Hi forum team,
I've posted this question on a different web based, diy audio forum but didn't want to be limited to just one audio expert's theoretical approach, so I'm gathering information from more than one source, in hopes of taking away a very carefully thought through set of plans.
I had a b'day last month, spent ** plus yrs on this earth 😎 . My girl (bless her heart), bought me an "IPOD Touch" as a gift, which I had no clue how to use; guess I'm still not over the "wave of technology" that cost me my "cassette tape" library, and now, threatens to take away my prized, "Rack-0-Relic" c.d. collection. Anyway, I've started building my "itunes" library/playlists, and loading them onto the ipod. Now I'm ready to tryout my new b'gift in the car. Fortunately for me, the 2012 4Runner is set-up with a factory "USB" connection port in the glovebox, so there's no need for an external iphone/ipod dock accessory. The first thing that I noticed upon playing the ipod in the car (not being biased), is that the music volume level is "at least" 6 to 10db softer, than when I listen to the radio or cd's; that's a HUGE difference. I checked everything e.g., wiring, itunes/ipod volume levels, "soundcheck", e.q., etc... but all checked out.
I went on-line to find out if anyone else had experienced the same, and someone reported that they had. They said that they'd found a product that resolved the issue, which (according to them) was caused by an impedance "mis-match"; low signal voltage fed into high "load" impedance. Apparently, driving a set of headphones, is much easier than driving a stereo "pre-amplifier". So, there's a device on the market called "PocketDock" made by "SendStation", an impedance "correction tool". It simply plugs into your ipod's usb connection port. From there, it has two output connections; a 3.5mm (1/8) audio jack, and one "mini usb" sync/charging port. Long story short I bought one, but it won't work because the PocketDock's "audio out", is assigned to the "AUX IN" jack on the dashboard; which has a touchscreen "assignment button". So you have to choose which media format (c.d., usb, aux, f.m., a.m., sirus, etc.) that you want to listen to; but not two at a time. Trouble is that with this device, you need both (aux and usb), operating together to work right; the aux, audio out works okay, but then you can't control the ipod from the touchscreen or steering wheel, which sorta defeats the intent. I'm sure it would work properly with a home stereo (L & R RCA), and a laptop w/ itunes. Here's the link to the "PocketDock":http://www.sendstation.com/us/products/pocketdock/lineout-miniusb.html
Now I still need a way to increase the U.S.B. audio signal from the ipod into the car's U.S.B. sync/audio port. Wondering if anyone knows, if there is a "Line output converter" type product on the market designed to drive a low voltage (likely -dbu in mV) audio signal up to "line level" (0dbu / .775v). Thanks so much for your help and patience with me; much appreciated!
rigtec, Cheers!
I've posted this question on a different web based, diy audio forum but didn't want to be limited to just one audio expert's theoretical approach, so I'm gathering information from more than one source, in hopes of taking away a very carefully thought through set of plans.
I had a b'day last month, spent ** plus yrs on this earth 😎 . My girl (bless her heart), bought me an "IPOD Touch" as a gift, which I had no clue how to use; guess I'm still not over the "wave of technology" that cost me my "cassette tape" library, and now, threatens to take away my prized, "Rack-0-Relic" c.d. collection. Anyway, I've started building my "itunes" library/playlists, and loading them onto the ipod. Now I'm ready to tryout my new b'gift in the car. Fortunately for me, the 2012 4Runner is set-up with a factory "USB" connection port in the glovebox, so there's no need for an external iphone/ipod dock accessory. The first thing that I noticed upon playing the ipod in the car (not being biased), is that the music volume level is "at least" 6 to 10db softer, than when I listen to the radio or cd's; that's a HUGE difference. I checked everything e.g., wiring, itunes/ipod volume levels, "soundcheck", e.q., etc... but all checked out.
I went on-line to find out if anyone else had experienced the same, and someone reported that they had. They said that they'd found a product that resolved the issue, which (according to them) was caused by an impedance "mis-match"; low signal voltage fed into high "load" impedance. Apparently, driving a set of headphones, is much easier than driving a stereo "pre-amplifier". So, there's a device on the market called "PocketDock" made by "SendStation", an impedance "correction tool". It simply plugs into your ipod's usb connection port. From there, it has two output connections; a 3.5mm (1/8) audio jack, and one "mini usb" sync/charging port. Long story short I bought one, but it won't work because the PocketDock's "audio out", is assigned to the "AUX IN" jack on the dashboard; which has a touchscreen "assignment button". So you have to choose which media format (c.d., usb, aux, f.m., a.m., sirus, etc.) that you want to listen to; but not two at a time. Trouble is that with this device, you need both (aux and usb), operating together to work right; the aux, audio out works okay, but then you can't control the ipod from the touchscreen or steering wheel, which sorta defeats the intent. I'm sure it would work properly with a home stereo (L & R RCA), and a laptop w/ itunes. Here's the link to the "PocketDock":http://www.sendstation.com/us/products/pocketdock/lineout-miniusb.html
Now I still need a way to increase the U.S.B. audio signal from the ipod into the car's U.S.B. sync/audio port. Wondering if anyone knows, if there is a "Line output converter" type product on the market designed to drive a low voltage (likely -dbu in mV) audio signal up to "line level" (0dbu / .775v). Thanks so much for your help and patience with me; much appreciated!
