Nelson Pass said:
Thank you very much Nelson for sharing a bit more and pointing to those 6moons.com excellent pic's.
Now is clear that the power supply is a CRCRC and no voltage reg for that matter.
What called my attention were those 4 seemingly AB 2W resistors midway on the main PCB, any clue?
Hi!
Nice review of the F2. I agree that its interior revealed a couple of things. There is no doubt about the power supply. CLC, and the board looks very similar to the one used in F1. (Or, is it the same?) As for the 2 w resistors, they look like source resistors (?). I can’t see if all six of them are in parallel or not. If not, then it looks like 3 of them might have some other purpose?
However,what confuses me is a big electrolytic capacitor near the CCS. I understand that the one near in/out connectors is the output coupling cap, 15.000 uF if I remember correctly.
But the other one (near the front plate) is puzzling me.
Nelson, is it too early for a hint?
By the way, have you noticed how pics are shot? It is possible to see that caps are rated at 85 deg.C, but the most interesting info, their value, is “On the dark side of the moon”
Best regards,
Vix
Nice review of the F2. I agree that its interior revealed a couple of things. There is no doubt about the power supply. CLC, and the board looks very similar to the one used in F1. (Or, is it the same?) As for the 2 w resistors, they look like source resistors (?). I can’t see if all six of them are in parallel or not. If not, then it looks like 3 of them might have some other purpose?
However,what confuses me is a big electrolytic capacitor near the CCS. I understand that the one near in/out connectors is the output coupling cap, 15.000 uF if I remember correctly.
But the other one (near the front plate) is puzzling me.
Nelson, is it too early for a hint?
By the way, have you noticed how pics are shot? It is possible to see that caps are rated at 85 deg.C, but the most interesting info, their value, is “On the dark side of the moon”
Best regards,
Vix
Vix,
I still belive the Power supply is a CRCRC. Part of the blue string of resistors is the second R (near where the PSU cables enter the board) and the lytic you mention near the CCS correspond to the last C which is bypassed by an orange film cap. I would also guess that all lytics (6 of them on each channel) are 15,000uf at 35V.
There are lots of blue power resistor which are rated at 3W. I have seen in the past that Nelson likes to parallel these in order to adjust values and give them a safe rating of 6W (2 parallels) good enough in the case of this circuit, but in this board there seem to be groups of three in some cases such as the source resistors. We still have some resistors to be identified such as the 4 seemingly Allen Bradly's 2W that sit half way on the board.
I still belive the Power supply is a CRCRC. Part of the blue string of resistors is the second R (near where the PSU cables enter the board) and the lytic you mention near the CCS correspond to the last C which is bypassed by an orange film cap. I would also guess that all lytics (6 of them on each channel) are 15,000uf at 35V.
There are lots of blue power resistor which are rated at 3W. I have seen in the past that Nelson likes to parallel these in order to adjust values and give them a safe rating of 6W (2 parallels) good enough in the case of this circuit, but in this board there seem to be groups of three in some cases such as the source resistors. We still have some resistors to be identified such as the 4 seemingly Allen Bradly's 2W that sit half way on the board.
Yes, its not the norm that NP uses part's like those. I wonder what the purpose of those are. I am sure NP had his reasons for using those, as always. A little hint here would be greatly appriciated
Also the "Daddy long legs" resistor puzzles me a bit. Can't imagine NP made a mistake on the board and had to P2P that resistor later on
Steen
BTW, Tony, your P-fets are on their way to Mexico
BTW, BTW Vix if you are talking about the carbon resistors, there is only 4
apassgear said:
Hi
Yes, I thought about this capacitor. So, you say it is just a power supply filter cap?
As for the resistors, I was thinking about those blue ones(nesr the gain mosfet), 6 of them, but three of them seem to be wired separately.
I also have no clue what those four (on the middle of the board) serve for. Only the Master could provide an answer
I suspect that there might be "something else" , which we haven't seen yet...
Regards,
Vix
Vix said:
Hi
Yes, I thought about this capacitor. So, you say it is just a power supply filter cap?
As for the resistors, I was thinking about those blue ones(nesr the gain mosfet), 6 of them, but three of them seem to be wired separately.
I also have no clue what those four (on the middle of the board) serve for. Only the Master could provide an answer
I suspect that there might be "something else" , which we haven't seen yet...
Regards,
Vix
Yes, thats a power supply filter, the last of the string of a CRCRC. Nelson aparently had the intention to put 2 of those lytics if you see the footprint on the board but finnaly decided to replace one of those with a film bypass, guess he found it was better soundwise.
All the components shown on the board are quite clear to me with a couple of exceptions.
Those 6 blue power resistors are 3 for the PSU last R and another 3 for the source resitor of Q1. The other 3 resistor near the back plate are the shunt resistor of the output. Maybe the Master found that using a higher wattage raiting (an array in this case) will lower noise.
"Daddy long legs" still puzzels me too. The only component I don't see clearly on that area is the 0.001u cap (C3 on the posted schem) but sincerely it does not look like a cap and the connection would not suggest this. There is a possibility though even if it is unlikely that could be a parallel resitor to R6, same schematic.
