Constructie Leach Amp 200W

[zal]

Orice trz finali complementari cu Uce peste 120V, Ic peste 10A, Pd peste 100W. Pot fi ?i 2SA1943/2SC5200 (din cei buni).

Dac? nu vrei s? folose?ti MPSA06/56, po?i folosi MPSA42/92 sorta?i cu beta minim 200; BC546/556B,C; 2SA970/2SC2240 sorta?i cu beta mai mic de 400, etc.

Cum s?-?i descriu ?n cuvinte un sunet? Doar audiofilii au talentul ?sta ?i nu e ceva pozitiv.

.............

P?n? la urm? totul se reduce la bani ?i chef de munc?.

[cristian_98]

Cablajul din linkul http://www.pavouk.org/hw/leachamp/en_index.html este ok, nu are probleme la masa?

[zal]

Dac? e vorba de ?sta http://www.pavouk.or...amp/layouts.pdf e cablajul de baz? Leach ptr ampliful ?sta, versiunea 4.5, folosit de ani de zile, ce probleme s? aib??

Editat Iunie 13, 2014 de zal

[cristian_98]

Scuze, dar ma refeream la cel desenat in eagle.

 

 

Scuzati va rog dublul post.

Influenteaza semnificativ sunetul daca pun rezistente cu toleranta de 5%? Sau pot folosi linistit astfel de rezistente?

Cablajul acela in Eagle e ok?

[cristian_98]

Buna seara...m-am apucat de acest amplificator, de cablajul postat de tine zal.

Sunt niste reglaje speciale la punerea in functiune a modulului, sau se regleaza biasul, se verifica offset-ul, se masoara tensiunea pe rezistentele de putere?

Trebuie sa urmaresc ceva special in constructia acestui amplificator?

[zal]

Dac? vrei s? ob?ii rezultate de ''farmacie'', folose?ti rez cu 1% ?i trz ?mperechea?i ?ntre ramuri ?i etaje, a?a ai siguran?a identit??ii celor dou? canale.

Totu?i, schemele total simetrice nu s?nt a?a preten?ioase, merg ?i rez cu 5%, multe inegalit??i se anuleaz? automat. R?m?ne ?mperecherea m?car a trz din diferen?iale, etajele pilot. Deriva la ie?ire nu va trece de 50mV. Singurele piese mai problematice s?nt condensatorii electrolitici, cei de pe pia?? s?nt slabi calitativ.

Reglajul ?l po?i face dup? indica?iile r?posatului M. Leach, de pe sait, cu aten?ionarea c? s?nt valabile ptr trz finali folosi?i acolo, ptr al?ii po?i regla mai simplu urm?rind ca tensiunea de polarizate b-e s? fie ?n jur de 550mV f?r? semnal, ??i vor lua ei Ic0 specific fiec?ruia, asta corespunde ?i cu tensiunea pe trz superdiod? conform lui Leach.

Initial Tests on the Completed Amplifier

 

When the amplifier is completed, the following tests should be made:

1. Test the power supply before installing fuses F2 - F5. The dc voltages should correspond to the values given in the power supply parts list for the transformer used. If the power supply is wired wrong, fuse F1 will blow. If a variac (variable autotransformer) is available, use it between the amplifier and the AC line to slowly increase the ac voltage from 0 V to 120 V AC for this test.
    
   
2. The filter caps must be discharged before installing F2 - F5. Do not short circuit the capacitors to discharge them! You will get a loud pop and a big spark. A 100 ohm 2 W resistor is recommended to discharge the capacitors, but it can get hot! Use pliers to hold the resistor across the terminals of each capacitor for at least 30 seconds to discharge the caps.
    
   
3. Adjust P1 on each circuit board for maximum resistance and install the power supply fuses. If the previous tests have been successful, you can proceed to the next step where you power up the amplifier. Again, I recommend the use of a variac to slowly increase the AC input voltage from 0 V to 120 V for this test. If you are unsure of anything, remove F2 - F5. Substitute a 100 ohm 1/4 W resistor for each of these fuses. You may wish to power up only one channel at a time.
    
   
4. With no load connected to the amp, it can be powered up. If anything is wrong, the 100 ohm resistors in place of the power supply fuses will limit the current. They will also smoke! The dc voltage drop across the 100 ohm resistors should be less than about 2.5 V (25 mA or less) if nothing is wrong. If this test is successful, turn the amp off and wait for the power supply to discharge. Remove the 100 ohm resistors and install F2 through F5.
   

