Monday 21 August 2023

Walus Audio 385 Overdrive

 This one has a pretty interesting backstory. It is supposed to be be based or simulate the tube section of Filmosound projector from the 1950s. After listening t o the demos it seems to be a Tweed style overdrive.

Schematic is avaiable HERE.


 



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21 comments:

  1. Tom21 August 2023 at 06:16

    Input is below Gain 2?

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  2. Mr.Baiser21 August 2023 at 10:48

    Not really close to a tweed amp.

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  3. Tom23 August 2023 at 11:27

    No power flow. All I found so far is Treble 1 and 2 and Bass 1 and 2 should be swapped.

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  4. Tom24 August 2023 at 22:41

    I couldn't get the Julia going either. I couldn't find anything obviously wrong with either of them but nada. Thanks for nothing Walrus Audio! Just kittens.

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    1. Tom25 August 2023 at 02:39

      Got it. Verified. Fried my diodes somehow. Swapped them and cleaned the joints with alcohol and it came on. It sounds pretty cool. It is somewhat tweedy. I think most amps were at that time. Very nice and punchy fuzzy drive. Sorry Walrus and thank you Anders.

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    2. fuzzhead26 August 2023 at 09:07

      Thanks Tom.

      Tagged.

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  5. Ben Spinks31 August 2023 at 22:22

    Just finished this and it sounds great, but there's something bugging me. Nothing sound related. More for my own educational benefit. I'm getting 4.5v on the drains of Q1 and Q2. Q3 is 16v drain and 4.5v gate. Q4 is the one that's baffling me. The trimmer for Q4 seems to make no difference to the drain, which remains at 16v, but seems to act more like a volume control. Presumably this is normal because the pedal sounds great and pretty much like all the demos, I just feel like I'm not understanding something here, if you get what I mean?

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    1. Tom2 September 2023 at 05:05

      This comment has been removed by the author.

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    2. Tom2 September 2023 at 09:03

      I found a conversation online stating that Q1, Q2 and Q4 should all be biased around 8.3v each. I don't like it as much now though haha. I'll have to tinker with the bias by ear. But that is where the FETs should be biased ideally according to WA. Makes sense. I hadn't considered the 1044's overall voltage increase.

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    3. Ben Spinks2 September 2023 at 11:36

      Cool thanks for that. I think I’m in agreement with you though. It sounds so good the way it is I think I’m going to leave it 😆.

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  6. Tom1 September 2023 at 05:20

    Yup, I had the same readings. It sounded so good I didn't question it. It is odd. I'd like to know what the reason is too.

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  7. ScottOldGuards18 October 2023 at 19:16

    Hey, J4, is that meant to be 100n film capacitor like the others (o15, c13)? The symbol has me thrown

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    1. Tom18 October 2023 at 20:37

      This comment has been removed by the author.

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    2. Tom18 October 2023 at 20:40

      It's meant to be 100nf ceramic. But a 100nf film would work fine too, in my experience.

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  8. ScottOldGuards2 November 2023 at 22:21

    Thanks for the help. Built two of these but only had enough j201s for the first. Decided to experiment with 5457s for the 2nd and whilst the sound is great, the volume is much lower. Any suggestions for component changes to raise the overall volume? I will be grabbing more 201s but figured I might as well see how well I can get it working with these for now

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    1. Tom3 November 2023 at 16:49

      Yeah, it's a cool one. It has a unique sound. JFETs are often temperamental. Personally, I'd hold out for some different parts rather than change the circuit. If you have any other FETs, try those.

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  9. NJGTR31 December 2023 at 05:28

    I just built this and it’s an awesome pedal. I used smd j201s, so I had fun making legs out of old resistor clippings. I own a 385 amp that I restored and this pedal does give the feel of a tube amp like a Filmosound with very natural gain. You can get a fairly clean to very dirty sound with this circuit , but I like it at the setting right before it starts breaking up. Thank you Anders!

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  10. brain5 February 2024 at 14:26

    This comment has been removed by the author.

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  11. brain6 February 2024 at 07:15

    Got to this one a little late, but I really dig it. Like Tom said above, gotta swap the wiring for treble 1 & 2 and also bass 1 & 2.

    but I also noticed that left the sweep of the bass knob reversed (less bass when dimed). fwiw, Anders' layout is correct per the schematic, I think the bass pot on the schematic was mislabeled.

    The order I wired it is (from top to bottom):

    bass 2
    treble 2
    treble 1
    bass 3
    bass 1
    treble 3

    everything seems to be working as expected now.

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    1. Tom13 March 2024 at 07:07

      Brain is right. Wiring was wonky. I just wired this up tonight and then saw this update. It all went so smoothly too. Haha. Anyway, As I see it it works as follows (again, from top to bottom)

      Bass 2
      Treble 2
      Treble 1
      Bass 1
      Bass 3
      Treble 3

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