BSIAB hell......help please.

Xavier · December 14, 2005, 12:56:21 PM

OK, 2nd attempt at building a BSIABII, and obviously it doesn't work. Zero sound.

Built following Torchy's vero layout, which I believe is correct. All transistors are J201 and have the right orientation (according to the vero layout, from above to below DSG, flat side facing left.

LED works..........

Wiring is correct and I'm using a "9 volt adaptor". Measuring 14,56 volts at the output......

Here are the transistor reads:

Q1

D 7,6v
S 0,2v
G 0v

Q2

D 14,56v
S 7,55v
G 6,93v

Q3

D 0v
S 0v
G 0v

Q4

D 14,43
S 8,05v
G 6,91v

Q5

D 10,76v
S 0,5v
G 0v

I've looked for shorts between traces but apparently there aren't.

The enclosure has been already built, so I must finish this....

Help....

aron · December 14, 2005, 01:12:27 PM

Q3 is completely dead. Something's obviously wrong there.

RDV · December 14, 2005, 01:12:46 PM

http://www.generalguitargadgets.com/diagrams/bsiab2_voltage_diagram.gif

RDV

Peter Snow · December 14, 2005, 04:01:41 PM

That's a real nice pic Ricky. It addresses all the FET concerns in one graphic

Since we are on the topic of FETs, I have a slightly related question. I always thought the Gate and Drain on FETs were somewhat interchangeable/reversible. Is this true in all circumstances or only in certain configurations?

Thanks,

Peter

aron · December 14, 2005, 05:33:29 PM

I asked this a while ago and I have been able to swap them around, but was told that it might indeed make a difference.

RDV · December 14, 2005, 08:31:33 PM

Quote from: Peter Snow on December 14, 2005, 04:01:41 PM
That's a real nice pic Ricky. It addresses all the FET concerns in one graphic

Thanks to J.D. Sleep. His site is full of things like that.

RDV

Xavier · December 15, 2005, 10:48:54 AM

OK. BSIABII boxed and working

Haven't had the time to use it with my setup. So far it's a mid-heavy distortion and apparently is nice. I guess it will need some tweaking. Sounds great for palm-muting and probably my search for a high gain diy distortion has ended. Really tight sounding (250 pF input cap !!!, isn't that too much?). Much better than other commercial stompboxes.

BTW , I've adjusted the internal trimmer by ear. Seems to be kind of a "master volume" control, at the moment is almost maxxed ,around a 75%. How should I tweak it?

After debugging, I've found out I forgot one of the small jumpers *DUMBASS* and the output lead going from the vol output to the switch was internally broken *did I say DUMBASS?*.......

Now on to the mosfet boost....

RDV · December 15, 2005, 10:51:46 AM

I love happy endings.

Just don't give up. Never give up.

RDV

mydementia · December 15, 2005, 10:56:20 AM

I'm also curious what we're supposed to be trimming with the trim pot. Mine definitely shapes the tone...from fizzy, flabby sounding to harsh and grating with some strange 'humps' in between. I'm still not completely satisfied with my BSIABII build...maybe getting the trimmer properly positioned will help!

Another anomoly (?) with my BSIABII is that it picks up RF (VHF?) for the first 5-10 minutes that it's plugged in...then it quiets down and 'plays nice' - thoughts?

Mike

Steben · December 15, 2005, 11:00:06 AM

Trimmers are mostly used to bias the output at about 1/2 of supply voltage (in the 9V case mostly 4,5Volts).
With the BSIAB it is only the case at the last FET, since the gain stages are self-biasing (phew...

). So try putting it around 5 Volts for more 2nd harmonic or just 4,5 to get plain common sense brown sound.

QuoteI love happy endings.

Just don't give up. Never give up.

RDV

Oh, yes, happy endings are even better when the quest was veeeeery long...
It's a pitty yet understandable my girlfriend doesn't share the same euphoria.Â

Xavier · December 15, 2005, 11:43:25 AM

Quote from: RDV on December 15, 2005, 10:51:46 AM
I love happy endings.

Just don't give up. Never give up.

RDV

Who's giving up?

. It really sounds nice. The problem is I've already filled the four spots in my pedalboard ,previously with non diy pedals, and now fully handmade.

I steal the small parts from our service department, but the enclosures and switches are expensive. I think the next step will be cheapo self made enclosures. I have four finished pedals, but I have like 7 populated pcb's awaiting to be boxed.

So many pedals to be built yet.......

Another idea I have in my head is a multi-fx. A long enclosure including a dynacomp or squeezer clone, OD, chorus, and PT80, with an AMZ buffer at the end.

aron · December 15, 2005, 12:59:13 PM

Quotetight sounding (250 pF input cap !!!, isn't that too much?)

That is not your input cap. That is a high end roll off. Please check your wiring again.

Aron

Xavier · December 15, 2005, 05:12:17 PM

Quote from: aron on December 15, 2005, 12:59:13 PM
Quotetight sounding (250 pF input cap !!!, isn't that too much?)

That is not your input cap. That is a high end roll off. Please check your wiring again.

Aron

C1 just before R1 is a high end roll off? I have the GGG schematic in front of me, and C1 is 250 pF

RDV · December 15, 2005, 05:13:41 PM

Yes, there is no in-line input cap on that pedal.

RDV

aron · December 15, 2005, 05:19:29 PM

QuoteC1 just before R1 is a high end roll off?

yep. Signal to ground. Not in series with the input. It's a high end roll off.

Xavier · December 15, 2005, 05:41:19 PM

Quote from: aron on December 15, 2005, 05:19:29 PM
QuoteC1 just before R1 is a high end roll off?

yep. Signal to ground. Not in series with the input. It's a high end roll off.

That shows my ignorance, sorry....

I've had the time to test it properly, and I really like how does it feel . The basic timbre is perfect and it's also easy to play. If you have a DS1 you'll know what I mean with this. Has the chug-chug factor I look for in dist pedals.

Obviously it's intended to be mid heavy. If only it had some more bass it would be perfect, but as there are not input caps to change, I gues the best solution would be to implement the SWTC or the AMZ presence control. Adding more bass in the first stages would spoil the concept behind this circuit, should be added after Q5...

Mine has been built using all J201's as there were no 2n5457 FET's available at the parts store. A little too compressed, as advised. Need to look for a different J201 sub.

Way different from the commercial dist pedals.

This is what a metal zone should be

aron · December 15, 2005, 06:24:02 PM

Adjust C5. Socket it and try 250pf, 120pf, etc....

Steben · December 16, 2005, 02:43:10 AM

I really favour the BMP style or AMZ style tone controls. I guess they are outdated for some, but they work. They really give back bass bottom to any circuit. A TS would benefit too.

Gringo · December 16, 2005, 08:03:50 AM

You can make c6 switchable, or just loose it, to remove some high end, making it sound "fuller".

Are you using a strat/single coil pickups?

Xavier · December 16, 2005, 10:11:09 AM

I like so much the basic timbre that so far I'm not touching anything. I've messed enough with this pedal. I'll put it aside my Rat in the pedalboard and see how giggable it is. My only concern is the apparent lack of bass, but I'll wait until my next band rehearsal. Thanks for the help !!!!

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BSIAB hell......help please.