yes, very clean work here, no doubt.
Do let us know if there is a change after replacing irf and then the pots.
yes 330pf can be left out, no problem, its just a part of i/p filter.
I really do not know if 2sk1530 can be a drop in replacements
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Rumina,
Nice build. All I can suggest is trying to swap out R10 and R21 from 1k to 500R or 2k and see if it gives you more room to adjust the offset. The DC balance point is not reached and perhaps the Vgs of the MOSFETs are so mismatched that the trimmer cannot reach it. Have you measured the Vgs of the MOSFETs?
Nice build. All I can suggest is trying to swap out R10 and R21 from 1k to 500R or 2k and see if it gives you more room to adjust the offset. The DC balance point is not reached and perhaps the Vgs of the MOSFETs are so mismatched that the trimmer cannot reach it. Have you measured the Vgs of the MOSFETs?
hi prasi and xrk971
thanks for your help.
the new irf610/9610 arrived and it looks much better, with a simple transistor tester i have a 2 pairs with vt 3.72volt and 3.76 volt. i checked the old the mouser one and the where 3.74 volt and 3.54 volt.
the new one behave fine and i can get a stable offset around 0 like i used to see. only thing to solve is that i can't get higher then ca 0.5 volt bias. p1 is at this point ca 2 ohm and p2 2 kohm.
should i change r10/r21 or should i try to change r2/r3 to 68ohm? was the idea to lower the r2/r3 because to much stress for the bc550/bc560?
thanks for your help.
the new irf610/9610 arrived and it looks much better, with a simple transistor tester i have a 2 pairs with vt 3.72volt and 3.76 volt. i checked the old the mouser one and the where 3.74 volt and 3.54 volt.
the new one behave fine and i can get a stable offset around 0 like i used to see. only thing to solve is that i can't get higher then ca 0.5 volt bias. p1 is at this point ca 2 ohm and p2 2 kohm.
should i change r10/r21 or should i try to change r2/r3 to 68ohm? was the idea to lower the r2/r3 because to much stress for the bc550/bc560?
hiprasi
runs stable since 1 1/2 hour so i could get good measurements:
a
bias 51.5ma
r2 59.7mv r3 51.6mv
r10 4.72v r11 4.87v
b
bias 48.6ma
r2 59.9mv r3 49.7mv
r10 4.62v t11 4.83v
this i with the pots max out , offset floats +/- 0.4 mv thats perfect
would be nice to get a bias of 80-100ma (0.8-1v), the heatsink should thake
runs stable since 1 1/2 hour so i could get good measurements:
a
bias 51.5ma
r2 59.7mv r3 51.6mv
r10 4.72v r11 4.87v
b
bias 48.6ma
r2 59.9mv r3 49.7mv
r10 4.62v t11 4.83v
this i with the pots max out , offset floats +/- 0.4 mv thats perfect
would be nice to get a bias of 80-100ma (0.8-1v), the heatsink should thake
With 68 ohm as per original schematic , bias can be adjusted easily above 150mA. Mine is set at 100mA because my heatsink is too small for 150mA.
Glad your DC offset is OK now.
Maybe Juma could tell you what to do for your bias but depending on your headphone 50mA bias should be sufficient.
BR,
Eric
Glad your DC offset is OK now.
Maybe Juma could tell you what to do for your bias but depending on your headphone 50mA bias should be sufficient.
BR,
Eric
Hi Eric
My thoughts exactly...
to rumina,
Sorry I forgot to mention and ask your latest resistor values.
The mentioned del V determines the current thro first stage and second stage...
first stage should be 1mA and second stage should be 4-5 mA.
If thats indeed correct, then I request Juma to post his suggestions here (hoping he still does look into this thread from time to time).
reg
Prasi
My thoughts exactly...
to rumina,
Sorry I forgot to mention and ask your latest resistor values.
The mentioned del V determines the current thro first stage and second stage...
first stage should be 1mA and second stage should be 4-5 mA.
If thats indeed correct, then I request Juma to post his suggestions here (hoping he still does look into this thread from time to time).
reg
Prasi
Yes, that's the spirit, show that lazy bastard who's the boss!
It's only that I don't exactly remember when did I become your employee... ***
I already wrote everything important about the circuit in this thread so only thing requested here is some browsing & reading...
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OMG Juma, aren't you being the arrogant ........???
I didnt expect this from you... and who are you calling lazy???? Me??, who did all the work to bring the design to the fore? or rumina/xrk/Eric ?? who is struggling with all efforts to get your design working in their particular builds...
whatever gave you the impression that I think i hired you as an employee... if you read my post in your senses, i only requested!, since you designed the circuit....
I did refer rumina to the all important post that you posted....
I am truely shocked.... that someone of such good standing (till today) in this great forum can post something like this...
Sorry people, I may be away from this thread for some time.
