Neazoi,
A kind of autobias can be done simply using a thermistor across the biasing resistors (increased in this case) such as in the Nelson Pass F5. The thermistor sensing the output devices temperature which follows the bias current.
A kind of autobias can be done simply using a thermistor across the biasing resistors (increased in this case) such as in the Nelson Pass F5. The thermistor sensing the output devices temperature which follows the bias current.
Just tried 0.5A bias level, it works in a very similar way. however the amplifier runs alot cooler and the high freqnecy performance is degraded slighty
i think this is due to the choice of output transistors, these seem to be much faster @ 1A than 0.5A......
hmm which way to go...
i think this is due to the choice of output transistors, these seem to be much faster @ 1A than 0.5A......
hmm which way to go...
f$%&*
just checked the resistive load i am using.... it is very reactive.....
damn it....
tried agoin no load both 0.5 and 1A have way less overshoot....
damn reactive component 🙂
any how....
just checked the resistive load i am using.... it is very reactive.....
damn it....
tried agoin no load both 0.5 and 1A have way less overshoot....
damn reactive component 🙂
any how....
heatsink temp was 48 degrees C absolute.
PS after readjusting to 0.53A bias (soldering resistors "piggybacked")
without the reactive load... (highly inductive) there is a small amount of overshoot. perfromance is much better
-Dan
Hi Dan,
This is interesting, since as you may recall I had issues with the output transistors on my last Le Monstre build. (In my case altering the feedback resistor to reduce the gain helped the sound a lot, although I'm still not convinced I have the optimum value). Overall, I am more interested in doing this circuit with modern equivalents than with the original parts, so if the optimal bias with modern output transistors is higher than Hiraga found that
would be useful info, especially since here they appear to be the only thing that isn't original...
Keep us posted !
Cheers
Nigel
bobodioulasso: hahahaa working for about 4 hours.
myself working for too long in the lab 🙂
Nigel: yes i remember now, the circuit is all original up to the output stage.
I will have to try this setup again with the resistor i used the last time i built a le monstre.... it has much less of a inductive nature.
It would really be nice to build this with some easy to source parts.
I dont see and issue with this just time and research... prior to doing that i think i will se how well this version drives my speakers/sounds
-Dan
myself working for too long in the lab 🙂
Nigel: yes i remember now, the circuit is all original up to the output stage.
I will have to try this setup again with the resistor i used the last time i built a le monstre.... it has much less of a inductive nature.
It would really be nice to build this with some easy to source parts.
I dont see and issue with this just time and research... prior to doing that i think i will se how well this version drives my speakers/sounds
-Dan
Daniel, you blew up the resistors? Do they overheat so much?
I can send you another quad for free if you like.
What do you mean by so reactive?
I am worried a bit about the internal junction temperature. The heat does not get dissipated directly from the heatsink, so if you push the transistor too much it may be destroyed..
Thermal feedback works ok but it is not so direct (wou have to wait for the heatsink to heat/cool to change the bias) and it compensates for the THERMAL drifting (warm up).
In the battery-only operation what is more important is to compensate for the VOLTAGE differences as the battery gets discharged. An LDR may solve this quickly, if someone design the system properly.
Last edited:
le class a- 4 ohms driving capability?
hi all,
i was running the 30 watts with microcap7 simulation, this configuration can't drive more then 6 ohms, did some one succeed to increase the driving to lower loads like 4 ohms?
any help is very much appreciated
best regards
Williams
hi all,
i was running the 30 watts with microcap7 simulation, this configuration can't drive more then 6 ohms, did some one succeed to increase the driving to lower loads like 4 ohms?
any help is very much appreciated
best regards
Williams
Hi Neazoi,
I did not blow any thing up.
I just adjusted the bias..
by "reactive" i mean the large adjustable wirewound resistor i used for the 8 Ohm load was too inductive.
-Dan
I did not blow any thing up.
I just adjusted the bias..
by "reactive" i mean the large adjustable wirewound resistor i used for the 8 Ohm load was too inductive.
-Dan
Yes i agree. But increasing slowly, step by step, the bias and allowing the heatsink to warm up and checking its temp - assuming the devices are properly mounted - should permit to aproach the limit.
Hi Guys,
Here is round two of testing.
still uncased, this time with non inductive resistor and less capacitive input lead.
PS the sig gen is a bit of a limiting factor here
See link:
Le monstre testing Round 2 pictures by danw1million - Photobucket
-Dan
Here is round two of testing.
still uncased, this time with non inductive resistor and less capacitive input lead.
PS the sig gen is a bit of a limiting factor here
See link:
Le monstre testing Round 2 pictures by danw1million - Photobucket
-Dan
I wish I had the equipment to do such extensive tests by myself 🙂
You still use the faster transistors right?
Hiraga vs. Pass F5
Dear All,
has anyone compared Hiraga amps (monstre or le classe A) with Pass F5.
I have build some monstres years ago an want to build annother amp.
since i have all necessary parts- i could build le classe or Pass F5.
Where are the benefits and where are the drawbacks?
Which sounds better?
best,
Ralf
Dear All,
has anyone compared Hiraga amps (monstre or le classe A) with Pass F5.
I have build some monstres years ago an want to build annother amp.
since i have all necessary parts- i could build le classe or Pass F5.
Where are the benefits and where are the drawbacks?
Which sounds better?
best,
Ralf
Hi Ralf!
Nice to see you again!🙂
Are you coming back from the Digital and Class D world?!?😉
I think the best would be if you would try the Profet amplifier!
Greets:
Tyimo
Nice to see you again!🙂
Are you coming back from the Digital and Class D world?!?😉
I think the best would be if you would try the Profet amplifier!
I can't answer to this question. It is on your taste. The F5 will sound different because the Mosfets.
Greets:
Tyimo