Phono Preamp. With transformer or fully active

Jensen named the parts of the Zobel Rdamp and Cdamp which clearly tells its purpose. I do not know of any phono stage inputs with those parts intentionally in place.

@intactaudio  Our preamps allow that- if we install the transformers internally (an option) then the output of the SUT is set up so the external loading strip on the preamp is loading the output of the transformer. If the transformer is external, obviously the same is true. So any Zobel or simple loading resistor can be installed with ease. I agree as well that if the aberrant behavior is a peak at 200KHz probably best leaving it alone.

I do not consider the use of the rather heavy secondary load in addition to a Zobel as a sonically acceptable solution.  

FWIW they *are* designed for that. I totally agree regarding your comments about bad core design- my comments  presume a decent transformer to start with :) ...   I think the 4722 cult has to do with a recording engineer named Eddie Ciletti.

@intactaudio
When I look at the specs of the 4722, it seems its bandwidth might be limited by the simple fact that it is meant to deal with a signal much stronger than that of a LOMC cartridge.  Or it might simply be that Altec didn't intend the application for much more than public address. But whatever the reason, by comparison on paper, any Jensen SUT transformer outperforms it in every way- take a look:
https://www.jensen-transformers.com/transformers/moving-coil/

 There's a bit of cult around the 4722, isn't there? One not from actual performance, right?

I chose the 4722 because it is a known device that represents the typical behavior of a microphone transformer pressed into SUT usage.

18:1 seems like a lot of stepup to me, but at the same time I suspect that 4722 is intended for an input inductance that is a bit different, being that its a mic transformer.

It is interesting to note that as the frequency response approaches flat at 20kHz the phase shift increases further down into the audio band. In this case it becomes the choice of the lesser of two evils. Since no two people hear the same, it is no wonder loading of cartridges is such a hotly contested subject when it comes to transformers. It is my belief that often times when you adjust cartridge loading via the secondary of a SUT, the sound (and measured response) of the transformer is what is heard. This change in sound is then falsely attributed to the cartridge seeing a different load.

@intactaudio Why would you want to adjust the cartridge loading? I agree entirely though that loading the transformer is for the benefit of the transformer and not the cartridge- what it appears you're also saying here. That is what I was saying earlier as well, if that was not clear.


An SUT that has troubles making it to 20KHz it is a bit troubling- I would expect 50-70KHz at least on a part with that little power requirement. But that is of course ignoring the inductance of the cartridge... But your graph didn't suggest anything about that. 

Are you the guys who do OTL amps?

Do you do “ just” phono pre’s ?

We do the OTL amps, but so far have avoided stand alone phono sections as we are convinced that they work better when they are integrated into the same chassis as the line stage, this due entirely to how the output of the preamp is connected into the line stage. When the connections are short and soldered, they seem to sound better.

@intactaudio I don't see you commenting about the transformer loading in your post. I know that this bit is problematic:

If you take a 2Ω cart and use a SUT designed for 40Ω, the LF extension will be down into and past record warp and tonearm resonance and the low impedance drive will cause an underdamped top end (HF peak in response)

-because our phono sections go down to about 2Hz, yet there are no problems with record warp and the like. Loading the transformer is well-known to control issues in the high end- the 'underdamped' part to which you refer. So while the inductance of the cartridge certainly plays a role, its not that hard to come up with the correct loading for the transformer to make it work.


However I agree that in most cases this is beyond most audiophiles, but this does not change what I wrote. An SUT made for a specific cartridge was probably made at the behest of the cartridge manufacturer; they would probably not be happy if that transformer were used with some other manufacturer's product. So its not surprising that they don't publish loading charts for other cartridges. But if the manufacturer of the transformer doesn't have a dog in the fight, then things are different- and I point to Jensen Transformers as one of the best examples of that. One glance at all the cartridges they list shows they've done their homework!

With one SUT you can't use all MC cartridges, such phono stage is not universal for all MC. It will work for some of them nicely, but if your cartridge impedance is very low (2 Ohm) or very high (40 Ohm) you can't use one SUT for both of them.

This statement is false. The use of an SUT depends heavily on how its loaded at its output. This in turn is dependent on the source impedance of the cartridge.  Transformers transform impedance and this goes both ways. So you can indeed use a transformer with a 2 ohm or 40 ohm cartridge, but the loading at the output of the transformer will be quite different! And its important that this is done correctly otherwise the SUT will not sound right to say the very least.

Most SUTs made for a specific cartridge are designed to be loaded at 47K by the phono preamp, with that specific cartridge as the input. That's why they appear to be 'Use specific'. But if you loaded that SUT correctly at its output you could use it with any cartridge. This is why Jensen Transformers (some of the very best made anywhere) can be used with any cartridge, and they have a chart that shows what the loading on the output should be with that cartridge.


I prefer no transformer at all; I find that even the best SUTs seem to take something away from the detail, even if they have plenty of bandwidth (which most do). Since I run an all-tube phono preamp, this requires that I use low noise tubes. Its a simple fact that if you have a phono section with direct-in capability, whether it is solid state or tube the active devices have been hand-picked. I've noticed with our preamps that people think they can just buy a premium tube off the shelf and expect it to work. While that is sometime true its really a craps-shoot; even a premium tube might not be as low noise as you might expect. With any high performance audio equipment you have to hand pick the devices. But the result is great transparency.