The KillerDAC Audio forum
General HIFI => Amplification (Pre/Power) => Topic started by: brenden on March 11, 2018, 12:26:48 AM
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Stax da 50 mono blocs now paired with the Stax CAX Pro .
These are the small brother to to my
Stax DA100 full class A amps .
The DA50 is 50 watts per channel
Modding has begun and already showing signs of greatness .
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Side view showing heatsinks . Stax used a liquid sodium cooling system for heatsinks .
Some of the mylar caps have been replaced with very rare Rubycon stlx film and foil non inductive caps .
These are fantastic sounding caps with extremely low esr and made by rubycon as a high end partner for their expensive black gate capacitors .
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This is the circuit board with th excellent 2sk 240 dual fet in can .
The larger brown 1uf bypass caps are gone . They really ruin the sound . They have been replaced with .01 uf auricaps . After that simple replacement it is a different amp altogether. Everything improved from bass mids and treble . Much better timbre and detail .
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Front .
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Nice toy to work on. It will be interesting to see the necessary modifications of a transistor amp.
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Probably easier than a cd player Steve . Best to start with a better mouse trap . Begin with amps that have good power supplies . I prefer fet inputs with bipolar outputs .
The Staxes have quality in all the main areas ,its just a matter of replacing the cheap mylar caps with top quality caps . I am beginning with caps from my parts box to get a baseline for improvements then may try some jupiters etc . So far results have been very encouraging. The areas for further improvement i see, seem to align with the key areas that Jupiters and Duelunds are good at . I may need some technical advice with input filtering at some stage but for now keeping the design mostly stock apart from reducing the bypass caps from 1uf to a quality .01uf ..
I have modded the DA100s and these are almost the same but only 50w so lessons learned form the DA100 willl be used on these .
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Work is progressing on the DA50 monos .
2 electrolytics in the super shunt regulators replaced with Elna Silmic 2 alpha super golds . All the small blue caps 0.1uf replaced with 0.01 uf Auricaps . The .01 size is so much more natural its not funny . I have proven this many times over. Curiously the big brother , Stax DA100 used all .01 uf caps and apart from the output transistors the circuit is identical to the DA50.
So how is it sounding ? Stunning. !
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More parts going in .
Hitachi Copper foil polystyrenes and Elna Silmic 2 Super Gold capacitors
Nothing but the best 😊
The two Silmics here are replacing the decoupling caps in the discrete super shunt regulators , which were 10 uf . It seems to be fairly common industry practise is to use these lower values after regulators , but after many experiments over the years , I have found that a minimum of 25uf to 100uf is needed to develop deeper bass and control of the deeper bass . Bypassinfg with a .01uf Auricap is essential for the highs and mids . The Elnas and Auricaps blend perfectly .
So , deeper and more controlled bass is exactly what i got as well as every other parameter improved also .
The copper foil polystyrenes replace the stendard aluminium foil polystyrenes .
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I have tried the Silmics 2s and they are nice but in general i prefer not to use any electrolytic capacitors, but we have to fit caps in constricted space so we use them. Auricaps are good and great value for money and obviously work well as a bypass cap.
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My opinion of electrolytics has changed over the years . The silmic 2 alpha super gold are a step up from the basic silmic 2 . By themselves they cant achieve the standards that you and i desire ,but when combined with a top class film bypass cap of the correct value my experience indicates that they can easily compete with a top quality film cap .
A top electrolytic is very good for bass and lower mids but doesnt have the beauty in the upper ranges . When combined with the auricap .01 the result is seamless .top quality sound from top to bottom .
There is no doubt there are other excellent film caps apart from auricaps that could work great . The Jupiter is another one that works really good .
If you use a second rate electrolytic with an average film cap you wiĺl get a second rate result .
Maybe one day soon i can demonstrate what can be done with a solid state amp whith the right treatment .
So far the Staxes are allowing the beauty of my 94 mk2 to shine .
The sound is refined , dynamic , and with a beauty rarely heard in commercial equipment . Gone is the bloat ,and smearing that i heard before the mods .
None of this comes cheap mind you .