Hello,

I think I finnaly have the time and space to make a valve amplifier. For my mainden project I need something simple. I was thinking of a mullard 3-3 remake or Sams 5 w design. http://circuitdiagram.net/5w-tube-amplifier-with-el84.html No question of 300Bs or expensive valves that may be blown to pieces when I toggle to ON. Your project looks even simpler. I like simple things. «Less is more». Would you advice this circuit to a newbie? Any advices?

Thanks,

Rui Duarte

Hi Costas,

The Zen amplifier is nice sounding amp. I constructed a temporary (one channel) version on some sort of a breadboard to experiment with this amp. I used an Amroh U72N opt which has an input impedance selectable with two taps: 1- 6000 to 8000 Ohm and 2 – 4000 to 6000 Ohm. The power supply for this experimental amp comes from a large stabilized power supply unit. It works great and I intent to build it as a permanent version. So I will need a power transformer for the supply. Now, here is my question: what kind of power transformer did you use and where did you get it? Do you know the specs of the original power transformer from Decware?

Regards,
Roland

Hi Costas,

I've been checking your site from time to time and finally decided to build this amplifier. I used to have a 12ax7 driven el84 SE amp before, but it needed some changes and therefore this one seemed like good alternative.

I made some minor modifications, and used my own PSU, but mainly the circuit is similar to yours. All in all this is a very good sounding amplifier with just enough power and warmth. Yet it's also so simple design to build so I would recommend it to anyone looking for a first tube project or anyone who needs a small amp with good sound.

This is the third day listening to the amp and the sound just keeps fascinating. The tubes are burnt in JJ's el84's accompanied by russian military grade 6n23p on the front.

Thanks for a great schematic and greetings from Finland!
-Lauri

Hello, Sarris,
Did you developed the B+ supplied in the same fashion as ZEN? 1 k 5 W wirewound resistor as a HV choke in CLC filter? With 275-0-275 V or 300-0-300 V from the power transformer?
Regards,
Goran

I have just scrapped a KT77 amp and would like to attempt a build based on your work. Can you send me the full schematic for this amp? Thank you!

That is a great looking project, I have two mono Mullard 3-3 transformer sets from VVT http://www.vvttransformers.co.uk/valve_tx_sets.htm

I am thinking this could work well if I were to do two monoblocks with EZ81s instead of the 5U/5Y3.

I'd be really happy if you would send me the power supply schematic too.

Many thanks Costas

Hey guys,

Just found this thread, and have a couple of comments.

I have a Decware SE84CSEX, and have modified it very extensively, and would like to offer some observations.

First, re: the 1K PSU dropping resistor should not be a 5W unit. That resistor dissipates approx 10W, and Steve uses a 50W Dale wirewound in that position.

second, as Costas and others have pointed out, this little amplifier has remarkable sonics. Depending upon your budget, DON'T SKIMP on component quality. this circuit, properly laid out and built w/ first class components, is capable of world class performance within its power ratings.

It can, however, IMHO, be significantly improved, most noticably by changing the bias on the 6922/6N1P driver tube and ridding the PS of electrolytics. Steves favors a light operating point on the 6922, approx 2 ma. The 6922 really starts to sing @ 5-6 ma, but it requires changing the cathode bias resistor to 470-500 ohms, and a minor change in the PS. I too have used the Russian 6h23n-ev ( cryoed ) in this position ( great tube ), but I prefer the sound of the 6N1P-ev properly biased, which it will not be w/ the current component values in Steves circuit. That tube really sings with 200v plate-cathode @ 10ma ( 200 ohm cathode bias resistor ), but will require a significant rework of the PS ( worth it though, again IMHO ).

If you can, do not use lytics in the PS. This amp is so revealing it lays bare the sound contributions of all components in the signal path, and lytics just flat out suck compared to the options. Solens of course are great in the PS, but the best are the motor run PIO caps, especially those made by ASC. They are big and a pain to implement, but absolutely essential for getting the best out of this circuit. The difference they make is not subtle.

I have done many other mods to this amp, including upgrading every component type inside ( i.e. different resistor types ( Shinkoh,Riken,Kiwame ) in all positions, cap types etc, and would, if there is an interest, make that info available to anyone.

Thanks Costas for bringing this amp to the attention of so many.

Cheers, Crazy Bill

Hello Crazy Bill,

I'd like to take you up on your generous offer to find out all about your modified Decware SE84CSEX. I've been interested in this circuit for a while now, and think it's time to finally build and listen. It would be great to be able to use your experience with mods before I start, especially your experience with the 6N1P-ev and 6H23N-ev driver valves and their need for higher bias currents. Any information you are prepared to make available would be greatly appreciated.

regards,
another_tube_lover