my modification of CFP

[Vizitator Stee]

change driver in mosfetdelete DC offset capacitor

[Blacksmith]

delete DC offset capacitor

Poti sa ne spui mai multe despre asta ? Ce avantaje aduce ?

[dinozoff]

Daca pot sa imi dau si eu cu parerea, conform upgrade-urilor facute la apliful JLH, care vizau tocmai elminarea condensatorului din bucla de reactie negativa, se imbunatatea raspunsul la frecvente joase (se mai afirma ca se evita neliniaritatea introdusa de un electrolitic). Oricum raspunsul la joase porneste practic de la DC, dar trebuie un filtru trece sus de 20 HZ la intrare ca sa nu amplifici infrasunete.Mai era totusi o problema si anume offsetul propriu-zis generat de diferentele de caracteristici ale tranzistorilor din LTP, inegalitati rezistenteetc. care este amplificat la iesire (chiar daca este un curect continuu, nu mai avem condensatoruk de blocare). Deci, as sugera introducerea unui pot pt reglajul offsetului la iesire, decuplari strong la sursa de curect consrant care alimenteaza LTP, eventual introducerea unei surse Wilson cu reistenta de polarizare fractionata, iar punctul comun legat la +ve printr-un condensator electrolitic - vezi varianta 12.a de la QUAD 405-PROIECT COMUN CU USERII a lui T. VICOL.

[danzup]

Ca sa inteleaga si Stee trebuie sa vorbiti in engleza sau italiana .Stee a vrut sa "decupleze" , sa imbunatateasca izolatia intre VAS si prefinali/finali folosind tranzistori mos .Ramane de vazut daca se confirma in practica .E o intreaga emulatie pe diy audio legat de amplificatorul lui Catalin/technomate ( am observat ca audiofilii greci si italieni mai ales sunt cei care il fac la greu acest amplificator... ) si Stee ( pentru ca il respecta pe Catalin ) a prezentat ce a postat el acolo , si aici , pentru ca Joy200 ( deja la versiunea 3 ) este pana la urma inventia si munca lui Catalin.@Stee : thank you mate for your posting . Keep up the good job .

[technomate]

Hello Stee .

This amp is far away from an state of the art....It is an very good compromise between number of pieces(transistors),power consumed(sounds like an A class) and sound(good linearity ,phase,thd slew rate ,etc).

 

Thank for your interest of this amp .With mosfet's I don't know ....I don't have sufficient theoretical informations to implement such a stage at this moment .I don't know where to buy...etc..

I am an bipolar In love but I'm curious about mosfets design.

For the capacitor...I'm a little afraid now to drop it ...The response of the amp will be also in dc ..I don't want that now but I will think at that advise .

About the amp ,like the diy forum,it is better to put 0.22 in emittor not in collector.I 'm thinking to put an resistence in the emittor of the vas (for safety ) although the amp is working verry good .

A happy new year to all !

[retrosong]

traduceti

[paul14]

"Acest amplificator este departe ca sa fie o piesa de arta. Este un bun compromis intre numarul de piese si sunet.Iti multumesc pt interesul aratat pt acest amplificator. Cu mosfetii nu stiu...Nu am suficienta teorie pt a implementa un astfel de stadiu la acest moment. Nu stiu de unde sa cumpar etc...Mie imi plac foarte mult bipolarii dar sunt curios si despre mosfeti.Despre condesator...Imi este putina teama sa-l elimin acum.. Raspunsul amplificatorului va fi de asemenea in DC.. Nu vreau asta acum dar o sa iau in considerare sfatul tau.Cat desprea amplificator, la fel cum zic cei pe diy forum, este mai bine sa pui 0,22 in emitor si nu in colector. Ma gandesc sa pun o rezistenta in emitorului VAS)pt siguranta) uan peste alta(totusi) amplificatorul functioneaza foarte bine"cam asta zic eu ca e traducerea. Sper sa nu fi gresit pt ca nu stiu despre ce se vorbeste acolo. Inafara ca se "cearta" pe un condesator si niste rezistente

[EmyRulz]

@techomateThe amp has an input capacitor so it still has a low frequency pole. About the 0.22 ohm resistors, I don't know what to say, but if you place them in the collectors, the CFP has greater open loop gain and consequently a higher feedback factor to reduce non-linearity. Considering this aspect, this could be a weak point for the mos-fet as driver because it has considerably lower transconductance compared to a bjt.

[danzup]

@techomateThe amp has an input capacitor so it still has a low frequency pole. About the 0.22 ohm resistors, I don't know what to say, but if you place them in the collectors, the CFP has greater open loop gain and consequently a higher feedback factor to reduce non-linearity. Considering this aspect, this could be a weak point for the mos-fet as driver because it has considerably lower transconductance compared to a bjt.

@EmyRulz : I think what Stee would try to do is use the mosfet for it`s characteristics of delivering high current for final transistors ( at more linear characteristics ! ) in a way that he presume that the final are not at the most correct point of delivery in the near of crossover point and to separate the two stages , even with a lower transconductance from mosfet .It remains to see if that is good .

[technomate]

@techomateThe amp has an input capacitor so it still has a low frequency pole. About the 0.22 ohm resistors, I don't know what to say, but if you place them in the collectors, the CFP has greater open loop gain and consequently a higher feedback factor to reduce non-linearity. Considering this aspect, this could be a weak point for the mos-fet as driver because it has considerably lower transconductance compared to a bjt.

I will remove it next year now.... ;;; "the CFP has greater open loop gain and consequently a higher feedback factor to reduce non-linearity" that why I put them in collector.But for 2-3 pairs the current sharing is almost inexistent.

[thefirstdj]

Aici e ca in filmele alea in care chinezii vorbesc intre ei in engleza!

[danzup]

Aici e ca in filmele alea in care chinezii vorbesc intre ei in engleza!

Nu frate !Stee nu e roman , din acesta cauza vorbim in engleza !

[cipriyan123]

se referea la discutia intre emyrulz si techomate.

[Sharky]

am deschis discutie despre subtitrari si limbi la sectiunea moderatorilor, dezbatem acolo.Am vorbit cu tata nostru Vasile si a fost de acord cu ideea mea.Subiectul nu va fi inchis, va ramane deschis, dar cei care posteaza sa faca bine sa posteze si in romana. Este un forum romanesc si nu trebuie sa ii defavorizam pe cei care nu cunosc limba engleza. Totodata cineva sa traduca cu Quote si spusele domnului Stee. Nu va fi un lucru prea greu deoarece se pare ca e zgarcit in cuvinte.Va rog sa va conformati.Multumesc pentru intelegere.Serban