, the 6AT6 might have been making a few odd noises. Anyway, the 6AT6 definitely enough gain do I put it back in for now.

    Having done enough experimenting, I plugged in the LP and, as expected, it took the Tele experience and raised it to the next level! LOTS of drive to say the least (I was playing the amp at noon on the volume with the LP volume on 2 (!!!) and thought it was sounding pretty good and then my wife starting flicking the basement lights and asked me if I could turn it down!).

    So...still a few wrinkles to iron out but I'm feeling pretty good right now...I think this is going to be fun!!!
     
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  4. bigguy12321

    bigguy12321 Tele-Meister

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    Sounds like you need to unhook that light switch...;)

    I defiantly found that there wasn't that much difference between the 6AT6 and the 6AV6 in real life usage. I just left in the 6AV6 and dialed the guitar down to get the distortion I wanted. The breakup was basically the same for both tubes but full distortion came at slightly different stages.

    What speaker are you using? Mine was built in a cab just large enough to fit chassis (flat plate) and speaker. 12in. very efficient speaker. I actually had to remove the NFR to get a good amount of dirt. As originally built mine was too clean. I would recommend a cab about the same size of a 5E3 Deluxe (16X20) with a 10 inch speaker. That size box with a 10 incher has been my favorite so far. Although I have been playing with dual speakers and have liked the sound of the spread that two speakers gives.



    As a side note about the noise. You've got some space issues to be sure but the biggest problems may be coming from the fact that you're OT is right next to the input tubes. A.C. next to sensitive input wiring can be an issue. Maybe try twisting the OT wires on the output side and making sure the heater wires are down in the corners of the chassis. I've had to build a small shield attached to the inside of the input jack to block "AC Voodo" from getting to that input. Similar to what is seen in the Uncle Doug video featuring his 1950's 5F2-A Home-Built Amp. I have done this when my OT was too close to the input jacks.

    Now comes the fun part. Playing with and through the amp that YOU built!!!

    Good job.

    a

    p.s. My wife stomps on the floor over my basement shop when I get too carried away. Same end result...
     
  5. debrad

    debrad TDPRI Member

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    Thanks for sharing your experiences with your build. So far I have just been running this head into the 12" cab of my Traynor YCV40 combo (I swapped out the original Celestion 70/80 with an Eminence Wizard several years ago) but my plan is to build a custom cab with either dimensions similar to those of the original 5E3 or 5F10 cabs at some point. I don't have any experience with 10" speakers other than playing a Fender Hot Rod Deville once or twice at my local Rehearsal Factory jam space but I've been reading many good things about them (and a few recommended speakers). Your comments just make the idea of a 10" cab all the more enticing!

    After speaking with @robrob over the weekend, I am planning to pick up a new pair of 6V6 output tubes...hopefully they fix rather large bias difference between the two I have in the amp right now and hopefully that, in turn, helps eliminate some of the noise I think I'm experiencing. I will also take your advice and look at some of the alternate approaches to quieting the hum.

    In the meantime, I have to get to work on that light switch...

    ; - )

    - brad -
     
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  6. debrad

    debrad TDPRI Member

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    My apologies again for hijacking @bigguy12321 's thread but I figured I should close the loop now that I've done so. Here is the final result of my Filmosound converted into a cathode biased 5F10 Harvard with an added FX Loop and switchable negative feedback. It's running into a 1x10" cabinet loaded with an early Eminence Legend speaker supposedly similar to the Legend 1028K but I cut the baffle for a 12" opening and built an adaptor ring to hold 10" speakers. So far I am really enjoying this one and, as you can see by the snow on the deck, the weather is making it easy to stay inside and crank things up!!!


    [​IMG]
     
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