Zoom Gear & Home Recording Forum

Hello friends!
As the topic title suggests, I have a problem with the high input sensitivity of the H2 line in.

My setup is this:
2 Studio Project B1 microphone
M-Audio Buddy mic preamp
Zoom H2

I use this setup for classical music recording; harpsichord, pipe organ and piano.

This is the problem:

Eg. recording of piano; mic distance of piano, around 6ft. Very hight level piece (eg. Liszt).

By connecting the audio output at Buddy "line in" of the Zoom H2, I noticed that this has a very significant input.
Adjust the gain from the Audio Buddy, it becomes very difficult, because the slightest movement of the potentiometer, resulting in big changes. Moreover, the potentiometer can not go beyond the first and half step (on seven) and, otherwise the signal distorts.
Of course, the microphone, there are switches to reduce the level (two positions,-10dB, and-20dB). But I do not like this system, because background noise increases.

The solution would be to modifying the Audio Buddy, with different potentiometer, which will allow me to have the distorted sound to end of step. Is there anyone who can help me?
I have no problems to soldering. If you can tell me what should I mount potentiometers, I thank you.

Best regards,

Lucas

I use an external attenuator in front of the H2 "Line In."

http://www.electronicplus.com/prodSearc ... mit=Search



This solution is a little more flexible than modifying your interface, you can use it for other connection scenarios. If you're handy with a soldering iron, you could make one of these, but unless you already have the parts laying around I imagine this one would cost less than buying the pieces at Radio Shack.

Fran

Thanks Fran
I wonder, this system increases the background noise? Because also on the microphones there are attenuator switches, but they add a bit of noise (not much, but this is present.)
The decision to change the gain potentiometer is for not change the background noise of the recording.
No problem for the changes: probably, I will use the audio buddy exclusively with Studio Project mics and Zoom H2, then this configuration will always remain. I would optimized the potentiometers for this configuration.
The problem is that I not have the schematic of audio buddy. But I could post pictures with the current potentiometers ...

Can you help?

When you attenuate the signal at the microphone you have to raise the gain in the preamp - I can't think of any other source of noise in this scenario. It is my understanding that the Audio Buddy has an issue with preamp noise, so this makes sense.

Putting the attenuation after the Audio Buddy will reduce preamp noise along with the signal attenuation. And I would think it would be easier to build your own attenuator rather than modifying the Audio Buddy. Two potentiometers (or even better, one ganged pot) and a couple of cables would do it.

I'm nearly totally ignorant of electronics, I wouldn't be able to help you modifying the Audio Buddy.

Fran

I'm wondering why everyone puts up with this nonsense from Zoom.

I bought an H2 in May. When I went to use it, to record court hearings, I discovered that the line input was acting like a mic input. I couldn't eliminate the distortion without using an attenuator. I carry a headphone volume control on me, and that works well. But I'd rather not have an additional point of failure. Also, I have a limited amount of time to set up my equipment. I would rather just plug a line output from my mixer into the zoom and have it work. I still must use audiocassettes, so I monitor the 3rd head output from a Marantz PMD222.

The other reason I bought the Zoom is to digitize music cassettes and vinyl records. An audio engineer once told me that using resistors to change input impedance reduces frequency response, so I really don't want to use a cheap attenuator, and I don't feel that I should have to buy an expensive one. After all, Zoom advertises that the H2 has a line-level input. And after 38 years of using audio equipment ranging from low-end consumer to good recording studio and sound reinforcement equipment, I never found a line input that was incompatible with any line output let alone an input that is incompatible with literally everything. Line inputs tend to be very forgiving. Whether one uses as a source a CD player, a television, a mixer, a VCR, a portable music player, a computer sound card, or an earphone jack from a portable cassette recorder, line-level inputs in everything from a cassette deck to computer speakers will still give you acceptable sound. But not the H2’s inputs! So I suggest that we all complain bitterly to Zoom and Samson for them to fix the problem. I don't know enough about electronics to know if new firmware could solve this problem, but the point is that the advertising and specs for the H2 are false.

Anyway, I returned the H2 and got it replaced. The replacement sounded terrible regardless of whether I used the line input, the mic input, or the built-in mics. When I returned it, the salesman checked the two units he had in stock, and all 3 had the same problem! After a few days, he called me and told me that the problem was solved with a firmware update. But the line input was still the same as my original H2. So here it is, 3 months later, and I still don’t have a properly functioning unit.

All that said, does anyone have an opinion on whether an attenuator can reduce frequency response?

