Shelter + BentAudio loading: field test

If anyone cares (if you do, see your doctor) I spent last Sunday playing with different impedance loads. Am I livin' or what?!

- Shelter 901, 0.5mV, 14 ohms internal impedance
- BentAudio Mu stepup transformers, wound for 20dB gain
- c-j PV-11 preamp with MM phono stage, fixed 47kohm load

These trannies have a VERY neat feature. John Chapman uses Stephens & Billington TX-103's and adds a pair of small binding posts across the secondaries. You can swap resistors in about 5 seconds to load at any value you choose, or leave the posts open for a load of 47Kohms (or whatever your phono stage provides). Not quite as sexy as the Aesthetix Rhea's remote-controlled loading, but infinitely flexible and a lot less than $4K. John included 15 pairs of resistors so I had lots of choices. Yum!

I had (mistakenly) been loaded at 100 ohms for the first month while I broke in the new rig, fine tuned VTF, VTA, etc. Shelter recommends 100 ohms only when going straight into a phono stage, 20 ohms for a tranny.

Having discovered my initial error, I swapped in the 19 ohm pair of resistors for my first test (closest I had to 20). After 4-5 sides of familiar material I had a good handle on it. Bass was slightly better than before (hard to believe) but HF's were too lightweight. All the tones were there but there was no impact at the top end. Low piano strings vibrated with a delicious, brassy growl, but middle to high piano strings just lacked that steely punch. On we go...

Twl likes his Shelter loaded at 40 ohms so I tried the 38 ohm resistors. Nope, a bit too high for my system. The bass was slightly weaker and the HF's took on a very slight etch. Fiddling VTF and VTA didn't remove the etch, so I decided it must be the loading. Next...

Back down to 25 ohms. AHH!!! Clean and solid tonality from top to bottom, more air, tighter imaging and a harmonic rightness to everything. Brubeck (Time Out) and the Julliard Quartet (Bartok #4) are more life size and physically present than ever. I think the "perfect" load for my system is probably around 23-24 ohms, but 25 is very, very close.

This assortment of resistors cost $15, so they were a very cost effective upgrade. (Second best ever I think. Twl's HiFi Mod is still the all time champ, even at full retail!)

BTW, another good feature of BentAudio's transformers is that the secondary windings are extended straight out of the can and terminated with RCA's. This eliminates an interconnect, an RCA connection and two solder joints. If you need stepups, I highly recommend these.

No affiliation, etc. etc. Just singin' in my brain!
Good work Doug.
Now if I could just find a keyboard that types short, sensible posts like yours...
Great post Doug and very timely. I too have the Shelter 901 and the Bent Audio transformers going into a 47ohm Trumpet phono. I currently have set to 100ohm and am now ready to start testing different resistors. I have made alot of changes to my system recently and have held off doing this until things broke in and settled. Once I have done this I will post my results as well.
Dmailer, do let us know your results. Always useful to compare. John Chapman didn't know why a cartridge would want to see different loads for transformer vs. phono stage. That's why I started @ 100. Audiobomber, Zaikesman and Sean educated me here last week, which convinced me to do the experiment. Love this place.
Then perhaps someone can educate me further in the event I am operating under a misconception. When Shelter recommends in its documentation that comes with the 501/901 that load shoul dbe "within 20 Ohm with step-up transformer" aren't they referring to the upper limit of the "static" impedance of the transformer, not the load impedance?
I don't know the answer to that one David.
Good question, David. I just assumed it was typical translated Japanese. ;) Maybe we should ask Axxis Distribution to get a clarification. Anybody buy a new Shelter recently? I bought mine used so feel a bit funny asking a lot of the distributor. All they've gotten from me is $7.50 for a stylus guard.

I have heard that Bent Audio uses in their kits the Roederstein resistors to load cartridges. Be advised that they are recently not as good sounding as they use to be (along with Holcos and many others). In fact I just trashed a fresh party of Roederstein because I just did not find them useable anymore.

