Newbie needs SUT / Denon 103r / loading help...trying to wrap my head around matching!

Hello all! I've spent the last day or two reading and re-reading old posts and web info regarding SUT's and loading but I'm nowhere near understanding well enough to know if I'm headed in the right direction. I purchased my first LOMC cart last week..a Denon 103r/output 0.25 mV. I installed the cart on my stock Thorens td 160 with tp16 tonearm. I had originally planned to use my Forte model 2 pre-amp with adjustable gain before purchasing an SUT. The pre-amp settings:

GAIN:
Switch 1 ON: low gain (40dB @1Khtz) suitable for the majority of moving magnet cartridges.
Switch 2 ON: medium gain (50dB @1 Khtz) suitable for many high output moving coil cartridges and special low impedance moving magnet cartridges.
Switch 3 ON: high gain (60 dB @1Khtz) suitable for the majority of low output moving coil cartridges.

IMPEDANCE LOAD: (switches 4, 5, and 6)
All three switches off: 47,000 Ohms
switch 4 ON: 100 Ohms
Switch 5 ON: 47 Ohms
Switch 6 ON: 22 Ohms

Before the cart arrived I purchased (without doing the research) a Denon AU- 300 SUT...was afraid that the pre-amps high gain setting would be insufficient.

Denon AU-300
Step up ratio: 1:10
Primary impedance: 40 ohms
Secondary impedance:4k ohms
Load impedance: 50k ohms or more

I originally read a post on the web (have since been able to find this info!) that someone had been happy with the combo...the AU-300 and the Denon 103r.
I'm aware now that the SUT impedance may be better matched with the Denon 103 rather than the 103r's low output impedance of 14 ohms. But I decided to listen last night when the cart arrived. After trying all three gain settings I settled on medium gain (50db setting without SUT) and an impedance load of 47K ohms. I tried all three impedance settings..the 22/47 and 100 but the 47k was the better sounding of the three. I was not expecting this...but not sure why...I guess after trying to digest all the confusing info I've been reading I thought the 100 ohm setting would be correct.? Anyway, I guess what I'm asking...and hoping for an easy/understandable solution...did I make a mistake in purchasing this particular SUT? Should I live with it for a while...and perhaps upgrade? Or should I return and really study and understand what is needed for my set-up. Sorry for such a long post and for seeking an easy way out when I should learn on this stuff!!

 

Your last paragraph about sums it up....SUTs are strange beings and research is needed. I'm still working on that myself.

The 103r is rated at 14 ohms, the plain Jane 103 is 40 ohms making it a perfect match for the AU-300 SUT (as that SUT was built to serve that cartridge). As far as gain is concerned the 103r made need a bit more as its output is .25 and the standard 103 is .3 so maybe the 50 db is the way to go...if your ears like it. Maybe you should consider buying a 103 and selling the 103r if you decide to keep that particular SUT. And/or play around with the switches on your preamp to find which sounds best to you, then that is the correct setting, which is what you've been doing. Maybe you've got everything just where you want it.

There are SUT manufacturers who can wind a SUT specifically for a cartridge.....will cost money, of course.

 

Thanks for the reply. Yes, I've got a lot to learn! I'm pretty sure I have everything dialed in as best as possible...the 47k impedance load surprised me though....started sounding good last night but too late for critical listening, will do that this evening. I did consider the 103 option this morning but since I just purchased the 103r I think I'll stick with it...would rather replace the SUT if needed. Hopefully, I'll figure this stuff out in the next few days and make a decision. Thanks again!

 

Are you set on getting a SUT? I went with a Lounge Audio Copla for my DL-103 and DL-301 MkII carts and have been quite pleased.

 

Thanks for the suggestion ranch 22b but for now I'd like to use and learn about SUT's. Besides, I'm currently using a LCR MKIII pre amp in one of my vintage systems and really enjoy where its being used. If I purchased the Copla I'd be tempted to pair it with the Lounge pre and that would really mess me up...I'd have to start moving components around searching for that synergy I believe I've found for three of my four systems. As difficult as it's been...the crash course in SUT's...focusing on this system would be easier then reconfiguring.

 

Most phono cartridge SUTs are designed to work with the 47K input impedance (load) setting on a MM preamp, so generally speaking, that is the only setting you should use. The 1:10 step up ratio is 20dB, so your total gain should be around 70dB when the preamp is set for 50dB. This is reasonable, as are your other findings. The 47K input impedance will be reflected to cartridge with value of 470 ohms (input impedance / windings ratio squared = 47000/100 = 470) , which is kind of high for the 103r, but obviously will work, many people like to use a lower value load on the cartridge, either by using a higher gain SUT or by changing the SUT primary load. Some change the secondary load, but that's not always advisable, depends on the SUT design.

 

Ha...funny, just bought a new suit...it killed me...would rather have spent the cash on records!

