Tube Town - Vanilla OD MKIII

[nomorebetts]

Hi all,

I was searching for a low voltage tube overdrive and stumbled across the Vanilla Over Drive at Tube Town.

https://www.tube-town.net/diy/lov/lov01-vanilla/lov01-vanillaoverdrive-en.html

Information seems to be fairly scarce so I was wondering if anyone here has built one?  Or knew of any sound clips floating around the net?

I plan on breadboarding it but I have a couple of questions regarding the schematic that maybe you smarter folks could answer.

  - Firstly, the boost switch seems to just add or omit a single resistor from the circuit, reducing the resistance to ground from the cathode of tube 1.  Is this a well known technique for boosting output from tubes?
  - The part of the circuit in red is a boost circuit.  I haven't studied many boost schems, does anyone recognise it?
  - What's the advantage of having the bypass after the first input stage?  (apart from being able to use the boost switch when the effect is not engaged) Also what's with C6 and R19 in bypass??? What disadvantages are there for bypass after input stage?

I think I really need to hit the breadboard... right now I'm thinking of changing the boost switch to put the red part of the circuit in or out and using normal true bypass.

Thanks for looking 

[caspercody]

I just bread boarded it, and I get a lot of background hum. This is my first try with building something with tubes. It sounds gated, or not biased.

[nomorebetts]

I'm not a tube expert either, but could the hum be caused by your power adapter? Is it well regulated?
I plan on bread boarding tonight so I'll see if I get the same result.

[caspercody]

I tried (2) different power supplies and same results. I will try a battery next time. I checked the voltages against what is shown on the schematic, and they are all really close to what they should be. I tried a audio probe approach and found the sound started humming got worse after the JFET. And the gating sound got worse after the (2nd) tube. I will try swapping the tubes and see if that changes the sound. I did not add the bypass option, so I do not have R19 or C6 in my circuit. And I have a BeavisAudio like box for my volume and jacks, so I did not put R20 in the circuit.

[duck_arse]

the boost switch switches in the cathode bypass cap, which increases the ac gain. it is used in the same way with valves, fets and transistors. the 47k is to prevent popping when switching.

the fet boost section looks like the same old single fet boost you see everywhere, probably recovering level and providing a constant load after the tone control. this looks like what I was/am going to put in my valvecaster.

r19 may be a divider to un-recover the level out, seeing as v1 is boosting and always in circuit. it will provide a "valve sound" high impedance buffer for your guitar at all times, because it is not bypassed.

but I'm not an expert either .... and I haven't read the web-page yet.

[nomorebetts]

the boost switch switches in the cathode bypass cap, which increases the ac gain. it is used in the same way with valves, fets and transistors. the 47k is to prevent popping when switching.

the fet boost section looks like the same old single fet boost you see everywhere, probably recovering level and providing a constant load after the tone control. this looks like what I was/am going to put in my valvecaster.

r19 may be a divider to un-recover the level out, seeing as v1 is boosting and always in circuit. it will provide a "valve sound" high impedance buffer for your guitar at all times, because it is not bypassed.

but I'm not an expert either .... and I haven't read the web-page yet.

Cheers!  Its making more sense to me now after reading your answers and the web page again.

I bread boarded this up and spent a couple of hours playing around with it.  Overall I like it and can see this replacing my Valvecaster.

I used two second hand 12au7 tubes from the 60s and I had to sub a j201 for the bf245 and a pot with the wrong taper for the tone pot.

Theres plenty of drive on tap with humbuckers! With or without the boost switch engaged - which gives a noticeable volume increase but isn't over the top.  I also stuck a SHO in front of it for shits and giggles and it turns into a distortion. 

When bypassing the red boost circuit, I can still get drive but not as much which is expected.  The gain pot isn't useable for its full travel either.  I think the circuit sounds better with it in and I plan on including it.

With single coils there is also drive.  Something I couldn't coax out of my Valvecaster without modding it, which I never got around to.  It's also no where near as dark sounding as the valvy and the tone control is useful, probably more so once I get the right taper.

I think its time to create a layout and play around with it more! 

[caspercody]

Any way to get a sound clip?

[duck_arse]

I dunno if I would use a j201 there. maybe a j210, or a 2n5457 or even an mpf102. but I'm like that.

