Is this preamp appropriate?

Guest
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric
 
On Monday, July 15, 2013 11:48:43 AM UTC-4, et...@whidbey.com wrote:
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be a
maximum volume and the car stereo must be at close to max volume for
regular listening.
Click to expand...
Two things to try: firstly, the Alpine stereo might have an input-level
adjustment (either hardware or software) that can be changed.
(it'd be embarassing to find that there was a 'mute' selection, or
the auxiliary input source wasn't selected, but... I've seen it happen).
One Alpine manual refers to 'AUX SETUP mode' ...

Second, a coupling transformer can match the headphone-output (100 ohms
or maybe less) to the line-input (usually 1000 ohms, sometimes as high
as 50k ohms) of the stereo. It'll take two, of course, for stereo; they're small.
 
<etpm@whidbey.com> schreef in bericht
news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric
Click to expand...
Well, as too often it's a maybe.

To tell something more I have to make some assumptions:
- Suppose the output of the MP3 player is meant to drive a low impedance
headphone. That requires (relative) low voltage and high curent.
- Suppose the Alpines input is a line input. That has a (relative again)
high input impedance so it requires high voltage but has no need for high
current.

Suppose you see the mismatch :)

Theoretically you can solve the problem using two audio tranformers with a
windings ratio of about 1:30. I don't know wether or not this transformers
are made but 1:8 or 1:10 will also do. Price tags I saw from about $20,- up
a piece (ex. VAT and shipment).

Now you amplifier comes into play. As an amplifier it will amplify the
voltage level by 40dB that's a 100 times. That may be way to much for your
Alpine but the volume control of the amplifier can handle this. So with a
little luck you're done.

But without luck? Well you may get noise or hum or distortion or even all of
them.

Noise is hard to fight. Putting a 100 Ohm or so resistor parallel to the
input of the amplifier may help.

Hum can be prevented by using well shielded cables and putting the amplifier
in a metal shield box.

Distortion may be caused by overloading the amplifier input. The 100 Ohm
resistor mentioned earlier may help. It can be lowered down to 33 Ohm if it
needs to.

I did, off course, not mention all possibilities but I, once more, suppose,
you can at least go for a try.

petrus bitbyter
 
On Mon, 15 Jul 2013, petrus bitbyter wrote:

etpm@whidbey.com> schreef in bericht
news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric

Well, as too often it's a maybe.

To tell something more I have to make some assumptions:
- Suppose the output of the MP3 player is meant to drive a low impedance
headphone. That requires (relative) low voltage and high curent.
Click to expand...
But what kind of low voltage?

"Line in" is always pretty vague. I have an amplifier fed from a VCR, a
DVD player and misc and I tend to have to adjust the volume control when
switching sources, proving that the standard isn't really much of a
standard.

That said, it seems to be generally assumed that "line level" is about 1
volt. And surely even a headphone output can supply somewhere around
that. The mismatch doesn't matter.

I've plugged various portable devices into that amplifier, my Sansa Fuze,
various portable CD players, a small am/fm headphone radio, and while
there might be some lower level with those as the source (I can't
remember) it wasn't a massive difference.

I like the comment from someone suggesting there's some mute or other
setting that needs to be changed on the radio. There seems to be way too
much difference in sound level.

Let's not forget that if some car radio has a jack intended for external
devices, it likely is expecting an MP3 player or a portable CD player,
plugging into their headphone jack. Why else would there be an input
jack?

The only other possibility is that the MP3 player has some blocking so the
volume can't be turned up too high. SOme of them do have a menu setting
to disable or enable this sort of thing, and if the problem isnt' a
setting on the radio, then the poster should look for some setting on the
MP3 player.

Michael
 
"Michael Black" <et472@ncf.ca> schreef in bericht
news:alpine.LNX.2.02.1307151818220.18553@darkstar.example.org...
On Mon, 15 Jul 2013, petrus bitbyter wrote:


etpm@whidbey.com> schreef in bericht
news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric

Well, as too often it's a maybe.

To tell something more I have to make some assumptions:
- Suppose the output of the MP3 player is meant to drive a low impedance
headphone. That requires (relative) low voltage and high curent.

But what kind of low voltage?

"Line in" is always pretty vague. I have an amplifier fed from a VCR, a
DVD player and misc and I tend to have to adjust the volume control when
switching sources, proving that the standard isn't really much of a
standard.

