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Need help with drum module hiss and clicks

Radon

Sep 10, 2023
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I've made a midi drum module and it works, only there is constant loud hiss and each trigger fired makes an audible click.
Do i need to decouple, isolate dc somewhere?

Any help apreciated
 

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kellys_eye

Jun 25, 2010
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there is constant loud hiss
Most likely from the digital board - use shielded cable for the audio between each board and separate the digital board from the other circuitry (distance). Each board seems to have the relevant decoupling but extra capacitance (10nF or 100nF on the supply lines) wouldn't go amiss.
 

73's de Edd

Aug 21, 2015
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Sir Radon . . . . .
My dealings with your situation was back in circa 1958 with an accompaniment sound effects electronics unit that a solo musician could use.
At that time it was all first generation transistors with NO I.C.'s yet being on the scene.
It had 3 sections just like yours does . . .the top white (pink) noise generation unit and the bottom, creating the specific different instrument voices of the unit.
They were blended to get the proper musical simulation effect if a heavy-medium-light "noise tail" was needed .

Your central unit uses a u-Processor brains to spit out triggers to all of the sound generation sections . . . . and repeat at required musical tempo timing .
In my case, this was all found to be using sequential transistor flip flop chains that outputted to hundreds of small signal diodes that steered into triggering a particular sound effect and then required further repeats with the music score.
One could individually trip an effect or there was a muuuuuulti pole switch that could select "programmed sequences" I remenmber FOXTROT-SAMBA-WALTZ-CHA_CHA-MARCH-TANGO-BOLERO-SHUFFLE-2BEAT-4BEAT, etc
Naturally that is what operation a solo musician would be choosing.
Instrument voices I remembered were sand block( thats where the white noise came in strong) . . . also on brushes.
Cymbal, bass drum, trap drum, conga drum,drumsticks,wood block were being other individual sounds.
The pots shown in the bottom board is where adjustment is need to trim in the "right"/ true instrument sound being created.
(BTW did your pots come selectively labeled and have paint drops sealing a setting, or did they give you resistance settings to set to ? )
They used schmitt trigger stages, critically tuned twin T circuits to be triggered, oscillators and blends and filters to create all of the distinct instrument sounds.
15 flip flop series arranged transistor oscillator pairs provided the sequential timing for the very longest tune sequence.
I had to reverse engineer and create a custom schematic and only made I copy and that was kept in the unit/ sent away.
(Any new fangled ZEE-ROCKS machine was being 25 miles away, burning 17cent gal gas.)

NOW . . . to help you . . . . I need mo' info than you have provided.
D-tronics, the site of your programmer /sequencer doesn't show me any equipment's internal photos.
Supply the source (kit) of your top noise generator and bottom instrument generator.
Initially evaluating I can see that your pink noise originates at top left corners 8 pin IC "PentaNoise" (proprietary techno gobbledy gook gibberish) generator
The next lower hex inverter pair are labeled as well as the powers 78L05 in upper top corner . . . is saying . . . me too . . .ME TOO . . .!
Then bottom . . . quasi . . . left corner is an op amp waiting to be identified.
Also, on it, track down pin 7 buss going right and later being labeled as [ ???Drive ???].
Also need confirmation of all weak showing TURQOISE Labels writing . . . one. . . .Decay is confirmed, others ? Also confirm another . . . as BLEND POT ?

On the bottom generator board confirm the ID of the left 8 pin IC, the transistor up at top above it as well as the central board located hex inverter, which may be the same one used on the other noise PCB.
We have to logically "consume" that all of the shown board flying wire interconnects had to come from the kits info.
(Dtronics . . . . .they say ? whaaaaaaaaat gives ?)
I second "The eyes" suggestion for additional filtering + shunting with .1ufd ceramic to the power supply connections at the kits boards.
Clicks may be due to direct DC connection between the noise generators output via the TURQ wire down to the bottom 8 pin IC's pin #2.
Try a .1 ufd paper or poly coupling /DC isolating cap inserted in series.

