THE STORY

Angelo is dedicated to my newborn son.
Angelo was born thinking of extrteme semplification and good sound. The idea was building a very straightforward amplifer with good power but using few components with low number of stages.

The minimun number of stages -if we leave behind one tube amplifiers (that's too little)-  is two: a driver and a final tube. But obtaining good sound with such a simple topology isn't so easy: there may be lot of problems.
The first is how to subdivide the overall amplification of the chain.

One idea is using hi power tubes with high mu. Leaving back penthodes Nowadays some power triodes with high mu  exists ( for example Svetlana's SV 572-160) but if you take a look at the curves,  they lack of linearity.
So I turned back  to the classical low mu choice or the final tube..

But so  the driver must accomplish two difficult and in some aspects contradictory tasks because It must at the same time:

• have good amplification. And this is  a classical  caracteristic of  low power, low noise tubes (like ecc83), wich however normally have high Ra.
• have good driving capabilities (i.e. low Ra) And this is normal for good  power - low amplification tubes

Here is the final result :

In this

As one can see in this circuit 6c45p is stretched near  the maximum availabe voltage: 200v. This is  to obtain the maximun swing for the output tube. Beside, i've decided to use x-former coupling to have maximum sound quality  and the best driving power for this stage, that can actually drive many output tubes (ie.  572-10 , 845 etc.)

This interstage xfrormer I've choose is the MT103s from Megahertz Audio.  I'ts a 10k-10k doube c- core made with 0.1mm iron sheets. In my opinon this irons has a very nice sonic performance, among the best I've ever experimented with.
I've choose a higher than necessary 10k-10k impendance to reduce distortion and because with this components you can experiment many other tubes around.

As a power tube, many choices are possible. To tell the truth I've made  quite a "conservative"  choice: 2a3. After all in my mind this should be a affordable and reliable amplifier. Other more expensive choices cold be 300Bs. In that case  you have only to higher AT and retune the 5k resistor accordingly

Here are some ideas to adapt this solution  to you listening pleasure:

• Angelo has very high amplification factor: normally you don't have to use a pre amplifier to listen to you CD player
• Use a very good volume pot (i'm using Sovtek x-former potentiometer (see project in my homepage)
• Some quick consideration about PS: if you want deep basses use a diode power supply if you want very clean voices and highs use tubes. My power supply uses EY82 for the anode section and for the negative bias section.
• 6c45p could oscillate in the RF region easyly: you can avoid that decupling each grid-pin with a 220 ohm 1/w metal film resistor. Also ground with a 0.1uf polyester cap each heather pin.

Listening Impressions

Listening chain:
 

CD Motor: CD Pro philips unit

DA Unit:    Built in Cd pro + DAC with two paralled 1541 and tube output stage (6c45p)

Preamp: passive with Sowther X-former volume control

Power Amp: Angelo

Speakers:  Hedlunds

Signal cables: DIY silver-teflon Cables

Speakers Cables: DIY silver-teflon Cables

From the first listening session it appeared clear that  Angelo had a clean  and unfatuigiun sound.

These are (in our  poor english) the impression we had:

• "Ambience": There is a very great sense of ambience . This is probably due to low phase rotations connected with low numbero of stages.
• " Easy Feeling" at normal levels  the sound comes out very unfatiguing.
• "Good Volume for chap money ": Its strange how this very simple amplifier with a couple of watts can play music with good volume. Besides, in some respect you can adjust the timbre choosing differnt 2a3s : From our subjective point of view Chinese offer a more "disco" sound with clear highs and deep basses. Sovteks are quite nice in the medium and medium bass section, the best  companion for my Hedlunds.

That's all folks, Listen - have a happy new year and ENJOY!
 

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