rigtec, Cheers!
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You don't listen to any USB audio, your adapter takes the line-out signal from the 30-pin dock connector and you may want to feed this into AUX-in of your car stereo. The USB connector is just for charging/power supply, it doesn't carry digital audio (in fact it could do so, but you'd need an auth IC from Apple to enable the iPod to do so - and guess what, you will not be able to buy that IC 😎).
So all you need is a small line-level pre-amp 🙂
BR,
Holgi
So all you need is a small line-level pre-amp 🙂
BR,
Holgi
Hi Holgi,
Thanks for your reply. Perhaps you misunderstood part of my post. I'm plugging a "USB 2.0" male (from the 30 pin IPOD dock connector cable), directly into an "audio USB port" located in the glovebox of my car; NOT using the "aux in" option. In addition to the USB being used as a charging/power station, it also serves as a means of communication (sync/data) between the IPOD and the ECU/HU "touchscreen" in the vehical.
And you're right, I'll need to use a small line level "pre-amp" to boost the IPOD's signal up some, in order for it to compete with the cd player/radio volume levels. In the link below, you can see the huge difference in output voltages between the ipod's line-out, and a typical car cd player.
Connect your Ipod to a Stereo
Thanks again for your help,
rigtec, cheers
A line level preamp or modification to the existing circuitry, between the USB port and the power amp... either way I think you'll need to obtain decent info on the OEM circuitry. You can't meaningfully amplify the serial digital signal, at least not without much difficulty AFAIK. Your link concerns itself with the dock line-out, because tackling the problem in the analog domain is most likely the only practical solution. Since you aren't dealing with a line-out, you need to find an equivalent point in your setup. If I had to guess, I'd say that is inside the head unit, if it does exist (all digital sources may use the same DAC).
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Hi sofaspud,
Thanks for your advice. I think I (may have) found a way to use the headphone out (3.5mm) jack on the ipod, and still include the 30 pin ipod connector, so that I don't lose the touchscreen functionality. Only a theory at this point, but through a series of adapters, I may be able to "re integrate" the headphone output signal into a 30 pin connector, using the same "numbered pins" as the original "line-out" pins coming from the ipod; it's the same signal, only somewhat amplified. I performed an "A/B" test to compare the output levels between the HP out, and the "line out" (via direct dock out), and the headphone out proved 2-3^x the output level.
I've already ordered the needed adapters/cables so if it works,
problem solved. If not... 
... "Wish me luck" lolthanks again, best to you, rigtec
I sincerely hope it works for you.
But...🙂
You may be able to re-integrate the signal into the 30-pin connector; it seems to me, though, that you need to re-integrate the signal into the USB connector.
But...🙂
You may be able to re-integrate the signal into the 30-pin connector; it seems to me, though, that you need to re-integrate the signal into the USB connector.
Ahhh-ha mate,Glad you mentioned that! Using a small devise known as the "PocketDock"(SendStation - Products - PocketDock Line Mini Out USB), I will attempt... to use it in the "reverse path order". The way it works: it plugs into the IPOD's 30 pin dock connector port. It assigns certain pins to a "mini usb" output port for "Charge/sync/audio", ipod to car media connection. It also assigns additional pins to an "Aux line-out" (a 3.5mm) port, which I don't use because that port doesn't support any sync or charging functionality; audio out only.
But, if I were to use two pocketdock devices, one at each end, I could feed the sync/charge/and headphone out from the ipod, into the aux and mini usb ports at the other end, thus integrating the HP out signal into the loop and into the car media port, using the same "numbered pins" that the pocketdock "selected" to use for communication and audio. I know it sounds very confusing in this brief project description, but I drew out a basic schematic just to see how it panned out, and it just may work. If not, I lose about $27 bucks in adapters, cables, and shipping; that's beans compared to the thousands I've thrown away in some other "Great ideas" I've had in the past. Hahahaha
Greg, (rigtec)
Well then, I'll post what I almost included in my last reply...
