Whoops

Re: Instrument to "Line Level"
« Reply #20 on: January 02, 2021, 01:49:57 PM »
Some metal guitar players report about whopping 4-5 volts p-t-p from the hottest passive pickups on the market.

Please show me, I would love to know those pickups because I never encountered that.

Are there any guitar amplifiers capable of dealing with 5V on it's input?


JohnRoberts

Re: Instrument to "Line Level"
« Reply #21 on: January 02, 2021, 02:03:21 PM »
Please show me, I would love to know those pickups because I never encountered that.

Are there any guitar amplifiers capable of dealing with 5V on it's input?
My information may be a little dated but back in the 80s when I designed an electronic direct box at Peavey I decided to take advantage of the in house expertise. First I asked the head of the guitar design/manufacture department and asked him about maximum pickup output voltages. I got the tilted head puppy dog look.

Then I asked the lead guitar amp design engineer hoping that he might have some objective information. Not much better but at least he was an EE so understood my question.

This was back 3-4 decades ago and the worst case for hot levels back then was from active guitar electronics powered by single 9V batteries. That translates to < 9V p-p by definition.

The amplifier input stages using tubes would overload relatively gracefully, solid state not as much but there was enough PS headroom in solid state inputs to trim back gain if needed.

Caveat I am not the guitar amp guy... but I have worked with a few.

JR   
It's nice to be nice....

dbelousov

Re: Instrument to "Line Level"
« Reply #22 on: January 02, 2021, 03:00:37 PM »
Please show me, I would love to know those pickups because I never encountered that.

Are there any guitar amplifiers capable of dealing with 5V on it's input?

My 7-string baritone has never be measured,  but it can't produce clean sound out of any of my studio amps. Really. Even at minimal gain it turns everything into hard crunch. It's equipped with the BK Nailbombs, as I said.

Sadly, I'm not a guitar player, so my knowledge of crazy-hot pickup market is limited and guitar players are not bother to measure their instruments. But I know for sure, that my client can't record one of his guitars with his Focusrite Clarett because its "instrument" input can't handle the output of the instrument. But who knows what rails there are.
Dmitry

john12ax7

Re: Instrument to "Line Level"
« Reply #23 on: January 02, 2021, 03:38:47 PM »
I've found 1Vpk (2Vpk-pk) tends to cover most guitars. However with very hot windings and some active designs greater levels and subsequent overloading of instrument inputs is not surprising. It is often intentional with amps much like using a pedal with its volume boosted.

These high levels might overload instrument inputs, but should not be an issue with ADC line inputs which can handle 12Vpk and higher.

dbelousov

Re: Instrument to "Line Level"
« Reply #24 on: January 02, 2021, 04:07:24 PM »
Yes, it's bothering me as well. My ADC has 20V rails on the input stage and 5V on the ADC IC and its driver. The specs show that it can handle as absolute maximum the rails +- 0,7V, because of diodes, I guess. And the input is differential. It's a lot! Thus, I suppose, the clipping is not "analog" in its nature.
Dmitry

dbelousov

Re: Instrument to "Line Level"
« Reply #25 on: January 02, 2021, 04:24:35 PM »
UPD. There is a small article.

https://ez.analog.com/b/engineerzone-spotlight/posts/adc-full-scale-input-power

"The full scale input of an ADC is the largest signal amplitude that can be delivered to the converter before the signal is clipped in its digital output representation. At full scale, the output uses the minimum and maximum codes of the ADC.  While some systems seek to maximize the dynamic range of the ADC by using as much of the effective input full scale as possible, a saturated ADC will add distortion and provide poor performance data."

So for the CS5381 FSI is 1.13Vpp. It's not so hard to overload it digitally despite the fact, that its analog part can handle more.
Dmitry

abbey road d enfer

Re: Instrument to "Line Level"
« Reply #26 on: January 02, 2021, 04:54:53 PM »
So for the CS5381 FSI is 1.13Vpp. It's not so hard to overload it digitally despite the fact, that its analog part can handle more.
Typically, ADC are preceded by an analog stage that reduces the signal amplitude. ADC's cannot be directly driven by the input signal.
They must be driven by low-passed low-Z signals.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

dbelousov

Re: Instrument to "Line Level"
« Reply #27 on: January 03, 2021, 01:20:23 AM »
Yes, I understand it. The PCM4222, on the other hand, has FSI 5.6Vpp, so the line level signal has to be amplified for it. My point here is what analog part of an ADC can handle doesn't matter. My converters can deliver about 16Vpp down to the ADC driver, the ADC driver is an r-t-r IC on the 5V rails, so it is 5Vpp here, but in the end it doesn't matter since the ADC IC clips digitally at 1.13Vpp anyway.
Dmitry

abbey road d enfer

Re: Instrument to "Line Level"
« Reply #28 on: January 03, 2021, 07:37:27 AM »
First I asked the head of the guitar design/manufacture department and asked him about maximum pickup output voltages. I got the tilted head puppy dog look.

Then I asked the lead guitar amp design engineer hoping that he might have some objective information. Not much better but at least he was an EE so understood my question.
That is quite surprizing.
When I designed an active DI box, that was 1974, and what put me in the pro audio business, the first thing I did was plugging a borrowed Les Paul and a friend's bass into my oscilloscope and bashed them. The voltage never exceeded 3Vp2p, including the initial pick attack; single notes produced a rather nice triangle wave. There are now p-u's that have more umphh than Gibson humbuckers, but I doubt thay produce enough to hit the rails of a 9v battery. I believe the 18v pedals work on the placebo effect,  or just allow adequate operation from rinsed-out batteries.
 I then drew the waveforms on transparent film, which I used for a lecture at the '77 AES convention in Paris.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

 

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