CHASM REVERB

[JZA]

I used the PDF and etched, I will be able to get and retest in an hour,  just hoping for an easy fix if you had encountered similar issue at some point.
It doesn't occur during bypass .
I will have a check around the osc switch first, otherwise works fine  .

Nice t know there is still life in this thread.

Thanks JZA

[deadastronaut]

it's alive...

yeah have a checkup with the osc switch, and check the wiring on the brick too...(theres a LOT of wiring in the pdf layout version, ..and easy to make a wrong connection...been there.)

the layout is very verified, so it will be ok....

[JZA]

It's alive,
After checking many things I tried with a battery and it worked perfect, I assume its the dc socket, was brand new but since I 1st connected it something wasn't right with the socket, the plug wouldn't sit right and was popping, u forgot about that , either it has a slight short or the rapid popping and clicking has messed up my power supply!
I will find out for sure tomorrow as It's getting really late.
One thing is for sure the build is perfect, just need a better supply of dc sockets in the future.
I will make up an enclosure for it tomorrow.
I wonder how many hours I can get out of the battery, I know reverbs generally  eat batteries for breakfast.  Will be interesting though.

Thanks deadastronaught, for your help and design, I wonder if you know of or are working on another pedal that makes use of that other brick, the one with many preset options?

JZA

[JZA]

****TYPO******
Where my post says " u forgot about that" should read "I forgot"
****************
It was getting very late, and my phone spell check is decidedly arrogant it seems.

Thanks again.
JZA

[JZA]

I play a lot of keyboards and would love a stereo version, especially as these bricks have 2 channels.
Not having the schematic for this circuit makes it difficult to establish how or your design works, are we controlling the parameters inside the brick or the actual sound path with these pots.
Do you think this design is adaptable or would this be a complete redesign...?

I found this thread when searching for a feedback circuit to use with the Belton brick. I was really happy to discover the added bonus of  oscillation feature too. Please let me know if stereo is an easy adaption or a complex affair.
.. thanks
JZA

[samhay]

The brick has two outputs, but they are not stereo - just two independent mono outputs.

[JZA]

right , I will take time to read up on the datasheets soon , just my over excited assumption.

Also I need to read up on Power supply and mixing negative ground / positive ground pedals and their supplies , I just connected a new dc connector socket to my chasm to find that motorboating sound again, however when i touched my (G4 Metal casing) laptop to type to you guys i noticed the metal had a mild fuzziness electric feeling !!!!


this is something i try to read up on but can't get a definitive answer too.

I am assuming now that this pedal is POSITIVELY GROUNDED?? 

(here i go assuming again)

I read a lot about some fuzz pedals being positive grounded (can i just abbreviate to PG/NG for this post)

I know this is not a fuzz pedal but it does make use of JFET and MOSfet

I have never used or owned fuzz with external ac/dc adapter , just my fuzzwah morley ... but it seems these pedals are the first build projects for most DIY pedal builders , giving them an early understanding in this topic of NPN PNP Germanium transistors etc..

I have built many pedals , I'm pretty sure most of them are PG except this CHASM and the LPB-1/2 I have ... there are maybe some EHX pedals I have that are NG but I have used batteries in those .

I am slowly getting a pedal board/rack together in my mind and will soon be buying a power supply / supplies for it , so i need to conquer the theory of this before I go any further .

As there was no schematic available for this build I hadn't really thought about this till now, but I am pretty sure that this is the reason for my Noises on this build , you see i am using the same 240v multi plug adapter for the pedals i am testing , some PG , some NG..

I am sorry to take this thread way off topic , If someone could link me to a good thread on this or a good read somewhere, I would be grateful .

and if you could clarify the grounding on this build to ease my weary logic.

The new DC socket is plastic mounted type which is new for me so just getting to grips with the terminals etc... having said that the metal one I used was motorboating before I mounted it into an enclosure.

it seems the more I write this post, the more questions I have on this topic as a whole and the motorboating issue as a whole ..
So I will stop here.

JZA

[JZA]

So just to clarify my last post if you havnt read all my questions regarding this build so far...

***Works fine with BATTERY.

***Motorboats with DC adapter (PG)

***Reverbs eat batteries for breakfast

***how to / where to plug in dc adapters (wall warts) to use both PG and NG pedals in the same studio / pedal board.

***which power supply (if any) can power both NG PG pedals at same time with individual isolation and multi voltage.

***can you even chain NG and PG pedals in same signal path ?

*** if not can we modify this CHASM build using to be NG (or vice versa if I'm getting confused what it actually is).


I especially like my last question as that seems to make a lot of sense to my problems,,,,

sorry for so many questions , but I'm sure this will help many DIY noobs out , if you can help.