I Suspect that there are some components under the board since the input cap is not seen and you can see the signal cables reaching the underside of the PCB. Something not very common on Nelson’s layout but remember that this amp is of limited production.
The blue cap near the output lytic seems to be the bypass. He has mention that it has a 1uf bypass, though it seems small for that value.
And of course we still have those 4 AB resistors with no clue to them. Maybe there are some other components beneath? Who knows but Nelson and those happy owners of F2's.
Yep, I hope Mr. Pass had a glass to many of that redwine, he apparently loves so much
Might bring him to say something about it I hope I love redwine also, by the way. My favourite is Saint Emillion. French, ofcourse!Yes, I do think so
I have had great results with that Zen regulator But I am not sure;! if NP managed to get this amp that quite, I am not sure it is needed at all? Has that anything to do with this being a Current-source amp???Steen
(not overheated anymore )
Blues said:
This was part of a last minute revision to reduce the turn-on
thump.
Vix said:
Same answer as above.
Vix said:I also have no clue what those four (on the middle of the board) serve for. Only the Master could provide an answer
Power supply decoupling, and they are inductive wire-wound
types.
"This was part of a last minute revision to reduce the turn-on
thump."
So this might well be a reduce value to R6. Smaller C5 could also help on this matter, think so.
"Power supply decoupling, and they are inductive wire-wound
types."
Interesting, but will have to think about this comment. Shunt wirewinds? ...new to me.
Thanks Nelson for giving us some more light to this wondefull amp as we have heard from others.
thump."
So this might well be a reduce value to R6. Smaller C5 could also help on this matter, think so.
"Power supply decoupling, and they are inductive wire-wound
types."
Interesting, but will have to think about this comment. Shunt wirewinds? ...new to me.
Thanks Nelson for giving us some more light to this wondefull amp as we have heard from others.
Hello,
Tony, Steen, thanks for info. Nelson, thank you very much.
My Zen V3 also had a slight turn-on thump. While this was negligible with mid-sensitivity speakers, it was strong enough to torment the Fostex FE 206 E. So, later I added a “Turn-on thump circuit” as described in the “Zen lite” (fig.14). It solved the problem completely.
If the F2 can endure two seconds of short-circuit at the output, then I see no reason this circuit can’t be used.
Even a regulator from ZEN V3 can be used, no problem. However, in the “Return of Zen” article, The Master wrote:
“I found that I preferred the sound of the PI filter over the regulated supply, although I can’t imagine why”.
Perhaps that’s why we don’t see a regulator in the F1 and F2.
Using those four resistors for power supply bypass is still puzzling me a bit.
Nelson, did F2 experience any instability? Or were the resistors employed solely to reduce the hum to a few picowatts?
Best regards,
Vix
Tony, Steen, thanks for info. Nelson, thank you very much.
My Zen V3 also had a slight turn-on thump. While this was negligible with mid-sensitivity speakers, it was strong enough to torment the Fostex FE 206 E. So, later I added a “Turn-on thump circuit” as described in the “Zen lite” (fig.14). It solved the problem completely.
If the F2 can endure two seconds of short-circuit at the output, then I see no reason this circuit can’t be used.
Even a regulator from ZEN V3 can be used, no problem. However, in the “Return of Zen” article, The Master wrote:
“I found that I preferred the sound of the PI filter over the regulated supply, although I can’t imagine why”.
Perhaps that’s why we don’t see a regulator in the F1 and F2.
Using those four resistors for power supply bypass is still puzzling me a bit.
Nelson, did F2 experience any instability? Or were the resistors employed solely to reduce the hum to a few picowatts?
Best regards,
Vix
Nelson Pass said:
I would imagine
in the RCRCRC network The last C is a film cap to ground.
Very interesting and innovative on a constant current draw solid state amp. It appears to me that this type of supply is applied more commonly to SET amps but with higher values of C of what apparently the F2 has. But in the end we have to admit that F2 is nearer to a SET amp as any before, of course to my knowledge.
Thanks again Nelson for your kind support.
Vix said:
So we will have to deal with that turn-on thump, not a pleasant issue.
Didn’t recall reading that comment from Nelson but is interesting to take in consideration.
Adding some sort of an L on a pi filter has been common practice on vacuum state. So it does not puzzle me.
I might conclude that a CLC or a CLCRC with wirewound R could be a very nice Pi filter for this amp. Though we are dealing with 3 amps so the coil will tend to be a rather big one even using a gapped EI core. But have done this before.
Tony,
In one of my posts in your thread about no-feedback Zen, I said NP would leave out the voltage regulator and just clean up the V+ rails with CRC type of filter...there it is using the inherent inductance & resistance of wirewounds. In parallel for better current/power capability.
Allan
In one of my posts in your thread about no-feedback Zen, I said NP would leave out the voltage regulator and just clean up the V+ rails with CRC type of filter...there it is using the inherent inductance & resistance of wirewounds. In parallel for better current/power capability.
Allan
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