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Fixed Attenuator Limiter
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Fixed Attenuator Limiter
pmboos
I have a Rare Waves Hydronium that has an accent in CV input. It expects voltages to be in 0 to +5V. My Future Retro Orb sequencer produces an accent signal that is 0 to +10V. What I'd like to do is halve it's output so it can never endanger the Hydronium (this is the primary combination I plan to use Orb driving the Hydronium, preferably through analog signals).

So is there a (preferably 1U) unit that can attenuate/limit this signal in fixed steps? I don't want to use a rotary knob (potentiometer) unless it has indents to hold it in a fixed location. A switch would be better.

Thanks in advance for any information!
Paul

PS - this will be going into an upcoming planned Power Lunch Eurorack and will most likely be the first module I buy and my first foray into full blown Eurorack - up until now I have only been buying semi-modular synths.
KSS
How about a solution which doesn't require any module at all?

Make an attenuating patch cord. This is easy to do with two resistors. One goes from signal to tip. The other from signal to the GND/0V/shield of the patchcord. If the two resistors are identical, the signal will be halved.

Altering one or the other can give you various amounts of attenuation.

Put a green heatshrink over the end of the patchcord with the new resistors to identify it, and with Green meaning "5" for electronic components, it's a reminder that this is not a normal patchcord. You could add a second band of brown for "0" to further remind this is a 50 per cent patch cord.

Diodes can similarly be used to make "one way" patchcords. Single diode from signal to tip. Generally put the cathode to the end with the diode. Put a black or white band on the cathode end to show which way signal and CV traffic can flow.
KSS
Here's a crop from the PAIA 4730 manual showing one way to make the patchcord. Here one end is a tip plug. Just ignore that and see it as another normal TS patch plug.

The use of these kinds of patch cords can be a very powerful tool in your patching arsenal!
KSS
Here's the diode OR type cord and another way to make the Attenuating patch cord.




If you still want a switch stepped module, seek out those designed for adding octaves or semitones. These are widely available in 1U for MU and narrow in other formats as "standards" and Yusynth has one which can be DIY'd.

Combine their one volt octave steps with an appropriate attenuating patch cord to get exactly what you want. Of course if you DIY you can create whatever step size you need.
abelovesfun
I agree that a patch cord or modifying the Jack would be good, but if you want a module, the AI010 is a passive triple attenuation mult in 2hp.
mskala
Do you actually need to limit or attenuate this voltage? Most modules that take a 0 to 5V logic input are quite content to receive 10V for logic "high"; the 5V specification is the minimum at which it promises to recognize the "high" state, not an absolute maximum with risk of damage if you provide more. I don't know the design of the Hydronium in particular, but it's usually expected that professionally-designed modules will not suffer damage on receiving any input voltage between the power rails.
pmboos
First, I appreciate the idea of not needing to get a module to accomplish the voltage reduction. I'm not handy with a soldering iron unless it is for soldring copper pipe together. I ruined an SK-1 trying to add a MIDI kit to it some years back. I suspect that while this is simpler, it isn't something I am going to try. So I'll probably look at some of the recommended modules.

On the question to whether I need it or not; this is mentioned in the Hydronium manual:

"To control the volume of each note independently, patch a CV sequencer to
the VELO IN jack. This accepts a variable voltage in the range 0 to +5 volts.

If your CV sequencer has ACC GATE output, you will need a voltage
processor module."

This led me to think I would need a module. Later in the manual specs it has this:

"VELO In
- Range 0 .. +5V. (20 kOhms impedance)"

It feels like the wrong voltage could damage it.

As far as the AI010 - this is really close to what I want. I would like the pots to be stepped as oppose to a continuous change. A switch with fixed output voltages would be better... Less changed of being knocked and then passing too much voltage through.

Thanks for all the great input!
pmboos
BTW, I asked this question in case I am missing something on ModularGrid. It appears all of the attenuators there are this same continuous voltage adjustment as opposed to being able to step limit it in fixed amounts.
The Grump
Just get one of these, meter the output and adjust to +5v, then wrap a piece of tape around the attenuator so that it doesn't move. Fixed, done.

https://www.perfectcircuit.com/koma-elektronik-attenuator-cable-1.html
pmboos
The Grump wrote:
Just get one of these, meter the output and adjust to +5v, then wrap a piece of tape around the attenuator so that it doesn't move. Fixed, done.

https://www.perfectcircuit.com/koma-elektronik-attenuator-cable-1.html


That might be a good idea if the thing itself didn't have an awful review...
mookmoof
The Mutable Instruments Links has an averager section with three inputs, which I believe works by just outputting 1/3 of each input. So if you just use one of the 3 inputs you should get 3.3 volts out if you put in 10. Seems like it should work for your needs, and there are no knobs - it's completely fixed.
pmboos
mookmoof wrote:
The Mutable Instruments Links has an averager section with three inputs, which I believe works by just outputting 1/3 of each input. So if you just use one of the 3 inputs you should get 3.3 volts out if you put in 10. Seems like it should work for your needs, and there are no knobs - it's completely fixed.


Cool thanks! Adding that to my list of utilities to acquire...
Synthiq
mskala wrote:
Do you actually need to limit or attenuate this voltage? Most modules that take a 0 to 5V logic input are quite content to receive 10V for logic "high"; the 5V specification is the minimum at which it promises to recognize the "high" state, not an absolute maximum with risk of damage if you provide more. I don't know the design of the Hydronium in particular, but it's usually expected that professionally-designed modules will not suffer damage on receiving any input voltage between the power rails.

I agree with mskala and also question if you need to do anything about the 10V. There is a schematic for the mainboard in the Hydronium Assembly Guide Supplement and there the gate input has a 20kohm input resistor followed by a 1N5233B 6V zener diode to ground before entering the CPU input pin. There is no schematic for expander board with the Velo input, but there is a 20kohm resistor, R9, and a 1N5233B zener diode, D1, next to the Velo input so it most likely identical to the Gate input. So I would suggest contacting Rare Waves before spending money on something you may not even need.



pmboos
Thanks now that I understand mskala's comment more with your additional details, I'll do just that. Best informed advice I have received on this thread.

Cheers,
Paul
Leverkusen
pmboos wrote:


On the question to whether I need it or not; this is mentioned in the Hydronium manual:

"To control the volume of each note independently, patch a CV sequencer to
the VELO IN jack. This accepts a variable voltage in the range 0 to +5 volts.

If your CV sequencer has ACC GATE output, you will need a voltage
processor module."


I don't have one of these but understand this part from the manual so that you need a voltage processor to dial in the wanted amount of accent from a acc gate as you can do with the dynamics knob when you use midi accents. Otherwise accents will be not very subtile. This should just affect the use of gates into the velocity input.
pmboos
@Leverkeusen Thanks for reminding me what I wrote before I did something stupid. Yeah, the manual is explicit isn't it?
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