Maximum Input Voltage

super_stewie · 4210

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Offline super_stewie

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on: November 05, 2014, 04:45:31 PM
I'm trying to piece together a modular synth, and I plan on using my crack + senn hd700 as my monitoring system. However, to avoid damage, I would like to know what the maximum input voltage on the crack is?


Offline mcandmar

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Reply #1 on: November 05, 2014, 05:12:13 PM
Dont know the actual answer, but its going to be pretty big being a valve amp, and when you do reach the limit its just going to clip the signal. Your not going to harm anything basically.

M.McCandless

Offline Doc B.

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Reply #2 on: November 06, 2014, 05:05:32 AM
That's what the volume control is for...

Dan "Doc B." Schmalle
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Offline Paul Birkeland

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Reply #3 on: November 06, 2014, 10:51:51 AM
The better question is how much output voltage would be ideal for driving your HD-700's satisfactorily with the Crack. I believe anything above 1V will do nicely, but the higher you go in voltage, the more hair trigger the volume pot on the Crack will become.

-PB

Paul "PB" Birkeland

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Offline super_stewie

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Reply #4 on: November 06, 2014, 10:57:34 AM
So the "volume" knob, is actually a gain knob? (I think I'm understanding that correctly).


Offline Paul Birkeland

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Reply #5 on: November 06, 2014, 11:07:06 AM
A gain knob can have some implications that it's actually modifying the operation of the circuit itself.  (Though that's not always the case) For example, if you were to have a knob that moved the screen voltage around on a pentode, you could change the gain of the pentode.  In solid state electronics, you'll see dip switches sometimes that can be used to adjust the feedback applied to an op-amp, and this would also be considered a gain control.

The volume knob in the Crack adjusts input sensitivity, with the gain of the circuit being otherwise unaffected. 

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline junkers

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Reply #6 on: November 12, 2014, 02:00:27 AM
Quote from: mcandmar on November 05, 2014, 05:12:13 PM
Dont know the actual answer, but its going to be pretty big being a valve amp, and when you do reach the limit its just going to clip the signal. Your not going to harm anything basically.
What would be pretty big? 5V? 10V? I am considering using a source that would send 2V DC to the amp. Hopefully there will be no damage, but will anything clip?


Offline Grainger49

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Reply #7 on: November 12, 2014, 02:26:19 AM
Junkers, what are you asking?  The specification of the maximum input voltage would be at the grid of the input tube.  The volume control is there to keep you from getting to the maximum input.  It selects the percentage of the input voltage that gets to the grid.  You would be at an unusable volume before you got to the maximum input.

Read the other responses and it should make sense to you.  Your source will send 2V to the Crack input only when it is at maximum volume of the source material. 

« Last Edit: November 12, 2014, 08:15:28 AM by Grainger49 »


Offline mcandmar

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Reply #8 on: November 12, 2014, 04:34:29 AM
Quote from: junkers on November 12, 2014, 02:00:27 AM
What would be pretty big? 5V? 10V? I am considering using a source that would send 2V DC to the amp. Hopefully there will be no damage, but will anything clip?

2v is perfectly normal. The standard line level output from any home audio equipment is approx 2v RMS, if you use a preamp you could possible put as much as 10v into the amp and it will still be fine, however the volume control will be almost useless as you will have to turn it all the way down to keep the output volume at sensible levels.   Basically amplifiers are designed with the assumption that the source input will be in the 1-2v range.  IF you need more its as simple as adding a few resistors to drop the voltage a bit.

Also i assume you mean AC and not DC?

M.McCandless

Offline Paul Birkeland

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Reply #9 on: November 12, 2014, 07:59:16 AM
Quote from: junkers on November 12, 2014, 02:00:27 AM
What would be pretty big? 5V? 10V? I am considering using a source that would send 2V DC to the amp. Hopefully there will be no damage, but will anything clip?

I think you could blow out the pot with 100V (AC).

If you clip the amp, you'll hear it, and it will be so dang loud that you can't listen to it. 

2V is a very common signal level, no problems there.
« Last Edit: November 14, 2014, 07:22:36 AM by Caucasian Blackplate »

Paul "PB" Birkeland

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Offline Paul Joppa

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Reply #10 on: November 12, 2014, 12:02:06 PM
But not DC! There is no input capacitor to isolate DC riding on the input.

Paul Joppa

Offline junkers

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Reply #11 on: March 31, 2016, 06:52:09 AM
Quote from: Paul Joppa on November 12, 2014, 12:02:06 PM
But not DC! There is no input capacitor to isolate DC riding on the input.

Just to confirm then, a DAC that will be outputting a 2V DC offset will be no bueno for the Crack then?


Offline Doc B.

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Reply #12 on: March 31, 2016, 09:44:42 AM
Wow, November 2014, this thread is a zombie. You really don't want to use gear that has a DC offset at the output with our products. If you do you will need to put a cap between the DAC output and input of the component it is connected to.

This is all moot if you are actually concerned about whether a DAC with 2V AC signal output and no DC will work. That is a more typical setup and would be fine.

Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline junkers

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Reply #13 on: March 31, 2016, 11:13:41 AM
Quote from: Doc B. on March 31, 2016, 09:44:42 AM
Wow, November 2014, this thread is a zombie. You really don't want to use gear that has a DC offset at the output with our products. If you do you will need to put a cap between the DAC output and input of the component it is connected to.

This is all moot if you are actually concerned about whether a DAC with 2V AC signal output and no DC will work. That is a more typical setup and would be fine.

Yeah, sorry for the necro, but I finally got my Crack, and wanted to double check.

Yes, it is 2V DC, so I will get some caps. Thanks for the reply!


Offline Paul Birkeland

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Reply #14 on: April 01, 2016, 07:15:30 AM
Quote from: junkers on March 31, 2016, 11:13:41 AM
Yeah, sorry for the necro, but I finally got my Crack, and wanted to double check.

Yes, it is 2V DC, so I will get some caps. Thanks for the reply!
What DAC do you have that puts out that kind of offset?  You may see a specification that is "Output voltage - 2V", which is the AC signal coming out of the DAC.

There's enough directly coupled solid state gear floating around that this is generally considered a very poor, irresponsible choice that will lead to speaker/headphone damage.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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