hi,
i'm trying to build an F1 amp for my k1000s and have been studying the specs and coming up with a BOM.
I am a total newb at this though, and i have some questions about the parts:
1. some resistors are labeled as 1 3W. does this mean
1 ohm 3W rated? also, what kind of resistor should be
used, metal oxide, wirewound etc? does it matter?
2. There's a 20V zener diode. i could only find one
kind of these, is there any other rating aside from
20V that i need to look for? like resistance or current?
3. there's also two 5K potentiometers. in the picture,
these look like blue squares with a round button. what
kind of potentiometer is this? the ones i found look
like volume knobs, can this be used too? there's also
some cermet pots, are these ok to use? what ratings other than 5k do i look for?
4. there are two thermistors in the PSU specs (labeled
as TH and TH located beside C2 adn C3). would these
be the same spec as TH1 and TH2?
thank you very much guys!
i'm trying to build an F1 amp for my k1000s and have been studying the specs and coming up with a BOM.
I am a total newb at this though, and i have some questions about the parts:
1. some resistors are labeled as 1 3W. does this mean
1 ohm 3W rated? also, what kind of resistor should be
used, metal oxide, wirewound etc? does it matter?
2. There's a 20V zener diode. i could only find one
kind of these, is there any other rating aside from
20V that i need to look for? like resistance or current?
3. there's also two 5K potentiometers. in the picture,
these look like blue squares with a round button. what
kind of potentiometer is this? the ones i found look
like volume knobs, can this be used too? there's also
some cermet pots, are these ok to use? what ratings other than 5k do i look for?
4. there are two thermistors in the PSU specs (labeled
as TH and TH located beside C2 adn C3). would these
be the same spec as TH1 and TH2?
thank you very much guys!
1: 1ohm/3Watt is correct. From the picture I believe Nelson uses wirewound.
2: You can’t go wrong with 1.5Watt Zener.
3: http://be.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=108553&N=401
Has some more data, This would be a good pot to use.
4: Nelson made the CL60 famous; they will all be the same type.
/Hugo
2: You can’t go wrong with 1.5Watt Zener.
3: http://be.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=108553&N=401
Has some more data, This would be a good pot to use.
4: Nelson made the CL60 famous; they will all be the same type.
/Hugo
Hi choariwap,
I have built a similar amp. There is a thread somewhere with details. Search for SOZ Transconductance. The resistors are Panasonic 3W metal oxide types. Any 3W resistors would do fine. The pots are 1/2W Bourns trimmers IIRC. At least that's what I used. Again this is not critical. And the zeners can be iN52xx or iN47xx series parts.
Cheers,
Graeme
I have built a similar amp. There is a thread somewhere with details. Search for SOZ Transconductance. The resistors are Panasonic 3W metal oxide types. Any 3W resistors would do fine. The pots are 1/2W Bourns trimmers IIRC. At least that's what I used. Again this is not critical. And the zeners can be iN52xx or iN47xx series parts.
Cheers,
Graeme
Hi Choaiwap,
I think you got all answers.
I just want to add some mud.
I have tried both metal oxide and wirewound resistors,
and found no real difference in sound while I prefer
wirewound power resistors.
I understand the protective 20V zener is there to limit maximum
Gate-to-Source voltage to 20V, and in normal operation, no
current flow through it. In my opinion, the probability of Vgs
exceeding 20V is very low. I just use small size (0.5W) two 9.1V
zeners in series. So far, so good.
Any NTC type of 10R/5A or similar is acceptable themistor.
F1 is the amplifier we should have. Enjoy!!!
I think you got all answers.
I just want to add some mud.
I have tried both metal oxide and wirewound resistors,
and found no real difference in sound while I prefer
wirewound power resistors.
I understand the protective 20V zener is there to limit maximum
Gate-to-Source voltage to 20V, and in normal operation, no
current flow through it. In my opinion, the probability of Vgs
exceeding 20V is very low. I just use small size (0.5W) two 9.1V
zeners in series. So far, so good.
