One newbie question about Supergreen/Mp20 NE5534/ Jensen

My Presonus Mp20 has the NE5534. The Supergreen also uses it.
There is a common mod for the Mp20 changing the OP-amps, but also the jensen transformers. On some clips I have heard, the difference on the Jensen is quite noticecable, compared to the generic ones.
The Supergreen is transformerless. What sonic diference adds a transformer like the Jensen on the Mp20, compared to the transformless design? Color? Warmth? Any Noise/floor influence?

any help?

Well , you could certainly use a transformer in front of a non-xfmr circuit , because of the impedance conversion they are usually stepup so
you get a modest gain increase from it and that will help with s/n
The common mode rejection on the balenced input is usually better
than the non xfmr and one might argue that transient response and high end will not be as good , depending on the quality of xfmr [ but that may
be a desirable thing for color ]

A good design of either will allow you to not worry about it and pay more
attention to what you are recording , never a bad thing .
The xfmrless s.s designs will be cheaper and lighter to build

Make your best guess , start from there and you are on your way to audio education , remember to listen with your ears

regards Greg

[quote author="okgb"]Well , you could certainly use a transformer in front of a non-xfmr circuit , because of the impedance conversion they are usually stepup so
you get a modest gain increase from it and that will help with s/n
The common mode rejection on the balenced input is usually better
than the non xfmr and one might argue that transient response and high end will not be as good , depending on the quality of xfmr [ but that may
be a desirable thing for color ]

A good design of either will allow you to not worry about it and pay more
attention to what you are recording , never a bad thing .
The xfmrless s.s designs will be cheaper and lighter to build

Make your best guess , start from there and you are on your way to audio education , remember to listen with your ears

regards Greg[/quote]

Thanks for the reply. As you tell can go either way, I guessing if could go both way, I mean, couldn´t be added a transf switchable in/out the circuit? I don´t know if is a fool idea, but if could be made, would be a nice 2 in 1 preamp, switchable depending on the audio source, likes, etc...
What about powering the Supergreen from battery and/or using a DC-Dc converter? Maybe I start another thread for this?

You get a modest gain increase from it and that will help with S/N.
The common mode rejection on the balanced input is usually better.

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For almost all designs SNR will not improve as you likely miss the OSI of the amplifier with a step-up transformer and for sure add some thermal noise. CMRR might possibly get a boost at least at low frequencies (below 1 kHz), but a well designed active input achieves better CMRR towards the higher frequency end. RFI protection should be better than without transformer.

Sonically the most important aspect will be largely increased distortion at low frequencies.

Samuel

Sonically the most important aspect will be largely increased distortion at low frequencies.

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So the mainly advantage is just to add some specific "color"?


Samuel, I remember you replied on the DC-DC converter thread I tried.
I wrote Motien and had no reply. Also have no reply on this forum about a posible design or comercial candidate.
I´m lookin for a way to build a portable battery powered Supergreen, any idea?

So the mainly advantage is just to add some specific "color"?

Click to expand...

That's the way I'd see it. With respect to switching the input transformer: basically possible, but not easy to realize on a given PCB design if you want to bypass the phantom power coupling capacitors.

I wrote Motien and had no reply. Also have no reply on this forum about a posible design or comercial candidate. I'm lookin for a way to build a portable battery powered Supergreen, any idea?

Click to expand...

I'd consider one of the numerous 12 V to +/-15 V DC-DC converters for the audio supply. A pack of six 1.5 V cells will provide pretty long power life. Adding a pair of 10 ohm + 10 uH/220 uF filter for each channel should get rid of the switching noise.

Phantom power is more of a problem--you might consider my 48 V DC-DC converter design (see some thread in the Drawing Board, still untested though), two stacked 24 V DC-DC converters or a +/-24 V DC-DC converter with floating outputs.

Samuel

Quote:
So the mainly advantage is just to add some specific "color"?

That's the way I'd see it. With respect to switching the input transformer: basically possible, but not easy to realize on a given PCB design if you want to bypass the phantom power coupling capacitors.

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Considering the color use, I really have no much interest on it for complicating the ciruitry.
Regarding the DC converters I started a new thread.
Thanks a lot, your replies was very useful for me.

Just one doubt, any experience about the use of the LT1357 on the Supergreen? could be used instead the Ne5534? would need to change teh +/- 20 volt?

It was one of the things that bothered Fred Forssell , with Millennia adding a switchable transformer to the input of some their products .

And i agree if not for whatever amount of coloration the gains of the xfmr
in this type of circuit may not match the cost .

I had in the past added low ratio Jensens to a Trident 65 , and it did indeed allow me to use less preamp gain and have a quieter channel ,
also in this case made the average sm 57 sound better as a practical result , it was however too expensive and not dramatic enough to do on many channels . i had faxed the circuit to jensen who made some
suggestions .

At least now we have some giving input for lagoausente , thanks

regards Greg

At least now we have some giving input for lagoausente , thanks "

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I feel something like in the jungle, a jungle of knowledge maybe. I should must start the reading of those big Meta books to can input something to the forum. The barrier is not laziness. I find interesting when reading. But the amount of data to read is really very big, and the time availbe usually so low that learning ends being a very slowly process, at least for me.

Allot of the learning is in the doing , the experience
combine that with the reading and you're on your way .

I don't mind asking though , because it's great when someone's wisdom
saves you from needless frustration ,

But as we say [ or some variation ] 1 gig is worth 5 rehearsals

good luck & skill , regards Greg