That said, it seems to be generally assumed that "line level" is about 1
volt. And surely even a headphone output can supply somewhere around
that. The mismatch doesn't matter.

I've plugged various portable devices into that amplifier, my Sansa Fuze,
various portable CD players, a small am/fm headphone radio, and while
there might be some lower level with those as the source (I can't
remember) it wasn't a massive difference.

I like the comment from someone suggesting there's some mute or other
setting that needs to be changed on the radio. There seems to be way too
much difference in sound level.

Let's not forget that if some car radio has a jack intended for external
devices, it likely is expecting an MP3 player or a portable CD player,
plugging into their headphone jack. Why else would there be an input jack?

The only other possibility is that the MP3 player has some blocking so the
volume can't be turned up too high. SOme of them do have a menu setting
to disable or enable this sort of thing, and if the problem isnt' a
setting on the radio, then the poster should look for some setting on the
MP3 player.

Michael
Click to expand...
Yeah, even now the list of possibilities has not been exhausted yet. But I -
once more - suppose the OP has enough info to try for a solution. If he
fails he can come back to report. You and I can be more specific once we
know more about the specifications of the equipment involved.

petrus bitbyter
 
On Mon, 15 Jul 2013 09:57:58 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Monday, July 15, 2013 11:48:43 AM UTC-4, et...@whidbey.com wrote:
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be a
maximum volume and the car stereo must be at close to max volume for
regular listening.

Two things to try: firstly, the Alpine stereo might have an input-level
adjustment (either hardware or software) that can be changed.
(it'd be embarassing to find that there was a 'mute' selection, or
the auxiliary input source wasn't selected, but... I've seen it happen).
One Alpine manual refers to 'AUX SETUP mode' ...

Second, a coupling transformer can match the headphone-output (100 ohms
or maybe less) to the line-input (usually 1000 ohms, sometimes as high
as 50k ohms) of the stereo. It'll take two, of course, for stereo; they're small.
Following your suggestions I plugged the MP3 player into the minijack
Click to expand...
and fiddled with the menus on the radio. Of all the options there is
no input level option for the minijack. So I think everything I can do
as far as plugging in and listening has been done. So then I looked
for a transformer as you suggested and was unable to find any that
match the specs you gave. So maybe I am looking in the wrong place.
Any links?
Thanks,
Eric
 
On Mon, 15 Jul 2013 23:36:51 +0200, "petrus bitbyter"
<petrus.bitbyter@hotmail.com> wrote:

etpm@whidbey.com> schreef in bericht
news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric

Well, as too often it's a maybe.

To tell something more I have to make some assumptions:
- Suppose the output of the MP3 player is meant to drive a low impedance
headphone. That requires (relative) low voltage and high curent.
- Suppose the Alpines input is a line input. That has a (relative again)
high input impedance so it requires high voltage but has no need for high
current.

Suppose you see the mismatch :)

Theoretically you can solve the problem using two audio tranformers with a
windings ratio of about 1:30. I don't know wether or not this transformers
are made but 1:8 or 1:10 will also do. Price tags I saw from about $20,- up
a piece (ex. VAT and shipment).

Now you amplifier comes into play. As an amplifier it will amplify the
voltage level by 40dB that's a 100 times. That may be way to much for your
Alpine but the volume control of the amplifier can handle this. So with a
little luck you're done.

But without luck? Well you may get noise or hum or distortion or even all of
them.

Noise is hard to fight. Putting a 100 Ohm or so resistor parallel to the
input of the amplifier may help.

Hum can be prevented by using well shielded cables and putting the amplifier
in a metal shield box.

Distortion may be caused by overloading the amplifier input. The 100 Ohm
resistor mentioned earlier may help. It can be lowered down to 33 Ohm if it
needs to.

I did, off course, not mention all possibilities but I, once more, suppose,
you can at least go for a try.

petrus bitbyter

Greetings Petrus,
Click to expand...
I'm going to look for small transformers in my junk pile to see if any
match the 1:30 or thereabouts spec and if I find any give 'em a try.
Thanks,
Eric
 
On Mon, 15 Jul 2013 23:37:32 -0400, Michael Black <et472@ncf.ca>
wrote:

On Mon, 15 Jul 2013, petrus bitbyter wrote:


etpm@whidbey.com> schreef in bericht
news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric

Well, as too often it's a maybe.

