Saturday, 2 September 2017

Diezel VH4

"Unlike traditional overdrive stomp boxes, the VH4 Pedal is a true preamp which delivers an authentic representation of its namesake – real Diezel tone – not emulated, not modeled, but sincerely reproduced. The entire signal architecture is faithful to the original: Bass, Mid, Treble and variable Deep and Presence controls allow you to tailor the uniquely Diezel Overdrive character. The command found in the Gain control gives a player everything they will ever need with lower gain settings producing the classic Diezel sparkle and chime to saturated mid-gain sounds, to scorching Diezel leads by cranking it all the way up.
As close to the original VH4 preamp, the VH4 pedal can be used as either an overdrive or as a standalone preamp to feed into your amps power section. What players take away by going direct into the power amp is all the dynamic, unfiltered Diezel tone by simply plugging into your amplifiers clean channel. Two outputs are provided with the first intended to connect to the front of a guitar amplifier and the second allows for a connection to a line-level power amp or power section of your amp via the Effects Return."
Original FSB thread and schematic available here.
This is a buffered effect.
Follow the layout's footswitch wiring.


Posted by at 15:38
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43 comments:

  1. Hozy312 September 2017 at 18:17

    Have to give this one a go. Superb layout as always. Great work Alex!

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  2. skajaquada2 September 2017 at 23:12

    I need to build this and compare it to the Diefet I built... :D

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  3. gavinmacneil3 September 2017 at 00:10

    it's huge! 7 pots on a overdrive!

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  4. Miquel3 September 2017 at 09:46

    Thanks!!!!!!!!

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  5. motterpaul4 September 2017 at 00:39

    This comment has been removed by the author.

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    1. motterpaul4 September 2017 at 00:43

      Maybe many of you remember this other Diezel VH4 pedal. I built three of these and loved them. Very different approach, though; 5 FETs that need to biased. http://4.bp.blogspot.com/-f4fgFVxv6Ls/U4-WSEDOjsI/AAAAAAAAHqk/DNSa458u7LA/s1600/Diefet+-+Diezel+VH4S+Simulator.png

      Will be interesting to see the difference if anyone does both.

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    2. Alltrax744 September 2017 at 09:49

      I built both, this VH4 is much better IMO, sounds tighter with more effective controls

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    3. Baldness5 September 2017 at 02:29

      SO this is verified?

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    4. Alltrax745 September 2017 at 09:57

      No, I built it with a pcb

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    5. Baldness6 September 2017 at 04:02

      ahh right on ty

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  6. Unknown5 September 2017 at 11:57

    this may be a silly comment but I assume I can just leave out the pre amp jack as its something I'll never use?

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    1. motterpaul5 September 2017 at 17:50

      Do you mean the "power out" jack - I am not sure why that is there (an extra 9v DC tap?)

      Delete
  7. Unknown5 September 2017 at 20:18

    I think its an additional output designed to be used before the power section of the amp, I don't use my fx loop so won't need it

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    1. Zach6 September 2017 at 00:25

      if you read what it says on the diezel's website about this pedal it states:

      Out to guitar amp: Connect to the front end of your amplifier.

      Out to power amp: Connect to rack mount power amplifier or the return jack of your amp’s effects loop.

      i believe the idea is that the power amp output is to use the pedal as a preamp rather than a distortion pedal

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  8. Unknown6 September 2017 at 07:41

    ah cheers Zach, I assume i can just leave it out, although might be useful as a pre amp

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    1. Zach6 September 2017 at 12:57

      Honestly I haven't had a chance to take a look st the schematic so I can't say yes or no. If it were me and I had the space in the enclosure I would keep it in cause even if you don't use it it's nice to have. Plus knowing me I'd say I don't need it then regret not putting it in and have to go back to put it in.

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    2. Unknown7 September 2017 at 08:32

      yes I think that's the best route, I had a nice delivery of 1590bb's yesterday and plenty of space on my board. there have been a couple of builds I've regretted leaving bits out of

      thanks buddy

      Delete
  9. Alltrax746 September 2017 at 16:40

    One thing to note, if you plan to power it with a 9V PS, omit the LM and add a link from I to O.
    This is what I did and it sounds great at 9v (didn't try 12v)

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  10. pakkee667 September 2017 at 06:29

    must built list on priority~ thanks the layout.
    btw,are there any replacement for lm2940?
    or can I omit it and feed in 15v reg charge-pump to 7660s pin-8?

