@clowkoy : The zeners are meant to provide stable voltages that are divided down by the 5k trimmer pots to set the mosfet currents. You most likely won't need more than 5 to 6V there so 9,1V zeners are rather high (but they do work). However, if you also have 10k for R7 and R8 then the 9.1V zeners are current starved (see ZM's post mentioned above) and no longer give the desired stable voltages. (This could allow the bias to drift say when there is some variation on your AC line.)
If you don't mind using multiple LEDs in place of a zener, have a look at the 2pico mod Colin linked above; it's really cool.
Cheers,
Dennis
If you don't mind using multiple LEDs in place of a zener, have a look at the 2pico mod Colin linked above; it's really cool.
Cheers,
Dennis
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@clowkoy - The 9V1 zeners were provided by @Nelson Pass himself with the kits. 9V1 has been what's been provided with the kits since the transition to the IRFP048 MOSFETs.
Put them in with confidence.
Of course, you can look at mods -- I'd actually encourage it, but I'm just confirming that the 9V1 zener is perfectly fine.
Put them in with confidence.
Of course, you can look at mods -- I'd actually encourage it, but I'm just confirming that the 9V1 zener is perfectly fine.
Again, I appreciate all your help.
I think I'll go with the 6.2 zeners and 3.3k resistors.
I think I'll go with the 6.2 zeners and 3.3k resistors.
Hello, with regards this, I got my kit a few weeks back with the 9,1v zenners but it shipped with 10k resistors and not the 3.3. Is this as you have inferred not going to work?@clowkoy - The 9V1 zeners were provided by @Nelson Pass himself with the kits. 9V1 has been what's been provided with the kits since the transition to the IRFP048 MOSFETs.
Put them in with confidence.
Of course, you can look at mods -- I'd actually encourage it, but I'm just confirming that the 9V1 zener is perfectly fine.
I was planning to do the LED mod, but I’m still acquiring the rest of the bits. Should I not worry and just dive into the LED mod.
The plan is dual mono in a 4U box, Nelson’s bipolar power supplies.
Busy going through all the posts looking for other mods before I commit to melting metal.
^ Install the parts you received in the kit, and it should work as Nelson intends. The packing list helpfully notes the PCB / schematic notations for each part.
I am not sure where I inferred it may not work.
I am not sure where I inferred it may not work.
For clarity in what I posted.
The parts supplied with the kit will work. (I did not make that clear.)
The 6.2v Zenners with 3k3 resistors is an improved system calculated to make the biasing more stable..
The three green LED systems represent "New thinking" on how to achieve the bias and incorporate some self-correction to variation with temperature.
My suggestion is that it is simpler to incorporate either of these on the first build than to go back and de-solder parts..
The parts supplied with the kit will work. (I did not make that clear.)
The 6.2v Zenners with 3k3 resistors is an improved system calculated to make the biasing more stable..
The three green LED systems represent "New thinking" on how to achieve the bias and incorporate some self-correction to variation with temperature.
My suggestion is that it is simpler to incorporate either of these on the first build than to go back and de-solder parts..
About a decade ago i ordered the F6 PCB and transformers from the shop.
About a year ago i got the idea that i should begin to assemble it.
Today i have finally reached Bias and everything looks good so far. (Except that one LED on the positive voltage power supply rail that i have put in the wrong way)
I am going to refer to this amp as vintage equipment when showing it to my friends.
Thanks to everyone in here for the enormous amount of information you have made available. It was a great help.
Special thanks to NP for releasing this excuse to have fun.
About a year ago i got the idea that i should begin to assemble it.
Today i have finally reached Bias and everything looks good so far. (Except that one LED on the positive voltage power supply rail that i have put in the wrong way)
I am going to refer to this amp as vintage equipment when showing it to my friends.
Thanks to everyone in here for the enormous amount of information you have made available. It was a great help.
Special thanks to NP for releasing this excuse to have fun.
Attachments
Sorry @ItsAllInMyHead it was @Dennis Hui post that said the 9.1v zener and the 10k resistor wouldn’t work (wrong gasses and small phone). That’s what’s been supplied with the kit. I guess I hadn’t realised the impact the main transistors have, I had assumed the they were much the same. I have just bought the green leds as that seems optimal. Two transformers and a new case inbound. Time to re-read the thread again…^ Install the parts you received in the kit, and it should work as Nelson intends. The packing list helpfully notes the PCB / schematic notations for each part.
I am not sure where I inferred it may not work.
Is there a wattage range for the dim bulb? I don't have a 100-wat bulb but I have a 60, 200 and 300 watt bulbs.
