Monday 29 July 2019

Pre Amp From Hell - Randall rg100es Pre Amp


 
Demo by MTK

 

12 comments:

  1. OMG I’ve so gotta build this tonight.

    Is it still unverified at this stage??

    ReplyDelete
  2. Ok cool.. I’m on it.. though only have 5.1v zen‘ son hand, but can’t see that being a huge issue..
    I’ll report back

    ReplyDelete
    Replies
    1. Cool! Yeah, 5,1v zeners shouldn't make a big difference

      Delete
  3. Got this one finished up yesterday. The overall tone of it is wonderful, rich, very full sounding, and I like the EQ a lot. When the Sustain Boost switch is on, the output drops significantly, that's to be expected when throwing diodes to ground. With a recovery stage added in, this will be a badass circuit. Sounds even better with an overdrive pushing it.

    I used 3.9v zeners and J201's. The Bass and Presence controls work backwards and the 1uF cap on Q2's source should be 10uF. Other than that, it's good to go. Clean layout.


    Build - https://i.imgur.com/O5RmhBs.jpg

    Demo - https://www.youtube.com/watch?v=bs7oS3TaF5A

    ReplyDelete
    Replies
    1. Awesome, man! Sounds great. Too bad about the volume drop...worth trying LEDs for the hard clippers for more volume?

      Delete
    2. I just swapped the single toggle for a double and tied in an LPB1 to the hard clipping side. Problem solved. I also added an LED to get some asymmetrical action going. This thing jams.

      https://i.imgur.com/Xlwla5X.jpg

      Delete
    3. Sweet! This is climbing higher on my "to build" list for sure...

      Delete
    4. @mtk Hey man, any way you could build me one of these with the volume drop fix and everything? I'd love to have one! email me at cromcastic@gmail.com

      Delete
    5. What's up, man! Thanks for reaching out. Unless I dismantled this for parts, I can box up this very circuit for you. I don't do anything with like 90% of the things I build, I just like the building part. lol I'll check the pile of circuits I've got and see if it's still alive.

      Delete
    6. Hey man, I built this too. I used 5v1 zeners and 2N5485s. It's not as gainy as yours... I'm guessing it's supposed to be gainy, considering that it's legendary for Pantera and Crowbar. I have other JFETs I could try, maybe that would help? Also, I like the idea of the LPB1, but I'm not sure how to connect it, and it's not very clear from the image you posted of it. Could you help me out with that? Thanks in advance!

      Delete
  4. Would you ever consider doing a randall rh200 preamp? Its one of my go to amps and its kinda hard to find, i wish more people knew about it because it slays man, no fizz at all.

    ReplyDelete