Rojo26

Yes, the sensitivity is too high on the line input but it can be controlled by the various methods suggested here. What do you regard as an "expensive attenuator"? The ones I have were specifically modified for me by the maker (because of the direction of the signal flow), they cost me 39GBP and, no, I haven't noticed any reduction in frequency response.


Jeff

I paid $169 US for the unit. I don't feel like looking up the exchange rate, but I assume that a GBP is worth more than a USD. That's a significant percentage of what I paid. That's like buying a new car for $20,000 and then having to spend $6000 on a fuel converter because not a single gas station in the continent sells fuel that will power the vehicle correctly.

But the 2 questions I should really ask are:

1. Has anyone encountered a line output that actually matches the line input of the H2?

2. If I were to use the headphone volume control on the input, woud THAT reduce the sound quality?

I have used the adjustable Headphone out on my Soundcraft mixer with no prblem.

Interesting. I have a cheap Radio Shack inline headphone volume control that I use to attenuate line level to mic level, and it has worked successfully on the H2 to attenuate to its bizarre line level. But I didn't think of going directly out of the mixer's headphone jack. Now I'm going to consult an audio engineer I know to ask for a truly professional opinion on whether that would reduce frequency response or any other component of the quality of the recording. I'll post his answer here.

Do I take it from the lack of response that nobody has discovered a line level in another device like the H2's?

Not necessarily... I, for one, bought the H2 as a stand-alone field recorder with no intention of ever using external microphones or line-in.

For the latter usage I have (now, and in order: Superscope PSD-300, BOSS BR600, HD16cd, R16, BOSS BR800 [terrible device with even less capability than the R16 for stand-alone work]).

Secondly, the only equipment I own with Line-Out is home/consumer gear, which is a much lower level than professional/studio mixers. And the PSD300 spec is unusual: 500mV & 2kOhm impedance.

Let me ramble a bit... P = V * I and I = V / R... So... 0.5V * 0.5V / 2000Ohm => 0.000125W or 0.125mW
[NOTE: these are DC computations, and audio is AC -- RMS is, I believe, VDC / 0.707]
The H2 is spec'd at -10dBm at 10kOhm. 1mW = 0dBm, so -10dBm = 0.1mW => 0.0001W = x^2 / 10000 => 0.0001 *10000 = x^2 => x = 1V

Off hand, the H2 looks less sensitive than my $700 PSD-300 with regards to line-level -- and I've used the line-out (tape-out) from my stereo system to feed the PSD-300 when transferring LPs to CD.

I haven't made enough sense of dBu to work out my BR600: -10dBu and 30kOhm (0dBu is the voltage that produces 1mW across 600Ohm)

The BR600 line-out is -10dBu @ 2kOhm and recommends the other equipment be 20kOhm on input.
The H2 states line-out is -10dBm, recommends 10kOhm on input equipment.
The closest I find in the PSD300 is 1V@2kOhm (which is twice the voltage given for the line-input!)
Manual for the PMD620 give line-out at 1V/10kOhm and line in at 0.5Vrms/20kOhm

The inputs of the HD16 (which does not have dedicated line-in) just register -50dBm to +4dBm via the pre-amp gain control (-50dBm is microphone level, and I'd guess the +4dBm is supposed to map to the professional +4dBu line-out signal). {if so, a -10dBm signal is 0.03 as strong: unless I should be using a factor of 20 rather than 10 as dBm is a power and not a voltage, in which case it is only 0.2 as strong}

You're obviously very well informed about the electrical characteristics of audio signals, and unfortunately, I don't have the time to study all the electronics math to follow most of your post. But the part I do understand is that your PSD 300 (which I had to look up to discover that it is a CD recorder) has a more sensitive line input than the H2, yet you have used it to successfully record audio from your consumer stereo amplifier. Well I can't even record from a line-out consumer DVD player and Behringer mixer onto the H2. So the only way to reconcile this apparent impossibility would be for us to get together and test your PSD300, our H2s, my DVD player and mixer, and your stereo equipment. Not much of a chance for that to happen.

My conclusion from this is either the spec of your PSD300 is wrong or my H2 is defective. Have you tried to record from your stereo onto your H2? If you can do that, either your stereo has a different output from mine or my H2 input is different from yours. I would appreciate it greatly if you could do a brief test record from your stereo onto your H2. Any normal-volume source material would be fine for this test.

Also, I've heard this before about consumer line level being lower than pro line level, although I haven't experienced that myself. I have often connected courtroom sound systems, some of which are fairly nice, to my low-end pro and even low-end consumer equipment with no trouble. Does the pro gear have to be higher-end pro gear before the line level is stronger? Would a Behringer mixer be considered pro gear or not for the purpose of calculating line levels? I get the same result on my H2 whether I record from the Behringer or the consumer DVD player. I'm going to ask my audio engineer friend about that too.

