Another sitar circuit

[Pedal love]

Everything looks ok, except the output pot ground/earphone ground, should be grounded with the in/out jack grounds.pl

[GREEN FUZ]

Yeah that`s what I thought. I just had them trailing off like that because graphically it was getting a bit messy. Thanks for that.

[spudulike]

Swap lugs 2 & 3 on the pot.

[col]

So how does the earphone/earphone coupling work? Is it like a transformer (a la Jawari?) or does it induce a vibration in the crystal earphone that is transmitted to the amp? Is it an induction or is it magic?

[Scotty Did]

I'm about to state something that I have known for a while and probably many others know but I just haven't seen any one state it like this cause it makes perfect sence to me.

the Earphones taped together.

   The basics- and earphone is just a speaker that is fixed next to your ear.  a microphone is basically a loud speaker wired in reverse. the 2 earphones taped to geter works like this.  the signal is being trasmited from the one earphone and picked up by the other one and sending it off to the guitar amp.
   The same exact thing was used to record the bass tracks on the beatles Paperback Writer.
   As for the type of earphone, you gotta think about what was available in 1967. so no micro headphone.  sony didn't introduce those till the 1980's. my guess is they just listed earphones cause they were easy to get a hold of.  I would think a pair of small speakers would work all the same like out of some cheap computer monitors.
   From what I can figure out. the earphones just deminish the signal. it's like hooking up a mic to your amp and micing a small speaker.
   Also this I would think wuld be obvious but remeber this was 1967 and what there was in terms of amps for the time.  there was no such thing as a distortion chanel, and the fuzz box was still relativly new.
   This was pre Sgt. Peppers.  so much has changed you have to think carfully about what you use.
   But do what ever you want listen to me or not.  have fun

[Scotty Did]

also the mono ear piece, something similar is available through RadioShack

part # 33-179

again I have noidea if that shit was available back then.  this was even before sterio really took off.  and FM was still relativly new.  i dunno. I'm gonna try some differant shit

[gez]

http://en.wikipedia.org/wiki/Crystal_earpiece

Similar principal to a reverb tank, minus the springs.  2 transducers, one provides a source of vibration the other picks it up.

[Scotty Did]

I would be a little hesatint on use that (yes I know I can't spell)

that's like straping 2 buzzers together right.  I would think right when you energize it, it would just make an awful sound.  I dunno

RRadioShack has a set of speakers that out can crack open and put together.  I would think that would be more true to the original consept.

Part # 40-1442

[gez]

I would think right when you energize it, it would just make an awful sound. 

I think that's the whole point of the circuit, the last thing you want is hi-fidelity.

I gave the transducer/reverb tank analogy to describe how the earphones are working, but having said that, those earphones are only little piezo speakers and are pretty lo-fi, plus transducers do a reasonable job in reverb tanks, so who knows, they might work well.

[Scotty Did]

I think that the main part of it it that the buzz comes from the transistors but the speakers cause some kind of ambiance or something.

I'm gonna try it once my chack hits my account.

I just need to find out if they are positive as to what the batterie is and where I'm suppose to connect it.  I have an Idea but I dunno.

also I'm gonna need to try some other transistors.  I wanna try some tip-42's.

if there is a reason not to tell me

[gez]

I think that the main part of it it that the buzz comes from the transistors but the speakers cause some kind of ambiance or something.

Sure, the circuit is going to provide some fuzz and rectification (note the lack of any bias resistor on the input of TR1*), but I'm pretty sure the earphones are acting as a high pass filter, or at least giving a healthy boost to uppermids (you often get a resonant peak with piezo type devices around that mark), and that is going to thin out the tone.  In this case, I should think that lo-fi rules.

Either way, I'll be interested to hear you findings! 

*  This is probably one of those rare cases when a leaky Ge might just prove to be the better choice for this transistor.

[GREEN FUZ]

I wanna try some tip-42's.

if there is a reason not to tell me

Can`t think of a reason not to use them just watch the pinouts as they`re not the same as the oc72`s.

[rocket]

I don't think that crystal earphones are the right thing here. They are purely capacitive and there would be no DC bias for the last transistor.
I think that magnetic speaker should be used.

did anyone try to get it work yet?

[reverberation66]

          good to see a bunch of other folks interested in this weirdo circuit, I've been thinking about building it myself, if I can score some of those earphones, I've had and seen tons of those over the years but don't have  any right now, surely radio shack has something suitable...one question at large here, these being oc72 pnp transistors, shouldn't this be positive ground? I'm pretty new to this stuff so I dunno...

[gez]

I don't think that crystal earphones are the right thing here. They are purely capacitive and there would be no DC bias for the last transistor.
I think that magnetic speaker should be used.

Had a look in an old Maplin catalogue and there are two types of earpiece.  The 'magnetic' type and the 'crystal' type.  As you point out, the later will block DC (if these type are little more than piezo transducers), but having said that the magnetic type only have 8ohms impedance.  With such a heavy load, it's unlikely there'd be much output, and with a leaky Ge there wouldn't be much in the way of current limiting from the earpiece, which wouldn't be so good.  Hmm...

In the interests of (audio) science, I placed a thin layer of polythene between a couple of disc transducers I had in my parts bin, taped them together and wired them up to a simple op-amp circuit.  As predicted, the sound was thin and tinny, so I'm pretty sure that's the reasoning behind using an earpiece.  Transducers could be used with this circuit if a bias resistor were used for TR3 and the piezos wired up like a cap.

[Scotty Did]

as luck would have it last night I was at my buddy's house and I got a couple of small magnetice speacers out of some old sterio speakers.  I think it should be close enough.  before I went to bed i bolded them together so now I just need to insulate them and wire um up.

I am haveing some second thoughts on the tip42's so I'm gonna try to find some AC128's from what I can find is a sutible replacement for the oc72.

usless some one that know's what there doing much better then me (which isn't hard to do) says it's ok to use those.

[rocket]

I think there is no reason to use (or waste) ge transitors in this circuit.

it should perfectly work with si. like 2n3906 or even 2n3904 with inverted battery.
in any case the biasing* should be reconsidered (also when using a tip142).

*which is purely based on ge leakage.

[dano12]

Or even simpler than transistors: how about a LM386 and two caps, just like the smokey amp?




Adjust gain to drive the eairpiece at the right level....

[Scotty Did]

Or even simpler than transistors: how about a LM386 and two caps, just like the smokey amp?




Adjust gain to drive the eairpiece at the right level....

that is what I was about to try today with my little jem

[sfx1999]

It looks like it is meant to drive speaker type headphones. You may get a good result by using speakers from old PCs.