Burn in Step up transformer with ipod.


Here is question for you guys. There are cd products out there that reduces the output of CD players to low levels so that they can burn in phonostages and step up transformers safely.

Most cs players output between 2-4 volts which can damage phono step ups. With an ipod, the headphone output is 30mv. If i pay a track via the ipod and connecting it to a step up transformer with rca and play at low volumes, wouldnt it be the same thing as what these products do?
leicachamp
play some tunes and you'll be OK.
If you turn the volume down to what a typical low output moving coil puts out it should work fine.

Anything around .2mv would be good. To much voltage will saturate the step up tranny.
Don't forget to load the transformer outputs. A 47k resistor across each output should work OK.
I dont think i can get the output to be as low as .2mv. I estimate at low volume the ipod would be pumping out 5-10mv. I have just finished a 24hr burn in session using my ipod and to my relief, no damage. I cant say whether it has improved the sound or not atm. Going to burn it a few more days.

I hear of theories of burning/damage the coils in Step up transformers but putting a too high signal, but i never read of an actual case!! Is it just a myth?

How much voltage can these transformers take?
I would buy the Granite Audio burn in disc...MM and also MC.
I dont think i can get the output to be as low as .2mv. I estimate at low volume the ipod would be pumping out 5-10mv. I have just finished a 24hr burn in session using my ipod and to my relief, no damage. I cant say whether it has improved the sound or not atm. Going to burn it a few more days.

I hear of theories of burning/damage the coils in Step up transformers but putting a too high signal, but i never read of an actual case!! Is it just a myth?

How much voltage can these transformers take?

Not sure how you are estimating the output. The impedance reflected back to the I Pod would be dependent on the turns ratio and the input impedance of the phono preamps input.

The situation you want to avoid is saturating the input coils. The saturation level is dependent on a lot of factors but I have found a tranny that spec'd max 1 volt in.

If you do not have a sensitive digital multi meter to check the voltage I suggest you actually listen to it while playing the I pod. Because of the RIAA curve it will sound like the bass knob was turned all the way up and then some, with the opposite for the treble. However if it is not distorted you are good to go.
Wouldn't the load at the input side be impacted by the load at the output side?
Get an inverse-RIAA device from Jim Hagerman. It does exactly what you're looking for, and it's a bargain.
There are some really inexpensive phono transformers available. That is if $20-$30 bucks is cheap enough for you. I can't remember theirs names or where to buy them but if I were looking I would bottom fish Ebay to start.
Kevin Carter of K&K Audio, the US distributor for Lundahl transformers burns in new MC transformers with line level signals. As long as transformer is properly loaded and phono stage is off or not connected I see no problem. In fact, burn in is quicker. I burned in a pair of LL1931AGs ($900ea Lundahl silver MC transformers) in this manner.
John. Thanks for the info.

Did you connect to the output of the step up transformer and load the inputs ?

It's interesting to hear that K&K burn their step up with line level signals. I have never read a direct case of a transformer damaged because of a high level signal, but there seems to be an urban myth that many folks out there have done irreversible damage to their step ups and phono stages.
Mechans, what makes you think I was looking for budget step ups?

My questions had nothing to do with the cost of step ups!
Line level signals are usually around 1 volt so probably not a big deal. However if the voltage is high enough you will saturate the the core of tranny. If done for extended periods you will eventually do damage to it.

Also, if your phono stage is on and you are feeding the tranny one volt I guarantee that you will severely overload the input. So hook up the tranny to the phono pre to "load" it but do not turn it on and risk damage.
I just fed the input with the phono pre turned off. You will probably want to use a high value of resistance as a load so as not to load down whatever device you are using to provide the signal too much. Remember, if the load resistor is on the secondary you will have to multiply the load resistance you want by the square of the transformer's turns ratio. e.g. for 47K at the input with a 10:1 transformer you would use a 4.7M resistor across the secondary.
I would err on the side of caution and not extrapolate from Kevin Carter's practices with the Lundahl transformer to other transformers, which may have higher step-up ratios and be different designs. Putting a 1 volt signal into a 20 db step-up will result in 10 volts on an output that is intended to handle a few millivolts.

