Plh

[posxia]

I am builting PLH just now,but it work unsuccessful.
can anybody help me?

A:
R6(221) means 221 Ohm or 220 Ohm?
R4(220) means 22 Ohm or 220 Ohm?

I consider R4(220) 22 Ohm


B:my vcc is 25V

but the voltage of the midpoint(left point of C4) is above to 17V,

THX!
😕

 

[Nelson Pass]

R4 is 220 ohms, but at 3W it is a 10% tolerance.

R6 is 221 ohm at 1/4 watt and 1% tolerance.

😎

 

[posxia]

Dear sir:

I finished the PLH, It sound good , but to small,maybe below 5w ,can anyone help me? thanks.

my dc voltage :+26V
output node voltage :+13V
output current: 1.2A

P1: 100 OHM
R1: 1k OHM
R7: 100K OHM
R8\R9: 0.22 OHM
P3: 100K OHM(about)

 

[gbullimore]

right, cases finished parts ready to order, just a couple of questions!

P2 needs to be 3w (10 turn or 1 turn)
i understand R4 being 3w also,
but P1 and R6 just 1/4 w ?
i asssume P1 (& P3) as a 10 turn to acuratly set the bias.

lastly whats the general opinion on running a 40v supply with 63v 10000uf cap 0.5ohm then 40v 10000x2 caps. this is in the external psu case with 48000uf in the amp case itself.
is it really bad to run a 40v cap at almost 40v? the ambient temp will be 25c or so.
can p2 be adjsuted whilst the amp is running?

ah and why does nowhere in the uk sell mica washers for T0-247? i can only find t0-220 in mica, or silicon in T0-247.

 

[h_a]

Don't forget your toroid outputs the 40V at given power rating. Below that you get an increased voltage! Idling voltage (no load) is usually 10-15% higher (see datasheet).

All the best, Hannes

 

[gbullimore]

but as it's class A the voltage sag on the supply will be fairly constant ?

also i need 5v supply for a psu voltage meter i'm using (just because i've got it spare)
the 40v is too high for a standard 3 terminal reg, can i use a 7805 with a 20v zenner in the gound leg to get 25v then feed that into another reg to get the 5v required?
is there any issue with putting zenners in the gound leg of the regulator to up the voltage?

 

[Nelson Pass]

The sag will be realtively constant.

BTW your meter may need an isolated supply. If so, one way
to get it is to wrap a few windings of your own around a
toroidal transformer. 5 volts is easy enough to get this way if
the transformer is not potted.

😎

 

[gbullimore]

ah thanks, i'll give that a go, much easier

 

[umut1001]

hi about plh

hi everyone.. i built this plh amp at this link
http://6moons.com/industryfeatures/zen/plh.pdf with 2 irf240 but they burned..and then i used 2irfp240because they are cheap..but i cant see 2amps bias through 0.47ohm resistors..there is 0.35volts maximum at this resistors..i am doing everything but nothing changes..output voltage is25volts dc now.gate to ground voltage is4.6volts and irf610 gate 8volts .power supply is strong enough toroidal transformer is 500watts.it produces 43volts dc..and i used total 38000uf capacitors..what can i do?
thank you very much for help

 

[Nelson Pass]

I think we need better information. Can you post a copy of
the schematic with the voltages you measure?

 

[umut1001]

hi again 🙂

hi ..here is the schematic..i wrote what i measured..the sound is very good..but i think if i can get more bias current it will be better.i couldnt do it..i dont know what to do...thank you for reply

 

[Nelson Pass]

P1 is used to adjust the bias. If you minimize the resistance
of P1 I would expect to see plenty of bias.

 

[umut1001]

i am doing everything but the bias is only 1.4 amps now

 

[umut1001]

i could find harris IRf610..i couldnt find an IR IRF610..which one is better ?Mr. Pass i will ask you lots of questions but i am afraid you will not answer all of them 🙂
thank you very much best wishes 🙂

 

[Zen Mod]

i am doing everything but the bias is only 1.4 amps now

decrease R6

 

[umut1001]

hi again🙂 about capacitors

hi again..i am making PLH an acustical guitar amp for my friend..also he wants to listen to music..for output cap i couldnt find a good capacitor 22000uf in my country..i found a very bad china ones..but i have different types of nichicon..12000uf and 10000uf.is it good to parallel different types?maybe there will be phase difference or sth like that ?.i have 18000uf capacitor but lover capacitor makes less bass..i have wharfedale 8.2 speakers and they have less bass too...and wanna ask if 105degrees capacitor better than 85degee ones?
thank you

 

[umut1001]

and another question

and the other question is which preamp is the best choice for plh amp?

 

[umut1001]

hi there is there anybody answers🙂

 

[Zen Mod]

hi there is there anybody answers🙂

make Treshold NS10 ; you'll find few threads in Pass board here

 

[mindengine]

How can I interpret I* in fig7 @ PLH?

I cant make meaning of R* in Fig 7.
Is that for feedback or shunt ?

Help !!!
Anyone can explain it to me?

Thanks.