Thaaaaaaaaaasit . . . . . . 'til I heers back from you . . . . . .

73's de Edd . . . . .

I perused the cafes menu, thinking of trying something totally new, then asked the waitress for a quickie and she then HARD slapped me.

The older, and more worldly wise woman, sitting next to me, then said
"it's pronounced 'quiche', dear" . . . . . . '(key+shut)'

.
 
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Radon

Sep 10, 2023
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Thank you, apologies for not posting sooner, I am getting schematics together and more info.
 

Radon

Sep 10, 2023
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Delta Prime Thanks, I have posted some schematics​

Bluejets Thanks, I have tried the 10nF on the power line and it helped, but I have no 100nF to try so will order.​

73's de Edd the pots had no paint spots. I will try the suggested caps, thanks.​



The noise board has a cymbal sound built around a 10406 cmos chip taken from an amdek drum machine this is fed to a 741 opamp based filter (hi hat filter pic), circled in red on the amdek_40106 image. Another 10406 is used to provide 2 square waves to create a metallic sound for a cowbell which is then fed to a vca. There is also a Pentanoise chip(pdf attached) that supplies white noise to 5 trigger,VCAs which are triggered by the DTronic board.

The VCAs are built around the percussive noise voice circuit(trigger vca pic)with the noise transistor section taken out as the noise is provided by the Pentanoise chip.

The blend pot will blend between the feed from the cymbal 10406 and noise from the Pentanoise. Each of the VCAs has a pot where it is marked decay of varying sizes to suit the sound.

The Kick, Snare, Toms etc are provided by the second board, this is basically a ComputaDrum circuit (PDF attached). 6 Twin T circuits built around a 4069ube chip. the rim shot is two Twin Ts fired together, and the snare shares the same trigger that goes to the noise board to provide the sound of the snares.
 

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Delta Prime

Jul 29, 2020
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You missed it but that was really my point........:rolleyes:
Two steps ahead brother. That was my intro.
While we're waiting for schematics...
Just curious.
Why bluejets?
I'm thinking your a fighter pilot?
 

Delta Prime

Jul 29, 2020
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Delta Prime Thanks, I have posted some schematics
Great job! Now there's too many of them. :) I'll return shortly.
Okay I'm back. Piece of cake. Show me your work. A photo of your your unit and the solder connections you made to it.
Please,thank you.
 
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Radon

Sep 10, 2023
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I've de-soldered some connections to troubleshoot, the original picture I posted shows all connections.
 

Delta Prime

Jul 29, 2020
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Now is not the time to be shy the engineering is sound I will not critique the components chosen in the schematic I need to assess the assembly, the symptoms you are describing points towards the assembly of the kit and that's you.
Show me your work please.
 

Radon

Sep 10, 2023
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Here is my work.
 

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Delta Prime

Jul 29, 2020
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Okay there's a problem!
I didn't get any garlic bread with my spaghetti. :p( I'm just kidding)
I'll return soon and thank you for the photos!
One last thing... Photos of the other side. thank you.
 

Radon

Sep 10, 2023
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The other side - Anti pasti
 

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Delta Prime

Jul 29, 2020
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Okay found your problem!
You got to take all this flux off the board. thaaaaaaaaat's it!
Screenshot_20230914_183047.jpg
 

Radon

Sep 10, 2023
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Learnt something today. Had no idea flux could be both conductive and corrosive.
Off to get some isopropyl alcohol.
Thanks Delta Prime. :)
 

Martaine2005

May 12, 2015
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What soldering iron are you using?.
It looks like you’re heating the components leads without the PCB pad, which causes the ‘blob’ of solder. Either that or your iron is not hot enough to quickly heat the pad as well.
Or of course, you’re removing the iron as soon as you see molten solder?. Keep the iron at board level in contact with component and board for a second or two after the solder melts.

1694863903108.png

Martin
 
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