Citronic AC-1USB Output Too Loud

[Carm99]

Hi
I have a Citronic AC-1USB.
When I run a turntable into it and then try to record it. The volume is too loud and distorting. In the red. Mainly 12” Singles. I haven't tried a CD into it yet. I'm wondering if there is any way to bring the volume down inside the unit itself. Change a part or two. Put a small pot somewhere as there are no adjustments at all in there. I'm looking for the schematic but not found one yet.
Heres the circuit board inside.
Cheers

[stj]

i have no idea what that is
but if you want to ajust the level of an audio signal then get a 10k potentiometer and connect the center pin to the destination, one of the side pins to the source and the other side pin to ground

[Carm99]

It's a usb audio interface but you can connect a turntable to it or another audio source.
I'm talking about the input via USB.
It's too loud for some reason.

[harp]

If you record on a computer, make sure that your inputs are not checked with "busting mode or so". That amplify input to very high level. Also, check where is input connected: in line-in or in mic... and review settings sliders.
That switch Line - Phono, what efect do on recording?
Is that device before work normal, on different computer?

I see jrc4580 opamps, maybe to adjust lower gain by replacing/adding some resistor in IC3 area...

And, on main chip legs... near LED, is this green corrosion, liquid damage?
Try to clean it with ipa and toothbrush.

[momaka]

1st: make sure input on the AC-1USB is set to PHONO and not LINE. A phono signal has to go through RIAA equalization (also usually a high-pass "rumble" filter), otherwise the signal will sound "teeny-tiny" with no bass.
2nd: as harp suggested, and this will also depend on the OS you're using, but make sure your input device is set up properly. Assuming Windows 7 or latter and with the AC-1USB connected to the system, go to your system sound icon in the taskbar and click it. On windows 7, you should see several sliders pop up. Go to the "system" sounds (IIRC that was the name) and look for your device under the "Recording" tab. Once you find it, click on Properties (or perhaps it was Settings) and make sure that a checkbox that says something to the extend of disable all audio enhancements on this device is checked.
3: If your device is not listed in the "Recordings" tab mentioned in step 2 above and if instead you are using your PC's line/mic input, make sure you are actually using the line level input and not the mic input. Furthermore, make sure MIC Boost feature is off/disabled. This and audio enhancements checkbox not being checked can result in distorted audio, including distorted bass.

I personally wouldn't use a USB device like that for capturing CDs. Most modern PCs have pretty decent audio hardware chips with quiet line input that you an hook the Line Out from the CD player directly to the PC (via. RCA-->1/4" cable adapter.)
For turntables, though, you'd either need software that can convert the non-RIAA-equalized recording to a properly equalized recording, or you have to go through your AC-1USB device (which I presume does this for you.)

[lti]

I think the CD player was suggested as a known good reference and not a convoluted attempt at ripping.

I have a similar device with a PCM2902 clone, and its line in is detected as a microphone. I've just found an application note from TI that acknowledges this, and it states that Windows adds its own amplification in software. In addition, I noticed that Windows 10 defaults to mono recording, and it has to be switched to stereo every time the interface is plugged in.
https://www.ti.com/lit/an/sbfa020/sb...e%252FPCM2900C
The PCM2900E that you have is actually the original version, which is confusing. The PCM290xB mentioned in that document is the USB 2.0 version (not that audio needs that much bandwidth).

Does your turntable have a built-in preamp? The preamp does the RIAA equalization and amplifies the signal from the cartridge (around 4-5mV) to line level. This USB interface also has its own preamp, so if your turntable has its own preamp, you need to put the line/phone switch on the "line" setting.

It's also possible that the gain of the internal preamp is too high, resulting in clipping. In that case, it gets a little more complicated to reduce the preamp gain while keeping the RIAA curve.

[stj]

not all audio is the same level.
common line levels are 100mV and 500mV
but record players are different, the pickup comes in 2 flavors - magnetic and ceramic.
i cant remember what ceramic outputs but it's over 10mV and clser to 40 or 50,
magnetic pickups output les than 10mV and closer to 5mV

not taking into account your deck may have some type of pre-amp in it.

[Carm99]

Hi
Im on a mac.
Theres no adjustments to make. I was looking for some.
I thought it being USB ,there might be software that accesses a chip in there to adjust it but no.
I need to try a loud CD through it. I'll then know if its the output side.
The owners of Citronic dont have a schematic for it , so how did they make it.
I cant see it being like that from factory. Maybe a component is gone somewhere.
I can always find another way but why not try to get it right if I can.
Its handy as you just plug the turntable straight in.
Here is a better photo.



Cheers

[stj]

does the shell or documentation mention input levels?

[Carm99]

No Its all fixed levels.
There should have been an adjustment in some way.
Any idea what voltages I should be seeing on those chips.
Ill hook up a CD later on to it.
Its either the input or output. Knowing those voltages might help.
Its a shame I cant get the schematic as that would help and we could see the whole thing and how it works.
Like I said I can always use something else but it would be good to try to make it work properly.
Cheers

[stj]

you can get a datasheet for the chip and calculate the gain of the op-amps

[Carm99]

Took some photos with a light under the board to see the tracks.

[Carm99]

Hi again.
I measured the voltages on the chips.
Im getting +4.9v+ on pin 8 but 0v on pin 4 on both of them.

[stj]

thats not important - you need to just build a small mixer or variable atenuator

[Carm99]

I was testing it again with a turntable and Albums are -6 to -8db.
12inch singles are very loud ,I don't know what level they are as they're in the Red most of the time.

[stj]

what deck is it?

[sam_sam_sam]

I was testing it again with a turntable and Albums are -6 to -8db.
12inch singles are very loud ,I don't know what level they are as they're in the Red most of the time.

Either you have no pot control for the preamp or there is something wrong with this device or the way you have it setup
Or you are using the wrong type of preamp for vinyl records because it has to match the type of cartridge that you are using

[petehall347]

try your records and switch to line . see if it sounds right then

[Carm99]

Hi
Its a 1210mk2. Cartridge is a Stanton 500.
The LPs are a nice volume. It actually sounds pretty good. I was playing all sorts. Al Jolson. Brenda Lee. George Jones. Del Reeves. Eddie Cochran.
I don't think it's made for 12” singles. If I somehow reduced the volume. The LPs would be too low then.
The 12s are more than 10db louder. Surprisingly ,one of the LPs peaked around -3.5db too ,but didnt go near 0db.
Yea I don't understand it either ,I've been playing vinyl for over 40 years. I've never known a phono input to be loud like that. From Amplifiers to Recievers and Various Mixers ,Record players.
It's great for LPs though.
Cheers.

[Carm99]

I've got a Rod Elliott P06 to build aswell. Plenty threads on that around.
I was talking to him about this unit. He says that you need a pot for audio. It makes no sense to not have one as you have no control over it.
I was trying to make this unit work alone without anything other than maybe putting a small pot in there maybe.
I could upgrade some of the caps in there to better the sound a bit but it works good for LPs.
Cheers