To tell something more I have to make some assumptions:
- Suppose the output of the MP3 player is meant to drive a low impedance
headphone. That requires (relative) low voltage and high curent.

But what kind of low voltage?

"Line in" is always pretty vague. I have an amplifier fed from a VCR, a
DVD player and misc and I tend to have to adjust the volume control when
switching sources, proving that the standard isn't really much of a
standard.

That said, it seems to be generally assumed that "line level" is about 1
volt. And surely even a headphone output can supply somewhere around
that. The mismatch doesn't matter.

I've plugged various portable devices into that amplifier, my Sansa Fuze,
various portable CD players, a small am/fm headphone radio, and while
there might be some lower level with those as the source (I can't
remember) it wasn't a massive difference.

I like the comment from someone suggesting there's some mute or other
setting that needs to be changed on the radio. There seems to be way too
much difference in sound level.

Let's not forget that if some car radio has a jack intended for external
devices, it likely is expecting an MP3 player or a portable CD player,
plugging into their headphone jack. Why else would there be an input
jack?

The only other possibility is that the MP3 player has some blocking so the
volume can't be turned up too high. SOme of them do have a menu setting
to disable or enable this sort of thing, and if the problem isnt' a
setting on the radio, then the poster should look for some setting on the
MP3 player.

Michael

Whether I plug in an iPad or a Sansa the result is the same. I need to
Click to expand...
turn the volume up high on the player and pretty high on the radio. I
have tried to get a manual for the radio just in case I am not doing
something right but Alpine says talk to Toyota and Toyota says to talk
to their manual printer and their manual printer says it's not
available. And the Scion forums have not been any help either.
Eric
 
On Tue, 16 Jul 2013 08:36:23 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Tuesday, July 16, 2013 11:24:47 AM UTC-4, et...@whidbey.com wrote:
On Mon, 15 Jul 2013 23:37:32 -0400, Michael Black <et472@ncf.ca

wrote:



On Mon, 15 Jul 2013, petrus bitbyter wrote:





etpm@whidbey.com> schreef in bericht

news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...

Greetings All,

My car has a minijack input for the Alpine stereo. When I plug in any

MP3 player the volume level is quite low. The MP3 player must be at

maximum volume and the car stereo must be at close to max volume for

regular listening. When playing a CD or listening to the radio the

stereo gets plenty loud enough before getting close to the maximum

volume setting. Since I like to buid kits I looked online and found

this one from Velleman:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262

Will this preamp work OK for amplifying the output from the MP3

player? My hearing isn't the best and this is in a car (Scion xB) so

audiophile quality isn't necessary, but I do have enough hearing left

to notice bad audio. Any thoughts? Is there a better kit available

that's not real expensive?

Thanks,

Eric



Well, as too often it's a maybe.



To tell something more I have to make some assumptions:

- Suppose the output of the MP3 player is meant to drive a low impedance

headphone. That requires (relative) low voltage and high curent.



But what kind of low voltage?



"Line in" is always pretty vague. I have an amplifier fed from a VCR, a

DVD player and misc and I tend to have to adjust the volume control when

switching sources, proving that the standard isn't really much of a

standard.



That said, it seems to be generally assumed that "line level" is about 1

volt. And surely even a headphone output can supply somewhere around

that. The mismatch doesn't matter.



I've plugged various portable devices into that amplifier, my Sansa Fuze,

various portable CD players, a small am/fm headphone radio, and while

there might be some lower level with those as the source (I can't

remember) it wasn't a massive difference.



I like the comment from someone suggesting there's some mute or other

setting that needs to be changed on the radio. There seems to be way too

much difference in sound level.



Let's not forget that if some car radio has a jack intended for external

devices, it likely is expecting an MP3 player or a portable CD player,

plugging into their headphone jack. Why else would there be an input

jack?



The only other possibility is that the MP3 player has some blocking so the

volume can't be turned up too high. SOme of them do have a menu setting

to disable or enable this sort of thing, and if the problem isnt' a

setting on the radio, then the poster should look for some setting on the

MP3 player.



Michael



Whether I plug in an iPad or a Sansa the result is the same. I need to

turn the volume up high on the player and pretty high on the radio. I

have tried to get a manual for the radio just in case I am not doing

something right but Alpine says talk to Toyota and Toyota says to talk

to their manual printer and their manual printer says it's not

available. And the Scion forums have not been any help either.