Good comments by JJ. Personally, though, I would not put a stepped up line-level signal into a phono stage whether it is turned on or not, especially if it is solid state. It's easy enough to get a resistor at Radio Shack or elsewhere and not take any chances.

Regards,
-- Al
If I plug the output of the mc transformer to a line input in the preamp( not phono) what load would that supply the mc transformer? Or does only a phono input provide the right load to the step up?

Also by plugging to the line input, that would prevent any damage to the phono stage.
If I plug the output of the mc transformer to a line input in the preamp( not phono) what load would that supply the mc transformer?
That's a good thought, at least potentially. The load impedance will be approximately equal to the specified input impedance of that input. Often 47K, and usually somewhere between around 20K and 100K.
Or does only a phono input provide the right load to the step up?
No. If the line level inputs and the phono input have a similar input impedance, the transformer (and the source) won't know the difference. But there would be much less chance of damaging a line level input than a phono input.

Still, though, I'd be hesitant to send 10 volts or so into a line level input of a solid state preamp for prolonged periods of time, even if it is turned off, without being familiar with the design of the input circuit or obtaining an ok from the manufacturer. I doubt that it would be a problem, though, with tube equipment.

Regards,
-- Al

I can't believe the amount misinformation and bad advice that is being spread on the web by these forums. Against my better judgement let's address some of the issues raised on this tread:
1 - an AC signal of .2-.3Vrms will not saturate the core of a MC transformer. It will in fact be more effective at demagnetizing the core than the typical .3-.4mV signal from a MC cartridge. BWT, it is a myth that prolonged core saturation will damage a MC transformer. Now if your source of a burn in signal has a DC offset at its output it will magnetize the core. In that case inserting a capacitor in series with the output will block any DC.
2 - you won't "burn out" the windings of a MC transformer by feeding it a line level signal. To see why consider this thought experiment. Take a large power transformer. Measure the DC resistance of its primary winding. Typically this is in the range of 0.3 ohms or so. Take a 0.3 ohm resistor and plug it into a wall socket. It will probably explode with a big puff of smoke. Now plug in the primary winding of the power transformer with an unloaded secondary. Same DC resistance but no fireworks. Why? Because the transformer's winding is an INDUCTOR! Inductors appose the flow of current. That's what they do. Now MC transformers do have fewer turns on their primary than line level input transformers (to better match the low impedance of a MC cart.) , they still have enough inductance that any line level signal will not "burn out" the windings. As a note, most manufactures of MC transformer use heavier guage wire on the primary of a MC transformer than they use on a line level input transformer to limit I*2R losses.
3 - as to using an inverse RIAA network this will certainly do no harm, I just don't see the point. These things are very useful for measuring a phono preamps frequency response. But if you have ever used one to do that with a MC transformer input you may be left wondering why your unit has no bass response. The reason for this is the MC transformer needs the low source impedance of a MC cart. The inverse RIAA network presents the transformer with a very high source impedance. The result of this interaction is a rolled off bass response. It actually might take longer to burn in your transformer with this lack of excitation from low frequency signals.
4 - as to the possibility of damaging a solid state phono pre by inputing a 10Vrms signal into a unit that is turned off, get real. If someone can come up with a real example of this, show me the circuit and I will eat my words. A well designed unit should not be damaged even turned on. If that signal some how shocked the input stage into some type of destructive oscillation then the unit was probably crap to begin with.
07-26-13: John_tracy
As to the possibility of damaging a solid state phono pre by inputing a 10Vrms signal into a unit that is turned off, get real. If someone can come up with a real example of this, show me the circuit and I will eat my words. A well designed unit should not be damaged even turned on. If that signal some how shocked the input stage into some type of destructive oscillation then the unit was probably crap to begin with.
John, take a look at the schematic shown on the last page of the manual for the Hagerman Bugle2 phono stage. Note that the input signal goes through a low value resistor into an OPA2134 op amp, which uses a FET input stage. Here is the datasheet for the OPA2134. Note in the Absolute Maximum Ratings listed on page 3 ("stresses above these ratings may cause permanent damage" as stated in note 1 below the listings) that the absolute maximum input voltage is specified as being 0.7 volts beyond the power supply "rails" (voltages) that are supplied to the device.

