That sounds interesting, George. Most cheap UL flameproof types steer away from carbon to Metal Oxide etc which may not be a good proposition for audio, nor thick film SMD, it seems.
Ahh...from the website they have one thru-hole range of CF resistors up to 1W. standard types with a flameproof lacquer only. I think it is much as the usual 1/4 - 1W types you buy, unfortunately. Perhaps they don't list the type you posted or it's SMD thick film?
Ahh...from the website they have one thru-hole range of CF resistors up to 1W. standard types with a flameproof lacquer only. I think it is much as the usual 1/4 - 1W types you buy, unfortunately. Perhaps they don't list the type you posted or it's SMD thick film?
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Thanks George.
Nice as they may be, I don't think I could wait out the non-stock lead time or minimum order quantity for NCR grade parts - not even listed on Yageo's website either.
They will still be helical cut and have variable inductance, like standard parts, according to the value and the resistivity of the carbon coating used in each resistance decade etc.
"Flameproof" has a strange industry definition. Here it means withstanding 4 x overvoltage for a second or so without arcing. Hmm.. so just make long resistors and you get "flameproof" ratings!
Ahh...you live and learn, eh?
Nice as they may be, I don't think I could wait out the non-stock lead time or minimum order quantity for NCR grade parts - not even listed on Yageo's website either.
They will still be helical cut and have variable inductance, like standard parts, according to the value and the resistivity of the carbon coating used in each resistance decade etc.
"Flameproof" has a strange industry definition. Here it means withstanding 4 x overvoltage for a second or so without arcing. Hmm.. so just make long resistors and you get "flameproof" ratings!
Ahh...you live and learn, eh?
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I don't think it's really critical, but carbon or ceramic composition will have the least inductance and so would be preferred, and maybe less expensive.
In any case, if the amplifier oscillates then it's really a design flaw; above picking a low-inductance resistor, I think it's misguided to focus on surge capability for a zobel resistor which is only in danger in the case of a flaw in the amplifier.
- keantoken
In any case, if the amplifier oscillates then it's really a design flaw; above picking a low-inductance resistor, I think it's misguided to focus on surge capability for a zobel resistor which is only in danger in the case of a flaw in the amplifier.
- keantoken
Ken, they'd be fine.....
I don't think the inductance is critical, either. There's 1.4uH on the output coil, and up to 0.5mH - 500 uH - in the crossover on the speaker, plus another 2000uH or so in the voice coil. It's possible we are concerned about something that is really not important here. What is important is the high frequency stability of the amp, of course.
Just use at least a 1W resistor on the Zobel and ensure always that it is mounted 1/8" above the pcb surface to proetect it against resistor self-immolation, a sure sign of electronic protest.
Cheers,
Hugh
I don't think the inductance is critical, either. There's 1.4uH on the output coil, and up to 0.5mH - 500 uH - in the crossover on the speaker, plus another 2000uH or so in the voice coil. It's possible we are concerned about something that is really not important here. What is important is the high frequency stability of the amp, of course.
Just use at least a 1W resistor on the Zobel and ensure always that it is mounted 1/8" above the pcb surface to proetect it against resistor self-immolation, a sure sign of electronic protest.
Cheers,
Hugh
It's Alive !
Many thanx to Hugh , Swordfishy and everyone involved in this project .
It's still in pieces on a table and not in my main system yet , but the sounds coming out of a lil pair of 601 B&W's is wonderful
this weekend i'll have a chance to put it into my main system and then report back , but so far very pleased .
Thanx everyone , cheers Woody
Many thanx to Hugh , Swordfishy and everyone involved in this project .
It's still in pieces on a table and not in my main system yet , but the sounds coming out of a lil pair of 601 B&W's is wonderful
this weekend i'll have a chance to put it into my main system and then report back , but so far very pleased .
Thanx everyone , cheers Woody
Gr8, Woody!!
We would really appreciate photos and a few comments on the sound quality.... you know the drill!
This amp, at 400mA quiescent, operates to just shy of 6W in Class A. This is a very generous margin, and is, I think, partly responsible for the wonderful sound quality.
No hum I hope?
If you have this problem, buy the score, teach the amp the words. It will never hum again..... (groan....)
Cheers,
Hugh
We would really appreciate photos and a few comments on the sound quality.... you know the drill!