Eric

I don't suppose you have 'scope or other test gear? (maybe a signal generator?)
I'd like to know the signal level from the mp3 and then see if it goes down when you plug it into the car stereo. (maybe you could split the audio cord and listen as you plug it in.) The amp you posted looks fine. As long as you power it from the car battery I assume there is not much chance it will overload the stereo input.

George H.
Greetings George,
Click to expand...
I do have a scope. A Tek 465B. Bought because it was recommended on
this group when I asked about one years ago. I will try to make up a
setup where I can measure the output from the MP3 player. What should
I look for? How many volts/div?
Thanks,
Eric
 
On Tuesday, July 16, 2013 11:24:47 AM UTC-4, et...@whidbey.com wrote:
On Mon, 15 Jul 2013 23:37:32 -0400, Michael Black <et472@ncf.ca

wrote:



On Mon, 15 Jul 2013, petrus bitbyter wrote:





etpm@whidbey.com> schreef in bericht

news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...

Greetings All,

My car has a minijack input for the Alpine stereo. When I plug in any

MP3 player the volume level is quite low. The MP3 player must be at

maximum volume and the car stereo must be at close to max volume for

regular listening. When playing a CD or listening to the radio the

stereo gets plenty loud enough before getting close to the maximum

volume setting. Since I like to buid kits I looked online and found

this one from Velleman:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262

Will this preamp work OK for amplifying the output from the MP3

player? My hearing isn't the best and this is in a car (Scion xB) so

audiophile quality isn't necessary, but I do have enough hearing left

to notice bad audio. Any thoughts? Is there a better kit available

that's not real expensive?

Thanks,

Eric



Well, as too often it's a maybe.



To tell something more I have to make some assumptions:

- Suppose the output of the MP3 player is meant to drive a low impedance

headphone. That requires (relative) low voltage and high curent.



But what kind of low voltage?



"Line in" is always pretty vague. I have an amplifier fed from a VCR, a

DVD player and misc and I tend to have to adjust the volume control when

switching sources, proving that the standard isn't really much of a

standard.



That said, it seems to be generally assumed that "line level" is about 1

volt. And surely even a headphone output can supply somewhere around

that. The mismatch doesn't matter.



I've plugged various portable devices into that amplifier, my Sansa Fuze,

various portable CD players, a small am/fm headphone radio, and while

there might be some lower level with those as the source (I can't

remember) it wasn't a massive difference.



I like the comment from someone suggesting there's some mute or other

setting that needs to be changed on the radio. There seems to be way too

much difference in sound level.



Let's not forget that if some car radio has a jack intended for external

devices, it likely is expecting an MP3 player or a portable CD player,

plugging into their headphone jack. Why else would there be an input

jack?



The only other possibility is that the MP3 player has some blocking so the

volume can't be turned up too high. SOme of them do have a menu setting

to disable or enable this sort of thing, and if the problem isnt' a

setting on the radio, then the poster should look for some setting on the

MP3 player.



Michael



Whether I plug in an iPad or a Sansa the result is the same. I need to

turn the volume up high on the player and pretty high on the radio. I

have tried to get a manual for the radio just in case I am not doing

something right but Alpine says talk to Toyota and Toyota says to talk

to their manual printer and their manual printer says it's not

available. And the Scion forums have not been any help either.

Eric
Click to expand...
I don't suppose you have 'scope or other test gear? (maybe a signal generator?)
I'd like to know the signal level from the mp3 and then see if it goes down when you plug it into the car stereo. (maybe you could split the audio cord and listen as you plug it in.) The amp you posted looks fine. As long as you power it from the car battery I assume there is not much chance it will overload the stereo input.

George H.
 
<etpm@whidbey.com> schreef in bericht
news:33pau81fvvuall17u7gvlnr4v462j43emh@4ax.com...
On Mon, 15 Jul 2013 23:36:51 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


etpm@whidbey.com> schreef in bericht
news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...
Greetings All,
My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low. The MP3 player must be at
maximum volume and the car stereo must be at close to max volume for
regular listening. When playing a CD or listening to the radio the
stereo gets plenty loud enough before getting close to the maximum
volume setting. Since I like to buid kits I looked online and found
this one from Velleman:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262
Will this preamp work OK for amplifying the output from the MP3
player? My hearing isn't the best and this is in a car (Scion xB) so
audiophile quality isn't necessary, but I do have enough hearing left
to notice bad audio. Any thoughts? Is there a better kit available
that's not real expensive?
Thanks,
Eric

Well, as too often it's a maybe.

