If anyone wants to help out a guy that usually only thinks about speakers, I need something (DIY module board, or..?) to put in front of an ICEpower 200ASC board, which:
- has a stereo input that will work reasonably well with typical portable player headphone outs.
- has, relatedly, enough gain, maybe 10-24dBish? (can't figure out the input sensitivity of the 200ASC, so..), and volume control.
- preferably can either run on the +/- 12VDC 300mA supply from the ICE.
- mixes to mono, or if not has outputs that can easily be summed without getting into trouble with the 10kΩ ICE input.
Those are the only requirements, but remote volume control would be really great. Additional types of input (high-z, digital, bluetooth..) would be a nice bonus, as would mixing capability, but trying to maximize price-performance here.
- has a stereo input that will work reasonably well with typical portable player headphone outs.
- has, relatedly, enough gain, maybe 10-24dBish? (can't figure out the input sensitivity of the 200ASC, so..), and volume control.
- preferably can either run on the +/- 12VDC 300mA supply from the ICE.
- mixes to mono, or if not has outputs that can easily be summed without getting into trouble with the 10kΩ ICE input.
Those are the only requirements, but remote volume control would be really great. Additional types of input (high-z, digital, bluetooth..) would be a nice bonus, as would mixing capability, but trying to maximize price-performance here.
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Before anything else, do you know that you need a preamp? Have you hooked up a CD (or similar) player to your amp? I'd expect most players--or most headphone outputs--to be able to drive your amp.
If not, the data sheet for the ICEpower 200 ASC (google "data ICEpower200ASC" sans quotes) is not a gold mine of information so some guesses, hopefully educated, are required. Guesses are not what you really want, and you don't want to head out on a shopping expedition either, but anyway some information might be helpful.
Generally, it doesn't sound like you want to solder parts together so your best bet is to go with anything on Amazon or eBay that calls itself a preamp board. By "best bet" I mean it will be entirely satisfactory. With little black chips audio excellence is a given.
<< has a stereo input that will work reasonably well with typical portable player headphone outs. >>
You can expect all such boards to work well being fed from headphone outputs, and all have stereo input/outputs.
To get a bit technical for a sec, with solid state all outputs are low impedance, and all inputs are high impedance. This works out well not by coincidence, but because the parts are designed this way.
The actual rule of thumb is that input impedance must be ten times the output impedance it's fed from. Ten times can be squeezed down to seven times, but this is unlikely to be a problem for you.
<< has, relatedly, enough gain, maybe 24dBish? (can't figure out the input sensitivity of the 200ASC, so..), and volume control. >>
Preamps--except the special case of microphone preamps--don't usually have all that much gain. Again, are you sure you need one?
A gain of 5 means 1 volt goes in, 5 volts come out.
Gain of 5 = 14dB. Gain of 10 = 20dB. Gain of 15 = 24dB. Gain of 20 = 26dB. Gain of 25 = 28dB. Gain of 30 = 30dB. Right, doubling the power doesn't double the decibels.
However, still assuming that you really need a preamp, you can be confident that any preamp board will drive any amp board. This is because the golden mean of audio is "line level" which is a nominal one volt. The standard is that all preamps output one volt, and all amps require one volt input to develop full power.
Two items of interest. The first is that "nominal" means the voltage actually varies all over the place, but you pick some value to work with, and that value is one volt. Second, there's actually more than one "line level" standard, but you won't go wrong with one volt.
<< preferably can either run on the +/- 12VDC 300mA supply from the ICE, or straight from the mains >>
Nothing runs plugged directly into the wall unless it has its own power supply. However your +/- 12VDC can be expected to run just about anything. Preamp power draw is in the low-milliamp range.
<< remote volume control would be really great >>
Can happen, shop around.
<< Additional types of input (high-z, digital, bluetooth..) would be a nice bonus >>
Keep shopping. A more-or-less technically standard input impedance for general use preamps is 47k. In real life most consumer preamps have at least 8k, which is fine, more than enough.
High-z is relative. Actual high impedance inputs are in the one-half to 1 megohm range (500k-1000k). They're for electric guitar and piezo pickups, that kind of thing, and they're risky because they can be noisy for reasons that are difficult to find. If you really need high-z a general purpose preamp won't do.
By the way, they're actually written the other way 'round. Zin means input impedance, Zout means output impedance, as in "a Zin of about 47k." But it will avoid confusion if just write "input impedance."
Bluetooth and digital are bolt-on additions, they have nothing to do with audio.
<< mixing capability >>
Preamps are one thing, mixers are another thing. A mixer is actually pretty much several preamps put into a single box, but keep your thinking straight.
<< mixes to mono, or if not has outputs that can easily be summed without getting into trouble with the 10k? ICE input. >>
The situation gets serious. All the so-called mono adapters I've seen simply short the left and right channels together, which is not what you want, or anybody should want. It seems you're going to have to heat up the soldering iron anyway. Go here:
Why Not Wye?
You're interested in the "Stereo-to-Mono Summing Box," figure 2. The "comments regarding values for Figure 1 apply equally here" add up to it will work for you. Preamps put out very little actual power so 1/8 watt resistors will do the job, but if you have higher wattage resistors lying around you can use them, it wont change anything.