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  11. Hozy3111 September 2017 at 19:27

    Call it verified! Built it on Saturday and couldn't get it to work. Went through all the usual debugging and just couldn't find anything. Was getting sound through but just a squeal. Anyway, came back to it tonight and first thing i noticed was i had D3 the wrong way round....Doh! Fixed that and now its alive and sounding great. Thanks Alex & the dudes at FSB.

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  12. Eric Pulido9 December 2017 at 16:15

    Would be ok to use other op amp like the NE5532 or RC4558, instead fo the opa2134?

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  13. pakkee661 April 2018 at 14:01

    built this, and get it works in board test, butthen no sound when I box it up, check the lm2940 is dead, place with 7812 and 7660s it works again.. but it no sound again now.. I read the positive voltage 6.1v at 074 pin.11 and 7.8v on pin4, is it possible?

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    1. Unknown16 July 2018 at 21:08

      I too was getting low voltage and ran into many problems trying to build it: noticed the D3-D4 we're getting too hot. I removed them and even though it was working there was the voltage doubler squeal, even though I used icl7660scpaz. Changed it with a max1044, which was working fine at the beginning noiseless, but the next day it was getting hot and squeeling again. My bad, since max1044 accepts max of 10 volts :) so I'll start over with a new 7660s. I'm feeding 18V to it, and use a simple 7812. Even though, I get oscillations when gain and presence pot are above 75%...

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    2. Unknown6 October 2018 at 15:39

      Vag McPan. Hello. I build it twice and it sounds great but in both pedals i get a high frequency when the gain is over 50%. when i roll the guitar volume down it is like an oscillator... did you find solution to your problem?

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    3. HurricaneHordak29 November 2018 at 22:25

      Me three. Anyone know how to remedy this?

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  14. Unknown12 April 2018 at 07:35

    what are the red squares in the schematic?

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  15. mr Eddy29 June 2018 at 07:03

    Thank you for the layout! What wattage should i take for the 10R resistors?

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  16. Nik24 September 2018 at 07:31

    This comment has been removed by the author.

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  17. blakol21 October 2018 at 08:28

    Did not the pin 4 of the oPA2134 need to be grounded?

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  18. Icziko23 March 2019 at 20:42

    No, it is -Vcc, in this case it is -12 VDC.

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  19. Icziko23 March 2019 at 20:43

    For anyone having problems with oscillations when Gain pot is above 60-75% - I recommend to shield Input and Gain wires as described on Freestompboxes forum: http://www.freestompboxes.org/viewtopic.php?f=1&t=28011&p=274921#p274921

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    1. Franck19 July 2019 at 11:17

      Hi please can you post the photo or explain a little beat because I can't see the photo in the forum you said ! I'm registered but don't have permission to the the file … Thx

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  20. debeo24 March 2019 at 14:18

    That was accidentally but I was connected "Middle 2,3" in place "SW6" on board, and... WOW!! KILLER!!
    It stays, altough I've lost Bass and Treble control! :)

    I'm connecting through "Power OUT jack" to 3PDT switch.

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  21. Kirkus8 June 2019 at 08:07

    This comment has been removed by the author.

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  22. santi13 November 2019 at 22:43

    This comment has been removed by the author.

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  23. santi13 November 2019 at 22:45



    hello everyone, congratulations for the scheme, I have a problem,the pedal works but the volume of the distortion is much lower than that of the clean, someone will help me please?thanks!!!!

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  24. Silva20 February 2020 at 06:45

    I just built this and I am having troubles. The pedal does not work at all when it is switched on. All I get is a high pitched whine. When the pedal is off, the gain knob somehow affects the bypass signal. When the gain knob is turned all the way down, the bypass works; if I turn it up, the signal disappears. I have checked every component and they are all in the right place and oriented correctly. I have resoldered every connection twice. Anyone have any ideas?

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    1. Silva20 February 2020 at 10:29

      OK, I was wrong. One of the 2.2 electrolytic caps was off by one hole. Now that that's fixed and everything is verified in the correct place and resoldered, nothing works at all. No signal going through to the amp either when the pedal is on or off. I'm at a loss.

      Does anyone have a pic of the offboard wiring? Wondering if I did something wrong there

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  25. Unknown1 February 2021 at 16:28

    This worked perfectly at first. Then, after about a week, I lost output level and the oscillation that many others described began. I ended up placing a buffered pedal before it and it resolved the oscillation. Later, I built a small opamp buffer to place between the input and circuit in, and it works perfectly. It tamed some of the extremely bony bass frequencies as well.

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