Recent content by EMan

  1. EMan

    Can a silver face Champ be modded to sound like a tweed Champ?

    MPO is similar to what's been stated, it would be pretty cheap for a tech to move a few wires around to replicate the older circuit. However, that's what you'll get - a new-ish Champ with a different circuit. The only thing that really sounds "tweed" are the old tweeds (( MPO again ))...
  2. EMan

    open back / closed back

    My 1X12 cab is convertable, meaning that the back panel is in 2 sections. The top panel is about 1/4 of the total rear area, and comes off. I like using it closed in conjunction with the open back Princeton.
  3. EMan

    Still need help with that Bias Circuit it does not work right.

    Glad it worked out, James!
  4. EMan

    what's the problem with fender's ultra-linear amps?

    I used a 135W UL Twin for almost a decade. I sold it around '89 as I was out of the band biz. Had a hankerin' for another one a few years ago...and the guy I had sold the amp to still had it!....and tripletts...so I got my old amp back. However, I digress - Any 6L6GC will live for a long...
  5. EMan

    Speaker impedance

    gpower - Don't take my word for it. Here's a Figure from a early '50's ear Tube Manual showing the effects of load resistance on a 6V6 - Of course, this only applies to resistors. Speakers 'can' be really funkay representations of a load, mainly due to the fact that their reactance can...
  6. EMan

    Speaker impedance

    "...Perceived output will also be almost halved..." That's not exactly the case. The actual difference in power at twice or half the 'marched load' is roughly 12%, which is ~ 1/2 dB. Here's the proof using a simple DC circuit, and two resistors. The Y-Axis "1" is maximum power to a load...
  7. EMan

    SF Champ

    Here's what I did with a similar constructed amp - I replaced the RCA jack with a 1/4" switched jack, and hardwired the internal speaker to the appropriate jack terminals. In that case, as long as nothing's plugged into the jack, the amp works normally. Plugging into the jack disconnects the...
  8. EMan

    ohms question

    The 'rule of thumb' for most amps that have a tube output section is that going twice or half what it is rated for is generally okay. If you have the option, a half rated load is a better choice. Where did the "10 ohm" reference come from...did you use a ohm meter and measure it?
  9. EMan

    There is a 78 DR Closet Classic I found for $800

    MPO - If I had an amp worth $5K+, It wouldn't be here for long...that's fer dang sure. Sounds like you enjoy playing more than you do collecting...so I'd take the cash, and get you something that doesn't make you cringe when someone drops their zig butt on it. As far as an $800 late SFDR...
  10. EMan

    Use of standby

    Scott - no, the circuits in my RCA19 are very much 'real', and even have a parts list...with complete transformer info as well! MPO is that if you have a STBY switch, you might as well use it...if you don't (like Princetons/Champs) you don't need to add one.
  11. EMan

    Use of standby

    If you peruse the old tube data books, and peer at the circuits that they put in the back endd of the books, you'll find a lot of amplifiers in various Class of Operation, as well as different power outputs and various output tubes. One of the 35W amps in the RCA19 book uses a 400-0-400 PT...
  12. EMan

    Could someone double check this circuit?

    As mentioned, if you want the most headroom, ditch the cathode biasing on the 6L6's and go fixed. Go take a look at the Silvertone 1484 (I'm pretty sure it's on schematic heaven). The one I had (with 2X12's) was a pretty clean amp, almost to 10, unless you really stepped on the guitar. It's...
  13. EMan

    Could someone double check this circuit?

    One thing I can see right off, is that the 6L6 screens are tied together. Typically, this is not a good thing, as they will 'pull' at each other without something to separate them.
  14. EMan

    SF Champ popped fuse, right after new capacitors

    Did you replace the fuse and try it again? My '62 Princeton blows it's fuse about once every two years....Power surge, mayhaps.
  15. EMan

    Impedence and Speaker Tone

    For general info, here's a good site that talks about tubes driving speakers - http://www.symphonysound.com/articles/tubefriendly.html




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