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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Feb Wed 28, 2018 3:56 pm 
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Location: Mountains of Mourne. Ireland.
Altoids (Curiously Strong Mints) stereo and mono 3.5mm sockets. Hot-melt glue.
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.. ▲ audio splitter.
http://www.reocities.com/n2uhc_2/audio_splitter.html

Greg.


Last edited by egg on Feb Wed 28, 2018 4:18 pm, edited 1 time in total.

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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Feb Wed 28, 2018 4:17 pm 
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Location: Gretna, Nebraska
I have had good luck with This radio shack audio transformer and the price is right.
https://www.radioshack.com/products/rad ... ransformer

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...... how hard can it be?


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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Feb Wed 28, 2018 4:40 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 2660
Location: Lexington, KY USA
When soldering wires to those little pins, use some small-gauge wire. Wire smaller than the pins. This way the wire will flex instead of the pin.

30ga wire wrap wire, or 28ga stranded. There is likely something you can use in your junk cable box. Ribbon cables, USB cables, and so on, have small gauge wires inside. If using scrap wire, be sure you can strip and solder it OK.

Use the small wire to make jumpers to connect to panel mounted jacks, or to heavier cables with plugs on the other end.

If you want to solder the transformer to a PCB, you might use something like these:

http://www.mpja.com/Protoboards-Set-Dou ... /32065+PB/

http://www.mpja.com/2-3_4in-X-1-3_16in- ... /31253+PB/

http://www.mpja.com/Protoboards/products/284/

The FR-4 material and plated-through holes are good features.

Ted


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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Mon 05, 2018 12:38 am 
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Joined: Feb Mon 13, 2017 10:46 pm
Posts: 158
Location: Atlanta GA
Update:

I finally finished testing this thing on my German radios and I could not be happier! Here are the photos of how I decided to mount this rig. Hopefully my solder job will be good enough. Man that was tough to work with such a small transformer. The problem I was having with the distortion in the mid-range disappeared once I soldered the leads to the transformer. Apparently my temporary connections were not making good enough contact. I have listened to this on a 1957 Nordmende and a 1962 Kuba for a couple hours and it seems that there is no distortion even if I turn the volume up all the way on the iPod. Although just for good measure I knock the volume down two clicks just to be sure and that seems to match the FM radio in volume. What surprised me the most is that there seems to be no loss of frequency response and there is no "hum" or added noise to speak of. The bass and treble seem to be full with no perceptible loss. Even running this thing on my 1979 Marantz receiver sounds good. I will order a couple more and make a box so that I can feed a stereo signal to my 1962 Kuba console stereo and my modern receivers.

Thanks for all those that chimed in on this thread. I could not have done this without your help. Especially Tom! Thank you again.
BB

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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Mon 05, 2018 3:50 am 
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Joined: Jun Mon 01, 2015 9:34 pm
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Location: Greenville, TX
Here is the transformer I have been using for a few years. Very small and can be mounted with double sided tape.

https://www.mouser.com/ProductDetail/Tr ... wlDA%3d%3d

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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Mon 05, 2018 5:29 am 
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Location: San Jose, CA USA
Dale,

That looks pretty good, and I like the price. Although the frequency response appears rather modest on the Mouser page, the spec sheet gives more detail and it looks reasonably good.

The output transformers on typical tube table radios don’t have very good frequency response, so using the transformer you’re suggesting would likely not restrict the range more than the output transformer already does.

Might be interesting to compare the sound from this one vs the more expensive transformer and see if there is any audible difference in sound quality.

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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Mon 05, 2018 1:53 pm 
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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Mon 05, 2018 2:38 pm 
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Joined: Feb Mon 13, 2017 10:46 pm
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Location: Atlanta GA
Paul,

I think I will give a couple of those MOUSER transformers a try. At that price I do not have much to lose. I will report back late this week to comment on how they sound compared to the one that I just used.


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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Fri 09, 2018 12:32 am 
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Joined: Feb Mon 13, 2017 10:46 pm
Posts: 158
Location: Atlanta GA
Just received the Mouser transformers and set them up together for a stereo installation. They do sound good with complete frequency response and no hum or distortion and they are very small. Compared to the transformer I ordered from Newark and posted on this thread last week this Mouser TF sounds about the same to my ears but it does not add as much volume as the Newark TF. I would say the Mouser splits the difference in volume gain that the Newark produces. Even so, it still does the trick and the price is right. If anything that Newark TF jumps the volume a bit too much as I have to cut the volume at the iPod to prevent distortion where as with the Mouser I do not have to do that.

Thanks to all for their input. Now on to trying to find suitable containers to mount these small transformers in.

BB


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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Fri 09, 2018 12:37 am 
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Location: Haledon, NJ, usa
bluebellyyankee wrote:
I know I have stumbled across this subject before on this forum but would somebody please point me in the right direction on what is needed in order to build a pre-amp so that I can raise the volume level from my iPod going into the tape input on a vintage radio? The volume level is about half what the FM radio produces. I have tried 4 different vintage German radios and they all have the same issue. I am having to turn up the volume knob about 2 to 3 times as much compared to listening to FM radio.


I assume Mouser is now the only source since radio shack is out of business.

Thanks,
BB

Make your input connection AFTER the vol control at the input to the 1st audio amp.
Then use the iPod vol .

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 Post subject: Re: Pre amplifier for iPod input to raise volume
PostPosted: Mar Fri 09, 2018 1:35 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: San Jose, CA USA
BB - thanks for the comparison. Very helpful for future reference. Now we have two different parts that we know work well, each with slightly different properties.

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Tom K6VL


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