Hugh or other builders,
Referring to Hugh's recommendation to change R6 from 10K/1W to a 15K/1W resistor. I have available some 15K/0.5W metal film resistors or some 22K/1W CMF type resistors. Are either of these workable in the R6 position and is one better than the other?
Thanks for the help,
MM
Referring to Hugh's recommendation to change R6 from 10K/1W to a 15K/1W resistor. I have available some 15K/0.5W metal film resistors or some 22K/1W CMF type resistors. Are either of these workable in the R6 position and is one better than the other?
Thanks for the help,
MM
Installed R6 15k ohm and changed the trimmer pot to 500R. The best I could do is around 225mV for the offset. Offset was jumping around like an Aussie jack rabbit 
. Trimmer did not really do much.
I am not happy with the flying leads and the way I have soldered up the boards with some components, so I am going to take a break, enjoy my holiday in Mexico, and then come back and rebuild ( ie: simplify ) portions of the board.
This amp is too good to walk away from, so thanks for all the help, and I will get back at the project in May 2023. Have a great new year and best wishes to all.
Adios Amigo's
. Trimmer did not really do much.I am not happy with the flying leads and the way I have soldered up the boards with some components, so I am going to take a break, enjoy my holiday in Mexico, and then come back and rebuild ( ie: simplify ) portions of the board.
This amp is too good to walk away from, so thanks for all the help, and I will get back at the project in May 2023. Have a great new year and best wishes to all.
Adios Amigo's
Hallow everyone.
Started reading from the first post till page 51 and after that I came here (page 134) and downloaded the "final" (?) schematic from post #2673. From everything I have read till now I didn't found any clear detailed description of the operation of this amplifier except of that in post #1006, #1007, #1010 and only for the input stage (Q1). Anyway.... Can someone tell me not "how good is this amplifier" (I have listened to the compares xrk has published in this thread ?) but what is the dynamic range of this amplifier. To make my self clear. They are very many records in Youtube where you can see instruments (in a classic orchestra) playing "pianissimo" , BUT you don't hear A THING because the feedback of the amplifier "keels" every small (but often) important detail (NO! It is NOT a bad recording. BBC don't make EVER bad recordings). Listening in a not so large sitting room late in night has the amplifier the "potency" to reproduce those small details when plays at, let say, 1~ 1,5W with rather sensitive speakers (I don't like at all headphones as you may conclude). Did someone measure the dynamic range of the amplifier? 60dB ? 80dB ? How many ?
Elias
Started reading from the first post till page 51 and after that I came here (page 134) and downloaded the "final" (?) schematic from post #2673. From everything I have read till now I didn't found any clear detailed description of the operation of this amplifier except of that in post #1006, #1007, #1010 and only for the input stage (Q1). Anyway.... Can someone tell me not "how good is this amplifier" (I have listened to the compares xrk has published in this thread ?) but what is the dynamic range of this amplifier. To make my self clear. They are very many records in Youtube where you can see instruments (in a classic orchestra) playing "pianissimo" , BUT you don't hear A THING because the feedback of the amplifier "keels" every small (but often) important detail (NO! It is NOT a bad recording. BBC don't make EVER bad recordings). Listening in a not so large sitting room late in night has the amplifier the "potency" to reproduce those small details when plays at, let say, 1~ 1,5W with rather sensitive speakers (I don't like at all headphones as you may conclude). Did someone measure the dynamic range of the amplifier? 60dB ? 80dB ? How many ?
Elias
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Hi Elias,
This is my personal opinion of course, but this amp is one of the best Class AB amps I have heard. Very good dynamics, non fatiguing, easy to listen to for all types of genres. Fairly easy to build and setup. There are some tricky aspects to setting the correct DC offset and bias currents but not too bad. I made a thread where you can listen to carefully recorded sound clips of this and other amps with same speakers source and signal levels.
https://www.diyaudio.com/community/threads/virtual-audition-of-very-simple-quasi-mosfet-amp.295286/
You can download the mp3 clips and listen for yourself.
Measured sound freq response at speaker of different amps:
Cheers,
X
This is my personal opinion of course, but this amp is one of the best Class AB amps I have heard. Very good dynamics, non fatiguing, easy to listen to for all types of genres. Fairly easy to build and setup. There are some tricky aspects to setting the correct DC offset and bias currents but not too bad. I made a thread where you can listen to carefully recorded sound clips of this and other amps with same speakers source and signal levels.
https://www.diyaudio.com/community/threads/virtual-audition-of-very-simple-quasi-mosfet-amp.295286/
You can download the mp3 clips and listen for yourself.
Measured sound freq response at speaker of different amps:
Cheers,
X
“Dynamics” is subjective in nature. How many dB means measurement. One correlation is to look at the damping factor at 50Hz where kick drum is. If it is >200, the bass is going to have good dynamics and control. Dynamics also depends on a speakers’s ability to respond near 50Hz and 120Hz where the “chest punch” lies. Single driver full range speakers won’t have this as much. Whereas a FAST/WAW design with a big woofer covering that range will be better.
X
I'm listening with my MA CHP-90 (I make changes also with my 2 different pairs of alnico drivers) in "free air" and in the clip I mentioned I can feel when the punch on "bongos" is with the palm or with the fingers. BUT when we have a classic orchestra ? Those tiny details in low volume ? I like classic music also .
Elias
I'm listening with my MA CHP-90 (I make changes also with my 2 different pairs of alnico drivers) in "free air" and in the clip I mentioned I can feel when the punch on "bongos" is with the palm or with the fingers. BUT when we have a classic orchestra ? Those tiny details in low volume ? I like classic music also .