[nomorebetts]

Any way to get a sound clip?

Unfortunately I don't have anyway of recording at the moment.  But I think my friend can.  I'll look into it.

I dunno if I would use a j201 there. maybe a j210, or a 2n5457 or even an mpf102. but I'm like that.

I think I have both 2n5457 and mpf102.  Which would you recommend?  Any reason why not j201? 

[caspercody]

If you have one, try a socket for the Jfet. That way you can try different Jfets to hear the difference.

If you have a Rock band or Guitar hero mic, you can use this with Windows recorder to record a cheap sound clip.

[duck_arse]

the j201 is a low current, low noise, pre-amp-ey type fet. I'm pretty sure the specified bf series fet would be a bit beefier, current wise, so I'd replace it with the beefier type noted. and I've got a set against the j201, I think.

try the 2n5457, an old favourite.

[nomorebetts]

Well its been a while 

But I have designed and verified my PCB layout.  It fits in a "landscape" 1590BB with the tubes and 2 out of 3 pots onboard.

Its sounding really nice.  Even at lower gain it really sweetens up the tone when ran into a solid state amp.  I ended up using a bf245 like the circuit called for.

But I'm not quite happy with it yet.  The bypass is way louder than unity, so I guess I will need to play with the values of R19 and C6.  Any ideas here?  Should I just change the resistor value and leave the cap alone?

Also there is some hiss once the volume pot is past 12 o clock.  Regardless of gain pot setting.  This could be my power supply.  I breadboarded the power supply they recommend: (http://www.tube-town.net/diy/lov/lov-power-eng.html)
But I only have a 12v adaptor so it brought the voltage down too low and the breadboard added even more hiss so it wasn't a good test.  I need to find another adaptor to test it.  Or should I use shielded wire for the input???

Cheers!

[nomorebetts]

I added the power supply circuit and am now using a 16v adapter.  It didn't remove the hiss entirely so its likely the nature of the beast or sheilded wire could help.  I'm just going to live with it as it's not really that bad.

Also bypass was actually pretty close to unity.  When I tested it that other time my amp was turned up much louder than when I normally play.  I just didn't notice 

I'll post some pictures and my layout soon!

[duck_arse]

what voltage are you running on the heaters?

[nomorebetts]

what voltage are you running on the heaters?

Roughly 12.10 volts.

[clipman3]

Roughly 12.10 volts.

I'd try running the heaters a little bit lower. Running the heaters on 11-11.5v vs a little over 12 can really lower the noise floor in some instances.

[nomorebetts]

Roughly 12.10 volts.

I'd try running the heaters a little bit lower. Running the heaters on 11-11.5v vs a little over 12 can really lower the noise floor in some instances.

Awesome I'll give that a go!

Here is my finished pedal

[nomorebetts]

Build one!!!!!! 

Schematic available here:
https://www.tube-town.net/diy/lov/lov01-vanilla/lov01-vanillaoverdrive-en.html

BOM:
https://dl.dropboxusercontent.com/u/75388200/Vanilla%20OD%20BOM.csv

PCB Layout:
https://dl.dropboxusercontent.com/u/75388200/Vanilla%20OD%20Layout%20-%20Pots%20on%20Back.pdf

Transfer:
https://dl.dropboxusercontent.com/u/75388200/Vanilla%20OD%20PCB%20-%20Pots%20on%20Back.pdf

Offboard Wiring:

[duck_arse]

I see an awv valve there. they don't turn up too often in the pictures section.

2 of my sisters used to work for miniwatt during the 60's, and neither ever brought home any bags of valves, worse luck.

[edit:] and the last time I saw a valve that colour blue, it was in real, expensive trouble.

[nomorebetts]

I see an awv valve there. they don't turn up too often in the pictures section.

2 of my sisters used to work for miniwatt during the 60's, and neither ever brought home any bags of valves, worse luck.

[edit:] and the last time I saw a valve that colour blue, it was in real, expensive trouble.

Haha the ol' led in the base of the valve trick!

I was lucky enough to pick up about 10 of these miniwatt 12au7s from ebay for a reasonable price.  I have no idea what they were pulled from and they were untested but all worked in my valvecaster so I was really happy that I took a chance on them.