That kind of absolute maximum specification of input voltage, specified relative to the supply rails, is very common in the case of op amps and other analog integrated circuits.

When the phono stage is turned off the supply rails are of course zero. Therefore at the positive and negative peaks of a 10 volt rms sinusoidal input that absolute maximum rating will be EXCEEDED by (10 x 1.414) - 0.7 = 13.4 volts. (The 1.414 factor converts rms to peak, of course).

And even when the device is powered up, its supply rails are approximately +/- 10 volts in this phono stage (as indicated on page 7 of the manual), and so the absolute maximum rating of its input will be violated by 3.4 volts at the positive and negative peaks of the waveform.

Will that damage the device, or degrade its long term reliability, if it were done for a prolonged amount of time during a burn-in process? I don't know. But it certainly strikes me as a significant risk, and as very bad practice.

That was the kind of situation I was envisioning when I offered my previous comment, not an oscillation scenario. And also in the back of my mind was the fact that bipolar transistors, which might be used in other designs, commonly have very low absolute maximum voltages specified for their base-to-emitter junctions in the reverse direction, in the neighborhood of 5 volts or so.

Regards,
-- Al
"BWT, it is a myth that prolonged core saturation will damage a MC transformer"

How so? Transformers can only handle so much wattage before they saturate. Extended saturation causes heat issues. Heat issues cause problems. What am I missing?

IMO and experience, it is never a good idea to use anything far outside its intended design parameters.
I am happy to report that no damage has been done to my step up. I have been feeding it with 10% to 60% of the volume of the ipod for approx 80hrs. Normal music signal was used.

Results: When i listened after burning at 10% volume around the 24hr mark, i could not really hear much difference. But now WOWWWWW, complete transformation. Bass is really deep and thunderous, mids and top really opened up. At the same thing it sounds very relaxed. I also find that it sounds louder at my previous volume level. This could be due to the Step up sounding a lot more dynamic.

I will continue burning in unit in the following weeks.The MC step up is the New York based Audio Labs T20. I also have a Lyra Erodion that i have been using for the past year, but which i will also burn in.

Thanks to al that have contributed to this thread.
If we analyze what a transformer is, it is a length of signal-conducting wire (s) that are wrapped around a permeable core. As a purely passive device, it has less to go wrong than with an active amplifier. The possible points of failure due to too-exuberant burn-in would be the core, and the wire.

Unlike a phono cartridge, a stepup transformer does not need to maintain a permanent magnetic field, therefore temporary saturation should not cause problems. However, I wonder how effective saturation will be in the burn-in process, since saturation will remove signal amplitude variations that the transformer core "sees".

If the current pushed through the signal wire is too high for its diameter, the wire will melt. But the wire diameters used in a transformer are certainly bigger than in a phono cartridge. It isn't so likely that a line-level signal will damage the wire.

If you use the output of a power amp to drive the transformer, or connect the transformer to the AC mains, certainly the signal wires could be damaged.

As long as you make sure that the current level used in the break-in process doesn't exceed the current-handling abilities of the transformer's internal signal wire (which will be affected by load / termination as well as signal level), I doubt if anything nasty will occur.

BTW, a transformer is a bi-directional device. Normally feeding a signal into the primary windings (normal input) will cause a stepped-up signal of equivalent power (higher voltage, lower-current) to appear at the secondary windings (normal output). However, the transformer can also be connected back-to-front and used as a step-down transformer - if you feed a signal into the secondary windings, you will get a stepped-down signal output from the transformer primaries (output signal voltage will be the inverse of the transformer's stepup ratio).

Needless to say, the above can be utilized when burning in an MC transformer (in which case, don't forget to load the primary windings).

hth, jonathan carr