ZM spent some time with Elephants, and their favorite way of amusing me was farting in my ears
lucky result is that I'm not hearing difference between decent parts ; dunno, maybe still not because of ears, but Elephants said to me that these parts are tiny, so .........
it must be change in Iq, or you're imagining ...... or you indeed had Drek wirewound resistors
however, if you change mosfets type, you'll hear difference
lucky result is that I'm not hearing difference between decent parts ; dunno, maybe still not because of ears, but Elephants said to me that these parts are tiny, so .........
it must be change in Iq, or you're imagining ...... or you indeed had Drek wirewound resistors
however, if you change mosfets type, you'll hear difference
1N5231 is 5.1V jobbie
regarding everything else - resolder and lift one leg of part , then check with measurement
band on diode body goes on side where stripe is on pcb ; you have that most likely in any basic electronics book, same as wiki page (click me!) and numerous tutorials
nothing wrong that you asked here, but reading these books can help you immensely in basics and later in advanced area, in much more effective and pleasant way than typing questions ...... especially when you read something you even don't know that you don't know
happens to me all the time
Thank you Zen,
The link is appreciated, don't know why I didn't think of wiki. And it did answer my question . . . I will read and try to absorb more.
I know enough to know that I don't really know anything. The problems come from not knowing what questions to ask.
I will press on.
ZM spent some time with Elephants, and their favorite way of amusing me was farting in my ears
lucky result is that I'm not hearing difference between decent parts ; dunno, maybe still not because of ears, but Elephants said to me that these parts are tiny, so .........
it must be change in Iq, or you're imagining ...... or you indeed had Drek wirewound resistors
however, if you change mosfets type, you'll hear difference
ZM has spent time in many meaningful ways and has valuable experience to share.
I shall change the MOSFETs when I get the opportunity. Do the IRFP150 need to be matched?
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I found the discussion of source resistance in one of the other F6 threads.
The diyAudio Firstwatt F6
I still really like the sound of the amp where I left it. After final thermal eq, bias is at 1.85A.
The diyAudio Firstwatt F6
I still really like the sound of the amp where I left it. After final thermal eq, bias is at 1.85A.
Anand,
Finally got back to the F6. As you suggested in post 3555 I measured the gate to source voltages for Q1 and Q2 as follows: Humming channel A Q1 4.35V Q2 4.37V
channel B Q1 4.68V Q2 4.68V
The odd thing is that the amp worked until I drew the spark. Thank you for the continuing support. Regards, Bill
Finally got back to the F6. As you suggested in post 3555 I measured the gate to source voltages for Q1 and Q2 as follows: Humming channel A Q1 4.35V Q2 4.37V
channel B Q1 4.68V Q2 4.68V
The odd thing is that the amp worked until I drew the spark. Thank you for the continuing support. Regards, Bill
Bill,
Can you measure across Z1 and Z2 of each of the channels? And remeasure on both sides of R11, relative to ground for each of the channels and report here? Recall that your voltages around R11 were a little unusual in post 3555.
Do your soldering joints look smooth and shiny? Have you posted hirez photos of your F6 channel A and channel B builds already?
Best,
Anand.
Can you measure across Z1 and Z2 of each of the channels? And remeasure on both sides of R11, relative to ground for each of the channels and report here? Recall that your voltages around R11 were a little unusual in post 3555.
Do your soldering joints look smooth and shiny? Have you posted hirez photos of your F6 channel A and channel B builds already?
Best,
Anand.
Bill,
So your zener voltages are fine, and now you have normal voltages on both sides of R11 for each channel as well.
Your MOSFETS clearly should be warm, so I am at a loss as to the source of your hum. Does it hum without a source connected to the amp? Does it hum with the input connected to ground? Have you tried a different source connected to the amp? I have a feeling we have answered these questions before. Check suspicious soldering joints as well as all grounds. Goes back to my post here.
I have looked at some of your previous pics of your build and it appears clean.
Best,
Anand.
So your zener voltages are fine, and now you have normal voltages on both sides of R11 for each channel as well.
Your MOSFETS clearly should be warm, so I am at a loss as to the source of your hum. Does it hum without a source connected to the amp? Does it hum with the input connected to ground? Have you tried a different source connected to the amp? I have a feeling we have answered these questions before. Check suspicious soldering joints as well as all grounds. Goes back to my post here.
