Sunday 31 March 2013

Behringer VT911 Vintage Tube Overdrive

Now that i'm back home, i thought i'd post a few more big ones for this month. You know. There's 31 days in march and we only had 28 layouts out.. So here's couple more to match the number of days. :)
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I never thought i'd draw up a Behringer original, but once i saw this it just made sense. IC pinout is matching the TL074, as there's not that much easily obtainable info around about the original "Coolaudio Quad Opamp". I'm just guessing that the pinout matches with TL074. Anyway.. This is quite nice and relatively simple 9V tube circuit. You should probably try out other pin-to-pin equivalent tubes in there too.

I'd really like to see this one done in 1590B with a tube socket on top :P




22 comments:

  1. There´s a modded version from Bajaman: http://i197.photobucket.com/albums/aa211/bajaman002/VT911schematicmodifiedbybaja.png

    Seems that this one have a more appropriated bias values and a better overall tone. There´s a "Bitmo" mod that some reports as very good too.


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    1. I knew this was going to be the first comment on this layout :D

      Bajaman version is drawn and ready to go - as soon as this is verified :)
      +m

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    2. Oh come on, Miro, don't do that to us... post the other one too so someone can verify the "good one" :P

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    3. I could remove this one too...
      +m

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    4. Nah, put 'em both up, if someone likes the original it's there to use...

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  2. it´s a shame... no TL074´s at my local supply :P

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    1. Ebay and Taydaelectronics are good places for sourcing. Usually you can get twhat you want pretty fast from tayda..
      +m

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    2. Yes Miro... i´ll "collect" some layouts in my long list of favorites from Tagboard and make one "big purchase" of components that i dont found in my country... by now, my tonebender trannies has finally arrived and i´ll have some "fun" experimenting with the temperature/biasing issues related to the germs :P

      P.S.: The matched set from Smallbear came with the Germ diode included, maybe with the leakage matched... who knows? anyway, was a nice bonus!

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  3. Can you check the switch wiring? Do both of those wires go to sw3? Is there no wire going to SW5?

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    1. Ha. I do have a slight labeling error :)

      The upper SW3 should be SW5. Now that i have the project open, i think i'll add one more link to get the input jack going stairght to board... Fix is coming in next 3 minutes...

      ..and done.
      +m

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    2. Fixed. Thanks onthetundra!
      +m

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  4. Well this one works! I built this as per your lovey layout, then modified it a touch to reflect the mods above. Now she's a great overdrive. Sounds really good in the lower half of the gain adjustment although flat out is quite a wild ride if your in the mood for that. It's hard too tell as its quite subtle but I do believe the tone knob is wired backwards. Like I said the tone does very little on my build. It stacks well into my barbershop with the sag half down. Yummy amppy goodness. As to be expected, it's VERY touch sensitive. Nice one guys! I do recommend the modded schematic if you can. The only thing I put back to stock layout was the output buffer stage which loaded down the output to almost in audible levels. Leave that as is (after the volume pot). Oh, almost forgot, I replaced the 1n4001 with a 1n5817 shottkey to beef the voltages up a touch. It helps with the heaters. Cheers dudes and sorry about the long message. Rock on!!!

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    1. Awesome, thanks for verifying Jeff :o)

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  5. Today I've been able to take a look to my brokn original one. I was lucky enough because the issue was just a pair of wires loose.

    The tube was in good condition ( a "Behringer" labled one, don't know which is the real brand,and so the board (many smd components) is ok too.

    Well, the sound.... really would not pay anything more than the 10 euros I paid for this. Not that it sounds bad, is just "another" overdrive. Not bad, but no way great, just a overdrive like the hundreds you can find anywhere.

    At least is super cheap :)

    BR

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  6. Hi folks, Can anyone verify where this project says 'RLED' what exactly does that mean, something between 2k2 or 4k7 ? thanks Jim

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    1. RLED is the CLR for the LED, which in this layout was placed on the board for convenience. The value of that depends on the LED you are using, a typical value is 1K. I use lower values for more brightness, though.

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    2. Well.. The value is per specific LED. For example, i use 33K every time i want a white LED. Some superbright blue ones need something like 180K or even higher to prevent you from burning your eyes. 1K is good for standard diffused red or green.
      +m

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    3. Definitely true.

      What kind of LEDs are you using? YMMV of course but I've never used a CLR that large. I have a waterclear blue LED in a Muff that's working off a 270 ohm resistor and it's bright, but not painfully so.

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  7. Thanks for the advice guys, I never though of this before, Im just using a super cheap mix of standard coloured leds I got off ebay and have used for all my projects. Most of them Ive used a 2K2 and some when the project has been specific and mentioned the value on the board. Do you know of a guide on how to choose or measure ? Thanks again.

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    1. Try different values for different LEDs on a breadboard. Or use a trimmer to find the value that is good for you. I use 1k for standard diffused red LEDs, and then I adjust the others to its brightness.

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    2. I usually use a battery, resistor and a LED to determine what value works :)
      +m

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  8. OK Ive finally done this and getting something however Im only achieving unity when the thing is full blast on all pots, I'm taking I should get some boost even if it is minor ? Heres my voltages across the chip incase it helps but I thought the looked ok : (pin,V) 1)2.71,2)2.71,3)2.43,4)5.45,5)3.33,6)2.71,7)2.71,8)3.3,9)2.7,10)2.7,11)0,12)2.7,13)2.7,14)2.7. and across the valve 1)3,4)8,6)4 there is nothing at the other pins of the valve? Any help much appreciated. Thanks Jim

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