Pojačavači sa SIT tranzistorima

[Aleks]

Šta znači A B C D ? Mislim u zvučnom smislu?

Čime poterati ovo? Jel može 6V6 (Salasov)?

Msm, ne merem da pravim, a možda i da? čisto informativno. Pre svega treba $$$ za 200W disipacije, pa onda ostalo...

[Zen Mod]

malo razlike u gainu , malo razlike u Rout , malo razlike u THD , pa cak i THD spectra (odnos izmedju 2nd i 3rd)

 

moze to da se svede i na 100-njak W disipacije , ne mora 200W , naravno uz manju snagu

[vladd]

Bolje bi cucnuo Iron, nego salasova igrarija.

Ja nekako ne volem da miksujem koncepcije.  

[Aleks]

10 hours ago, Zen Mod said:

malo razlike u gainu , malo razlike u Rout , malo razlike u THD , pa cak i THD spectra (odnos izmedju 2nd i 3rd)

 

moze to da se svede i na 100-njak W disipacije , ne mora 200W , naravno uz manju snagu

Može ovako?

[Zen Mod]

aha

samo drain od SIT-a oznaci voltazu kako bi trebalo , volt-dva manje od U/2

[Mikorist]

16 hours ago, Zen Mod said:

iteracija ampa koji je Nele skontao sa 2SK77B

Da li se meni čini da i Nele prelazi na 2SK182 / THF51 

[Mikorist]

Ovo je deo iz Neletovog Manual  za SIT3

Quote

 

Introduction to and History of Static Induction Transistors
In the mid 1970's a special variety of Jfet invented in Japan called a Static
Induction Transistor (SIT) found its way into the “VFET” power amplifiers
produced by Yamaha and Sony. These amplifiers were produced for several
years and then discontinued, but are still highly regarded in the high end audio
community.
SIT devices have a unique characteristic which is of particular value for audio
amplifiers. Quoting inventor Nishizawa's patent abstract, “(The) drain-current to
drain-voltage characteristic simulates the anode-current to anode-voltage
characteristic of the Triode vacuum tube very closely.” They have found use in
radar and other exotic applications, but after Sony and Yamaha ceased
production, versions suitable for audio power amplification have been highly
prized and difficult to obtain.
There has been renewed interest in SITs, partly because two companies have
stepped up to the plate and spent the money required to fabricate new devices
suitable for audio power amplifiers. The first of these is Digital Do Main in
Japan, which has produced amplifiers based on newer versions of original
Yamaha Silicon parts. The other is First Watt, which arranged for a production
run of a new SIT device using a newer Silicon Carbide process by SemiSouth.
It is that “Triode characteristic” which makes the SIT so special. Your ordinary
power Jfet or Mosfet is a voltage variable current source with a set of curves
which looks like a Pentode tube:

By contrast, the SIT is a voltage variable resistor with a set of curves that look
like a Triode:

Audiophiles often go to great expense to achieve as little as 5 watts of power
using Triodes because of their specific sonic character. Unfortunately Triode
performance is limited partly by the need to transform the high voltage / low
current operation of the Triode down to the low voltage / high current domain of
loudspeakers. This means a power transformer and the distortion comes with it.
Of course it would be nice if Triodes drove speakers without transformers.
It has been a goal of some designers to get transistors to sound like Triodes,
with very limited success. Fets can sound like Pentodes, but it takes a particular
set of gyrations to make a Fet do the Triode trick.
Then there are those who think that nothing less than a glowing bottle will satisfy
tube aficionados. Perhaps that is true, but it isn't going to keep me from trying.
There are two things we want out of a solid state device for this purpose. First,
we want a “square law” input characteristic like that of tubes. Fortunately, Fets
do that already – the current through the Fet is a good square law function of the
Gate to Source voltage.
Second, we want a low Drain resistance, equivalent to the Plate impedance of
the Triode. This is where gain device can be regarded as a variable resistor
instead of a variable current source. 