This amp, at 400mA quiescent, operates to just shy of 6W in Class A. This is a very generous margin, and is, I think, partly responsible for the wonderful sound quality.
No hum I hope?
If you have this problem, buy the score, teach the amp the words. It will never hum again..... (groan....)
Cheers,
Hugh
What a great project!
Exactly what I was looking for.
Sadly I was too late for the first group buy.
Now I´m little afraid of missing the second because 2 weeks holiday in the desert!
Hugh
Would you please set me on the list of the (hopefully comming) next group buy for:
2 sets with parts (i.e. 4 pcb)
Thanks for your effort and all the other experts in sharing ideas and this wonderfull design.
Best regards
Exactly what I was looking for.
Sadly I was too late for the first group buy.
Now I´m little afraid of missing the second because 2 weeks holiday in the desert!
Hugh
Would you please set me on the list of the (hopefully comming) next group buy for:
2 sets with parts (i.e. 4 pcb)
Thanks for your effort and all the other experts in sharing ideas and this wonderfull design.
Best regards
Hugh's answer when i asked the same question " I measure the bias current across the 0.1R source resistors. I set 40mV, which corresponds exactly to 400mA. You'd find it's rock steady and quite non-critical to set. The use of three diodes in a string and a much reduced rheostat (read 'pot') all in series makes this adjustment a doddle. "
Hugh , could you add this to your tutorial for us newb's ? actually after you told me , it all became very clear .
cheers Woody
Steve, Woody,
I amended this in the build instructions:
My apologies, difficult to put it all in first shot.....
Sonocon,
I'm waiting for two things before commencing another group buy.
#1 We need another ten people to chime in with their assessment of the amp. If the consensus is positive for all ten, no major problems, then it is likely the design is mature enough for a second group buy. I have received criticisms of hum in the design, which I personally have not experienced (in fact it's the quietest design I've ever 'heard'!), but which I must take seriously.
#2 I would prefer another twenty five orders, that is, fifty pcbs. Then an order for 100 boards is viable and I will have a reserve.
Cheers,
Hugh
I amended this in the build instructions:
My apologies, difficult to put it all in first shot.....
Sonocon,
I'm waiting for two things before commencing another group buy.
#1 We need another ten people to chime in with their assessment of the amp. If the consensus is positive for all ten, no major problems, then it is likely the design is mature enough for a second group buy. I have received criticisms of hum in the design, which I personally have not experienced (in fact it's the quietest design I've ever 'heard'!), but which I must take seriously.
#2 I would prefer another twenty five orders, that is, fifty pcbs. Then an order for 100 boards is viable and I will have a reserve.
Cheers,
Hugh
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First impressions .....
Last nite I fired her up for the first time . initial adjustment was easy as pie and has remained very stable . after an hour or so hooked it up to a pair of b&w bookshelfs and ok , nice , but nothing really stood out . there was no Wow can you feel that bass or OMG what brilliant highs . instead as i listened longer the wow factor came in the way of " damn this is really very pleasant and well balanced sound" .
Today I hooked it up into my main system and gave it a really good workout from both digital (cd) and analog (vinyl) sources ranging from Sugarland and Tanya Tucker to Creedence Clearwater Revival and Jimi Hendrix . Listening right now to the Gary Burton Quartet and Pat Methany .
Female vocals superb and acoustic guitar you can feel the strings on your fingertips . The piano test not so much . ok but not outstanding . To me at least , it seems to be very tolerant of less than great sources . unlike some other amps i've played with however still sounds outstandingly accurate with good ones .
I know it's only been one day of seriously casual listening , but if I was to sum up my impressions of this amp I'd have to say that it was very "smooth" and very satisfying . totally non fatiguing . I've been listening to it's beautiful sounds going on 12 hrs now and I'm very impressed . Definitely a keeper
System :
NAD preamp
Yamaha cd player
Micro-Seiki dd40/denon 103r turntable/cart
ADS LS1230 speakers
other builds :
Peter Daniels gainclone
Pass F5
Cheers , Woody
Last nite I fired her up for the first time . initial adjustment was easy as pie and has remained very stable . after an hour or so hooked it up to a pair of b&w bookshelfs and ok , nice , but nothing really stood out . there was no Wow can you feel that bass or OMG what brilliant highs . instead as i listened longer the wow factor came in the way of " damn this is really very pleasant and well balanced sound" .
