Skip to main content ↑ ↓

Notice

Please note that most of the software linked on this forum is likely to be safe to use. If you are unsure, feel free to ask in the relevant topics, or send a private message to an administrator or moderator. To help curb the problems of false positives, or in the event that you do find actual malware, you can contribute through the article linked here.
Topic: Sound cards for recording FM radio on a PC (Read 6919 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

Sound cards for recording FM radio on a PC

Dear All,

I'm new to the H-Audio forums. I have a renewed interest in recording classical music from FM radio, thanks to the poor quality of DAB radio in the UK.

I acquired a Denon TU260 Mark II Hi-Fi tuner and a M-Audio Revolution 7.1 sound card (after seeing complimentary comments in this forum). However, I immediately found that the the output from the Denon was too high for the line-input on the Revo 7.1, and had to put in about 20 dB of attenuation (via a potential divider) to prevent clipping of the signal. All my recording was carried out via the 'Total Recorder' package using Ogg Vorbis (at Q6 & Q7 settings) or the Lame 3.97b2 encoder (at high quality settings of -V0, -V1 or -V2), so I expected good results.

However, I found that both the audible and recorded results were poor in the low frequency end of the audio spectrum, particularly in loud passages involving double basses and drums. This spoils my recordings, and I notice the deleterious effect on playback quality when listening to the files through my iAudio U2 music player

What is the reason for this? Could it be one of the following:-

-- Low frequency response of Revo 7.1 only down to 40 Hz, while many other cards go down to 20 Hz;
-- Poor impedance matching of Denon tuner source to line input;
-- ADCs (Analogue to Digital Convertors) not good enough;
-- FM signal strength from transmitter (my signal seems strong enough using a T-aerial);

Would I be better served getting a superior card with a decent variable gain/attenuation input and better ADCs (EMU 1820, for example). I know this last kit does allow some control over the input signals.

I also have an older Pioneer tuner that does not require so much attenuation to match its output signal to the line input, but my results are scarcely any better.

Look forward to your advice. I'm sure many other people have the same problem.

Kind regards

LongJohn

Sound cards for recording FM radio on a PC

Reply #1 –
At least do a little experimenting before buying different equipment. Download Audacity and record in uncompressed WAV format. Listen to that result as-is to make certain that your problems are not with something else in your process.
http://audacity.sourceforge.net/

I don't know about the E-mu card in particular, but input level control on line inputs is very uncommon. The E-mu has microphone preamps, and those always have gain controls. Are you sure that isn't what you are calling variable input? You certainly don't want to input a tuner via those.

Unfortunately, consumer audio equipment is quite variable as regards signal levels, but 20dB over clipping seems extremely extreme. I have recorded from the tuner sections of two different receivers and a Technics tuner into an M-Audio Audiophile 2496 without ever coming near clipping. That doesn't mean I would not get clipping levels from some equipment (a few trials recording from the analogue output of my CD player has produced occasional clipping from some CDs), but I can't imagine needing more than a few dB attenuation on a line level signal. It really sounds like something else is wrong in your setup.

I very recently ran some low frequency tests using software generated signals sent D to A to D between soundcards in several computers. Results varied because the different soundcards do not work exactly to the same standard either, but the Audiophile's response was not down until 8Hz from another Audiophile and 4Hz from an Echo Mia. The Mia, which records any external signal at 2dB lower than the Audiophile, was up to that level by 7Hz. My lowest frequency signal, 1Hz, was down from 10.6 to 14.8 dB, depending on source and target soundcards, but was still recorded as a good sine wave in all cases.

Sound cards for recording FM radio on a PC

Reply #2 –
One can easily see that M-Audio does not expect any professional use from the Revolution 7.1 (not to say that other kinds of audio use are not completely legitimate) -- they do not even specify the nominal or peak input levels for the card. HOWEVER, the documentation does clearly say that the control panel provides input level control for both the microphone and line inputs.

Although it might explain the extreme attenuation you need, it is probably a safe guess that you are not using the microphone input, since that is mono only, but what happens when you adjust the input level on the line input via the card's control panel?

If you record with Audacity you have some sort of VU meters. What do they show as you adjust the input controls?

The meters on the control panel of the Audiophile are much better than Audacity's. Does the Revolution 7.1 panel provide decent VU meters?

Sound cards for recording FM radio on a PC

Reply #3 –
Sorry about the late reply.