Why do we want this characteristic? Three reasons - first, it allows a single
gain stage with both voltage and current gain, and having a high input
impedance and low output impedance without a feedback loop or degeneration.
Second, this character allows “working the load-line” - the particular description
of the path of the gain device through the voltage/current region in the course of
amplifying into the loudspeaker. By choosing this line wisely, you can achieve
intrinsically lower distortion. Pentodes and Mosfets aren't as good at this.
Third, like Triodes, SITs have a soft overload characteristic. When over-driven
on peaks they present compressed, rounded waveforms instead of sharp
clipping, the result being that they are more graceful under pressure.
The entire effort revolves around simplicity and minimalism in circuit design.
Certainly you can get good objective performance with multi-stage circuits and
negative feedback. What we want is the sound that can be had from a single
gain stage operated single-ended Class A without feedback or degeneration. We
want it with a high input impedance and a low output impedance, and we want it
with reasonably low and simple distortion.
It is worth noting that the original efforts by Sony and Yamaha were not
minimalist – they contained many parts in multiple gain stages and used a
generous amount of feedback. Forty years later, the emphasis is on using the
character of the SIT to achieve performance in a simple circuit.
There are several reasons for the push toward minimalism. The first is simply
aesthetic – there is much to admire about an amplifier which performs well with
only one transistor. And of course there is an attractive challenge, which is
“How good can you make such an amplifier?”
There is another, more practical reason to explore simple circuits. It is generally
agreed that if you are going to have distortion, you will want it in a low order
harmonic form, kept to only second and third harmonic if possible. A singleended
Class A device is going to generally give you the simplest version of this.

Lots of audiophiles dislike the sound of negative feedback (or at least think they
do). It is true that while negative feedback reduces the amount of distortion, it
does tend to re-arrange it so that the character is more complex.
Minimalism is the raison d'etre for SIT devices in audio. With them you can get
good objective and subjective performance from a single SIT in a very simple
circuit.

 

 

Pametnom dosta . . .

[Mikorist]

23 hours ago, Vix said:

A i kondovi ogoljeni, negde procitah da tako bolje zvuce

A ne videh ni osigurac

Ko ne čuje razliku između ogoljenog i neogoljenog konda - ne može sebe nazivati audiofilom.

[vladd]

Ko ne pije vino iz Gaskonje, ne moz' da bude audiofil, ic...  

[Zen Mod]

kujgabe,uskoro ce pravim jedan, za napolje

Dakle,opet razvoj....

[Impuls]

On 10/6/2018 at 11:35 PM, Zen Mod said:

 

ja mislim da ovo nece da radi. ili da preciziram, siguran sam da nece raditi

[Zen Mod]

sto?

[Impuls]

zakucali ste ulaz na zenericu, nedostaje otpornik izmedju. A ovi 0.1 otpornici ce zavisiti od gornjeg feta da se ujednaci izlazna impedansa donje i gornje periode. mozda je nelson bas odabrao fet sa slicnom karakteristikom thf-u. treba snimiti harmonite pri razlicitim nivoima glasnoce da e vidi poklapanje gornje i donje periode

[Zen Mod]

tesko da ce na gate da udje 18Vpp signal ikada

 

ako udje , u problemu si

 

 

[Impuls]

zakucao si ulaz na 9v1. signal ce ici kroz zenericu a ne kroz thf. Ako si ulaz thf zakucao za 9,1V sta t vredi signal da dolazi kad je on uvek na 9v1. Bilo bi ispravno da ste napravili negativan referentni napon za gejt ali mora otpornikda bude prema tom naponu da postoji sving na gejtu. Ne interesuje me sta je nelson pricao na baf-u, kazem kako treba elektronicki

[Zen Mod]

-B je prednapon za biasovanje SIT-a , za 3A je red velicine par volti

9V1 je zastita gate-a ........ SIT-ovi su osetljivi na preveliki negativni prednapon