To tell something more I have to make some assumptions:
- Suppose the output of the MP3 player is meant to drive a low impedance
headphone. That requires (relative) low voltage and high curent.
- Suppose the Alpines input is a line input. That has a (relative again)
high input impedance so it requires high voltage but has no need for high
current.

Suppose you see the mismatch :)

Theoretically you can solve the problem using two audio tranformers with a
windings ratio of about 1:30. I don't know wether or not this transformers
are made but 1:8 or 1:10 will also do. Price tags I saw from about $20,-
up
a piece (ex. VAT and shipment).

Now you amplifier comes into play. As an amplifier it will amplify the
voltage level by 40dB that's a 100 times. That may be way to much for your
Alpine but the volume control of the amplifier can handle this. So with a
little luck you're done.

But without luck? Well you may get noise or hum or distortion or even all
of
them.

Noise is hard to fight. Putting a 100 Ohm or so resistor parallel to the
input of the amplifier may help.

Hum can be prevented by using well shielded cables and putting the
amplifier
in a metal shield box.

Distortion may be caused by overloading the amplifier input. The 100 Ohm
resistor mentioned earlier may help. It can be lowered down to 33 Ohm if
it
needs to.

I did, off course, not mention all possibilities but I, once more,
suppose,
you can at least go for a try.

petrus bitbyter

Greetings Petrus,
I'm going to look for small transformers in my junk pile to see if any
match the 1:30 or thereabouts spec and if I find any give 'em a try.
Thanks,
Eric
Click to expand...
Just to try any small transformer between 220:5V to 220:24V will be of
interest. Though I think you will loose higher frequencies as these are
mains transformers. I expect output transformers from old transistor
amplifiers will do better... If only you can still find them. Remember the
1:30 windings are a theoretical value. A 1:10 is more likely to be found and
usefull.

petrus bitbyter
 
On Tuesday, July 16, 2013 12:46:51 PM UTC-4, et...@whidbey.com wrote:
On Tue, 16 Jul 2013 08:36:23 -0700 (PDT), George Herold

gherold@teachspin.com> wrote:



On Tuesday, July 16, 2013 11:24:47 AM UTC-4, et...@whidbey.com wrote:

On Mon, 15 Jul 2013 23:37:32 -0400, Michael Black <et472@ncf.ca



wrote:







On Mon, 15 Jul 2013, petrus bitbyter wrote:











etpm@whidbey.com> schreef in bericht



news:ep58u8d6uhhj9m9rk0er459ufkojogfkd7@4ax.com...



Greetings All,



My car has a minijack input for the Alpine stereo. When I plug in any



MP3 player the volume level is quite low. The MP3 player must be at



maximum volume and the car stereo must be at close to max volume for



regular listening. When playing a CD or listening to the radio the



stereo gets plenty loud enough before getting close to the maximum



volume setting. Since I like to buid kits I looked online and found



this one from Velleman:



http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-262



Will this preamp work OK for amplifying the output from the MP3



player? My hearing isn't the best and this is in a car (Scion xB) so



audiophile quality isn't necessary, but I do have enough hearing left



to notice bad audio. Any thoughts? Is there a better kit available



that's not real expensive?



Thanks,



Eric







Well, as too often it's a maybe.







To tell something more I have to make some assumptions:



- Suppose the output of the MP3 player is meant to drive a low impedance



headphone. That requires (relative) low voltage and high curent.







But what kind of low voltage?







"Line in" is always pretty vague. I have an amplifier fed from a VCR, a



DVD player and misc and I tend to have to adjust the volume control when



switching sources, proving that the standard isn't really much of a



standard.







That said, it seems to be generally assumed that "line level" is about 1



volt. And surely even a headphone output can supply somewhere around



that. The mismatch doesn't matter.







I've plugged various portable devices into that amplifier, my Sansa Fuze,



various portable CD players, a small am/fm headphone radio, and while



there might be some lower level with those as the source (I can't



remember) it wasn't a massive difference.







I like the comment from someone suggesting there's some mute or other



setting that needs to be changed on the radio. There seems to be way too



much difference in sound level.







