Step Up Transformer Question
Ok, so bear with me as this is new terrain for me. I was quite happy with how things were sounding and then I accidentally bumped the stylus of my Cadenza Black and snapped the cantilever clean off. I did some research and ultimately decided to have Steve at VAS at fix my cartridge but it was going to take a few weeks and there was going to be no way to play the Christmas vinyl that my wife loves so much. She told me to buy another cartridge so we could have Christmas records. I was stunned. I found a great deal on a Winfeld Ti on this site and pulled the trigger. I've got it on my table and it sounds amazing.
After speaking with Steve though, I'm going to trade in my Cadenza and have him build me a wood body cartridge to have something different. It will also be 0.2mv output. I think I've got the 2nd arm situation sorted (gonna buy a Wand and a pod to mount it on) which leaves the phono pre. I love my Rogers PA-2 and it is switchable between MC and MM with 2 different inputs in the back. Finally got the SUT part. I've been looking and trying to figure things out. I spoke with Roger and he said the transformer built into the PA-2 is 1:10 and with that I can achieve 70 or so dB of gain. I did a lot of reading and looking and while I'm sure a 4k+ SUT is amazing that's just not where I'm at with all the other expenses at the moment. I saw the Bellari MT502 was a stereophole recommended component for many years and Amazon had one on sale for like $349 or something. Figured can't hurt to try it, it's Amazon so I can always return it. I plugged it in with some admittedly questionable interconnects I had lying around and when I put the phono stage k there was a bit more hum than I'm used to but I said let's have a listen. Holy shit. This little thing blew my mind. Better impact, tighter bass, more space around instruments so better staging, improved transients. This puts me in an interesting place.
This is an extremely inexpensive piece and it has changed my system quite a bit. I think the little extra gain I get even at 1:12 brings the cartridge to life. My question is where do I go from here? Bob's makes the sky 30 which is switchable from 1:15 to 1:30 which I like because I can play with the gain tubes in my preamp and potentially go to a quieter 12au7 than the 12ax7 that's currently in there. Will that be a real improvement? Less hum? Had also considered ordering a Rothwell from jolly old England but can't find much on them. Thoughts? I'd like to keep this sub 1k or so for now. Maybe I'll save up for a big boy SUT later.
Something wrong with the numbers 0.2 mv into 10x transformer is only 2mv signal out, that's too low for some/many phono inputs. Would cause volume controls near max, perhaps the volume control/circuit is noisy when raised so much. 10x is only +20db. do you mean SUT xFactor 10 combined with the MM Phono gain will be 70db? If something is great, but it hums, it ain't great.
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I have and had several SUT - and there is difference- not sure why - I had an inexpensive Denon AU-300LC- that was thin sounding... I use now an E.A.R MC 3 (there is a newer model MC4) which is great. Also a Dynavector SUP-200 which is still in a box but apparently also good. but I can attest firmly to the E.A.R. . the Phono is in a nu-vista Preamp with mm Phono. Cartridge is MC Ortofon Kontrapunkt b YMMV of course - but this is my experience |
mdmoore, I advised against replacing a 12AX7 with a 12AU7 first and foremost because those two tubes are electrically very different from one another. Upon further thought, I do seem to recall that there is something out there where the manufacturer officially OKs such a tube swap. I can conceive of doing it if there is some sort of switch that changes the load resistor and other parameters, when the user makes such a drastic change in tube types. Is that so, in the case of your unit? Do I recall correctly that you have a Bellari? The second reason I reacted so negatively is that I and many other hobbyists do not much like the sound of a 12AU7, when it is used for gain, typically in a linestage. Using a 12AU7 in a phono gain stage seems impossible; you would get very little phono gain, nowhere near even the 40db typically associated with MM stages. So, to sum up, the 12AU7 would be current starved in a 12AX7 socket, would result in very inadequate gain even for an MM cartridge, and would sound bad even if changes were made to the circuit so the 12AU7 would run properly. Better candidates would be 5751 (check me on the numerical designation of this tube, which is a standard replacement for 12AX7 when users want slightly less gain), 12AT7 (which also would run better if the circuit for a 12AX7 was slightly modified), and those are your best bet. There are some others in the 12A?7 series, e.g., 12AY7 and 12AV7 that might work, especially 12AY7, but the circuit really ought to be re-worked for such swaps. |
@rmdmoore When using a SUT there is a possibility Hum can occur. One cause of this can be using a RCA Connection that does not have a good bite. The most simple method to try to remove/ substantially reduce a Hum, is to move the SUT around in relation to the Phon' and TT. Typically a movement away from both will start to create a change to the level being heard. As short Cables are recommended between SUT > Phon' the movement of the SUT with a short cable may not be enough to have an effective control. It has been a very long time since I done this, but in the past have also had good success using a very small gauge earth wire to bridge across connectors on the SUT. From recollection the Bridging has been done in line and not across channels. As for Cable selection, for quite some time now I have been an advocate of a Cable using PC Triple C wire for the Signal Path. My recommendation for RCA Connectors are outlined in a earlier post. |
@elliottbnewcombjr you got it. The total gain with the inbuilt SUT and 12ax7s in P place is 70db. My understanding is that if I place a 1:10 SUT on the MM input it will have the same. @lewm I appreciate what you're saying and in truth, yes, I agree with not liking 12au7s in my line stage. I had a Rogue RP-7 and did a lot of tube rolling and in the end just didn't like it that much. I switched over to linestages with 6sn7 and I love them. You should check out the design of the Rogers PA-2 which is my phono stage. As I said, different tubes in one of the gain stages is how you adjust the gain of the unit. It's a pretty cool design. When I had a Hana ML cart, 12au7 were great, when I had the cadenza black, 12av7 worked well, with the current cart I need all the gain so 12ax7. @pindac I did move it around some and the hum didn't change much. Maybe the issue is more that the crappy RCAs have loosely goosey connectors that hum some. I ordered some new cables that should have better connectors and shielding so we'll see. |