[Impuls]

Hoces da kazes na semi nedostaje sklop za biasovanje sit-a? Zar nij jednostanije bilo iskoristiti vec tu zenericu samo dodati trimer za biasovanje sit-a? To znaci da ovaj sklop ne radi jer mu nedostaje jos sklopova za rad

[Zen Mod]

pa vidi se iz aviona da ga nema .... mislim - luk i voda - otpornik i zenerica i kond i trimpot

pogledaj linkovani snimak , pricao je 20 minuta o konceptu , kao i pokazao merenja napravljenog primerka

[Impuls]

ja sam banuo na semu koju ste  stavili i sa takvom konfiguracijom vieo da ne moze raditi. nisam gledao video i nisam zakljucio iz date seme da je -b napon za biasovanje vec mi je izgledalo kao da je to negativan napon za polarisanje zenerice. U redu upao sam nepripremljen u temu pa cu je ubuduce preskociti jer me ne interesuje pojacalo za koje moram da vijam tranzistor a kad crkne da se oprostim od njega. Ako i budem poklonio paznju uradicu sa necim dostupnim a da se zadrzi pecat koji amp daje. Shvatam da je trenutni hajp za sit pojacavacima ali mislim da se moze uraditi i nesto drukcije a da radi posao isto ili mozda bolje sa drukcijim tranzistorima imozda bi trebalo malo tragati za nekim savremenijim koji bi zadovoljio buducnost na neko vreme. Ako je igbt mogao da zameni ulaz feta a izlaz bipolarca onda ce i neka kombinacija dva poluprovodnika da zameni sit adekvatno

[Zen Mod]

pogledaj snimak ;

po prakticno istoj semi ali sa dovitljivim trikovima je dao kako da napravis sa modernim i nabavljivim IXYS mosfetima ...... mozes da odradis i scale down

 

i na kraju dobijes amp za tepsiju ribe

 

uopste nije poenta u SIT-u kao jedinom resenju , nego je SIT odredjena referenca rezultata , razumevanje zasto je referenca i sta se moze nauciti iz toga

hype ili moda naokolo, svejedno ...... ja se ovim ne bavim da bih uvek imao sledece najbolje , nego mi je prvenstveno zabavno

s druge strane , zasto ne iskoristiti zabavu da svima bude bolje - em nesto naucim , nekome napravim nesto sto nikad ne bi mogao drugacije da ima , em se zaradi kinta za prsute i vina

 

edit: kako mislis da crkne 400-500W tranzistor , jos narocito ako znas sta radis ?

 

[vladd]

7 hours ago, Impuls said:

Ako je igbt mogao da zameni ulaz feta a izlaz bipolarca onda ce i neka kombinacija dva poluprovodnika da zameni sit adekvatno

To je nesto kao dedukcija nevine domacice?  

Nece se to dogoditi, iz vise razloga, i ne moze da se dogodi, i nema potrebe, posto se oni "ozbiljni", koji razvijaju komponente, bave uveliko vrlo visokim frekvencijama. Audio je u velikom zapecku..

SIT je definitivno komponenta koja je tehnoloski ostala u svom prostoru i vremenu nastanka, i kao takva vrhunska za vec, vrlo opravdano izhajpovanu konfiguracije SE, ali znacajno bolje nego u varijanti triode.

U svakom slucaju, SIT je obesmislio SETOTL, sa nekoliko desetina mocnih trioda(za nakapavanje nekih struja), nikada uparenih, u tehnickom smislu, u nekom raspojasavanju druge vrste ionako nema zdrave logike...

[neskor]

19 minutes ago, vladd said:

SIT je definitivno komponenta koja je tehnoloski ostala u svom prostoru i vremenu nastanka, i kao takva vrhunska za vec, vrlo opravdano izhajpovanu konfiguracije SE, ali znacajno bolje nego u varijanti triode.

zivi bili, pa videli