I am missing working with people who are helpful by nature like APEX/AKSA/Valery/ OStripper... truly genuine people
reg
Prasi
I didnt expect this from you... and who are you calling lazy???? Me??, who did all the work to bring the design to the fore? or rumina/xrk/Eric ?? who is struggling with all efforts to get your design working in their particular builds...
whatever gave you the impression that I think i hired you as an employee... if you read my post in your senses, i only requested!, since you designed the circuit....
I did refer rumina to the all important post that you posted....
I am truely shocked.... that someone of such good standing (till today) in this great forum can post something like this...
Sorry people, I may be away from this thread for some time.
I am missing working with people who are helpful by nature like APEX/AKSA/Valery/ OStripper... truly genuine people
reg
Prasi
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Prasi, your command of English language is obviously lacking.
You made a request to me as if I was the lazy employee of yours.
Here you can learn how to make a polite request in English:
Polite Requests | Learn English
You made a request to me as if I was the lazy employee of yours.
Here you can learn how to make a polite request in English:
Polite Requests | Learn English
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You should try some of your own advice! There are people in this forum from all countries and cultures speaking all languages. Prasi was simply asking for a little advice from someone he obviously used to hold some respect for. Obviously the respect wasn't warranted. If you had a proper grasp of the English language you should have been able to figure that out on your own.
Originally Posted by prasi
... I request Juma to...
We are all learning English as a foreign Language.
From: https://www.merriam-webster.com/dictionary/request
Definition of request for English Language Learners
From: Request | Define Request at Dictionary.com
verb (used with object)
6. to ask for, especially politely or formally: He requested permission to speak.
7. to ask or beg; bid (usually followed by a clause or an infinitive): to request that he leave; to request to be excused.
8. to ask or beg (someone) to do something: He requested me to go.
An externally hosted image should be here but it was not working when we last tested it.
... I request Juma to...
We are all learning English as a foreign Language.
From: https://www.merriam-webster.com/dictionary/request
Definition of request for English Language Learners
- : to ask for (something) in a polite or formal way
- : to ask (someone) to do something in a polite or formal way
From: Request | Define Request at Dictionary.com
verb (used with object)
6. to ask for, especially politely or formally: He requested permission to speak.
7. to ask or beg; bid (usually followed by a clause or an infinitive): to request that he leave; to request to be excused.
8. to ask or beg (someone) to do something: He requested me to go.
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Not quite.
There are a lot of us here that are still learning English as our native language and still not getting it right !
Even though I have been talking english for >64years, this technical Forum has from time to time reminded me that I have more to learn.
exact andrew, life is learning till the last hour.
mouser was fast, the 68ohm resistors are soldered for r2/r3 and now everything is perfect. have a bias around 100ma and the offset is stable floating +- 0.4mv after 2h. i didn't need to change r10/r21 to get the bias down to 0v. amp gets warm but verry moderat due the big heatsink. now i have to wait for the 10k poti to arrive.
would like to thanks prasi and xrk971 for your help. sorry for my laziness didn't match the mosfet, often the adjustment range is big enough for a 2 mosfet design, learned something new. sorry prasi that you get troubled asking questions for me.
nedd to punish myselft for that:
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
mouser was fast, the 68ohm resistors are soldered for r2/r3 and now everything is perfect. have a bias around 100ma and the offset is stable floating +- 0.4mv after 2h. i didn't need to change r10/r21 to get the bias down to 0v. amp gets warm but verry moderat due the big heatsink. now i have to wait for the 10k poti to arrive.
would like to thanks prasi and xrk971 for your help. sorry for my laziness didn't match the mosfet, often the adjustment range is big enough for a 2 mosfet design, learned something new. sorry prasi that you get troubled asking questions for me.
nedd to punish myselft for that:
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
hi eric
i couldn't get the bias higher then 50ma with r2/r3 47ohm, with 68ohm the range is perfect for the recommend 50-100ma, can go up to ca 130ma now.
i will post my expierence with this amp as soon the pot is mounted and 100h passed (i let every amp run in when i know that the thermal stability is ok for this time to test the circuit/parts and to settle the components). i build this amp because i'm a great fan of my pass f5t, with the toshiba transitors and thoshiba mosfets he sounds great, quite similar to a ksa100 or ksa5, detailed, warm with a great flow of music and a little bit of extra bass. since i buyed a ksa100 over 20 years ago i'm addicted to this sound signature.
i couldn't get the bias higher then 50ma with r2/r3 47ohm, with 68ohm the range is perfect for the recommend 50-100ma, can go up to ca 130ma now.
i will post my expierence with this amp as soon the pot is mounted and 100h passed (i let every amp run in when i know that the thermal stability is ok for this time to test the circuit/parts and to settle the components). i build this amp because i'm a great fan of my pass f5t, with the toshiba transitors and thoshiba mosfets he sounds great, quite similar to a ksa100 or ksa5, detailed, warm with a great flow of music and a little bit of extra bass. since i buyed a ksa100 over 20 years ago i'm addicted to this sound signature.