I hope these vague guesses might be of some help.
.
Before anything else, do you know that you need a preamp? Have you hooked up a CD (or similar) player to your amp? I'd expect most players--or most headphone outputs--to be able to drive your amp.
If not, the data sheet for the ICEpower 200 ASC (google "data ICEpower200ASC" sans quotes) is not a gold mine of information so some guesses, hopefully educated, are required. Guesses are not what you really want, and you don't want to head out on a shopping expedition either, but anyway some information might be helpful.
Generally, it doesn't sound like you want to solder parts together so your best bet is to go with anything on Amazon or eBay that calls itself a preamp board. By "best bet" I mean it will be entirely satisfactory. With little black chips audio excellence is a given.
<< has a stereo input that will work reasonably well with typical portable player headphone outs. >>
You can expect all such boards to work well being fed from headphone outputs, and all have stereo input/outputs.
To get a bit technical for a sec, with solid state all outputs are low impedance, and all inputs are high impedance. This works out well not by coincidence, but because the parts are designed this way.
The actual rule of thumb is that input impedance must be ten times the output impedance it's fed from. Ten times can be squeezed down to seven times, but this is unlikely to be a problem for you.
<< has, relatedly, enough gain, maybe 24dBish? (can't figure out the input sensitivity of the 200ASC, so..), and volume control. >>
Preamps--except the special case of microphone preamps--don't usually have all that much gain. Again, are you sure you need one?
A gain of 5 means 1 volt goes in, 5 volts come out.
Gain of 5 = 14dB. Gain of 10 = 20dB. Gain of 15 = 24dB. Gain of 20 = 26dB. Gain of 25 = 28dB. Gain of 30 = 30dB. Right, doubling the power doesn't double the decibels.
However, still assuming that you really need a preamp, you can be confident that any preamp board will drive any amp board. This is because the golden mean of audio is "line level" which is a nominal one volt. The standard is that all preamps output one volt, and all amps require one volt input to develop full power.
Two items of interest. The first is that "nominal" means the voltage actually varies all over the place, but you pick some value to work with, and that value is one volt. Second, there's actually more than one "line level" standard, but you won't go wrong with one volt.
<< preferably can either run on the +/- 12VDC 300mA supply from the ICE, or straight from the mains >>
Nothing runs plugged directly into the wall unless it has its own power supply. However your +/- 12VDC can be expected to run just about anything. Preamp power draw is in the low-milliamp range.
<< remote volume control would be really great >>
Can happen, shop around.
<< Additional types of input (high-z, digital, bluetooth..) would be a nice bonus >>
Keep shopping. A more-or-less technically standard input impedance for general use preamps is 47k. In real life most consumer preamps have at least 8k, which is fine, more than enough.
High-z is relative. Actual high impedance inputs are in the one-half to 1 megohm range (500k-1000k). They're for electric guitar and piezo pickups, that kind of thing, and they're risky because they can be noisy for reasons that are difficult to find. If you really need high-z a general purpose preamp won't do.
By the way, they're actually written the other way 'round. Zin means input impedance, Zout means output impedance, as in "a Zin of about 47k." But it will avoid confusion if just write "input impedance."
Bluetooth and digital are bolt-on additions, they have nothing to do with audio.
<< mixing capability >>
Preamps are one thing, mixers are another thing. A mixer is actually pretty much several preamps put into a single box, but keep your thinking straight.
<< mixes to mono, or if not has outputs that can easily be summed without getting into trouble with the 10k? ICE input. >>
The situation gets serious. All the so-called mono adapters I've seen simply short the left and right channels together, which is not what you want, or anybody should want. It seems you're going to have to heat up the soldering iron anyway. Go here:
Why Not Wye?
You're interested in the "Stereo-to-Mono Summing Box," figure 2. The "comments regarding values for Figure 1 apply equally here" add up to it will work for you. Preamps put out very little actual power so 1/8 watt resistors will do the job, but if you have higher wattage resistors lying around you can use them, it wont change anything.
I hope these vague guesses might be of some help.
.
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Gosh, that's a lot of typing, thanks for your time! I think I may have accidentally come off a little more clueless than I am...
Good question. I want a preamp because connecting an unknown variety of portable players, I want to always be able to drive the amp to full output, control the input level outside of the player without causing problems, and sum without causing problems. It just seems like the best idea.
I can solder just fine, it just seems unlikely that a 100% scratch build is the most cost effective way to do this (and of course not the easiest). Open to whatever looks like a good solution.
That sounds like a lovely standard, but I've never heard of it before, and neither has anything I own, it would seem...
I know what it means, and I mentioned it because they are commonly packaged with line level inputs in mini mixer units, which would be appropriate. In fact, I may just hack up one of Rolls mini-mixer products for this ($25-35 ebay) if I don't come up with a more appealing idea.
Bluetooth audio and digital audio have plenty to do with audio... There are a lot of do-it-all-on-one-board attempts out there these days, and I was just saying I'm open to such features.
You seem to have noticed your own contradiction there.
I know, when I said "mixes to mono, or if not has outputs that can easily be summed without getting into trouble with the 10kΩ ICE input", I was referring to adding a summing circuit without an additional active buffer. Shouldn't be a big problem in most cases, but worth mentioning I thought.
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