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Is a Step-up Transformer needed?

Hi, I am using a Denon DL-103 with an Output Voltage of 0.3mV and a recommended load resistance of 100 Ohms or more except when transformer is provided (direct quote from instruction manual) and a Pro-Ject Tube Box SE which can be set to either 100 Ohm, 220 Ohm or 1kOhm. I am confused about the output voltage issue. Can I use any of these settings without the step-up transformer? Thanks.
128x128tarraga
mb1audio02
188 posts
 

Dear Thuchan, Do you have some general criteria for SUT's use?

Should they be used by all LOMC or is the output not relevant?


An SUT (Some call them Head Amps) are needed if your phono stage doesn't have enough gain to deal with a low output cartridge. For example, if you have a phono preamp that supports MM only and you have a LOMC, you would need an SUT because a lot more gain is needed for that type of cart. 


This particular case is interesting because the OP has a phono pre that should support a LOMC, but in reality the lower the voltage, the higher the quality of phono stage is needed for comparable SQ. Especially since his phono pre uses tubes. With a cart output of .3, you're asking a lot from the phono stage. It will be pushed right to its limit. 

In my opinion, its 50/50. Try the Pro Ject first, by itself, and if it sounds OK that's all you need. If you get some noise or distortion, then it would be wise to switch back to MM and use a SUT.






tarraga's avatar
tarraga OP
15 posts
 
Thank you all. It seems to be sounding fine through the PJ.
bimasta's avatar
bimasta
227 posts
 
"An SUT (Some call them Head Amps) are needed if your phono stage doesn't have enough gain to deal with a low output cartridge."

This may be pedantic, mb1, but I think SUT is specifically a passive step-up using transformers (hence the "T" in SUT), while a head-amp uses active electronics to boost the signal; it needs a power supply, an SUT doesn't.

Their merits are debated. SUTs are 'pure' — head-amps add distortion.
But SUTs pick up hum — head amps don't. But head-amps are noisy — SUTs are dead-silent. Some head-amps use batteries to solve the noise issue. My head-amp plugs into the wall, but I improvised a battery supply (easy, it only needs 12V). Frankly, I hear no difference, no noise either way — but I learned long ago my ears aren't golden... and turning 70 didn't improve them.

I have both SUT and head-amp. I usually decide which to use depending on cartridge, trial and error to see which match I prefer.

But I have a new principle — I use my head-amp when using a passive line preamp to drive my power amp, because passives can lack dynamics and 'flatten' the music — the head-amp, being active, restores dynamics: I can clearly hear more rhythmic drive and sonic contrasts.

But when using a normal active line preamp, I use the SUT, because I'm not lacking dynamics. I get the SUT's purity, without the trade-offs.

Maybe just my latest meaningless fad, but so far seems to work for me.

Another virtue of head-amps is they usually offer more adjustments (impedance, even capacitance) than SUTs, to cater to different LOMCs' requirements.

Hope this makes sense...
czarivey
5,679 posts
 
bimasta, 
I use substantially simpler and cheaper solution which is high output cartridges. No need for neither head amp or SUT. 
Direct to phono preamp works best.
john_tracy
341 posts
 
SUTs are 'pure' — head-amps add distortion

Transformers are NOT without their own distortion. Some just prefer that to the distortions generated by active devices such as FETs.

Some head-amps use batteries to solve the noise issue.

Batteries will not eliminate the inherent thermal noise of the individual components themselves. Current flowing though any resistance generates noise.
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