Unfortunately I don't have a dual RCA to mini-TRS stereo cable so such a test may take a while.

As for signals -- part of the problem in working out what is what is the change in reference. Consumer line-level is "nominally" -10dBV into 1kOhm, that is 10dB below the reference of 1V (unclear if that is DC, AC sine wave, or RMS for general signals). 1V into 1kOhm results in a power level of 1mW.

Pro-gear line level is +4dBu (where "u" means "unloaded" -- or 600Ohm) and the reference voltage is whatever voltage produces 1mW in the 600Ohm. Since the impedance is a different reference, the Voltage needed to produce the same power level will be different.

Then Zoom comes alone and cites -10dBm, where "m" is traditionally 1 milliWatt -- a /power/ measurement, not a voltage measurement! And this is where I tend to get confused as I think power measurements are a factor of 20, not 10...

dBm = 20 * log(p1/p2)

where voltage is

dBV = 10 * log(v1/v2)

(The 10* is part of what makes it a "deci-Bell measurement)

10 * log(0.1V/1V) => -10dBV

20 * log(0.316mW/1mW) => -10dBm

I won't claim my math or the interpretation is correct; I'm just trying to match things found in places like Wikipedia (google: wiki line level), which does list raw voltages (which I interpret means impedance neutral) and pro level IS much higher... Not sure it is 14dB higher, which would be a factor of 25 (making that 0.1V consumer level a 2.5V pro level? Way too high -- so I'm sure somewhere one needs to factor in the impedance to work out power levels and compare them... That's what I was trying but probably got lost and confused myself)

Another factor to consider is that the PSD300 record level (which I'm sure affects incoming line level data too) may be on the analog side and the digital conversion only takes place to write to the CD... So what would I set the PSD300 record level at to treat it as the H2 front-end A/D signal level? (Even more confusing, the PSD300 RCA inputs are the "Aux In" which is a different sensitivity than the XLR/TS front jacks which have switches for mic/line level; front jack "line" mode is 500mV@2kOhm, rear Aux jack is 800mV@23kOhm).

{I'd bought the PSD300 years ago when I was still taking Mandolin lessons as it has the ability to do independent time/pitch shift on playback.

It incidentally also has the ability to do digital->digital CD copying
}

It may be possible to ignore the impedance on the input side, since the normal recommendation is for the inputs to higher than the output source; one wants to develop a voltage without actually transferring power [just the opposite of radio transmitter to antenna, where one WANTS all the power to transfer, so one wants matched impedances] (one reason for the -10dBV consumer reference is that it can be generated using battery powered units, the +4dBu apparently drains batteries much faster)

Not relevant, but maybe of interest -- in a comparison of time-base accuracy (for use with video recorders) the PSD300 was the second most accurate (the BOSS BR600 I have was the most accurate) -- see: http://www.camcorderinfo.com/bbs/showpo ... ostcount=1

You might not be sure of things, but I could only wish I knew as much as you.

0 dBm defines the *voltage* required for a power of 1 mW across 600 ohm, i.e. 0.775 volt rms.

So, the use of dBm by Zoom is utter nonsense. It implies that the device has indeed an input impedance of the said 600 ohm. Zoom say on their website that the H2 has an input impedance of 10 kOhm and I'll let you do the maths to find out what voltage would be required to get to 1 mW in that case.

The correct unit would be the dBu, "u" as in "unloaded", for all those cases where the load impedance is considerably higher than that of the source. Again: 0 dBu = 0.775 v rms with the voltage being multiplied (or divided) by a factor of 2 for every 6 dB.

Zoom do indeed state that the H2's line input has a sensitivity of -10 "dBm". Make that dBu and it's the equivalent of 0.245 v rms or 245 mV.

Ralf

Oh boy do I feel your angst, rojo26.

Surely line-in recording isn't meant to be this complicated!? With everything else, I just plug in and record!

After some suggestions from Wulfraed, I have recorded into other 'old school' sources... namely a tape deck, CD recorder and also the PC. Levels set around -2db with the quick turn of a dial (to leave some room for spikes), and voila! - fuss free, clean results. Plug in to the H2 and bounce the level at around -2db and WOAH! - distortion, distortion, distortion.

I just don't get it?

That's the way it works. Find a workaround or get another recorder. Whining won't help. Not even at -10 dB. ;-)

Ralf