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.
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?!
System:
- 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!
System:
- 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!