what type of biasing is this?

[djmiyta]

After almost 3 years I finally got the correct transistors for my much anticipated Openhaus pedal Madbean's Orifice. Sadly it sounded about the same as with the other transistors I've tried. Saying this exact same thing on another forum someone mentioned that possibly the transistors are not biased. Well I'll take any troubleshooting advice or direction to get this SOB working properly. My issue is I think I know which transistors I need to bias (definitely not sure though) but trying to research how to bias ( without a build Doc telling me what trimmer goes to what transistor) I've found there are a few different biasing circuits like Common Emitter Transistor Biasing , fixed base biasing a transistor , collector feedback biasing and 1 or 3 other ways.

I've uploaded the build docs for the Orifice that has the schematic .

Could ANY of you fine people take a minute to look at the schematic and.....

1- tell me what biasing is being used
2 - what transistors I need to bias
3 - what resistor numbers are the biasing resistors

Somebody , anybody help a fool out. Although not a 100% sure I'm pretty sure I can figure it out with those questions answered , but don't be surprised when I show back up with twice as many questions
.
The issue I'm having is this is supposed to be a monster high gain crunch beast. Mine is not. Having gone over my build several times I did find a wrong valued resistor. I had a 150 ohm in R7 the build worked but VERY mild overdrive putting in the correct value made the pedal go from super light overdrive to really light distortion. So I'm wondering if I upped R7 from 100k to say 110 or 120-130k could get it into the territory I'm wanting to hear.
It's only because of my mistake that I know R7 adds crunch but that is all I know.

Thank you any and everyone who takes their own time to read about my Openhaus issues. ANY help is so, so appreciated.

 

[djmiyta]

Also if anyone does take a look could you tell the purpose of switch 1? seems like a bypass or cutoff

 

[Bambalam]

I'm taking a guess here. Looks like biasing is done with fixed value resistors as opposed to a trimmer pot.

Q2, Q3, and Q4 appear to be the transistors to bias.

For Q2: R19 and R21
For Q3: R23 and R24
For Q4: R27 and R29

SW1: Low-High Gain

 

[djmiyta]

I'm taking a guess here. Looks like biasing is done with fixed value resistors as opposed to a trimmer pot.

Q2, Q3, and Q4 appear to be the transistors to bias.

For Q2: R19 and R21
For Q3: R23 and R24
For Q4: R27 and R29

SW1: Low-High Gain

Ahhhh thank you so much . Thats the kind of info I was hoping for . In my searching it seems there are different transistor configurations and I had no clue where to start with that. Now I got a experimenting point . Again many thanks

 

[Chuck D. Bones]

This circuit is self-biasing. You should not need to tweak anything except selecting Q6. Is Q6 germanium? I'm too lazy to look up the parts list. If you can see your way clear to posting a parts list and measure the voltages on Q6-C and Q3-C, I might be able to verify whether your circuit is working right one not.

Q2 & Q5 are active constant-current loads for Q6 & Q2, respectively.

The GAIN/MODE switch selects the 2nd stage (IC1B) gain and 4th stage (Q2-Q4) gain. Depending on the switch position, one is set to high gain and the other to low gain, relatively speaking.

 

[djmiyta]

This circuit is self-biasing. You should not need to tweak anything except selecting Q6. Is Q6 germanium? I'm too lazy to look up the parts list. If you can see your way clear to posting a parts list and measure the voltages on Q6-C and Q3-C, I might be able to verify whether your circuit is working right one not.

Q2 & Q5 are active constant-current loads for Q6 & Q2, respectively.

The GAIN/MODE switch selects the 2nd stage (IC1B) gain and 4th stage (Q2-Q4) gain. Depending on the switch position, one is set to high gain and the other to low gain, relatively speaking

Thank you for your input and your time. I'm always happy when I get words of wisdom from your fantastic brain. I always have a lot to research afterwards though (not a complaint whatsoever.) Things like active constant current loads and I think of my kids and their diapers. Yes the 2n1306 transistors are NPN germaniums I picked up from Small Bear. I won't be home until Saturday maybe Sunday for the parts list and to get the voltages .

Edit: was able to get the build docs for it. It has the layout ,solder mask, scheme, and parts list. When I get home I'll get those voltages and some pictures.
Thanks again

 

[djmiyta]

I apologize I answered without double checking. No, Q6 is not germanium it calls for it being 2n5457.
q1 = 78l15
q2 = lnd150n3-g
q3 = 2n1306
q4 = 2n1306
q5 = lnd150n3-g
q6 = 2n5457

and the voltages
Vin @ 18.04v
q1
in = 17.31v
grd = 0
out = 15.17

q2
d = 15.17v
g = 7.10v
s = 7.51v

q3
e = 5.86v
b = 2.2v
c = 7.24v

q4
e = 2.905v
b = 0.902v
c = 176.6mV

q5
d = 15.17v
g = 7.10v
s = 8.32v

q6
d = 8.24v
g = 0.7mV
s = 199.9mV

I know you only asked for q3 and q6 but I figured the more info the better maybe something will jump out at you
One thing I caught looking at the scheme was 2n5457 is DSG and the layout has it DGS so I swapped the leads I think the rest are right.
Seeing that Q3 and Q4 are both npn germaniums seems there is quite a difference in their voltages. I don't know if thats correct or not but to me somethings off. Wish I had some legit numbers to compare to.
Hope you can see something and I can take this off my bucket list and onto my pedal board. anxiously waiting (knowing I just posted this ) to hear back.
And again I thank you for your time.

