More MP3 power!

[v-bro]

Hi I have been looking around for a solution to crank up the gain a bit of my MP3 player. I always skip a heartbeat when I switch to CD....

So now early in the morning I seem to have found a passive solution! I would like to know if there are any negative side effects that I don't know of or didn't think about because it just seems too simple to be true....

I had two OEP A262A2E audio transformers from a PCB I found in the dump at work. The ratio is 1+1:2+2. So I connected the primary windings in parallel and the secondary in series to go for max gain...

I've once read in the tube forum that the more transformers between audio stages the better. With this thought in the back of my head I just thought to give it a try

It sure sounds a lot more powerfull Tomorrow I'll test it at more power, have to think about the neighbours right now....

I'll stay in touch.

[v-bro]

Ok, I tested it to the max. today, on my AMP32 it eventually overloads the input and the amp shows distortion.

It works best if I go to several power amps with splitter cables. The extra voltage helps a lot to maintain a powerfull signal.

Today I went from my MP3 player through the transformers into two PLLXO filters (a lowpass and a highpass, both @ 200hz aprox.) and went from the lowpass into a parallelled AMP9 (made it two channel...) on two 10" subwoofers (one left one right... ) and from the highpass into an AMP32 on two small 2-way bookshelve speakers....

The sound seems to be much nicer with the transformers inbetween, much more dynamic, deeper bass and lots more output...so I'm quite happy

It also seems to be a good solution to use before a PLLXO filter to compensate for the insertion loss (and to keep the load to the source a bit easier)

[BWRX]

An even cheaper option would be to attenuate the output of your CD player to match the output of your MP3 player.

[v-bro]

Ok, you're right, but I like to play loud every now and than. So a bit extra power can't hurt, the input of my amp can handle higher voltage than the mp3 player can deliver...

Another advantage is that it eliminates ground loop noise. I made a usb 5V supply from 12V in the car, normally when I operate the amp and the player from the same 12V supply I get terrible noise, now that's away too!

Another thing I can try now is bypassing the input caps, as DC can't enter through the transformers anyway...

[BWRX]

You don't want DC across a transformer winding. It's just like an inductor and current will easily flow through it. Usually a capacitor is connected in series with a transformer winding to ensure that a DC voltage is not placed across a tranformer winding.

[Pano]

Sounds like you are trading current for voltage. Not a bad trade if your source has enough current, and your iPod should.

It is the opposite of what happens in the output stage of a tube amp. There you trade voltage for current.

I've always liked transformer coupled circuits in pro audio and in Hi-Fi. Done right, they seem to sound richer and more natural then many actively coupled circuits. But they can be heavy and expensive, that's the down side.

You can't just replace the input caps with transformers, because there is 2.5V between the input and ground. That's what the cap is there to block. You can try connecting the transformer secondary between the input cap and the Biascap pin (pin 16 on the TA2024). This puts each end of the secondary at 2.5V so no DC current flows. I've had some success with this.

Do this AT YOUR OWN RISK! Get it wrong and you can fry the chip and/or damage you speakers.

[v-bro]

Thanks for your response,

Originally posted by BWRX
You don't want DC across a transformer winding. It's just like an inductor and current will easily flow through it. Usually a capacitor is connected in series with a transformer winding to ensure that a DC voltage is not placed across a tranformer winding.

I'm not worried about blowing up the transformers, but after what Panomaniac wrote I think I'd better not try, as I do worry about blowing up the amp....

Originally posted by panomaniac
[B]Sounds like you are trading current for voltage. Not a bad trade if your source has enough current, and your iPod should.

Well it's a flashmemory player, but I figured any headphone output is designed rather to deliver current than voltage...
It sure sounds great...

Originally posted by panomaniac

I've always liked transformer coupled circuits in pro audio and in Hi-Fi. Done right, they seem to sound richer and more natural then many actively coupled circuits. But they can be heavy and expensive, that's the down side.

The OEP transformers are quite light and small actually...

I've also created a PLLXO notch filter box, all passive. I wired two 110mH coils on a stack of I-pieces from an old E-I core transformer. They have quite some resistance, but the sound seems to benefit from this...The box has a switch for two different cap values and a switch for two different resistor values. It also features a potmeter that enables you to adjust the depth of the 'dip'. I went from my MP3 player to the transformer box and than through the notch box and than into an 41hz AMP32, the sound from my fullrange PVC portable mini speakers is really good with the trannybox and notchbox inbetween.

I A/B tested between a setup with the tranny+notch box and another without (same amp and speakers) and the results are quite phenomenal IMO. Bass really has that basskick power and the coarse midrange area flattens out nicely. The high frequency range is much better with my home-wound coils when compared to ready made ferrite chokes...(same value, only my coils are 150 ohm and the ready made chokes are 75 ohm. With the ready made coils the high frequency range seems to suffer...).

Anyway, today I had a smile on my face when I tested the trannybox in my car...

Will shoot some pics soon....

[v-bro]

Hmm, still no camera, maybe tomorrow....
(have to borrow it, mine's broken...)

But I wound new coils, these measure a very nice 33 to 35 ohms resistance at about 100mH. And they sound a lot better strange enough. This time I usede the 'E' plates from the E-I transformer core and cut the side legs from the 'E' in a way that I have two 'L' shapes. This way I can mount a ring around it without the risk of it slipping off. After the amount of turns needed to get 110mH on the previous core I allready was in the range of more than 1 H!

I used it on the speakers here:
Portable sound system gallery...

And it makes them sound quite grown up.

But, to keep a bit more on-topic

Here's something else going on to enhance the power of MP3:
6SL7 or 6SL7GT for broken Tubalizer

Still waiting on the valves, but can't wait to try something like Alastair was so kind to share....(his 12 volt tube preamp schematic )

Cheers to all!