Step Up Transformer Question

@atmasphere Ralph, thanks so much for your input. Yes, the plan is to use the MM input and which has about 45-50db of gain with the current tube complement. I should really only need about another 20db which, if I understand correctly, would be a 1:10 transformer. That's what is in my unit on the MC side according to the designer. Seems like that's really all I need then. There are some good deals on recently discontinued Hafler SUTs that had Jensen transformers in them. Anybody have any experience with those? 

@theflattire this is super useful information. As I said, I'm using some crappy found interconnects to go from the SUT to the phono. I have some better shielded low capacitance cables coming soon. Maybe those will solve the hum problem. Seems like Ned Clayton is on vacation based on his eBay profile so I'll check back after the holidays. Wondering about those James audio SUTs though. I found some straight transformers online but not mounted in a box. They don't appear to be octal but likely a couple different set of turns so more connections. Did someone make a box for you or did you find one already put together? 

Thanks for all the input.

@lewm I know subbing 12au7 for 12ax7 seems off but the amp is designed to take 12au7, 12av7, or 12ax7. Each has increasing gain but also increasing noise so if I can get more gain out of the transformer then maybe I can use a quieter lower gain tube. 

@dogberry I had asked Steve what I should get and he was kind of elusive. I named a bunch of different things including an Entre, and an FRT thinking to myself that this isn't technology that's changed a lot so maybe an older high quality adjustable one would be good. He said "they're too old". He told me to not get a bobs devices. I'm wondering if he was trying to lead me to to his own one that I had somehow not realized he makes. Also, what switch are you using?  I think that the higher gain SUT might sound better enough that I'd want to use it for both cartridges. I did text Steve and ask him if his SUT would be a good choice but I'm yet to hear back as it's Christmas. 

Overall, it seems to me that with a 6ohm internal impedance what I want is an SUT with more turns, probably 30 or 40, to better match the cartridge. I think that will produce more gain that what I need with the 12ax7 so going back to 12au7 and letting the transofrmer do more of the work is gonna be the answer. 

Thanks, everyone. This has been incredibly informative. Any addition thoughts are appreciated. 

Might as well ask this audience... What phono cables are you using? I don't want to go crazy. Found some on eBay that look fair, low capacitance with good shielding. 

@tomic601 you are correct sir. My wife is an absolute saint. She mostlybsupoorts my hobby and doesn't ask too many questions. She even used the turntable sometimes!

@elliottbnewcombjr was that TT set up with a SUT? I'm definitely getting more hum with the SUT and I'm attributing some of that to one of the cables in usong being crappy and picking up a lot of hum. Could be placement of the SUT but when I picked it up and moved it around it didnt seem to change much. 

@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. 

@elliottbnewcombjr the Bellari SUT I have now to play with has 1:30 as well and when I switch to that the hum does not go away. I really think it's cable related but can't prove that until I get more cables. 

@pindac you did mention the sculpture A prior. What turns ratio did you use for a 0.2mv cart?

@terry9 I've looked at that option a little bit. There are even some premade boxes to put SUTs in online. You can buy kits from lundahl's US importer and I've thought about that as well vs getting a Rothwell from the UK with decent lundahl units in it. 

Again, thanks everyone for all the input. Super helpful. 

@pindac I'm chatting with an eBay builder about building one with lundahl 1941s. The core is listed as amorphous. Is that what you're talking about? 

@pindac I see now on the Erhard audio page the area that lists nano crystalline transformers but I don't see any that are marked as SUTs. Will have to give them a call

@rrc4860 thanks for that input. I was looking at the MCX which is 1:10 and a bit more expensive. Thinking there just be a higher quality transformer inside? I'll call the guy at Britaudio next week. 

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@mulveling I appreciate your input. I spoke with Roger at Roger's High Fidelity who makesy phono stage and he said that the 20db I'd get with 1:10 will get me a total of 70db of gain which is what I'm currently using with the built in SUT. It seems quite good with my Windfeld Ti. Ralph from Atma-Sphere also mentioned, as did Roger, that a lower ratio will be less prone to noise. I'm waiting on some new cables to come next week to see if I can eliminate some of the hum I'm getting with the Bellari. As you said, might need to try different grounding schemes. I feel like that's a whole other thread, lol

@mulveling it's funny, that's what I was initially thinking. I messaged Ned Clayton about an SUT that would have some adjustability so I can play with different gan ratios and then I can adjust my tubes in my phono pre accordingly. I'll probably end up doing that. 

@mulveling so the new cables came and I was able to eliminate the hum. Once I did that I played with things a bit. Started at 1:12 with maximum gain in my phononsrage. This sounded great. It seemed to have more body and depth than whatever SUT is in my phono stage. Next, I switched the SUT to 1:30 and decreased the gain in my phono stage a bit. This sounded even better. More air around instruments, felt like I could really hear the room on some recordings. 

Seems to me you were right, that once I got the hum situation squared more gain in the transformer and less in the phono stage was the way to go. Feel like 1:30 with max gain will be too much and overload things. 

I appreciate all the input from everyone regarding SUTs. I think, for now, I'm going to stick with the little Bellari. Seems to be excellent bang for the buck. At some point down the road I'll get something big boy but for now, while I'm adding a second tonearm and cartridge, this will do. 

@lewm the Bellari has a switch that changes the turns ratio between 1:12 and 1:30. If you're asking how I'm reducing gain in my phono stage, I'm changing tubes. It's a strange design but in my Rogers PA-2 the way you adjust gain is by switching out the tubes in one of the gain stages.