JZA

[bluebunny]

I am assuming now that this pedal is POSITIVELY GROUNDED?? 

Nooooooo!      Sorry, "no": the CHASM is most definitely negative ground.  Like the majority of other pedal designs you'll see around here.  This is a gross over-simplification, but you tend to find that builds involving Ge PNPs are positive ground, but they're in a minority.

[deadastronaut]

^ yep..


IT IS NOT POSITIVE GROUND!!!!!!!! i never build pos ground pedals, i can't be arsed with that lark...

you should be using a tip negative 9v psu.....(get a good one) being cheap on a 9v psu is just not worth it....


the chasm has a reverse polarity protection diode, ....going by the sound of it , it needed it..

[Jdansti]

@JZA: You may be confusing positive ground and positive sleeve on the DC jack.

We use plastic DC jacks that are wired with the positive on the sleeve and the negative on the tip. This is because most pedals and pedal wall warts are wired this way. The positive sleeve is insulated from the enclosure because the jack is plastic. The enclosure and board are wired such that they have a negative ground.

[JZA]

JZA: You may be confusing positive ground and positive sleeve on the DC jack.

Yes that's exactly what one of my confusions are.

I find most my pedals are negative ground but nearly all use the positive tip method.

However that is pretty trvial as these circuits will only work one way, I just flip polarity on the adapter and make sure the 9v always meets the 1n4001, so even without schematic its pretty obvious.

I fail to figure why it doesn't motorboat with battery?? So you see now why I have to doubt y most basic understanding of electric logic!!!

So if someone has an idea on that ?

It should be stated that my dc adapter works fine with all my pedals and I had the same  issue before I enclosed the build.

[Jdansti]

This is strange. Are you connecting the battery and adapter to the exact same points?

[JZA]

This is strange. Are you connecting the battery and adapter to the exact same points?

Yes , the same solder points ... Not using the 3rd lug at all on dc socket... Not using battery in the build other than to test !

It works fine with battery and technically fine with DC except for the whining motorboating tone ?

You're damn right its strange !!!

Thats why I was doubting my setup and other things using power sources.. and finally got to doubting the grounding , which i knew people would jump on me for )

Still as a wise man once said " I Don't Honestly Know" what it could be.

I do know that this is my 1st digital build, and that wasn't on ourpose , I originally was looking for a spring reverb tank circuit etc... and got this far down the rabbit hole to find that digital can have Noise issues ))))))

Hey , thanks for thinking for me, let me know if you have any ideas , no matter how silly ... I have bought another Voltage regulator, as this a new component for me to be working with , I can't tell how to test it and it is possible (my only guess) that the regulator is drawing too much current through ?  obviously the battery can only give so much current so is possible that the dc could be allowing the voltage regulator more current than battery.

let me just try this new regulator...  at least its a TO92 this time ... just reading up on its datasheet though before fitting it

Thanks JD!
JZA

[Jdansti]

Voltage readings during your testing would help.

[bluebunny]

. . . its a TO92 this time ...

If you had a TO220 package last time (7805), this one (78L05) "faces the other way".

BTW, what DC PSU are you using?

[deadastronaut]

new batch of pcbs just in,  if anyone wants one..or two...etc

£11.00 GBP posted worldwide. pm me ok.

[SISKO]

Can i sub J201s for the 5457?

[deadastronaut]

yep...i used 5457's in my last build IIRC.

[0ron124]

A few quick questions. Sorry for my noobyness on this.

1) I have been unable to find a 22k Lin pot anywhere to use for the Decay knob. Can I just use a 25k in place of it or do you know of a place I can order one in the US?

2) I was also unable to find a LM7805 voltage regulator on Mouser, Mammoth or Small Bear Elec. To my knowledge/understanding a LM78L05ACZ would work fine correct? If so is the orientation the same as the 7805?

3) Was there an offboard wiring diagram anywhere? I might have missed it but I didn't see one anywhere as to how the jacks should be wired up.

4) I'm assuming it uses Mono/Mono jacks on the input and outputs?

5) What size enclosure is the PCB layout meant for? Assuming 125B should work fine...looks like most builds are 1590BB anyone fit it in anything smaller (excluding crazy stuff like 1590A)?

Thanks in advance!