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Added an SUT...not sure I understood this

I just added a Denon AU-320 step-up transformer in between my AT-OC9XML cart and my ARC SP-14 preamp.  I am glad that the (relatively quiet) hum that had been present before is now gone...and I mean gone...since that was what motivated me to add an SUT.

However:

I sort of expected that I would also experience a noticeable increase in gain.  Specifically, using the 40-ohm (10X) tap, I would have expected maybe a 6-8 dB increase in volume, and more with the 3 ohm tap.  I am not hearing that, and in fact am getting the opposite effect.  This means I actually have to peg the volume control if I want to achieve 95 dB levels at my listening position, something I rarely, but still occasionally, do.

Also, I removed the 22-ohm loading resistor upon connecting the SUT.  I noticed previously that a 40-ohm loading still had the cart sounding pretty bright.  But with no loading and using the 40-ohm tap, things sound natural.  I sort of expected I was going to need to add a 40-ohm resistor (at the tonearm) to achieve the same loading.

All of this confuses me; I'm happy so far with the sound yet perplexed.  Perhaps some good Samaritan here will be able to explain why I am hearing what I am hearing.  in the meantime, I'm just going to enjoy my quieter background. 

woofhaven1992
intactaudio
307 posts
 

apologies to all for veering off topic here....

@dover 

I have yet to se actual measured frequency sweeps from a MC cartridge that show the ""rolled off" top end you suggest above.  Can you point me to some?

The only reason I took the time to write my post with regards to published specifications and recommended load was to inform the thousands of readers of these forums whom do not post, but might rely on what they read in the thread.

I have the same belief.... kinda...  I was just trying to point out to the 'thousands of readers of this thread' that the whole concept of "current injection" flies 100% in the face of blind adherence to the manufacturers minimum load spec.  ie...I see the natural conclusion of your logic to be:  if 100Ω is the minimum <3Ω cannot sound good so it need not be tried.

dave

dover
2,318 posts
 

@intactaudio 

Once again, please read my posts more thoroughly - here is what I posted initially

What I would suggest is get a pair of 470ohm resistors and try running the OC9 straight into your SP14 loaded at 470ohms. This will give you a direct comparison with and without the step up with the same loading. 

The SP14 does not use current injection mode. Your insistence on bringing into the discussion another variable ( current mode ) that is irrelevant to the OP's issues only serves to add more confusion to an already confused OP. 

intactaudio
307 posts
 

@dover 

the last post in this thread from the OP is below:

@dover The sheet that came with my cart says 20 ohms. AT has not been consistent with their specs on the OC9 series.  More importantly, it sounds better around 20 ohms than at 100.  Plenty of people agree with me on this.  I'm not going to load it at 100 just because you won't stop yelling at me.  I'm going to load it at whatever achieves the best sound in my system. 

to which you responded with the text quoted in my first post here where you insisted there must be something wrong with his system.  

I applaud and support the OP's POV that what sounds best is best. I brought current injection into the topic because it is a perfect example on how an amplification method that many find appealing provides a load that is in stark contrast with what any cartridge manufacturer suggests as optimal.  I for one would like to see more discussion about how to reconcile this discrepancy.

dave

 

dover
2,318 posts
 

@intactaudio 

Then why don't you start your own thread on "loading - voltage vs current mode amplification of moving coil cartridges".

Do you understand the difference between voltage and current ?

If you start a new thread there are many knowledgeable folk on the forum who can help you.

 

 

rauliruegas
13,128 posts
 

Dear @dover  : He already did it in this thread and in the cartridge loading one too. I can't understand why came here again with the same topic but is up to him:

 

R.

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