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Trafomatic Audio Luna LCR phonostage

These days I am looking into tube phono stages a lot. Especially phonostages which are within $5-6k and that can serve in a serious high end system. While I know that solid state phonostages have traditionally been known for their low noise and high dynamic presentation, I still believe that harmonics that tubes preserve (and SS throw away) can be a great asset to the end result i.e music. And if well designed tubes can do low noise and high dynamic range too.

I know that an all-tube 70db phono gain is a steep challenge and while there are manufacturers who have attempted it (e.g Aesthetix, NVO), the response from the users have been mixed. I am more for the conventional approach of using a top quality tube MM stage with a top quality SUT (matched to the cartridge) or FET stage. In this realm there are not many serious options in the $5k range if I look around. The few that I have looked at are:

Allnic H1500 II SE
Luxman EQ-500
EAR 88PB
Herron VTPH-2 
Leben RS-30EQ

Then there are some full function tube preamps which do have very competitive in-built phonostages like the Shindo Masseto, Manley Steelhead, CAT Ultimate etc.

Here is another one that looks like very good contender for a top quality tube phonostage in this budget:
http://www.trafomaticaudio.com/products/luna/

An LCR design using an all-out tube design with interstage transformers and output transformers, so absolutely no capacitor in the path. MC stage is handled by Lundahl 1941 amorphous cobalt core SUTs. This looks like a no compromise assault for this price category. I have not yet heard it but whenever I have heard Trafomatic products I have always come back with a smile. They have been consistently balanced and musical without any typical voicing artifacts. They never sounded like a product that has been hastily put together or built out of a garage. For a tube amp I have never heard them having any hum or noise issues. In fact I have always found his amps to have a very matured sound. In that regards this is a phono stage I am excited about. If anyone gets an opportunity to hear them, do share your thoughts here.
pani
lewm
13,010 posts
 
Pani, I think I was misunderstood.  I did not mean for my comments to imply that transformer-coupling cannot work well and sound great. My point was that using a SUT between a LOMC cartridge and a phono stage per se limits the impedance with which you can load the cartridge. This is only because the turns ratio of the SUT determines the impedance "seen" by the cartridge looking in to the phono input. Case in point, the Luna starts at 100R and goes down from there.  Most LOMCs will work fine into a 100R load, but lately it has been my observation that many LOMCs can sound even better with less of a load.  I spent the last two nights, in fact, listening to two different LOMC cartridges with load 47K ohms. I found that I slightly preferred that to 100R or even 1000R. (Load is selectable on my MP1.)

In the case of the Luna, and without having seen the schematic, I wager that the interstage transformer was necessary for the sole purpose of reducing the output impedance of the stage driving the LCR correction circuit; the impedance has to match that of the LCR module, and most require 600R, although in recent years LCRs that need to see higher impedances have been devised, when the needed inductors can be precisely wound.  This is not necessarily a bad thing; it just is what it is.

lewm
13,010 posts
 
Pani, Also, prepare yourself for the onslaught of the Herron-lovers. There are many of them here, so many that I don’t doubt its excellence. Keep in mind that the Herron uses an "old fashioned" CR type of RIAA correction and no transformers in the signal path. There are many paths to Nirvana.

(I still want to hear the older Trafomatic phono that places the RIAA correction in the plate circuit of the input tube.)

Tom, Have you posted the schematic of your "interstage LCR" phono design? I certainly remain interested in LCR and even LR phono correction.

tomwh
150 posts
 
Lewm

I do not schematic software.  But a quick over view.  It is a 3 stage with the Riaa correction between the 1st and 2nd tube.  The 3rd tube can be 2a3 1 to 1 out and still have low output impedance.  Or your use a higher gain tube 2 to 1 step down to get a lower impedance. On the first 2 tubes I am using diode bias and the 3rd is fixed.  Each tube has its own choke tube power supply.  And separate filament power supply for each tube.

I am using Dave Slagle 7k chokes for riaa so opens up many tube options.  In regards to sut loading I have a separate box with 4 pair of different suts and replaceable resistors to load before after or both.  So I can go from 0 to anything.

The reason I posted here is it sounds like Pani is looking for something that has body and soul.  If hi fi was his thing the options are endless.  I realize pretty much no one wants to be over the top like what I built but I think the interstage/lcr is going get you pretty close to a home run!!!

Enjoy the ride
Tom
lewm
13,010 posts
 
And I think it's a mistake to think that any particular topology is per se going to sound great regardless of who designed it and regardless of parts quality.  In your case, you got chokes made by Dave Slagle, i.e., the highest quality I can imagine.  Do we know that the Trafomatic sourced their chokes from an equally prestigious source?   Plus, you describe your phono stage that is off the charts for more reasons than just the quality of your chokes, or the 7K value of your LCR that permits a much more simpatico tube circuit than does the typical 600R LCR module.  In a commercial product, and given Pani's lack of DIY expertise, I would almost say that simpler (CR correction) is likely to be better, on a dollar for dollar basis, but of course there are exceptions to any rule.  For sure, the Trafo deserves an audition.  By the way too, not everyone is crazy about interstage transformers, even those who like transformers and tubes. I'm just saying.  I personally have no opinion on that score (use of interstage transformers per se), because I do not feel qualified to have one.
tomwh
150 posts
 
Lewm

It is fun to go through a mental process and or research.  But when it is all said and done we have to listen to our decisions.  The only reason I I posted was from Pani post it sounded like he could hear what interstages could do.

If you need to prove to your self that interstages are a waste of money without listening to them;  besides the band width issues your can not hold the riaa adjustment as close as with a r/c circuit.
Maybe Dave Slagle non LCR phono stage.  I am pretty sure he is using lower impedance tubes so he can reduce load resistor values.  He thinks you can get pretty close to a LCR unit.

If you are interested on how build and or understand phono stages Morgan Jones second or third ed. Valve Amplifiers is a must have.  He is very much a numbers guy but is very through.

Once you get a understanding of tube amps you will see there are not that many variations as the marketing department would lead you to believe. In fact in all the experiments I have done the simple circuit is the best.  No ccs tube or transistor.  No cathode followers.
No grid stop resistors.  No cathode bias caps you get the idea.  Been there done it more times than I like to remember.

So if Pani is interested if he can find out how many stages and who's chokes and transformers.  Also tube types.  Maybe it will help you with your concerns.

Enjoy the ride
Tom




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