The new production of the Roedersteins has very distinct upper mid-range acceleration and a slightest more then necessary paunch at HF. In many bad hi-fi components it considered as an evidence of quality but it is not. Also, believe you or not be the new Roedersteins kind of bleach sound and make it very boring. I have seen a number of the Roedersteins using audio components that use to be OK but their newer production is total shit. I never knew the reasons until I ordered some newest Roedersteins for one my projects: the answer came immediately. I got rid the Roedersteins and continue to use the RN resistors.

From what you said and knowing the “metal” you dealing with I feel that you may find it worth to get rid of the Roederstein and do again your little research.

Good luck,
Romy The Cat

Great post, thank you for the tip. I don't know what resistors BentAudio uses, but I was actually thinking of buying a few pairs of Vishays to give values right around my discovered sweet spot of 22-25 ohms. You're recommending RN, which I assume is another brand name/manufacturer (right?) Any experience with RN vs. Vishay? If you haven't guessed, I'm no engineer! :)

Since I haven't tried other resistors, I naturally haven't noticed a, "distinct upper mid-range acceleration and a slightest more then necessary paunch (punch?) at HF". If the Roedersteins do this, more neutral resistors would probably be optimal at a somewhat higher load. Any guess how much higher vs. my present 22-25 ohms, just so I don't have to try a zillion pairs?

FWIW, I don't think anyone would call our present sound "bleached" or "boring", but who knows. We've never heard another high end system, so we're groping our way forward step by step.

After going back and forth between 36ohm and 50ohm I have settled on the 50ohm setting for my Shelter 901, Bent Audio, Trumpet combination . In my system the 36ohm seems to take too much of the leading edge transients out. The 50ohm setting is more open and not as closed in. I am sure that the setting one uses is all system dependent as well as personal taste. The rest of my system is Redpont TT w/ Kuzma Reference arm, Lamm LL2 line stage, Lamm ML1 amps, and Vienna Acoustics Mahler speakers. On audio asylum I read a post regarding resistors saying that the nude Vishays were the very best. Has anyone tried these and know where to obtain them?
Dmailer, thanks for the update. I'm sure you're right about the "best" setting being system dependent. Your Trumpet/Lamm electronics are certainly very different from my c-j stuff.

It may also be listener dependent of course. My partner has not heard the system since I "reloaded" it. He's more sensitive to leading edge transients than I am, and may well prefer a higher setting than the 25 ohms I preferred. Of course he also likes powerful bass, so who knows?!

I echo your call for resistor sources and advice. Anyone?
OK, guys, I have been reading this thread & also Romy's fruitful comments (!).

I have a question for all of you: how does the quality of the loading resistors make any difference at all to the sound?

The loading resistors are connected between the phono input & GROUND or step-up xformer secondary output & GROUND. Thus, the loading resistors are *not* in the signal path. There might be some shunt signal current (coming from the cartridge) flowing thru these loading resistors to GROUND but the other end of the resistor is not connected to the phono pre in. These resistors *should* not affect the sound at all. Are you guys just going over-board selecting high-grade resistors for simply no reason?

You can see this on Jim Hagerman's website where he has explained cartridge loading. Notice that the loading resistor is connected to ground (in parallel with the load capacitance, which represents the phono pre input capacitance + interconnect cable capacitance).
Any *useful* comments would be appreciated.
Romy's post was actually about the best I've seen from him. Love and kisses his way!

I personally have no clue if the quality of resistors used for tranny loading would or "should" be audible. Perhaps we just have lingering audiophilia nervosa. At least this outbreak of the disease will be cheap to treat and limited to a few wacko's with stepup trannies!

Lew Johnson of c-j heard audible differences when he changed non-signal path resistors in their Premier and ART preamps. He can't explain why, but it's been confirmed by other listeners.

The designers of Dmailer's Redpoint TT and my Teres both hear audible differences between electrical components in the motor control circuits. That's a good deal further from the signal path than a phono load resistor. I don't think they know why either.

What fun would all this be without a few mysteries?