And we are off! Dual mono, using Nelson’s Bi-Polar power (I am lazy and liked that I could buy a kit).
Started today. Hadn’t bought enough green LEDs (classic read the instructions moment). So soldering on hold. Also thinking about wire connectors as I need to buy them too.
Pondering layout, it’s snug and I think I will stand the toroids up at the front. Need to play about and source a decent bracket (x2) if I do that. Any suggestions gratefully received.
Usual thanks to Mr Pass, the DIY Audio Store and the merry band of hero’s on here 🥳👏🫡
Started today. Hadn’t bought enough green LEDs (classic read the instructions moment). So soldering on hold. Also thinking about wire connectors as I need to buy them too.
Pondering layout, it’s snug and I think I will stand the toroids up at the front. Need to play about and source a decent bracket (x2) if I do that. Any suggestions gratefully received.
Usual thanks to Mr Pass, the DIY Audio Store and the merry band of hero’s on here 🥳👏🫡
I thought you might like an update.
The amp has now been playing for a week without any issues.
It is by far the best amplifier i have ever had.
It knocks the socks of my Purifi based mono blocks that i was very impressed with.
Confusingly, this newfound audio nirvana has left me wondering what else i might be missing. Questions like "What difference would dual mono power supplies make?" keeps crossing my mind. This is clearly the completion of my transition to a greedy boy.
I think ill go listen to some music 😀
The amp has now been playing for a week without any issues.
It is by far the best amplifier i have ever had.
It knocks the socks of my Purifi based mono blocks that i was very impressed with.
Confusingly, this newfound audio nirvana has left me wondering what else i might be missing. Questions like "What difference would dual mono power supplies make?" keeps crossing my mind. This is clearly the completion of my transition to a greedy boy.
I think ill go listen to some music 😀
Found some brackets at the local hardware store, so the layout is coming on.
Does anyone know the part number for the kit blue LEDs? I put red ones in my first F6 and figured I would swap at the same time I retro the ZenMod green LEDs.
I just need to think about the various board connectors and wiring, none of which I have. I would prefer to solder them all, but I like the ease of removal should I want to tweak later.
If anyone has any observations on the layout please do holler, I’d really appreciate that before I cut metal.
Does anyone know the part number for the kit blue LEDs? I put red ones in my first F6 and figured I would swap at the same time I retro the ZenMod green LEDs.
I just need to think about the various board connectors and wiring, none of which I have. I would prefer to solder them all, but I like the ease of removal should I want to tweak later.
If anyone has any observations on the layout please do holler, I’d really appreciate that before I cut metal.
Attachments
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This is basically how I did mine (also dual mono). Worked out quite well.Found some brackets at the local hardware store, so the layout is coming on.
Does anyone know the part number for the kit blue LEDs? I put red ones in my first F6 and figured I would swap at the same time I retro the ZenMod green LEDs.
I just need to think about the various board connectors and wiring, none of which I have. I would prefer to solder them all, but I like the ease of removal should I want to tweak later.
If anyone has any observations on the layout please do holler, I’d really appreciate that before I cut metal.
Halauhula:
They're either #6-32 or M4 standoffs; I have more of the latter in stock but it honestly could have been either. They have very similar diameters and both are quite sturdy. My Imperial supply was largely purchased at Grainger.com which, when Imperial was my standard years ago, periodically offered standoffs at very steep discounts. Grainger's regular pricing seems ridiculous to me. I've almost entirely migrated to metric standoffs and fasteners which I purchase at AliExpress.com. Again, I look for the occasional sale (the prices are already low and the sales there typically provide incremental discounts of 5-15%) and buy in bulk. Shipping from China usually takes about 10 days.
Regards,
Scott
They're either #6-32 or M4 standoffs; I have more of the latter in stock but it honestly could have been either. They have very similar diameters and both are quite sturdy. My Imperial supply was largely purchased at Grainger.com which, when Imperial was my standard years ago, periodically offered standoffs at very steep discounts. Grainger's regular pricing seems ridiculous to me. I've almost entirely migrated to metric standoffs and fasteners which I purchase at AliExpress.com. Again, I look for the occasional sale (the prices are already low and the sales there typically provide incremental discounts of 5-15%) and buy in bulk. Shipping from China usually takes about 10 days.
Regards,
Scott
@SRMcGee: thank you for the info! I had priced out 8-32 at Fastenall, and they were quite expensive. 6-32 should be more reasonable, and since you are satisfied with their sturdiness, I will go with that. I will also look at metric but I think China tariffs and aluminum tariffs are going to significantly reduce price advantage of AliXpress.
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