JCM800 6V6/6L6/EL34 in a Princeton Reverb Chassis

Discussion in 'Shock Brother's DIY Amps' started by robrob, May 1, 2019.

  1. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The amp is derived from the Princeton Reverb so PR speakers should hold up. At least no one has blown one up yet.
     
  2. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    In reply to Wally: I don't think that link is too bad. And in your own opinion you give two (similar) reasonings where I read one should have a speaker with a higher power rating.

    In reply to Rob: I've looked at the original Princeton reverb and two reissues. All have a much higher power rating speaker:

    Original: 12-15W amp, 50W Jensen c10n
    65 RI: 22W amp, 100W Jensen c12k (200W musical power?)
    68 RI: 22W amp, 70W Celestion G12V-70

    I've little to no experience, but the information I have (been given) still gives me the feeling that one 20-25 W speaker is not enough. Am I missing something?
     
  3. Wally

    Wally Telefied Ad Free Member

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    1) the original BF/SF Princeton/Princeton Reverb amps rarely might have come with a C10N. Most of them had an Oxford 10J4 or perhaps a Jensen C10R. Those speakers would perhaps have been 20 watt speakers. There have been reports of a C0N having been used. I have never seen such. If that happened, I would think it would have been a case where there were no other options but to install the higher power...and more expensive...speaker because there were no low wattage speakers available that day.

    2) I believe in using at least twice the handling capability compared to output power. Ommv and...playing styles determine what a speaker undergoes. A 5 watt amp can take out a fairly high capability speaker if one goes about it a certain way.
     
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  4. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The double-the-amp-watt-rating speaker rule isn't hard and fast but it is conservative and good advice.

    From the Weber Speaker website on a Princeton Reverb replacement speaker:

    "The favorite for Princeton Reverb:
    (if you use no pedals for dirt and you want the speaker to break up a little):[10F150T, 8 ohm, 25w, light dope]
    (if you use pedals for dirt or you want the speaker to stay cleaner): [10F150T, 8 ohm, 50w, light dope]. "

    Since the JCM800 6V6 is a much higher gain amp than the Princeton Reverb it wouldn't hurt to go with a 40 or 50 watt rated speaker. I'll add some info on this to the JCM800 6V6 webpage.
     
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  5. NSB_Chris

    NSB_Chris Tele-Meister

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    My build has started.

    IMG_3462.jpg

    I have a gutted silver face twin reverb cabinet. I purchased an undrilled steel chassis with a right angle face. This will have two inputs with separate preamp circuits as I posted before in this thread, one trying to honor Rob's circuit and one tamed a bit. They mix in before the power section. This will be the "RR800V TWIN". The chassis has been drilled and painted. Front pannel was made with water-slide decals and clear coat. Most components have been mounted and eaters are wired. I will work on the front panel pots and main board tomorrow.

    Right now the cabinet has two 16 ohm greenbacks in it as I have been using it as an extension 2x12 speaker cabinet because it has the tilt back arms. I purchased two green baret speakers, but stupidly got 8 ohm, so the only way I can use them in this cabinet with this amp is with the 6V6 and the 16 ohm OT tap. Might leave in the greenbacks to see if I want to run it with 6V6 or EL34 power tubes. If it works of course!
     
  6. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    I'm thinking about building this also. I will be following this thread closely, especially @NSB_Chris' build because I'm also very interested in a clean channel in the same amp.

    I like the Blencowe-correct heater wiring. You don't see it that often. I also didn't, because I couldn't get it done. Probably my wires were too thick. What thickness have you used? Any tips and tricks? Did you pre-tin the wires?

    What are the heater wires connected to on your AC/DC board?

    Can you give any more info about the chassis work: painting, water slide decals, clear coat, ...?
     
  7. NSB_Chris

    NSB_Chris Tele-Meister

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    This was the first time I wired the heaters straight back from the sockets to the corner. All my previous builds I flew them Fender style. Running them straight back was a lot easier in my opinion. I used 18ga for everything but the last 3 preamp sockets where I use 20ga.
    I never liked running the heater wires to the pilot light and then back across to the sockets and this amp I am using LED pilot anyway. I just terminated the heater wires from the transformer on the board and then put separate turrets for the wires going to the sockets. Hopefully this works out ok. I put the resistor and diode for the LED pilot on the board for easy change-out. The LEDs were uncomfortably bright on the last amp I built and it was not easy to change them out. This way I have easy access to switch if I need to.

    I added a lot of extra turrets on the AC/DC board and the main board to make connections easy. Little extra cost, more holes to drill and more turrets to swage, but I find it easier to wire up the components and hopefully easier to troubleshoot and change components in the future if needed.

    I used laser printer water slide decals for the graphics. I have used the inkjet printer water slides before and the ink can run a little on those if you end up messing with them too much. Laser worked much better!. Painting is simple. I used automobile wet sandable primer on the bare metal. Light wet sand with 400 grit sandpaper before the color coat. 4 or 5 very light coats of color to give enough thickness to sand smooth before stickers go on. Wet sanded with 400 grit until reasonably smooth where the stickers go. Waited 24 hours before sliding on the stickers. I let the stickers set for 12 to 24 hours and then clear coated with several coats of satin clear. I think this is the basic process that many are using on this forum. I should have used Crylon paint but used Rust-Oleum because it was convenient at my local store. Seems to work fine.
     
    Last edited: Aug 16, 2019 at 7:59 PM
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  8. NSB_Chris

    NSB_Chris Tele-Meister

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    More progress, but still a long way to go!

    IMG_3465.jpg IMG_3466.jpg
     
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