Hi,
Here're my last questions before I can buy all the stuff for my Aleph 60 and start the building process 😀
1) What are the values of R1 and R8. There's only an * on the schematics?
2) R19 = 5622 = 5.622k = 5.62k ?
3) R21 = 1501 = 1.501k = 1.5k ?
4) On the Aleph 2, there was a thermistor in the power supply (plus the one to the ground). Why is this thermistor missing? Will the amp power up smoothly ?
5) Same question regarding the missing capacitor between C20 and Q4 (Aleph 60)?
6) Is it OK to use 5% 3W resistors?
thanks,
Gabriel
Here're my last questions before I can buy all the stuff for my Aleph 60 and start the building process 😀
1) What are the values of R1 and R8. There's only an * on the schematics?
2) R19 = 5622 = 5.622k = 5.62k ?
3) R21 = 1501 = 1.501k = 1.5k ?
4) On the Aleph 2, there was a thermistor in the power supply (plus the one to the ground). Why is this thermistor missing? Will the amp power up smoothly ?
5) Same question regarding the missing capacitor between C20 and Q4 (Aleph 60)?
6) Is it OK to use 5% 3W resistors?
thanks,
Gabriel
For Aleph 60, R8 can be used to adjust any DC offset, if it occurs. R19 is 5.62K and R21 is 1.5K. Hope that helps.. Also, careful with the value of R19, this resistor sets the bias..
Warning: I'm short on sleep and cross-eyed as a result...
but I think R19 is more likely to be 56.2k
I used the Panasonic 3W resistors from Digikey; they're 5% and work just fine.
The thermistor is to slow inrush when you first turn the amp on. Feel free to put one in if you like. Either way, be sure to use a fairly hefty switch. If all else fails, buy a double pole switch and wire the two sides in parallel. The next step after that is to put a 600V .1uF (some people say .01uF) cap across the switch to suppress the spark as the switch makes or breaks contact. If you really want to guild the lily, build a slow start circuit or use a Variac to bring the thing up.
The cap can be added if you like. It's there for stability. I changed my mind about ten or twenty times as I was building my amps, eventually deciding not to put it in...but I hedged my bets by making a place for it on the circuit board, and bought the caps anyway just in case I decided to put them in late some Saturday night. Mine are stable, but then I run them into a very tame load--both pairs are pushing purely resistive drivers. If I were using electrostats or something really freaky, I would consider using the cap.
Grey
but I think R19 is more likely to be 56.2k
I used the Panasonic 3W resistors from Digikey; they're 5% and work just fine.
The thermistor is to slow inrush when you first turn the amp on. Feel free to put one in if you like. Either way, be sure to use a fairly hefty switch. If all else fails, buy a double pole switch and wire the two sides in parallel. The next step after that is to put a 600V .1uF (some people say .01uF) cap across the switch to suppress the spark as the switch makes or breaks contact. If you really want to guild the lily, build a slow start circuit or use a Variac to bring the thing up.
The cap can be added if you like. It's there for stability. I changed my mind about ten or twenty times as I was building my amps, eventually deciding not to put it in...but I hedged my bets by making a place for it on the circuit board, and bought the caps anyway just in case I decided to put them in late some Saturday night. Mine are stable, but then I run them into a very tame load--both pairs are pushing purely resistive drivers. If I were using electrostats or something really freaky, I would consider using the cap.
Grey
In some schematics Mr. Pass uses this convention: resistor values are given as "three digit and multiplier", which means that 1000 in the schematic is a 100 ohm resistor, 1001=1k, 1002=10k and so on..
Karen
You leave that fine lady alone. She may be the only touch of class on this whole sorrid forum!
H.H.
You leave that fine lady alone. She may be the only touch of class on this whole sorrid forum!
H.H.
S'alright, dahlin', I'll take you out.
Given some of the disjointed nonsense I've been spouting recently, it's a wonder they haven't pulled the plug on me. Once I get a little sleep, maybe I'll be more coherent, myself.
Grey
Given some of the disjointed nonsense I've been spouting recently, it's a wonder they haven't pulled the plug on me. Once I get a little sleep, maybe I'll be more coherent, myself.
Grey
Hi,
I've made the layout this weekend. I would appreciate your comments.
Driver and power supply:
Output stage:
best regards,
Gabriel
I've made the layout this weekend. I would appreciate your comments.
Driver and power supply:
An externally hosted image should be here but it was not working when we last tested it.
Output stage:
An externally hosted image should be here but it was not working when we last tested it.
best regards,
Gabriel
Trace width to MOSFET stages
Hello Gabster!
I would make more wide traces from PSU to MOSFET stage connectors (pads), and to the power resistors.
I think those are not enough wide, compare to the others. It looks from the picture between 80-100mils.
What is the width of them?
BR,
Hello Gabster!
I would make more wide traces from PSU to MOSFET stage connectors (pads), and to the power resistors.
I think those are not enough wide, compare to the others. It looks from the picture between 80-100mils.
What is the width of them?
BR,
These are 75 mils. Are large do you think they should be? I should be easy to go up to 100 mils.
I think it should be a bit more wide.
Only on that areas, where the current is higher, than normal. You can check in the schematics easily (FETs drain, source and power resistors, output, etc).
I would go up to 120-150mils, or even more...
Especially at drain, source and power resistor and out areas.
But, it is depend on you, of course.
In construction I would use 70um copper FR4 (hard to get it)
But the normal (35um) is the most popular.
Do not go down to 17.5um FR4.
I post now my version (NOT final) of Aleph 3 pcb.
I am working on it to get a little bit shorter signal path, but it have to look nice also. So, I have criterias...
This is some kind of mix from Kristijan-k and my ideas.
BR,
Only on that areas, where the current is higher, than normal. You can check in the schematics easily (FETs drain, source and power resistors, output, etc).
I would go up to 120-150mils, or even more...
Especially at drain, source and power resistor and out areas.
But, it is depend on you, of course.
In construction I would use 70um copper FR4 (hard to get it)
But the normal (35um) is the most popular.
Do not go down to 17.5um FR4.
I post now my version (NOT final) of Aleph 3 pcb.
I am working on it to get a little bit shorter signal path, but it have to look nice also. So, I have criterias...
This is some kind of mix from Kristijan-k and my ideas.
BR,
Attachments
Hi,
I've updated the layout above according to these considerations. The traces from ±35V as well as the one to the power output resistors are now 200 mils wide. The only one which is smaller (125 mils) is the one between the output power resistors and the SOURCES/R pad (right).
I've updated the layout above according to these considerations. The traces from ±35V as well as the one to the power output resistors are now 200 mils wide. The only one which is smaller (125 mils) is the one between the output power resistors and the SOURCES/R pad (right).
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