I do have a VU meter in both the Revolution 7.1 software and in 'Total Recorder'. The porblem I have is that the input signal from the Tuner is too large and that I lose low frequency information.

Without the added potentiometer, I found that turning the input line-in level down all the way was insufficient to stop the the clipping during recording of the signal from the tuner.

regards

LongJohn

Sound cards for recording FM radio on a PC

Reply #4 –
So what about the input level control that M-Audio says is there? What does it do?

There is something very peculiar and not at all normal with the levels you say you have.

Sound cards for recording FM radio on a PC

Reply #5 –
Thanks for your help, Andy and all,

The line-in input in the Revo 7.1 can be controlled from the Revo software or from Total Recorder (each one will control the line-input of the other). The effect of attempting to reduce the input seems to give only 20dB of reduction (I know that's a factor of 10 in gain!). If you try to go to the full range of 40dB, this turns out to be useless. The control over actual hardware input signal is lost after the initial 20dB reduction. Amazingly, 20dB is still not enough to cut down the Denon 260L input. My Pioneer tuner behaves better than this, and I only need about 10dB of input reduction.

I ought to do some actual measurements of output with a 'scope.

The point really is: Does anyone know of a suitable card that will handle the Denon 260L Mark II?

cheers

LJ

Sound cards for recording FM radio on a PC

Reply #6 –
Quote from: LongJohn on
The point really is: Does anyone know of a suitable card that will handle the Denon 260L Mark II?


Did you try to loop in your Revo 7.1 into a HiFi amplifier's tape section yet ? This might just remove possible impedance mismatches between tuner and soundcard ...
The name was Plex The Ripper, not Jack The Ripper

Sound cards for recording FM radio on a PC

Reply #7 –
A difficulty here is that you really don't know if the problem is the soundcard or the tuner. As I indicated above, my experience with tuners is quite different. The signal output comes nowhere near to clipping with Audiophiles. I also have an Echo Mia. It records any given input 2dB lower than the Audiophile, so there are two soundcards that should work fine. I don't think there is anything at all unusual about their signal level handling.

On the other hand, if the tuner really is putting out a much higher than line level signal, why don't you have trouble running it in analogue mode through a regular preamp/amplifier? Do you have to have the volume control exceptionally low in order to avoid over driving the output?

Perhaps your soundcard is the problem because it is defective. What kind of results do you get recording from other line level sources? You surely can't have a whole stable full of unusually high output devices.

Is it possible the actual construction is wrong and the microphone input is switched with the line level input? Your results might be explainable if you were really recording the tuner through the microphone preamp. What happens if you record into the jack that is supposed to the microphone preamp input?

Sound cards for recording FM radio on a PC

Reply #8 –
Quote from: LongJohn on
put in about 20 dB of attenuation (via a potential divider) to prevent clipping of the signal.
results were poor in the low frequency end of the audio

What is the reason for this? Could it be one of the following:-
-- Poor impedance matching of Denon tuner source to line input;
Thats the most likely reason that could affect low frequency response, unless you have faulty hardware.
Your "potential divider" is the first and main suspect.
When the pot is a bad match, it could form RC filter together with input or output DC blocking capacitors, that could start cutting into low frequency response. Cutoff frequency should also depend on the position of the pot

My advice would be to try to reduce tuner output as little as possible with resistive divider, and do the most of attenuation in sound card.

There are many standards for line level. Some consider 100mV as line level, some consider 1V. 20db input attenuation is supposed to cover these. If thats not enough, then your tuner should be outputting over 1V, like 3V, which sounds like headphone output levels. I suppose that isn't configurable in the tuner somehow? If the lineout of tuner is driving headphones okay, it should be pretty low-impedance output, and could use quite low-impedance potentiometer (0.5k-1k).
It really really did sound different. Not in a placebo way.

Sound cards for recording FM radio on a PC

Reply #9 –
Quote
My advice would be to try to reduce tuner output as little as possible with resistive divider, and do the most of attenuation in sound card.

There are many standards for line level. Some consider 100mV as line level, some consider 1V. 20db input attenuation is supposed to cover these. If thats not enough, then your tuner should be outputting over 1V, like 3V, which sounds like headphone output levels. I suppose that isn't configurable in the tuner somehow? If the lineout of tuner is driving headphones okay, it should be pretty low-impedance output, and could use quite low-impedance potentiometer (0.5k-1k).


Now that's a good, convincing answer. Thankyou very much!

regards

LJ