I have looked at some of your previous pics of your build and it appears clean.
Best,
Anand.
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Reply to Poseiden's Voice and Zen Mod
Gentlemens . . .
I finally got around to poking around my F6 with the 1K resistor in the place of R7. The Zener diodes I am using came with the kit. There were 2 different ones that were ID'd with markings that I was able to make out by taking photos and blowing them up. Both diodes had some writing on them, with 59 being what I could make out for Z1 and the Z2 diodes had 23 written on them. I measured the voltages and current across the Z1s and Z2s. They were 5.07V(20.9 mA) for the Z1s and 6.03V(6.4 mA) for the Z2s. While the 20.9 mA value is higher than the max value of 18 mA ZenMod quoted, it is within ~10% that measurement.
So gents . . . should I be concerned?
rolf
Gentlemens . . .
I finally got around to poking around my F6 with the 1K resistor in the place of R7. The Zener diodes I am using came with the kit. There were 2 different ones that were ID'd with markings that I was able to make out by taking photos and blowing them up. Both diodes had some writing on them, with 59 being what I could make out for Z1 and the Z2 diodes had 23 written on them. I measured the voltages and current across the Z1s and Z2s. They were 5.07V(20.9 mA) for the Z1s and 6.03V(6.4 mA) for the Z2s. While the 20.9 mA value is higher than the max value of 18 mA ZenMod quoted, it is within ~10% that measurement.
So gents . . . should I be concerned?
rolf
Bill,
If there is hum audible with the In(+) connected to ground then the amp is at fault and not the Oppo. The fact that the hum is lower in volume is important. I don't think your passive parts are at fault here, but I am wondering if others recommend trying a new set of matched pair of JFETS, IRPF240's, etc...I would make 100% sure your soldering is good on the JFETS in particular and they are handled gently. I have an ESD sheet on my bench that is grounded along with a wrist wrap whenever I am handling JFETS.
Best,
Anand.
If there is hum audible with the In(+) connected to ground then the amp is at fault and not the Oppo. The fact that the hum is lower in volume is important. I don't think your passive parts are at fault here, but I am wondering if others recommend trying a new set of matched pair of JFETS, IRPF240's, etc...I would make 100% sure your soldering is good on the JFETS in particular and they are handled gently. I have an ESD sheet on my bench that is grounded along with a wrist wrap whenever I am handling JFETS.
Best,
Anand.
Rolf, just to be sure you didn’t misread ZMs post. He thought 18ma was ALREADY not good (too much!), and now you are pushing 20mA. Please, re-read the warnings everyone raised when you mentioned that 1K resistor.
I believe most said that this probably suggested problems elsewhere.
Sorry! Rafa.
Finally, complete my long-standing F6 amp.
This is one of my first Nelson's design ClassA amp that i started building when i first joined this forum, it has been singing naked on the bench all along with different power supply used.
I am using 2 PicoDumbs' green led mods and used slightly beefier mosfets. Currently running at 1.65A bias. Heatsinks temp is mostly arround 56 degC.
Found a really cheap chassis from Aliexpress that fits Conrad's heatsinks perfectly.
The Smps is from Micro-Audio (Cresnet) 600W +/- 25Vdc.
Its filtering capacitor bank is 44,000uF per rail. Powering up successfully without any issues every time. The F6 is totally quiet when the music paused, with no hums and hiss!
Many thanks to Nelson, Jim(6L6) ,2 PicoDumbs, TunstenAudio and many others for sharing their design and mods generously.
This is one of my first Nelson's design ClassA amp that i started building when i first joined this forum, it has been singing naked on the bench all along with different power supply used.
I am using 2 PicoDumbs' green led mods and used slightly beefier mosfets. Currently running at 1.65A bias. Heatsinks temp is mostly arround 56 degC.
Found a really cheap chassis from Aliexpress that fits Conrad's heatsinks perfectly.
The Smps is from Micro-Audio (Cresnet) 600W +/- 25Vdc.
Its filtering capacitor bank is 44,000uF per rail. Powering up successfully without any issues every time. The F6 is totally quiet when the music paused, with no hums and hiss!
Many thanks to Nelson, Jim(6L6) ,2 PicoDumbs, TunstenAudio and many others for sharing their design and mods generously.