Setting the Bias Current

 

If the preceding tests are successful, the next step is to set the bias currents in the output stages. This is done as follows:

1. The power should be turned off and the power supply discharged.
    
   
2. Remove F2 and clip an ammeter across the fuse terminals.
    
   
3. Power the amp up with no input signal or load. Adjust P1 for the channel connected to F2 for a current of 100 mA. Be careful. Once I accidentally blew the output transistors in one channel of an amplifier I was building when I mistakenly tried to adjust P1 for the wrong channel.
    
   
4. As the amp warms up, the current will drift. Readjust P1 until the drift stops. This will take about 10 minutes.
    
   
5. Turn the amp off. Wait until the power supply discharges, then install F2.
    
   
6. Remove F3 and repeat this procedure for the other channel.
    
   
7. When the bias is adjusted properly, a dc voltmeter will read close to 3.4 V across Q7, i.e. across the collectors of Q12 and Q13. The collector of these transistors is the round metal case.
   

 

Editat Iunie 15, 2014 de zal

[cristian_98]

Inca ceva...

daca nu am conzii de 390, 180, 47, 10pF ce pot pune?

dar semireglabilul de 2k? Am doar de 1K sau 5K.

[zal]

Astea s?nt piese ce se g?sesc oriunde ?i cost? c?t semin?ele, dac? totu?i nu g?se?ti exact acele valori, po?i folosi urm?toarele:

• C1 - 390 pF mica 330-430-470pF/63...250V ceramic, stiroflex.
  
• C2, C3, C15, C16, C23, C24 - 0.1 uF, 100 V film
  
• C12, C25 0,1uF/250V
  
• C7, C17, C18 - 0.1 uF, 50 V film
  
• C4, C5, C13, C14, C21, C22 - 100 uF, 63...100V radial electrolytic
  
• C6 - Either a single non-polar capacitor or two polar capacitors can be used for C6. I recommend the non-polar capacitor. In this case, use a 220 uF, 16 V bi-polar electrolytic in the holes for C6A and solder a short circuit jumper in the holes for C6B. (Failure to install this jumper will result in the loss of all bass response.) For two polar capacitors, use a 330-470 uF, 16-50V radial electrolytic for C6A and C6B
  
• C8 - 180 pF mica 150-160-200-220pF/250V ceramic, stiroflex
  
• C9 - 47 pF mica 43-51pF/250V ceramic, stiroflex
  
• C10, C11 - 10 pF mica 12-15-18-22pF/250V ceramic
  
• C19, C20 - 0.01 uF, 50 V film
  

Dac? nu g?se?ti semireglabili de 2...2,2k, pui de 5k ?n paralel cu 3,3...3,9k.

Editat Iunie 16, 2014 de zal

[cristian_98]

Am gasit un semireglabil de 1k5, trebuie sa il inseriez cu 500 ohmi,n?

[zal]

Pui R27 de 1,8k. Faci un singur amplif?

[cristian_98]

Nu. Momentan astept cmanda cu piese pentru un modul, iar daca sunetul va fi mai deosebit si intr-adevar se poate porni cu volumul la maxim neauzindu-se nimic in boxe, il fac si pe al doilea si un smps pentru ele.

Ce parere ai, suna mai bine,mai altfel decat un amplificator fara simetrie totala?

[zal]

P?rerea mea e c? sun? mult mai bine, asta depinde ?i de restul lan?ului, surse de semnal, corec?ii ?i boxe.

Dintre avantajele constructive ale amplifurilor total simetrice: s?nt rapide, stabile, rezist? la abuzuri mai bine ca restul, dac? cade o ramur? de alimentare intr? automat ?n mut, nu au pocnet la pornire (sau e foarte redus), ??i p?streaz? simetria p?n? la desc?rcarea aliment?rii ?i cel pu?in cele pe care le-am f?cut se puteau porni cu volumul la maxim, evident cu semnal (nu ?tiu cine ar face asta totu?i). ?n general nu au nevoie de protec?ii, dou? siguran?e pe alimentare s?nt suficiente.

Dezavantaje: mai multe piese sortate ?i ?mperecheate.

.............

Poate voi posta ?n cur?nd un amplif mai vechi.

[cristian_98]

Si inca ceva...

Pentru 2 astfel de module, cam ce putere ar trebui sa aiba smps-ul?

[Letcon]

si intr-adevar se poate porni cu volumul la maxim neauzindu-se nimic in boxe

La ce te ajuta sa pornesti un amplificator cu volumul la maxim,fara semnal...ca eu cel putin asa am inteles ca ai vrea sa faci?

Sau tu confunzi zgomotul(brumul) ce se aude in cazul in care exista bucle de masa sau etc. cu pocnetul de la pornire?

Sau nu am inteles eu...

[zal]

Eu am ?n?eles c? e vorba de volum la maxim cu semnal. Asta verific? reglajul protec?iilor, dar s? nu devin? un obicei.