Does anyone know or have this pedal-BiyangOTD-100

[Crawf]

Hi, I recently bought this tube distortion (made in china) pedal on e-bay having hankered another since offloading my Tubeking, so i was wondering if anyone had one and if so what they thought of it.
My issues with the pedal are, its far too bright,treble control is right down to get the brightness i like,
its far too bassy, bass control is nearly off to get the amount i like plus its mega loud which makes it had to play in the house,last thing ,it runs off a 6v PSU so i cant have run from my boss PSU(well i've not tried in case i fry something!)
Pot values are Volume B50K, Treble B1M, Bass B1M and Gain B470K
I can post a pic if the board if someone can remind me how to do it and if i can preform a few simple mods to remedy the issues i have i can no problem, if anybody has any thoughts on this it would be great to hear them, thanks Crawf.

[brett]

Hi
those Biyang pedals are cool looking, but I've wondered how good they are.  IIRC they wholesale for only US$30.
You can often fix up flabby bass on a 12AX7-based circuit by decreasing the size of the cathode bypass capacitor.  Standard, it will probably be somewhere from 4.7 to 22uF.
For brightness, look for a small value capacitor bypassing the volume control (ie from lug 3 to 2).  If such a cap exists, try disconnecting it. 
Alternatively, there might be a cap and resistor in parallel between the first and second stages (which has less impedance to highs than lows). Typically, the values would be something like 470k and 470pF.  Again, disconnect the cap.  To see this type of thing, look up a schematic of how to add a bright switch to an Epiphone Junior.

It would really help to have a schematic available.... Any chance?
cheers

[Crawf]

Hi Brett, thanks for replying, unfortunatley i dont have a schematic although i have e-mailed the company for one, what i have done is to change the treble and bass pots to half their original value, 1M to 470K and that has helped, i also messed about with differant valves but eventually settled on the original Electro Harmonix  12AX7.
My only other issue is that its 6V which means i need a PSU dedicated to that pedal when all the others are running  off 9V, but if ot sounds good its a small price to pay,  cheers Crawford.

[jakenold]

Please note that it is running at 6V AC, as it is probably running the valve at high voltage. If you wanna make it fit your current setup (this requires a power supply capable of delivering AC), you chould change the transformer inside. Get one with the same secondary voltage, but with a primary made for your current power supply.

Beware that Biyang claims it draws around 1A. Maybe it's best to leave it alone.

Kind regards, Jake

[Paul Perry (Frostwave)]

That sounds an ideal candidate for mods, being as all the hard parts (the tube mounting) is done already!
And yeah, no point trying to replace the 6V AC input with anything else..

As a matter of interest, is there a manufacturer name on the transformer?

[Crawf]

Hi, Afraid i cant see any name on the transformer, as far as the 6v goes, does that mean although its only 6v going in, there are higher voltages inside? if there are i'll leave it be, thanks Crawf.

[Caferacernoc]

Any luck on a schematic?

[Caferacernoc]

So this pedal is confusing. They market it in three versions. Value, with a 6ax7 tube. Plus standard and Pro, which come with a 12ax7 tube. All versions have the same power supply and they imply that the only difference is the tube. 12ax7 and 6ax7 don't have the same heater voltage requirement so what the heck is going on?

[dan5150]

So I picked up one these things for $20 off of CL the other day. It's in fine condition, and doesn't sound bad, at all. In fact, when plugged into my Epi Valve Jr. it really makes that little amp roar!

Obviously, I opened it up to see what was inside. It looks to have a 6ax7 tube (which I never heard of until now). I intially assumed that it was similar to a ToneBone where it used the tube simply as a clipping diode. But the fact that it has a transformer on the inside, now makes me wonder if it running the tube at higher voltage.

There is a small solder "jumper" on the little board where the tube socket is mounted that looks to configure it between 6ax7 and 12ax7.

Since I know very little about tubes, what would be the expected tonal difference each? Is it worth trying to swap the tube?

Here is a picture of the board. This isn't exact, but it is prety close:

[jazbo8]

The tubes all sound different, so the different versions will sound different, you can definitely swap the tubes yourself to find out... And they are not being use as "clipping diode", the 6/12AX family of tubes are probably the most popular dual triode tubes for audio application, especially for guitar amps. The 6AX7 uses different heater voltage than the 12AX7 (see the spec sheet at http://drtube.com/datasheets/12ax7-sylvania1955.pdf). The jumper on the tube board most likely just switches the voltage applied to the heater pins.

some drive mods are on http://www.google.com.hk/url?sa=t&source=web&cd=1&ved=0CBgQFjAA&url=http%3A%2F%2Ffreestompboxes.org%2Fviewtopic.php%3Ff%3D11%26t%3D4411&ei=WLpYTpbRApHOrQeCm_XdCg&usg=AFQjCNFzq_qJ6fqiW_oMs_ajy9m56RmdOw

You can really tweak the tonestack to get the sound you want, you can find the Baxandall/James circuit at http://amps.zugster.net/articles/tone-stacks

But what is an interplay-jack?

Jaz

[dan5150]

But what is an interplay-jack?

Good question. On the case, it is marked as "switch". It is an 1/8" jack. I can't find a manual or documentation for this thing so I have no idea what it does.