Maestro Filter Sample/hold questions

[newperson]

Hi,

I see that people have been having ticking problems from this project in the past posts.  Is it so loud that it is not recommended to build?  Which one is a better build, Tonepad or GGG?

Thanks for any suggestions,
Paul.

[newperson]

any thoughts?

[Ry]

Do a search for posts by me on the subject and you can decide for yourself it you want to build one.

In short, I really like the way the Tonepad one sounds, once all of the bugs are worked out.  I have built both, however, and they are both nice.

To fix the Tonepad one, I moved the noise part of the circuit to a perf board.  I made sure that the noise transistor was placed at a point far from the other transistors so that there would be a minimum of bleedthough.  It worked like a charm.

If you really want to build this pedal, it is worth your time to start with the Tonepad layout and plan on doing what I did with the noise source.  It takes a bit more planning and work but the results are great.

Ry

[LP Hovercraft]

Speaking for GGG/moosapotamus' layout-I wired that one up really sloppily and still had no ticking.  Maybe I'm just lucky.  Have you searched the posts on alternate LFO ideas for this build?  Quite interesting stuff, there, esp. Mark Hammer's post about using an obnoxious AM sports talk show to modulate the filter sweep.    I'd highly recommend the build to someone who has more than ten projects under their belt, definitely not one for a beginner or the squeamish.  I was just jamming out on mine with a bass guitar last night for about four hours-that thing's FUN!

[newperson]

Ok,

I am going to try the GGG layout because I have already made the board.  I started to put in the resistors tonight and after I got finished I noticed on the schematic that it calls for 1/2watt.  So now I have a bit of unsoldering to do. 

This brings me to my question.  On the parts list it shows:

Transistors
1 - 2N3904
1 - 2N3906
3 - BF245A  JFETs
1 - 2N5088

ICs
2 - 3080
3 - 741

But on the Schematic it shows:
2N4303 and MPS5172 for Q1?

Is 2N4303 the three BF245A Jfets and
2N5088 for the MPS5172 for Q1?


Thanks for any help,
Paul.

[newperson]

Some more part questions,
The project calls for two different ICs, 3080t and a 741.  Does this crossing work?

the 3080 crosses to 628-80130BLM  is this correct?
Mfr. Part #:   S-80130BLMC-JEP-T2   
Mfr:   Seiko Instruments       
Category:   Voltage Detectors - ICs
Description:   Seiko CMOS Voltage Detectors SOT-23-5 3.0V 1.5uA CMOS

and does the 741 go to:
Mouser Part #:   512-KA741       
Mfr. Part #:   KA741       Data Sheet
Mfr:   Fairchild Semiconductor       
Category:   Amplifier ICs
Description:   Fairchild Amplifiers DIP-8 DISC BY MFG 7/03 - RoHS non-compliant/CONTAINS Pb

If none of this is correct can someone point me to the right parts?

Thanks again for any help,
Paul.

[newperson]

Ok,

I see that small bear sells a 741.  Is this the correct IC?
I also see the he sells a CA3080E.  Is this the correct IC?  It calls for a 3080T.  What does the last letter stand for?

_Paul.

[nelson]

CA3080 is fine, just make sure you get the DIP8 package (8 pin chip) and not the can package, otherwise you will be bending leads to fit it in a socket.

the 741 is just a bog standard single opamp, any single opamp will do like TL071.

The S+H isnt recommended for beginners. I would cut your teeth on about ten other projects first. Its a hard build, it needs a charge pump, or a diff PSU. Why not go for a slightly simpler project? Rebote 2.5 delay? small clone chorus?

[PB Wilson]

How important is it to use 1/2 watt resistors?

[BILLYL]

Ry-

Do you have a photo of what you did to modify the Tonepad circuit that you would share?  Also what chips and transistors did you use?