If it doesn't work, there's always USB>DAC>amp>ADC>USB.
It sounds a lot like what you've put together.
Definitely worth a $27 gamble! Good luck!
If it doesn't work, there's always USB>DAC>amp>ADC>USB.
It sounds a lot like what you've put together.
Definitely worth a $27 gamble! Good luck!
Hi sofa'
Here's a basic diagram that I drew using only one "PocketDock", but should work none the less. Hope you can make out the labeled items in the circuit. I realized that it could be done with just 1 PD but with adapters in it's place. These are the parts on order. If I still need a line level boost, then I'll get a pre-amp. Here's a link to that:
http://www.zimbio.com/go/byoIdSDOSE...TC-780LC-Stereo-Line-Level-Booster/B000RZXAHI
Here's a basic diagram that I drew using only one "PocketDock", but should work none the less. Hope you can make out the labeled items in the circuit. I realized that it could be done with just 1 PD but with adapters in it's place. These are the parts on order. If I still need a line level boost, then I'll get a pre-amp. Here's a link to that:
http://www.zimbio.com/go/byoIdSDOSE...TC-780LC-Stereo-Line-Level-Booster/B000RZXAHI
Attachments
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And here, once again, is what a "PocketDock" looks like; may help with understanding/visualizing the schematic diagram.
SendStation - Products - PocketDock Line Mini Out USB
SendStation - Products - PocketDock Line Mini Out USB
Hey sofaspud,
You mentioned a DAC. Would this help eradicate my IPOD volume level trouble, or do I still need a pre-amp as well?
Audioengine D1 Digital-to-analog converter/headphone amplifier at Crutchfield.com
Greg
You mentioned a DAC. Would this help eradicate my IPOD volume level trouble, or do I still need a pre-amp as well?
Audioengine D1 Digital-to-analog converter/headphone amplifier at Crutchfield.com
Greg
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There are numerous members here who know much more about DAC features than I do and are better qualified to give an answer. (But, hey, that hasn't deterred me before!🙂) Without knowing specifics, I would guess the answer is yes, some DACs will output a stronger analog signal than others. But the problem of converting that back to digital USB format remains.
Hahahaha!! Love the honesty; always works for me! Okay, I'm looking at some car audio (12v) headphone amplifiers (3-4w/ch) as possible options. Still must figure out how to implement an amp into the "aux or USB" port, and not lose touchscreen function; 😕 gets tricky!
thx again!
First thing: USB carries a digital stream 😱
Second : you don't need any power with line level signals, you just need to raise the level - which is voltage and not current or mixed (power)
So a X10 amplifier is what you need -doable with some transistors/fets/ICs & a bunch of resistors and caps + the necessary power supply ( usually from 10 to 30 V ). That (pre)amplifier would work best if inserted on line, before the plug into the receiver, so if your efforts in trying to individuate the various pin assignments were succesfull, you should be able to find the two wires (plus the Ground) that carry the L and R signals.
This would lend to a dissection of the cable ( unless you are using the HP ipod output, which is not line out level but has also some power to drive HPs ) and a little ( shielded) box in a pass-thru fashion, with an extra wire for Vsupply -and GND, obviously !
Otherwise, there's the remote possibility to vary the gain of the amplifier inside the radio ( no good for various reasons ) or checking if there is some attenuation before its input - so you may select with a switch for hi-low gain
Second : you don't need any power with line level signals, you just need to raise the level - which is voltage and not current or mixed (power)
So a X10 amplifier is what you need -doable with some transistors/fets/ICs & a bunch of resistors and caps + the necessary power supply ( usually from 10 to 30 V ). That (pre)amplifier would work best if inserted on line, before the plug into the receiver, so if your efforts in trying to individuate the various pin assignments were succesfull, you should be able to find the two wires (plus the Ground) that carry the L and R signals.
This would lend to a dissection of the cable ( unless you are using the HP ipod output, which is not line out level but has also some power to drive HPs ) and a little ( shielded) box in a pass-thru fashion, with an extra wire for Vsupply -and GND, obviously !
Otherwise, there's the remote possibility to vary the gain of the amplifier inside the radio ( no good for various reasons ) or checking if there is some attenuation before its input - so you may select with a switch for hi-low gain
Hi pico'ws
You may have believed that I'm a neuclear physicist, but I'm not; just some dumb @ss, trying to figure out how to bring up the ipod output level a bit. I know nothing about building amps, IC, DAC/ADC or vice versa (my tech experience is in indus'l A/C/refrig). I do however, appreciate your ITT insight.
