Calibrating a Drawmer DS201 gate

[fazeka]

Hi all,

I have a DS201 (circa 1992) I am going to recap, some of the caps are bulging.

Researching online, found this thread on calibration:

https://www.gearslutz.com/board/geekslutz-forum/742361-drawmer-ds-201-basic-calibration.html

Assuming I need to do the above calibration after changing out the caps, I don't have a means to generate a square wave signal. As per the cal instructions:

"To test the Key Inputs, use a fixed-level, unbalanced, square wave signal of +4dBu (1.23V RMS) at 100Hz with 1ms pulse duration."

Uncertain of what can be produced on my PC, can anyone provide a wave of such for, say, a couple of minutes?

Cheers,
Chris

 

[radardoug]

If youhave any kind of DAW, you can generate that signal yourself. Audacity is free on the web. Please engage brain before posting.

 

[fazeka]

Thanks radardoug. Sorry for the inconvenience. 

 

[Whoops]

If youhave any kind of DAW, you can generate that signal yourself. Audacity is free on the web. Please engage brain before posting.

Thats a realy rude comment, shame on you

 

[Whoops]

Assuming I need to do the above calibration after changing out the caps, I don't have a means to generate a square wave signal. As per the cal instructions:

"To test the Key Inputs, use a fixed-level, unbalanced, square wave signal of +4dBu (1.23V RMS) at 100Hz with 1ms pulse duration."

Uncertain of what can be produced on my PC, can anyone provide a wave of such for, say, a couple of minutes?

Cheers,
Chris

Making your PC and soundcard providing a Square wave is easy, I normally use Pro Tools and it's own plugin called signal generator for that.
The not so easy part is achieving the desired amplitude of the signal you are outputing, in this case you need +4dBu (1.23V RMS) , I guess you have to measure the voltage that you are outputting until you achieve the desired level. I never done that but its totally possible

 

[[silent:arts]]

Just because of the recap you don't need to calibrate.

 

[Walrus]

"To test the Key Inputs, use a fixed-level, unbalanced, square wave signal of +4dBu (1.23V RMS) at 100Hz with 1ms pulse duration."

Maybe it's old age, but I'm finding it harder to understand some instructions the first time of reading, but surely a100Hz square wave has a duration of  10mS per cycle. Therefore a 1mS pulse duration wouldn't even give you half a cycle of 100Hz??

 

[analogguru]

"To test the Key Inputs, use a fixed-level, unbalanced, square wave signal of +4dBu (1.23V RMS) at 100Hz with 1ms pulse duration."

Maybe it's old age, but I'm finding it harder to understand some instructions the first time of reading, but surely a100Hz square wave has a duration of  10mS per cycle. ......

.... at 50% duty cycle.  With a different pulse-with it looks different.  1ms/9ms is still 100 Hz.

 

[fazeka]

Wow. Thanks everyone for the replies! =)

Making your PC and soundcard providing a Square wave is easy, I normally use Pro Tools and it's own plugin called signal generator for that.
The not so easy part is achieving the desired amplitude of the signal you are outputing, in this case you need +4dBu (1.23V RMS) , I guess you have to measure the voltage that you are outputting until you achieve the desired level. I never done that but its totally possible

I was thinking about outputting at -18dBfs as a rough start and then measure with my 'scope?

Just because of the recap you don't need to calibrate.

That's what I was wondering... but let me ask... does this assume all caps are replaced with exact values? what if a few of the values of caps are not exact (i.e., replacing 4.7uF with 5.6uF or 6.8uF)...?

Maybe it's old age, but I'm finding it harder to understand some instructions the first time of reading, but surely a100Hz square wave has a duration of  10mS per cycle. ......

.... at 50% duty cycle.  With a different pulse-with it looks different.  1ms/9ms is still 100 Hz.

Therefore a 1mS pulse duration wouldn't even give you half a cycle of 100Hz??

Again, something I am confused on... I created last night on my home PC a square wave at 100Hz using Audacity... how is the pulse duration measured?


          |<------->|
_____          _____
|        |          |        |
|        |_____|        |__
 
OR

                    |<-->|
_____          _____
        |          |        |
        |_____|        |__

Thanks,
Chris

 

[Andy Peters]

Again, something I am confused on... I created last night on my home PC a square wave at 100Hz using Audacity... how is the pulse duration measured?


          |<------->|
_____          _____
|        |          |        |
|        |_____|        |__
 
OR

                    |<-->|
_____          _____
        |          |        |
        |_____|        |__

Thanks,
Chris

The latter is the pulse width (or duration. The former is the period (which is the reciprocal of the frequency). The instructions say to output a wave of 100 Hz, so your period is 10 ms. Duration or pulse width is 1 ms.  This represents a 10% duty cycle (time signal is high divided by period).

-a

 

[Andy Peters]

"To test the Key Inputs, use a fixed-level, unbalanced, square wave signal of +4dBu (1.23V RMS) at 100Hz with 1ms pulse duration."

Maybe it's old age, but I'm finding it harder to understand some instructions the first time of reading, but surely a100Hz square wave has a duration of  10mS per cycle. Therefore a 1mS pulse duration wouldn't even give you half a cycle of 100Hz??

No. The period of the wave is 10 ms. The pulse width is 1 ms. They just want a square wave with a 10% duty cycle.

 

[Andy Peters]

Just because of the recap you don't need to calibrate.

That's what I was wondering... but let me ask... does this assume all caps are replaced with exact values? what if a few of the values of caps are not exact (i.e., replacing 4.7uF with 5.6uF or 6.8uF)...?[./quote]

If those caps are power-supply bypass caps, then no calibration is necessary because they don't affect circuit operation.

If the caps are part of a timing circuit, their values are critical, so you should replace them with the correct value!

 

[fazeka]

If those caps are power-supply bypass caps, then no calibration is necessary because they don't affect circuit operation.

If the caps are part of a timing circuit, their values are critical, so you should replace them with the correct value!

Hi Andy,

OK, just curious as this is what I suspected. I ordered the correct values!

Although, Mouser tricked me on one of the caps. Said was in-stock, but later when I checked status of my order after it shipped, said that particular value cap was "on order" with delivery of September...  I hate having to wait on parts/reopening up equipment again.

While ordering, it showed 'in stock' when I clicked 'order'...  :

 

[fazeka]

OK, I generated the square wave in Audacity.

Question: How can I change the pulse duration to 1mS? The wave shows a pulse duration of 5mS:

 

[radardoug]

You can hand draw it. Go to maximum magnification. Ctrl 1 lots of times.