Thanks
Bill

[vacuumdust]

I built it from the GGG layout.   Works perfectly.  Make sure you're JFET's are oriented properly.  There was some discrepencey between layout and photos.  I would suggest using sockets for ALL trans.   I also swapped the trimpots for regular pots.  There's a lot of usable sounds in there.  No ticking problems.  The noise transistor is extremely important to the fidelity/quality of the S&H.  I ended up with a pn2222a...the 2n3904 worked and I left it like that for months and switched to the pn2222a on a whim and the randomness and fidelity of the effect increased 10 fold...Coolest pedal i've ever built.

[newperson]

Hi,

I have ten working builds, (neovibe, pt80, bsiab2, MK2pro, rubys, rockets, omnidrive, frob., etc)  but I still don't know that much.  I just find it will work out better if I ask questions before there is a problem to make sure that there will not be a problem.  There are so many people on this forum that give such useful information, like youself, it is hard not to ask anything that might help from having a problem.  I am still having a hard time knowing what all the part numbers cross to.  Seems like everyone puts a different number on the same part to show it is their brand.  Thanks for answering the question and not just telling me to try something else.

What transistor is in Q1?
and
Should I use the transistors that are on the schematic?  Or did my guessings work for the part layout vs. the schematic?

What transistors did you (anyone) use for each socket?

Thanks again,
_Paul.

[PB Wilson]

 I also swapped the trimpots for regular pots. 

What do each of them do in the circuit?

[Ry]

BILLYL -
I can post a picture of what I did for the Tonepad circuit, I just need to find a place to host it so that I can link to it.  It really doesn't show anything that I haven't described.  I will work on that tomorrow, but I promise very little.

newperson -
For both the Tonepad and GGG layouts, these are the transistors I used:
As far as transistors, I used 2222 for the noise source and J201 for FETS and a 3906 for the pnp transistor.  I used a TL072 for the dual op amps in the Tonepad version, single 741 op amps for the GGG version.  I'm not certain which layout you're asking about the chips and transistors for, so I'm not calling them by their schematic designations.

vacuumdust -
It's interesting that you moved the trimpots to regular pots.  I tried really hard to tune in a good sound with mine and I'd be less than thrilled if they got moved by accident as they would if they were mounted off of the circuit board.

PB Wilson -
One of the trimpots tunes in the noise source (the 10k one).  I forget what the other does, but it seems like it affected the amount of bleedthrough (ticking) of the noise source...however I may be wrong about that one.

[newperson]

HI,

Thanks for replying.  I am using the GGG layout.  Could you tell me which order you put them in?  I see that the layout and the parts list are two different ones.  I am trying to put together an order to finish this board up.

Just to guess,
I see Q1-Q6.
Q1 has EBC so that is a ?
Q2 has DSG so that is a J201?
Q3 has EBC so that is a ?
Q4 has EBC so that is a ?
Q5 has DSG so that is a J201?
Q6 has DSG so that is a J201?

What is the difference between what you have used and the
2N3904
2N3906
BF245A
2N5088
Thanks again,
Paul.

"I used 2222 for the noise source and J201 for FETS and a 3906 for the pnp transistor....single 741 op amps for the GGG version"

[Ry]

Notice how Q1 has the arrow pointing outwards towards R3 and C2?  This outward pointing arrow is how the schematic indicates that it is an NPN transistor.  This could be a number of different types, a 2222, 3904, 5888...almost any npn will do.  I think that I used a 5088 for this one.  Q4 is also an NPN, and is the noise transistor.  I used a 2222 here. 

Q3 has an arrow pointing inwards to the 'base' of the transistor.  This means that it is a PNP type transistor.  I used a 3906 for this one.

As you have noticed, both NPN and PNP type transistors have the same pin designations, Emitter, Base and Collector.  The difference is in how they are activated.  I would highly recommend a book like 'The Art of Electronics' by Horowitz and Hill.  It's full of information like this.

I highly recommend socketing all of the transistors (I would consider it mandatory for the Q4 so that you can audition different ones).  And as always, check a data sheet for the pinouts of the transistors you get.

You have correctly identified Q2, Q5 and Q6 as J201 FETs.

Good luck!

Ry