Maybe you could repeat what you've already explained, again, "in english", as to increase my chances of getting it. Though I can use a soldering iron, I know I can't reconfigure any of the circuit boards e.g., HU, the car's ecu, or the IPOD's I.C. I gotta find a way to increase the line output w/o modifying the electronic components; there must be a way...
Greg, regards
You may have believed that I'm a neuclear physicist, but I'm not; just some dumb @ss, trying to figure out how to bring up the ipod output level a bit. I know nothing about building amps, IC, DAC/ADC or vice versa (my tech experience is in indus'l A/C/refrig). I do however, appreciate your ITT insight.
Maybe you could repeat what you've already explained, again, "in english", as to increase my chances of getting it. Though I can use a soldering iron, I know I can't reconfigure any of the circuit boards e.g., HU, the car's ecu, or the IPOD's I.C. I gotta find a way to increase the line output w/o modifying the electronic components; there must be a way...
Greg, regards
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I've found this circuit on the web that may suit for the duty
And also looking for 'preamplifier schematic fet' I found this page (that circuit needs higher Vs , which isn't a bad thing as it allows to be battery operated...like three little 12 V batteries in series) Cascode amplifier. Theory and working. Cascode amplifier using FET, BJT, Miller effect
Note that each schematic is mono 😛
Once done and tested, it needs to be wired between the ipod and the HU input (aux). AFAIK the ipod makes line out L&R available only on that pin strip, being the HP output amplified. So you need to find the wires carrying the signals and put the preamp in there...just some surgical operation 😱
And also looking for 'preamplifier schematic fet' I found this page (that circuit needs higher Vs , which isn't a bad thing as it allows to be battery operated...like three little 12 V batteries in series) Cascode amplifier. Theory and working. Cascode amplifier using FET, BJT, Miller effect
Note that each schematic is mono 😛
Once done and tested, it needs to be wired between the ipod and the HU input (aux). AFAIK the ipod makes line out L&R available only on that pin strip, being the HP output amplified. So you need to find the wires carrying the signals and put the preamp in there...just some surgical operation 😱
Attachments
I think I may have found the pinouts for the IPOD. Here, pins# 3 & 4 are labeled "line-out R (+), and line-out L (+). Pin# 11 = grd (-) for both audio R & L (+)'s.
Apple iPod, iPhone (2g, 3g), iPad Dock connector pinout diagram @ pinouts.ru So I think your saying that I would need two (2) of these mono amps, stacked together (in shielded box), located between the IPOD and the AUX analog input in the car??
Would it be a fair statement to say that, someone is (likely) already mass producing these lil' amps at the commercial level? Because this is a car audio project, I'll have only 12VDC available for power/charging. Do I have any other, perhaps more practical options "in your opinion"?
PS: Since I'll need to get out all my electronics handbooks from high school, Think I'll just build a new spaceship instead.
Greg
IMO 
You have to find the colors inside the multi-stranded wire that correspond to those pins.
If noone finds any faults in that circuit, you may give it a try.
A printed circuit board is more practical...
A 9 V battery housed inside the box with a switch and a led, so you won't need extra cables. Preamplifiers absorb pretty little current so it can last long.
I don't think that it easy to find PCBs or kits for something like that - it's another era !
A little perforated board for experimenting and also for the final arrangement would work too.
Tony
You have to find the colors inside the multi-stranded wire that correspond to those pins.
If noone finds any faults in that circuit, you may give it a try.
A printed circuit board is more practical...
A 9 V battery housed inside the box with a switch and a led, so you won't need extra cables. Preamplifiers absorb pretty little current so it can last long.
I don't think that it easy to find PCBs or kits for something like that - it's another era !
A little perforated board for experimenting and also for the final arrangement would work too.
Tony
Is this still relevant? I don't see any mention of it in these past few posts. Just boosting iPod audio into an aux jack is a cakewalk; a 12V-powered CMoy headphone amp would be ideal for newbie builders.
I'm afraid if the head unit's source selector is set to AUX, it isn't going to enable and process its USB input.
Hi sofa'
That's true! The previous poster was addressing a completely different (but valid) phase of this project; the DAC /amplification aspect, "quite complicated", so I was focusing on only that for the moment.
You're right again. That is still very relevant. I want to "Introduce" the "headphone-out" signal ("see handwritten diagram: 1'st page, 9'th post") from the IPOD, into the "female" 30 pin to USB connection in the glovebox if... I can do it w/o risk of damaging any of the electronic components in the circuitry. I won't know if it'll work until the adapters/cables arrive. I also have my eye on a 12V pre-amp I saw on-line last night; "see link" Picture 1 of 6 for Boostaroo Revolution R234-MC by UpBeat Audio
Guess we'll see
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