I've mentioned before Sabrotone's stripped down Openhaus called Lighthaus. It really is one my absolute favorite pedals the eq section is awesome and pairs really well before or after other dirt pedals. I don't think anyone would be disappointed building it.. Just FYI to anyone looking for a really good overdrive. Effects layout blogspot has a perfboard layout for it that I used. He does awesome layouts.

 

[Chuck D. Bones]

Q3's emitter voltage looks wrong. Recheck it. Also verify R24 & R35 are the correct values.

Q4's voltages are wrong. Q3-B connects to Q4-C, so their voltages should be the same and according to your measurements, they're not. Recheck all of you measurements. While you're at it, verify that pins 1 & 7 on all of the opamps are close to Vref.

What started as a question about the circuit design has turned into a troubleshooting thread, so please do the usual stuff and recheck all of your components, solder joints, etc. Post hi-res pix of both sides of the board so we know what we're dealing with here. Identify anything you did that is not per the drawing.

Is the expression pedal jack wired per the schematic?

I have found several layouts on effectslayouts that have errors and don't work. The vast majority of the stuff is good, but I'd check anything I find there before building it. Just sayin'.

 

[Paradox916]

Yep!

This is conformation bias.

 

[djmiyta]

Q3's emitter voltage looks wrong. Recheck it. Also verify R24 & R35 are the correct values.

Q4's voltages are wrong. Q3-B connects to Q4-C, so their voltages should be the same and according to your measurements, they're not. Recheck all of you measurements. While you're at it, verify that pins 1 & 7 on all of the opamps are close to Vref.

What started as a question about the circuit design has turned into a troubleshooting thread, so please do the usual stuff and recheck all of your components, solder joints, etc. Post hi-res pix of both sides of the board so we know what we're dealing with here. Identify anything you did that is not per the drawing.

Is the expression pedal jack wired per the schematic?

I have found several layouts on effectslayouts that have errors and don't work. The vast majority of the stuff is good, but I'd check anything I find there before building

Thank you very much your help is very much appreciated . I will definitely check over EVERYTHING again.
I have no doubts that you have found errors in some of his layouts because so have I, but I will say I've built around 80-100 (if not more) pedals from that site and only twice did I find a layout issue from his end, all other build issues were from my lousy building techniques as I'm sure this issue with the openhaus is and I don't want to be misunderstood that my original question was not hinting towards Beans's layout having an issue as I ALWAYS suspect my problems with a build to be on my end first because they 99.99999999% of the time have been.
But regardless, the Lighthaus is a damn good O.D. and with you're incredible and vast knowledge I could see you making some killer upgrades/mods to it but that is only from my very limited knowledge of this hobby.
Once I did those voltage readings though I had a gut instinct that they were not right. I just don't know the why's and how's of it .
There is 2 things I did not do.
1 - I ran out of toggle switches so I soldered 2 wires i and twisted them together for the SW1 not the gain mode switch but SW1. Since I can't switch it with no switch maybe that's a n issue and without looking at it at the moment.
2 - I don't think I did an expression pedal jack but I'm not sure there is one on Madbean's layout maybe I missed it but I don't think so.

as ugly as the build is I will get some pictures up of it and check those places you told me to check. I'm going out of town again after x-mas so it may be a week before I can get to the pics and checking it over . Hope you got a bit of patience and can continue to help me out. I've been wanting this pedal for a long time now. Though it's only happened 3 or 4 times building something and it does'nt live up to my hype and hope praying this one does'nt become # 5.

 

[djmiyta]

Yep!

This is conformation bias.

Thank you for the homework assignment. Never heard that term before but I'm sure there is a whole lot I've never heard before so off to Google school I go
Thanks for the input.

 

[Paradox916]

Thank you for the homework assignment. Never heard that term before but I'm sure there is a whole lot I've never heard before so off to Google school I go
Thanks for the input.

It was supposed to be a joke… they can’t all be winners I guess….

 

[djmiyta]

Awww damn and I've seen/read your sense of humor too
But it's too late man I'm down that rabbit hole and I'll find the answers

 

[Chuck D. Bones]

Awww damn and I've seen/read your sense of humor too
But it's too late man I'm down that rabbit hole and I'll find the answers

That's right, don't give up.

It was supposed to be a joke… they can’t all be winners I guess….

Wrong forum. You want https://forum.pedalpcb.com/threads/more-jokes.8168/.

Confirmation bias is a real thing. Conformation bias I don't know. So many people use their phones for messaging and don't proof-read before hitting send.

 

[Nostradoomus]

Confirmation bias is a real thing. Conformation bias I don't know. So many people use their phones for messaging and don't proof-read before hitting send.

Gotta up that corroboration bias.

 

[Fama]

Confirmation bias is a real thing.

Is that where you start thinking differently once you join a protestant church?

Sorry, sorry, I'll walk myself out.

 

[Paradox916]

That's right, don't give up.


Wrong forum. You want https://forum.pedalpcb.com/threads/more-jokes.8168/.

Confirmation bias is a real thing. Conformation bias I don't know. So many people use their phones for messaging and don't proof-read before hitting send.

I give you top shelf mediocre comedy and you offer me semantics?!… but seriously I’m guilty of this A LOT!

 

[jwin615]

I believe 2N1306 are EBC, tab on emitter. May want to check their orientation