Monday, 27 July 2020

DAM GT-73 Graveyard Tramp

A cool sounding Fuzz Face derivate. Note that the value of the volume potentiometer is unknown but we found out that 250k or 500k sounding good. Also, the fuzz control is wired backwards per original but if you want a normal counter clcokwise control, just swap 1 and 3 lugs and use a 1kC pot. OC82D transistor might be a bit hard to come by so try others that suits your taste.

 








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31 comments:

  1. Andrew28 July 2020 at 13:26

    Hello - I can't see the resistor going to the collector of Q1. Awesome site by the way.

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    1. fuzzhead28 July 2020 at 15:28

      This comment has been removed by the author.

      Delete
    2. fuzzhead28 July 2020 at 17:09

      Nevermind about my comment above. The layout is the verified one. Q1 collector is connected to 15k through the jumper that is connected to the base of Q2.

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    3. Andrew29 July 2020 at 09:34

      All good - am I going blind or has the schem and layout been updated?

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  2. AlexS28 July 2020 at 18:18

    I used a C1k and 2n2222a/GT404B. You can try a lot of combos.

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  3. Brain29 July 2020 at 23:49

    2N2907 and NTE404 for me, and it sounds great!

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  4. Mulekicker30 July 2020 at 00:25

    Damnit Anders, every time I start to catch up on my build list you add something I gotta check out. I'm finishing your old layout for the Boozearound right now.

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  5. giudis27 August 2020 at 01:58

    In the D*A*M page I had understood that it is common negative ground... 🤔
    https://www.stompboxes.co.uk/GT-73.html

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    1. fuzzhead27 August 2020 at 19:15

      Hmmm, are you sure? All my tracing files indicates that it runs on negative power supply/positive ground. Not sure why they added a DC jack to this one since most of their other PNP fuzzes runs on battry only.

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    2. giudis27 August 2020 at 19:28

      Precisely! DC confused me....

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    3. fuzzhead27 August 2020 at 19:58

      Well, you can use a DC jack with negative power supply, just make sure to not daisy chain it or bad things will happen...:-/

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    4. giudis27 August 2020 at 22:47

      at this link I've posted some picture of the stripboard and I have started a discussion...
      https://www.freestompboxes.org/viewtopic.php?f=33&t=30839&p=281889#p281889

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  6. giudis27 August 2020 at 19:41

    This comment has been removed by the author.

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  7. Squirrels16 October 2020 at 03:06

    This comment has been removed by the author.

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  8. Squirrels16 October 2020 at 03:07


    Quick question... the output caps on the schematic and layout down match up, which one is correct?

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    1. fuzzhead16 October 2020 at 09:05

      Output cap is 100nF, schematic is now updated.

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  9. Squirrels9 December 2020 at 03:44

    Just built it, works well but didn’t really mess with it yet. I also noticed that the layout used 820r and 4.7k resistors as opposed to the 470r and 8.2k ones on the schematic... which ones are correct?

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    1. fuzzhead9 December 2020 at 04:27

      The correct values is 4,7k/820ohm.

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    2. Squirrels9 December 2020 at 04:59

      Thank for the quick reply. I’ll plug it in tomorrow and let you know how it sounds.

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  10. Squirrels15 December 2020 at 20:52

    Not bad, not great either. I used a BC109C for Q1 and a 2N1304 (hFe ~115) for Q2. I read that the 109 was the NPN equivilant to the BC179, maybe it would sound better with a lower gain silicon in Q1, it’s very muffled but not in a good way. I think I’m going to give the Voidmaster a shot next. Fuzz Face/One Knob Fuzz designs with a lower input cap seem to be more of my liking.

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  11. Squirrels15 December 2020 at 20:57

    It could just be my build or my rig too. DAM layouts never let me down before, I wouldn’t be surprised if it was just my build. Thanks for the layout, I hope you didn’t take that as insulting because it was definitely not meant to be.

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    1. fuzzhead16 December 2020 at 08:36

      No worries, man. it is not my favorite fuzz face iether, Generally I prefer low gain in Q1 and higher gain in Q2, otherwise I feel something is missing...

      Void Master on the other hand sounds really good, just uploaded a three knob version (internal trimmers on the outside).

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  12. Squirrels4 January 2021 at 03:54

    Do you think a higher gain germanium in Q2 would make it sound better considering that’s what a conventional Fuzz Face would use?

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    1. fuzzhead4 January 2021 at 07:58

      Yes, a higher gain ge for Q2 and a lower gain silicon for Q1.

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  13. Squirrels4 January 2021 at 13:00

    So it’s the same concept in a hybrid? I went With NPN transistors, I Googled the BC179 equivalent and came up with a BC109C which is pretty high gain for Q1. Q2 was a 2N1304 that measured about 117 and the bias was about 4.9 volts. I have two CV7007 (I think) from a Hoof I built and didn’t like that measured close to 300 that may sound better with a high gain Q1. Maybe just making it a straight up germanium would sound better? What did you use for transistors in this one?

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    1. fuzzhead4 January 2021 at 14:03

      Yes, it worked the same for me with the hybrid setup. I ended up with a BC179B (hfe 250) for Q1 and a 2N1309 (Hfe 320) for Q2. Also tried some obscure soviet trannies, P30 (hfe 260) and Gt109V (hfe 560!!!). Also BC559 is the TO92 equivalent of BC179....
      For an NPN build BC109B/BC549B would work for Q1 and maybe a 2N1306/08 for Q2....
      A bet that an all ge build would work as well but the character of the fuzz may be different.

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  14. Squirrels4 January 2021 at 18:10

    That’s for the info. I dropped in a 2N3391 (260) and a CV7321 (~295) and the results were much better. Not muffled like it was with more clarity but still in the Fuzz Face family. I have another CV7321 (not a 7007 like I thought) so I think I need to rebuild the hybrid Fuzzbud again. I had an A100k for the volume pot but swapped in an A250k and it was also an improvement. I want to try out a 500k but I don’t have any right now. I should do a small order and pick up parts for the Voidmaster. What did you settle in for the volume pot?

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    1. fuzzhead4 January 2021 at 18:51

      Yeah, I found out that a 250k pot works best, 500k was a bit hefty and bassy.
      Hybrid Fuzzbud you say? Tell me more!

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    2. Squirrels4 January 2021 at 21:57

      There was a layout for it on Tagboard’s forum, it had a fuzz pot and used a 2N1306 for Q2. I used a higher gain Q1 and a 2N1304 for Q2 and it didn’t sound very good. I’ll have to rebuild it with the other CV7321. Maybe just the single knob version.

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  15. ev31 August 2021 at 03:42

    so this doesnt work with a regular power supply?

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