 

Thanks Davey...helpful insight...makes sense now, regarding 47k input impedance. Would you recommend a different SUT..with higher gain? Thanks

 

I don't have experience with the 103r, but there are a few past threads here discussing using both the 103 and 103r with various SUTs. Here's a couple below, but you may have already been through them ...

Best step up tranny for Denon Dl 103R

To SUT or not to SUT with a Denon DL-103?

 

Thanks...I'll check it out!

 

I use a 10:1 SUT with a 103r and have a 36.5K resistor in place which gives it a loading just over 200 Ohm

 

Interesting read: step-up transformers for Denon cartridges


DL-103R
This cartridge is a revised version of the DL103 and has a slightly lower output voltage of 0.25mV, but has the advantage of a significantly lower source impedance of 14 ohms. The theoretical optimum turns ratio for maximum voltage transfer with this cartridge is 1:60. However, 1:60 is a huge ratio with serious practical compromises on performance. Even if it was possible to get acceptable performance from a 1:60 transformer there would still be another issue: output voltage. The output voltage from the transformer which would be fed into the phonostage would be 15mV - significantly more than a typical moving magnet cartridge - and would risk overload or severely curtailed headroom. Clearly, aiming for maximum voltage from the transformer has led to a poor choice for the turns ratio.
So what would be a better ratio? A sensible criterion would be to aim for 5mV output from the transformer. This would give a good signal level into the following phonostage and give a good signal-to-noise ratio without the risk of overload, and the lower turns ratio required for 5mV would give better performance. The turns ratio required for a 5mV output would be 1:24. However, a 1:20 ratio would give still produce 4.5mV - only 1dB less than the 1:24 transformer. Anything in the range 1:20 to 1:24 would be a very good choice for the DL-103R.
A suitable transformer from the Rothwell range would be the MCL.

 

I moved from MM carts to a DL-103 about 7 years ago using a Denon AU-305. Im still using the 305, but have moved to using a 103R and am still very happy with what I am hearing. My signal chain is DL-103R > AU-305 (1:10) > Project Tube Box DS (set to 50dB) > Nakamichi SR-3A.

Is there a better SUT match for the 103R? I can't speak to other SUTs, though based on what you have illustrated above, I'd say start with the AU-300 into the pre using switch 2 (50dB). Looking forward to hearing your thoughts.

 

Thanks for the input, all useful. Still learning...took a break yesterday after finding/reading some new info. Trabik, looks like we are almost in the same boat...but your SUT is more versatile regarding impedance, correct? I've been listening for the last few days using the 50dB setting on my pre. Will post thoughts soon...thanks!

 

@bayen it does appear as though the Tube Box is more versatile in regards to impedance, but I’m not using that feature at all. I’m using an input impedance of 47kohms, much like the “all three switches off” setting you should use.

Hope you’re having fun and that it is sounding great!

 

It sounds like you've gotten it figured out already, if the sut has no settings and your phono stage is set at 47k then I would set the gain as high as you can where you are getting the best volume without distortion. That's what I do at least. The budgie sut I use has hi and lo switches and despite being advised to use the high ratio I actually prefer the low with a 103.

 

These days Rothwell recommends the newer Headspace for the 103r Headspace mc headamp

This is a very flexible option, something I'm considering using in conjunction with my 103r / 100 ohm impedance Music Hall PA 1.2 phonostage although Rothwell did comment on this combo: "the 100 ohms input impedance of the mc phonostage is a touch on the low side, theoretically at least. However, a quick calculation suggests the difference between a 100 ohm load and a 140 ohm load is only 0.3dB anyway. Whether or not there would be an audible and significant difference in tonal balance, I can only guess. I guess not. At least not enough to lose sleep over."

 

Thanks for the input and useful information. It's been about two weeks and I understand LOMC/SUT matching a little better. I decided to purchase a Denon 103 to match my Denon AU-300 step up transformer....so keep your eyes peeled, I'll be listing the Denon 103r with less than three hours play time in the classifieds. I love both carts...tempted to keep the 103r and upgrade SUT in near future...but I'm saving for new speakers! I've listened to the 103 every night this week and have rediscovered many LP's...amazing separation and large, deep soundstage...can't believe how amazing drums and bass sound...I can actually hear the attack of certain notes/chords...and vocal nuances are also very clear. I can only imagine how the next level LOMC/SUT's must sound! Thanks again

 

The Denon 103R sounds best with a load of 500-700 ohms

 

168 here

 

No. For most listeners, the best sound will be with a load of between 10 times and 20 times the cartridge's coil impedance. In this case, for a 14 Ohm cart, between 140 to 280 ohms. So, 168 would usually be just about right. But sometimes much higher can sound very good also. So it is possible, for a given audio system, that 500 to 700 is just fine. Listening and experimenting is the key to getting it right for YOUR system and YOUR taste.