Today I hooked it up into my main system and gave it a really good workout from both digital (cd) and analog (vinyl) sources ranging from Sugarland and Tanya Tucker to Creedence Clearwater Revival and Jimi Hendrix . Listening right now to the Gary Burton Quartet and Pat Methany .
Female vocals superb and acoustic guitar you can feel the strings on your fingertips . The piano test not so much . ok but not outstanding . To me at least , it seems to be very tolerant of less than great sources . unlike some other amps i've played with however still sounds outstandingly accurate with good ones .
I know it's only been one day of seriously casual
listening , but if I was to sum up my impressions of this amp I'd have to say that it was very "smooth" and very satisfying . totally non fatiguing . I've been listening to it's beautiful sounds going on 12 hrs now and I'm very impressed . Definitely a keeper System :
NAD preamp
Yamaha cd player
Micro-Seiki dd40/denon 103r turntable/cart
ADS LS1230 speakers
other builds :
Peter Daniels gainclone
Pass F5
Cheers , Woody
Thanks Woody, great assessment.
Glad it doesn't hum. You obviously bought the score before you auditioned? Knew the words?
Mine too is laid out on a table - actually, a sturdy piece of cardboard - and there is no hum on mine either.... a couple of guys are experiencing hum issues and it could be the earthing to mains ground.
I have orders for maybe 8 boards now, only 42 to go.
I will start another thread.....
Thanks again, these impressions are incredibly important for guys considering building the FetZilla. And yes, this is a 'late night single malt whisky' amplifier!
Oh, and I should ask, you've built an F5. I've not heard one yet, but people say they are wonderful. How does the FetZilla compare? From an examination of the topology, I'd say the F5 would be more accurate, but not quite as laid back?
Cheers,
Hugh
Glad it doesn't hum. You obviously bought the score before you auditioned? Knew the words?
Mine too is laid out on a table - actually, a sturdy piece of cardboard - and there is no hum on mine either.... a couple of guys are experiencing hum issues and it could be the earthing to mains ground.
I have orders for maybe 8 boards now, only 42 to go.
I will start another thread.....
Thanks again, these impressions are incredibly important for guys considering building the FetZilla. And yes, this is a 'late night single malt whisky' amplifier!
Oh, and I should ask, you've built an F5. I've not heard one yet, but people say they are wonderful. How does the FetZilla compare? From an examination of the topology, I'd say the F5 would be more accurate, but not quite as laid back?
Cheers,
Hugh
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"And yes, this is a 'late night single malt whisky' amplifier!" exzactly i couldn't have said it better !
is this the amp that will make everyone that builds it stop searching for something more ? naaaa , however right now it's top tier in my system and even if it gets displaced i'll have a switch for those times i need that 'late night single malt whisky' amplifier!" sound .
yes it's that good !!!
thing is , saying that any amp is this or that is sooo subjective and the sound you hear is not just the amp , but the whole string of everything from your source to your speakers to the room then to your ears .
comparing it to an F5 ... two completely different sonic characteristics . I invested a lot of time and money building my F5 and personally I was disappointed . That said , it was a great learning experience and I'm sure it will not be the last Nelson Pass design that i build . let's say analytical vs. laid back , but remember that's my build in my system and my ears .
orders for only 4 other boards ? geez Hugh you've missed a lot of requests . you really need a new thread to keep track . i've probably counted at least 2 dozen besides mine .
cheers Woody
i couldn't have said it better ! is this the amp that will make everyone that builds it stop searching for something more ? naaaa , however right now it's top tier in my system and even if it gets displaced i'll have a switch for those times i need that 'late night single malt whisky' amplifier!" sound .
yes it's that good !!!
thing is , saying that any amp is this or that is sooo subjective and the sound you hear is not just the amp , but the whole string of everything from your source to your speakers to the room then to your ears .
comparing it to an F5 ... two completely different sonic characteristics . I invested a lot of time and money building my F5 and personally I was disappointed . That said , it was a great learning experience and I'm sure it will not be the last Nelson Pass design that i build . let's say analytical vs. laid back , but remember that's my build in my system and my ears .
orders for only 4 other boards ? geez Hugh you've missed a lot of requests . you really need a new thread to keep track . i've probably counted at least 2 dozen besides mine .
cheers Woody
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