Sound Card: What Kind Do You Use To Drive Your Transmitter?

To actually feed my transmitter, I use the output from the stock HP "on the motherboard soundcard" that doesn't work very well for much else. I have another card I use for recording and studio, but it isn't the one that outputs to the transmitter.

The stock HP output that normally goes to headphones or computer speakers (in fact, half of it *does* go to my computer speakers) out into something much like the "brick wall" project I outlined in another thread, except the one I use is germanium diodes and the the amp from a cheap walkman type clone before the diode clamp instead of a bigger amp as I mentioned in that example with the LEDs.

The line output straight from a battery powered CD player also works fine with the same transmitter input, but I didn't like the sound quality feeding it straight from the soundcard output since it seemed thin when it was clear and distorted if I tried to turn it up enough that it didn't sound "thin". The very cheap (like a 5$ one) tape walkman clone's amps did a nice job of fattening up the sound, and the pots and diode clamp keep it at a manageable voltage swing so the transmitter stays happy.

I *used* to also have a parametric 3 band (Radio Shack) in the hardware soundchain, but I've taken it out since largely I had it there to trim out some AC hum, and I recently got some assorted ferrites from tearing down a couple old computers for JBE (JunkBox Enrichment) and they took care of the residual bit of hum. I also had been using it to take down at 16khz, but I've found it actually sounds better if I leave the high end intact. I don't run stereo, my station is mono FM, so it's not going to interfere with the stereo pilot and etc. And it simply sounds better running it straight without the additional EQ stage.

I also don't use pre-emphasis or compression because at least my few listeners prefer the sound without them. Tried them, asked opinions, got rid of them.

My *theory* would be that the soundcard output, especially when being split between the computer speakers and the transmitter, is just a bit too weak to really drive a (or at least my) transmitter. Voltage looked fine, so I'd guess at possibly not enough current or perhaps the impedance was just too far off. But a little extra amplification and trimming it down to size helped a lot for getting a decent sound. Might also be as simple as "headroom". You might go for something more elegant than cobbling a walkman clone that eats tapes, like designing an op-amp or small transistor amp that would actually give the voltage swing and current your transmitter is expecting to see? I'm a crude sort though, and have a hatred of throwing away any subassembly in good working condition, so I tend to prefer to jury-rig from such things rather than tossing them in the trash.

Daniel

ESI Juli@ Soundcards in all my studio PC's

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Moderator Hunterdonfree
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Turtle Beach Montego. I don't know what the output impedance is, but it runs my SSTRAN just fine.

For help evaluating sound cards, get a copy of RightMark Audio Analyser: http://audio.rightmark.org/index_new.shtml. One easy test is to patch the output of a card to its input. RMAA will generate graphs showing frequency response, noise, etc. You'd be surprised how badly some big-name cards perform.

I'm just getting back into this, so I haven't settled on a final configuration yet. But recently, I picked up a Creative Audigy 4 24/96 PCI sound card for my Dell for $20 at Office Depot. Although the motherboard audio isn't bad, the new 24/96 card sounds noticeably better. Since my format is classical, I want to put the best sound on the air that I reasonably can. For AM, however, I don't think anything better than the Audigy card is really warranted. The SSTRAN has a high input impedance and can be driven by just about any kind of sound card that you might care to use.

If I had a Rangemaster transmitter, I would probably drive it with a professional board, or else a small mixer like a Shure M267 with a balanced 600 Ohm output. That would also help solve the hum problems that a lot of people seem to have. Incidentally, I am really disappointed about the story that was reported on here last month about the company that makes the Rangemaster. I would have considered buying one at some point, but not after reading about that little incident.

One thing that has a major impact on the sound quality is the format you use for storing audio files. I can't afford the drive space to use .wav or lossless .wma files, so I'm forced to use some sort of lossy compression. I can definitely hear the sound quality degradation using .mp3 at 128 kb/sec. My friends tell me they like Ogg Vorbis, but so far the tests I've done on my Kubuntu Linux box, which has Ogg capability, are underwhelming. So for the moment, I'm using .wma with VBR (variable bit rate) compression. The main drawback with this is that I can't play these files on an iPOD, and it's nice to be able to use the iPOD as a temporary porgram source when the need arises.

WEAK-AM
Classical Music and More!

Why don't you use the LAME encoder with "preset standard" or "preset insane" if you must. Both presets create VBR files. LAME is one of the best MP3 encoders and it is free. Unless you have golden ears, I don't think you'll be able to tell the difference between "preset standard" and the original CD.

For ripping CD's to MP3, use Exact Audio Copy (EAC), in combination with LAME. The commercial programs won't do any better. For using LAME by itself, there are many GUI wrappers like RazorLame available.

If you are encoding mono audio material, there is no reason to encode to a stereo MP3. In fact, if you tell LAME to create a mono file, you can use about half the bitrate you would use for stereo.

