" MONOtriodino 3 " a  2a3 DHT SE amplifier

 

"Il triodino" in english "the little triode" is our reference amplifier for low wattage applications, together with the pre-amplifier Euridice.



The project was originally published in the italian review "costruire Hi-Fi" during year 1996 in a couple of issues starting from  number 19 and following.

In our opinion this has been one of the best engineered yet simple project, developed with great accuracy from the  "Gruppo Euterpe" (Euterpe Team). This team collected for a short time the best audio developers availabe in Italy, with the aim to create the best sounding chain, from Vinyl player to loudspeaker.

Very soon different views and attitude toward money broke the team, but still some "pearls" had already been born,  like "triodino 3" and "Euridice".

Originally the project had been developed with great flexibility: 2a3 or 300B could be used as final tube, while it was possible to use different driving topologies like mu-follower,  SRPP, single  end.
 
 

THE ORIGINAL PROJECT

Here is the original schematic:

.


 And of the power supply:



We started working around the 6SN7 driver building the mu-follower topology but soon after we  tryed also:

After several listening sessions, we were already undecided, and a bit unsatisfied, no one emerged as the "all season" choice. Even if cathode follower and SRPP were almost immediately abandoned, the  choice remained between mu-follower and "single endend". For some time we let them live togheter, with a double switch, but of course this wasn't a true decision ;)

Finally  we resolved ourselves once for all when we connected this amplifier to the lowther "side vivace".
Suddently the SRPP & the mu follower drivers appeared with poor resolution of details, and less "clear" than "single ended", expecially during low volume passages. the coiche was made: Old simple "sigle ended" was the best.

But  Why then  all that fuss around high-performance topologies???.....
Well, we think that  probably the interest around all that complicated circuits is also sometimes a matter of fashion, and also a "sale hint".
Clearly  mu follower had more impact and dinamics, also from an electrichal point of wiev (driving capabilities, band, slew rate) this was clearly outstanding SE.
But the sound seemed very often too "bumby" and "louder", and also a bit "cold" or, like Andrea claimed at the end of one of those night listening session,  "without soul".
Of corse  a lot is a question of  the downstream hi-fi chain and, as usual, of taste.

To come to the end of the story, I would suggest mu-follower if power is the matter, expecially with low efficency speakers. So you can obtain half a watt more driving 2a3 to the limit and sometimes this is the "little more" that let you live in peace with your sistem  (we've drived a couple of 87 db minimonitors and the "limes" with this little moster whit very nice result. BNut of course  the 300B was clerly a better choice in this situation).

Otherwise if you have 92 db or more  please give "single ended" a try. At the beginning you'll be a little disappointed with the lower frequency extension and little more power, but after a couple of days you'll find difficult to leave the sweetness and easyness of listening of this choice.
 


OUR REVISED VERSION

 

Here is the actual project.
Each channel is separately build, in a dual-mono configuration, with 100% power supply redundancy.

Power Supply section


 

Amplifier Section:
 

Hey!, Look at it for a moment: wouldn't you say that it resembles  another top class amplifier? The answer is at the end of the page (*)... ;).

NOTE ON COMPONENT USED

 Please note that to reach top level preformance you must use  use the suggested supplier for each component.

Now let's take a look inside:


A sheet of   teflon has been used to hold all the components in place.
As you can see particular care has been put in cabling. By the way we suggest to use silver-teflon cable , available at RS in different colors and thickness at your conveninece.Ground wire is  silver plated.
Cabinet is made of olive-tree wood.
 

After spending  a lot of time (&money!) refining the values and  supplier for each componets and now we can say that this little jewel is a true reference.
The sound is very pleasant rich of detail and, with lowter, can express top of class dinamics and presence .
 

ENJOY! and please let us know of any improvements/problems you'll  find with.

Alessandro & Andrea

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(*) take a look to H. Reichert  "Flash & Blood"... we've reached a very close topology.... ;) 1