1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

Trem and basic circuit help

Discussion in 'Shock Brother's DIY Amps' started by ejb222, Sep 15, 2015.

  1. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    I'm restarting an amp I attempted to build a few years ago, as I never finished it. You guys were such a huge help last time, I'm hoping to capitalize on your intellect and hospitality once again. :cool:

    It's a simple parallel 6v6 amp with 6SL7 preamp. But this time I'd like to add a tremolo. I've attached the schematic. Pardon my untidy and incomplete work as I'm still figuring out DIYLC.

    If you could help me with these points it would be a huge help:

    1. I stole the tremolo right off a schematic from a Ampeg R-12-R as it uses the 6SL7 I'm hoping to use. Should this be switched or can I used a larger Strength pot to basically shut it off at full resistance?

    2. How similarly should this stage be biased compared to the previous gain stages? I liked the idea of using an LED to also display the frequency...Any issues with this?

    3. Unrelated: what is your choice over the usual Princeton Tone Controls for a SE amp?

    Hope this isn't too much for one thread. Thanks in advance, you guys rock!
     

    Attached Files:

  2. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,040
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    I'll bump with a question or two that are probably in others' minds. Why has this basic amp not been finished, and why would you not want to get the basic amp going before attempting this modification/addition to that basic circuit?
     
  3. tubeswell

    tubeswell Friend of Leo's

    Posts:
    2,434
    Joined:
    Jul 1, 2008
    Location:
    NZ
  4. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
  5. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    Good questions. How would you go about building the base circuit first then adding the tremolo later if desired? Would build the amp then rehouse afterwards? Would you build in a large chassis with dummy tube for trem circuit to come later?
     
  6. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,040
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Ejb222 wrote: "I'm restarting an amp I attempted to build a few years ago, as I never finished it."

    I took this to mean that you got into the build and stopped for some reason. If the amp has not left the 'design stage', then by all means design and build what it is that you want to build.
     
  7. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    Lol. Yeah that amp was built partially, sold, then disassembled. So I'm starting from scratch. I would like to rebuild it, because it sounded great, and would like to actually have a complete amp ;)

    Only thing I have so far is a 12" Eminence Red Fang, some 6V6s and a red base 5961 hopefully delivered this week.
     
  8. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,040
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Yeah, I have some NOS/NIB glass envelope 6SL7's sitting around waiting for something to do, too. Good luck with the project.
     
  9. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    Thanks. Could you help me out a sec? I assumed that the output signal from the tremolo circuit could go directly to the grid of the output tube where your signal would normally go? Is this possible? Is it preferable? I've seen schematics where the tremolo circuit is tied to the cathode of the first preamp triode. Wouldnt this create issues? I was hoping to have a tremolo like my Silvertone 1474 that is always on but you can "turn it off" by basically turning the speed and strength to 0. I can't find the schematic for the specific 1474 I own in order to see how they did this.
    This is pretty new to me, so please pardon silly questions.
     
  10. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,040
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    If you read Merlin and Aiken, you will know more than I can share with you. I don't design amps. There are a lot of ways to apply a bias vary trem....at almost any point in the circuit, it seems. Take a look at all of the Fender bias vary terms....they have applied a bias vary at different points in the circuit for different amps. I am partial to the 5G9 Tremolux/6G2Princeton/BF Princeton approach.
    Re: the Silvertone 1474. Have you checked the schematic at Schematic Heaven for that circuit?
    Side note: The Rickenbacker B9A is a single ended amp with trem. I treasure my 1964, solid copper chassis B9A. The schematic for that is at Schematic Heaven under post '70's amps....regardless of the year of manfacture.
     
  11. Fred Mertz

    Fred Mertz Tele-Afflicted

    Posts:
    1,440
    Joined:
    Nov 11, 2011
    Location:
    Indiana
  12. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,040
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Fred, that VIbroChamp's trem circuit acts on the cathode of the driver....just as the Ric B9A does. + 1 on the wheel thing. They are still round, aren't they?
     
    Last edited: Sep 29, 2015
  13. tubeswell

    tubeswell Friend of Leo's

    Posts:
    2,434
    Joined:
    Jul 1, 2008
    Location:
    NZ
    JM2CW, why not start by copying a tried and true design for the tremolo? If you want trem with a SE amp, look at the how the AA764 vibrochamp inserts the trem wiggle (at the cathode of the 2nd pre-amp stage).
     
  14. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    Ok. Made some revisions. I'm still going to give the Reverberocket tremolo circuit a shot on my '48 Valco-ish circuit. I think I got it right this time.
    Also I am going to try the Moonlight Tone Stack. Heard good things.

    Any comments or suggestions? Any ideas as to what I could do with the other triode not being used?
     

    Attached Files:

  15. Fred Mertz

    Fred Mertz Tele-Afflicted

    Posts:
    1,440
    Joined:
    Nov 11, 2011
    Location:
    Indiana
    My suggestion would be to wire it up and see what happens. Troubleshoot from there. You have had several suggestions that you chose to ignore. If you want to be the designer, why ask?
     
  16. bwacke

    bwacke Tele-Meister Gold Supporter

    Posts:
    368
    Joined:
    Oct 28, 2007
    Location:
    Toledo, OH
    ejb222,

    You'll need to ground the common line under the cathode and phase shift resistors of the oscillator or it will not work at all. Also, you may have to experiment with a higher value for the 270K resistor feeding the trem to the grids of the 6V6's because I'm guessing the existing value will drop the audio signal level as you turn the intensity pot toward the grounded end.
     
  17. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,040
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    +1 with Fred. There is no teacher like experience....wire it up. If it doesn't work, figure out why.
     
  18. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    I didn't think I was ignoring any advice....It was advised to used a tried and true tremolo circuit, I pulled one from a Reverberocket that uses the same tube that I own. Not sure how that is ignoring advice?

    I forgot to add the ground symbol to the schematic after I shifted everything around so I could fit it in...oops. Not sure how the 270k resistor will effect that. The reverberocket uses 270k resistors...I'm running with it and will definitely have a clue where to look now that you brought it to light...otherwise, I'd probably be scratching my head for a while. Thank you
     
  19. Fred Mertz

    Fred Mertz Tele-Afflicted

    Posts:
    1,440
    Joined:
    Nov 11, 2011
    Location:
    Indiana
    It's good to see that you have it all figured out. Kudos on your communication skills.:rolleyes:
     
  20. ejb222

    ejb222 Tele-Holic

    Posts:
    616
    Joined:
    Jul 12, 2008
    Location:
    Massachusetts
    Perhaps you could use your superior communication skills to reiterate something you apparently thought I missed, rather than hiding behind sarcastic digs. I think you'll find that to be more effective in getting your point across while also not insulting people. But perhaps you know no other way.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.