Any NTC type of 10R/5A or similar is acceptable themistor.
F1 is the amplifier we should have. Enjoy!!!
thanks for all the replies that takes care of the components.
now, i have somemore questions
1. what heatsink specs should i look for? i've been shopping on rs and farnell and the most reasonable ones i found are 300x300x40. what measurements would be enough for the f1?
2. on thermal pads: i have been tinkering with PC parts before and the general consensus for pc parts is that thermal grease is better than pads (something like arctic silever5). but in audio circles silpads are recommended over thermal grease. why is this so? i would imagine that conductivity issues would also be critical for sensistive PC parts like the processor.
thanks to everyone again!
that takes care of the components.now, i have somemore questions
1. what heatsink specs should i look for? i've been shopping on rs and farnell and the most reasonable ones i found are 300x300x40. what measurements would be enough for the f1?
2. on thermal pads: i have been tinkering with PC parts before and the general consensus for pc parts is that thermal grease is better than pads (something like arctic silever5). but in audio circles silpads are recommended over thermal grease. why is this so? i would imagine that conductivity issues would also be critical for sensistive PC parts like the processor.
thanks to everyone again!
You can calculate the heat sink pretty accurate by multiplying the thermal resistance with the power to dissipate. E.g.: the mentioned heat sink has a thermal resistance of 0.28°C/W, the power to dissipate is 100W per channel. 0.28 * 100 = 28. Add the ambient temperature to that number and you’re done.
If you can get your hands on good, (read thin) mica, you might try them.
Silpad is easier to work with, as you don’t need the grease.
Have a look at the different datasheets provide by Farnell. Search for SIL-PAD and KAPTON.
/Hugo
If you can get your hands on good, (read thin) mica, you might try them.
Silpad is easier to work with, as you don’t need the grease.
Have a look at the different datasheets provide by Farnell. Search for SIL-PAD and KAPTON.
/Hugo
awpagan said:
Adresses, phone and bank account numbers from 30 years ago.
Biggest problem are passwords, i remember everyone i ever used, but knowing which one is the latest is a bummer.
It's like toiletpaper in the supermarket, 50 different types and brands but not a clue which one to buy.
(i know a few who bring their 1 & only along when they go transcontinental. trans-incontinental ?)
jacco vermeulen said:
Adresses, phone and bank account numbers from 30 years ago.
Biggest problem are passwords, i remember everyone i ever used, but knowing which one is the latest is a bummer.
It's like toiletpaper in the supermarket, 50 different types and brands but not a clue which one to buy.
(i know a few who bring their 1 & only along when they go transcontinental. trans-incontinental ?)
Is the "1 and only" the same as "the 1 that must be odey'd"
allan
Sorry guys for hijacking the thread
thanks again for the responses!
i'm almost there in terms of BOM... one last thing (i hope) to ask:
i've been looking for a toroidal transfo over at rs and farnell, but the best one i could find is a clairtronic 300VA 18V one. Will this be enough? I read in other posts that recommended is around 400-500VA.
thanks!
i'm almost there in terms of BOM... one last thing (i hope) to ask:
i've been looking for a toroidal transfo over at rs and farnell, but the best one i could find is a clairtronic 300VA 18V one. Will this be enough? I read in other posts that recommended is around 400-500VA.
thanks!
hi guys,
me again
i've shopped around for heatsinks and the best one i can find is .3 C/W (measures ar 300x300x40).
ambient temps where i live would be around 25 - 30 C.
this would put operating temp at 55 - 60C. is this feasible for the F1 or would i need to augment the heatsink? (thinking of some fans for a bit of active cooling)
thanks!
me again
i've shopped around for heatsinks and the best one i can find is .3 C/W (measures ar 300x300x40).
ambient temps where i live would be around 25 - 30 C.
this would put operating temp at 55 - 60C. is this feasible for the F1 or would i need to augment the heatsink? (thinking of some fans for a bit of active cooling)
thanks!
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