Elias
X
I'm following in Youtube many channels. Yours of course, nandape's (spcjpnorg), thimios, real world audio, JohnAudioTech,.. among many others. Especially the last I mention is very high in my appreciation for a very specific reason. John is analyzing in a very clear and comprehensive manner for everything he is designing ON THE BENCH ! He have made an amplifier - the JAT-501 - and (to my knowledge) it is a very good one without many gigles and whistles in design, but most important, he explains the value for every component, currents and voltages in the schema and on pcb. I don't want to compare with what is the common practice in very many of the threads. For anyone who speaks English (in elementary school level) and knows Ohm's and Kirchhoff's laws his channel is a real school. I make this statement as a professional engineer in electronics.
You wrote in your post before the previous
"There are some tricky aspects to setting the correct DC offset and bias currents but not too bad."
Yes . Explanation came at post #1006, #1007, #1010
Maybe this amplifier it is the perfect one and attracted my interest but the common practice I mentioned earlier makes me extremely cautious.
Elias
I'm following in Youtube many channels. Yours of course, nandape's (spcjpnorg), thimios, real world audio, JohnAudioTech,.. among many others. Especially the last I mention is very high in my appreciation for a very specific reason. John is analyzing in a very clear and comprehensive manner for everything he is designing ON THE BENCH ! He have made an amplifier - the JAT-501 - and (to my knowledge) it is a very good one without many gigles and whistles in design, but most important, he explains the value for every component, currents and voltages in the schema and on pcb. I don't want to compare with what is the common practice in very many of the threads. For anyone who speaks English (in elementary school level) and knows Ohm's and Kirchhoff's laws his channel is a real school. I make this statement as a professional engineer in electronics.
You wrote in your post before the previous
"There are some tricky aspects to setting the correct DC offset and bias currents but not too bad."
Yes . Explanation came at post #1006, #1007, #1010Maybe this amplifier it is the perfect one and attracted my interest but the common practice I mentioned earlier makes me extremely cautious.
Elias
Elias,
Dynamics are not easy to assess. A very low noise floor might indicate wonderful dynamics, or a very high slew rate might seem better. As XRK has mentioned, and he's measured just about everything, dynamic perception is largely objective.
Consequently it's tricky to be objective about the subjective, but if you have listened to many amplifiers you will know that not one amp does everything well, and you have to choose your poison..........
I would suggest of this amp which is an easy listening amplifier, very low listener fatigue and good for long sessions. And very good bass and imaging........
Hugh
Dynamics are not easy to assess. A very low noise floor might indicate wonderful dynamics, or a very high slew rate might seem better. As XRK has mentioned, and he's measured just about everything, dynamic perception is largely objective.
Consequently it's tricky to be objective about the subjective, but if you have listened to many amplifiers you will know that not one amp does everything well, and you have to choose your poison..........
I would suggest of this amp which is an easy listening amplifier, very low listener fatigue and good for long sessions. And very good bass and imaging........
Hugh
Hugh
I just can guess that you claim (and the design attracted my interest). Speaking about "dynamics". Feedback worries me more. To explain my self (as English is not my native language), how many dB lower to the "dominant signal" the circuit considers that this "tiny signal" (but it is a real signal -not an error) is an error and eliminates it ? That is what I'm asking about. If you read my 2 ~ 3 last posts and you like classic music I believe that you understand my point of view. Of course I like rather high damping factor and very high slew rate. Something more. I like to test the stability (torture) of amplifiers and power supplies with rectangular signal at full power at 8 Ohm load in parallel with 470nF.
Elias
I just can guess that you claim (and the design attracted my interest). Speaking about "dynamics". Feedback worries me more. To explain my self (as English is not my native language), how many dB lower to the "dominant signal" the circuit considers that this "tiny signal" (but it is a real signal -not an error) is an error and eliminates it ? That is what I'm asking about. If you read my 2 ~ 3 last posts and you like classic music I believe that you understand my point of view. Of course I like rather high damping factor and very high slew rate. Something more. I like to test the stability (torture) of amplifiers and power supplies with rectangular signal at full power at 8 Ohm load in parallel with 470nF.
Elias
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Hi,
du lack of time i am changing one more time my plans. I give up with the full DIY mono chassis. Instead of i order a HIFI2000 3U Dissipant case. They have 2 300x120x40mm heatsink with 10mm base. I havec order the 4mm front plate. I will made a custom DIY Front (veneered plywood). I don't change the dual mono configuration. I will just apply layout and wiring skills from Bonsai.
Need yet some drilling and tapping ....
I read whole tread and came on a mistake on my board : in feedback circuit i have 1k8/68 resistors that give me 27db gain .... i will change the 68r with a 82r.
du lack of time i am changing one more time my plans. I give up with the full DIY mono chassis. Instead of i order a HIFI2000 3U Dissipant case. They have 2 300x120x40mm heatsink with 10mm base. I havec order the 4mm front plate. I will made a custom DIY Front (veneered plywood). I don't change the dual mono configuration. I will just apply layout and wiring skills from Bonsai.
Need yet some drilling and tapping ....
I read whole tread and came on a mistake on my board : in feedback circuit i have 1k8/68 resistors that give me 27db gain .... i will change the 68r with a 82r.
Hi
Look at Big Quasi at post #1334.
I can remember that I saw a PCB layout for this as well, but unfortunately I`m not able to find it.
And I don't know if it`s still an unproven design or if it is build by someone.
Lydlaug