Can Anyone Learn Me About MC Step Up Transformers?

Prime Minister

Site Owner
Staff member
My experience with step up transformers and MC cartridges is limited, and my understanding of them is even more limited. My direct experience was with a pair of Altec 4722 transformers, and with them, I got some of the most beautiful phono sound I've ever heard. But seeing as how they have green paint, they now cost a fortune and are off of my shopping list.

So, what do I need to understand if I want some great sounding MC Transformers? What should I pass on? What should I budget to get something really good?
 
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fiddlefye

Senior Member
My experience with step up transformers and MC cartridges is limited, and my understanding of them is even more limited. My direct experience was with a pair of Altec 4722 transformers, and with them, I got some of the most beautiful phono sound I've ever heard. But seeing as how they have green paint, they now cost a fortune and are off of my shopping list.

So, what do I need to understand if I want some great sounding MC Transformers? What should I pass on? What should I budget to get something really good?
Thinking of coming over to the Dark Side (or is that "seeing the light?") ;)

I gather there are two parts to the equation. Without excellent transformers well-matched to the task little will be accomplished. From there it must surely but up to careful implementation and construction.

I have the same Microtrans-based Redboy trans as JohnVF has and it is marvelous. I've had a couple of other, lesser units in past and the difference is notable. I've run it with carts that had as little as .18mV and as high as .4mV and it worked well across the range.
 

Redboy

Knobophobe
SUTs are a little tricky to get right, but not as mysterious as you might think. They are not as versatile as some active gain stages because you can't just turn a knob to change the operating parameters, but their sheer simplicity is their strength - an SUT is the closest you can get to "wire with gain".

The key parameters to look for are good frequency response and an appropriate gain (step up) ratio for your cartridge and phonostage. You want enough voltage gain to drive your preamp, obviously. But the transformer's gain also dictates the reflected impedance, which is the impedance presented to your phonostage through the transformer, and vice versa.

Get good frequency response, enough gain, and a copacetic impedance match and you're golden. :)
 

Redboy

Knobophobe
Oh, and the budget question...

Expect to pay $250 and up for good SUTs. Sky's the limit, but I think you'll see seriously diminishing returns after $400 or so. YMMV depending on your wallet and your definition of "expensive" but I can't think of many transformers below that price point that I'd bother with.

Some vintage transformers can sound amazing, and their scarcity drives prices commensurately once people figure out what they are. Your green Altecs are in that category.
 

Prime Minister

Site Owner
Staff member
Oh, and the budget question...

Expect to pay $250 and up for good SUTs. Sky's the limit, but I think you'll see seriously diminishing returns after $400 or so. YMMV depending on your wallet and your definition of "expensive" but I can't think of many transformers below that price point that I'd bother with.
That all sounds reasonable to me. You selling any now?
 
I've had good experience with Altec 15095 transformers as SUTs, if you can get away with a 1:10 step up ratio. They are sensitive to loading and aren't at their best when loaded with the typical 47K MM input stage. I've found that they sound really good if you reduce the loading to the 10K to 15K range. Tune by ear to get the sound that's the best match for your system. They typically go for a lot less than Altec 4722s.
---Gary
 
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mhardy6647

Señor Member
I've got nothin' to add... but I'm postin' to this thread anyway 😎
Well worth experimenting with SUTs. I think there is much to be said for passive increase in signal voltage vs. adding an additional active gain stage... but that's just an opinion, and not a particularly well-informed one at that.
 

Salectric

Senior Member
The Jensen JT-44DX is a great budget SUT. It has a 1:10 ratio which worked just fine with all of the cartridges I’ve owned. It was included in the Cary PH-301 MC phono preamp so the folks at Cary evidently thought it was close to a universal transformer.

I bought a pair of the Jensens back in the late 1990s and mounted them in a little aluminum box with some hardwired output cables. That served me well for nearly 20 years. I now use Slagle 1:10 transformers which do sound slightly better but they also cost a whole lot more.
 
The input of the phono stage normally sets the loading of the SUT transformer. A typical MM stage has an input load of 47k ohms. If one puts another resistor across the output of the SUT then that new resistor will be in parallel with the MM input resistance after one connects the SUT to the phono stage. The effective load seen by the SUT is then the parallel resistance of these two resistors. Here's the equation for those two resistors in parallel:
R_load = (R_sut x 47,000) / (R_sut + 47, 000)
Solving this equation for R_load of 10k ohms gives an R_sut = 12,700 ohms
Solving for R_load of 15k ohms gives an R_sut = 22,000 ohms

I typically get out my clip leads and try out different values of resistance until I find what the right value is for my set up. You can then solder the resistor in place or just keep using the clip leads. If you're building your own SUT then you can also add small binding posts to make swapping resistors easier.
---Gary
 

Alexz

Junior Member
Actually transformer are design to have a specific load on the secondary as best for ringing and high rolloff. Some manufacturers are providing optimized load figures (for instance Hashimoto recommends 2.7k )
If transformer is designed to have a 47K load and reflected load (0.47k for 1:10 or 117R for 1:20) is not the best for the cartridge, better to add additional load on the primary of the transformer.
 
My experience with step up transformers and MC cartridges is limited, and my understanding of them is even more limited. My direct experience was with a pair of Altec 4722 transformers, and with them, I got some of the most beautiful phono sound I've ever heard. But seeing as how they have green paint, they now cost a fortune and are off of my shopping list.

So, what do I need to understand if I want some great sounding MC Transformers? What should I pass on? What should I budget to get something really good?
dear mr. pm,
Can't speak to your personal tastes, (love the P8), but I would suggest if possible a step up that has switchable gain and loading.
I've gone thru about 5 step up's myself (including a 4722) and they all sounded OK but something seemed missing.
When I purchased my P5 (2nd hand, mint) I purchased a new cartridge, a AT 33ev. (10 ohm internal resistance, .3 mv
output), I also came into possession of a Bob's Device's 1131...woo wee !! This step up was a definite STEP UP !
The spec sheet said use the Low setting, (26db gain and 130 ohm resistance). Long story short, while moving equipment around
I accidentally flipped the switch to high (32db gain and 30 ohm resistance)...YoowwZaaaa !! Color and texture and
musicality jump by an order of magnitude by at least 2. Without being flippant, so much for the math. Good luck on your
cartridgeIMG_1368.jpg and step up journey.
regards....mike
 

Salectric

Senior Member
dear mr. pm,
Can't speak to your personal tastes, (love the P8), but I would suggest if possible a step up that has switchable gain and loading.
I've gone thru about 5 step up's myself (including a 4722) and they all sounded OK but something seemed missing.
When I purchased my P5 (2nd hand, mint) I purchased a new cartridge, a AT 33ev. (10 ohm internal resistance, .3 mv
output), I also came into possession of a Bob's Device's 1131...woo wee !! This step up was a definite STEP UP !
The spec sheet said use the Low setting, (26db gain and 130 ohm resistance). Long story short, while moving equipment around
I accidentally flipped the switch to high (32db gain and 30 ohm resistance)...YoowwZaaaa !! Color and texture and
musicality jump by an order of magnitude by at least 2. Without being flippant, so much for the math. Good luck on your
cartridgeView attachment 12874 and step up journey.
regards....mike
You are a lucky fellow to have one of those Fi preamps. There were only a few made. I heard one at DejaVu Audio back around 1999. The system sounded very nice as I recall but we didn’t swap preamps so I can’t say what contribution the Fi was making.
 
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