Mojoe,

You certainly can't beat the price of the LAME encoder or EAC. Although, I read the instructions on EAC for getting CD's to rip error-free, and I'm not sure I have the time and patience to go through that much trouble considering that I want to convert my entire classical library. But I still might give it a try.

As far as encoding in MP3 is concerned, my understanding would be that no matter what encoder you use, the results are going to be pretty much the same for a given bitrate. Microsoft has a web site that lets you listen to the same tracks encoded in MP3 and WMA. It's no contest. And, as others have noted, MP3's are not even in the same zip code as good quality audio. The fact that so many young people have grown up listening to them and thinking they are hearing "good" audio doesn't change this, unfortunately.

Your comment on ripping to mono is spot on, but I think I want to preserve my library in stereo even if that takes up more space. For one thing, I have always thought about going to c-QUAM AM stereo. I have to check on whether Chris Cuff is still making his encoder.

WEAK-AM
Classical Music and More!

Are you using the speaker out or the line out? I have never had a problem using either with several different soundcards,SB16,SBAudigy or onboard junque. It always takes some twiddling of the levels but always sounded great when adjusted properly. I always use some kind of load on the speaker outs,they may do funny things without it.
Regards,Lee
http://www.freewebs.com/wilcomlabs/index.htm

I have ripped quite a few CD's with EAC and don't think it is any more complicated than any of the other software out there. In fact, EAC is pretty much preconfigured to use LAME upon installation. As for the time involved, it will take quite a while to rip a huge CD collection, no matter what software you use. I would start a CD rip and go do something else until it was done.

I haven't looked at the latest version of EAC to see if they are now using the "-preset standard" LAME option. They were using some other options that the "-preset standard" option now supercedes. Changing the encoding parameters is very easy.

To give you an idea of file size, I have 762 songs (rock, jazz, blues, classical) encoded using "-preset standard" and they take up 3.3GB total. Considering the size of today's hard drives, this isn't much.

I don't know what you have been reading, but there is nothing preventing an MP3 from sounding as good as the other encoders. Your original post mentioned 128Kbit MP3's (CBR I assume). Yes, this is a common format for downloadable music, but it sounds like crap. Have you actually listened to an MP3 created by LAME, using the "-preset standard" setting? As I said before, I don't think you will be able to tell it from the original CD in a blind test.

As for the Microsoft web site, they are somewhat biased, don't you think? Having said that, for CBR, low bitrate encodes, yes, WMA can sound better than MP3. However, if you aren't trying to encode at minimal bitrates, the differences dissapear. Also, as you have noted yourself, WMA isn't playable on your iPod (and many other players).

It doesn't matter to me whether you use WMA, MP3, OGG, FLAC, etc. I just wanted to point out that high quality MP3 files that surpass the common downloadable variety can be made quite easily. Before believing what Microsoft or others want to tell you (even what I am telling you), you should actually listen to good quality MP3's.

The main reason I use MP3 is that it is widely supported. Every portable player and every computer will play them. This is not true of the other formats. With the correct encoding settings, the quality is as good as any of the other encoders.

You did not mention your budget ... I recently got a Digigram VX 222 v2 stereo sound card for a "white box" Win XP Pro PC I am putting together as music server for a highend stereo system. The card features balanced XLR analog and digital inputs and outputs and is about $400. I understand that Digigrams are used in many broadcast FM stations for both airsound and production studio PCs. From what I can hear so far it's a very nice unit although I do not yet have all the stereo components in place. I have not really done any "yardcasting" (P15 FM) with it yet. I have tried the card with unbalanced consumer grade hi fi stuff using an XLR to RCA converter and it sounds very good.

Another (and cheaper) alternative might be a consumer hi-fi "wireless music system" kit. I think that Logitech and x10 (maybe Linksys too) might have (or have had) devices that plug into a USB port and transmit stereo hi-fi music over a cordless phone frequency (like 2.4 GHz) to a dedicated receiver that has RCA jack output. I don't know how good they are, but presumably they should be consumer hi-fi quality (which should be better than AM or your present sound card) and with a USB connector by-pass your PC's sound card completely. Kinda like the "poor man's STL" even though wireless is not the issue.

John,

This information may be too dated to be useful but I use a Sound Blaster 16 PCI card with the line output to drive my transmitters.

It seems that any card with a standard line output would work for a tx. with a high impedance line input. It should also work for a transformer linked system but it might require using the speaker output instead of the line output. Since every line input I have seen on equipment uses a capacitor to block DC maybe there is a problem with the DC continuity that is presented with a transformer on a line output from the sound card. You could try putting a 10 uF cap in series for the Rangemaster audio circuit. Just something to consider.

Neil

I am experimenting with the many options put forth.

TNX Again.

WDCX AM1610 Part 15
John
Owner-Operator-Chief Engineer-Program Manager