Let's not forget that if some car radio has a jack intended for external



devices, it likely is expecting an MP3 player or a portable CD player,



plugging into their headphone jack. Why else would there be an input



jack?







The only other possibility is that the MP3 player has some blocking so the



volume can't be turned up too high. SOme of them do have a menu setting



to disable or enable this sort of thing, and if the problem isnt' a



setting on the radio, then the poster should look for some setting on the



MP3 player.







Michael







Whether I plug in an iPad or a Sansa the result is the same. I need to



turn the volume up high on the player and pretty high on the radio. I



have tried to get a manual for the radio just in case I am not doing



something right but Alpine says talk to Toyota and Toyota says to talk



to their manual printer and their manual printer says it's not



available. And the Scion forums have not been any help either.



Eric



I don't suppose you have 'scope or other test gear? (maybe a signal generator?)

I'd like to know the signal level from the mp3 and then see if it goes down when you plug it into the car stereo. (maybe you could split the audio cord and listen as you plug it in.) The amp you posted looks fine. As long as you power it from the car battery I assume there is not much chance it will overload the stereo input.



George H.

Greetings George,

I do have a scope. A Tek 465B. Bought because it was recommended on

this group when I asked about one years ago. I will try to make up a

setup where I can measure the output from the MP3 player. What should

I look for? How many volts/div?

Thanks,

Eric
Click to expand...
Geesh I have no idea. :^)...(we need some audio guy to answer.)
OK my computer has a little audio output. I plug a ~35 ohm ear bud into it.
There's about 100 mV p-p (peak to peak) with the ear bud plugged in. Without the ear bud the signal is more like 400-500 mV p-p. So I'd like to see that the mp3 output doesn't drop too much when it's plugged into the amp.

George H.
 
On Tuesday, July 16, 2013 8:18:23 AM UTC-7, et...@whidbey.com wrote:
On Mon, 15 Jul 2013 09:57:58 -0700 (PDT), whit3rd <whit3rd@gmail.com

wrote:



On Monday, July 15, 2013 11:48:43 AM UTC-4, et...@whidbey.com wrote:

My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low.

Two things to try: firstly, the Alpine stereo might have an input-level
adjustment (either hardware or software) that can be changed.

...Second, a coupling transformer can match the headphone-output (100 ohms
or maybe less) to the line-input (usually 1000 ohms, sometimes as high
as 50k ohms) of the stereo.
Click to expand...
In terms of places to look, if you can find a similar non-OEM stereo at
<http://www.alpine-usa.com/support>
you can try to download its manual for more info.

As for a good source of audio matching transformers: I dunno. There's microphone
adapter units (somewhat pricey), and maybe <http://www.edcorusa.com/c/94/com10>
(but I've not done any business with them). Audio matching transformers
have kinda ... dried up and disappeared from the usual distributors.
 
On Fri, 26 Jul 2013, whit3rd wrote:

On Tuesday, July 16, 2013 8:18:23 AM UTC-7, et...@whidbey.com wrote:
On Mon, 15 Jul 2013 09:57:58 -0700 (PDT), whit3rd <whit3rd@gmail.com

wrote:



On Monday, July 15, 2013 11:48:43 AM UTC-4, et...@whidbey.com wrote:

My car has a minijack input for the Alpine stereo. When I plug in any
MP3 player the volume level is quite low.

Two things to try: firstly, the Alpine stereo might have an input-level
adjustment (either hardware or software) that can be changed.

...Second, a coupling transformer can match the headphone-output (100 ohms
or maybe less) to the line-input (usually 1000 ohms, sometimes as high
as 50k ohms) of the stereo.

In terms of places to look, if you can find a similar non-OEM stereo at
http://www.alpine-usa.com/support
you can try to download its manual for more info.

As for a good source of audio matching transformers: I dunno. There's microphone
adapter units (somewhat pricey), and maybe <http://www.edcorusa.com/c/94/com10
(but I've not done any business with them). Audio matching transformers
have kinda ... dried up and disappeared from the usual distributors.


There was a time, likely brief, when tv sets seemed to include audio
Click to expand...
transformers to feed external circuits.

There was a period 20 years ago when one tv repair store reliably tossed
tv sets once a week, and I'd come upon them. And I have a scrap of
circuit board from that period, two matching audio transformers that must
have been for isolating the headphone jack or even "audio output" jacks.
I have no idea how common that was, and likely by now those tv sets have
already all been scrapped.

Michael
 
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