Thank you Sander for the vote of confidence. I am banging my head now trying figure out the heat sinks. R-Theta (local company) has a nice thermal simulator on their siteSSassen said:
that helps a great deal. Still heat sinks are a real challenge. I have several old Bryston amps here that I intend to gut and re-use the boxes, switches, connectors, etc., - they are real nice.
Would it be fair to say that if I reduce the amp's Class A power by a factor of 2, from 100W to 50 W, I can increase the heat sink thermal resistance by a factor of 2, going from 0.25 as specified to let's say 0.5?
Vadim
Vadim,
What matters is the maximum Top of the output transistors, i.e. their maximum allowed temperature when in use. The other thing to consider is the temperature of the heatsink itself, anything over 55C is just not comfortable to touch. Also factor in hot days, when it is 35C (or more) you need to have enough reserve so the output transistors don't burn up.
Suppose you bias the amplifier so each transistor has 50W to dissipate (that's about the safe limit), that's 200W total. You can calculate the needed thermal resistance of the heatsink:
Tamb : 25C (ambient temp)
Tmax heatsink : 55C
Pin : 200W
Tmax heatsink = Tamb + X * Pin
55 = 25 + X * 200
30 = X * 200
X = 30/200 = 0.15 K/W or C/W
So the minimum thermal resistance of the heatsink has to be 0.15K/W, you need to repeat this simple calculation for your specific case.
Cheers,
Sander.
What matters is the maximum Top of the output transistors, i.e. their maximum allowed temperature when in use. The other thing to consider is the temperature of the heatsink itself, anything over 55C is just not comfortable to touch. Also factor in hot days, when it is 35C (or more) you need to have enough reserve so the output transistors don't burn up.
Suppose you bias the amplifier so each transistor has 50W to dissipate (that's about the safe limit), that's 200W total. You can calculate the needed thermal resistance of the heatsink:
Tamb : 25C (ambient temp)
Tmax heatsink : 55C
Pin : 200W
Tmax heatsink = Tamb + X * Pin
55 = 25 + X * 200
30 = X * 200
X = 30/200 = 0.15 K/W or C/W
So the minimum thermal resistance of the heatsink has to be 0.15K/W, you need to repeat this simple calculation for your specific case.
Cheers,
Sander.
This is great. I will re-compute for the output of 50W into 6 Ohm. Chances are
I will have to make a DIY heat sink with L-sections fixed to a rectangular
Base. We'll see. So far it looks like the fins might be around 12 cm long with
2.5 cm spacing. The Base might be 15 mm thick, 10cm tall and 30 cm long
This is per channel. It is doable and cheap. I can attach the L-sections to the
base with bolts.
Vadim
I will have to make a DIY heat sink with L-sections fixed to a rectangular
Base. We'll see. So far it looks like the fins might be around 12 cm long with
2.5 cm spacing. The Base might be 15 mm thick, 10cm tall and 30 cm long
This is per channel. It is doable and cheap. I can attach the L-sections to the
base with bolts.
Vadim
ok
Great, looks like there are only a few of us making this, lets keep in touch on this thread.
My parts list should be up soon. I never have been able to figure out those molex connectors so appreciate the help on 'connectors' section vs. mouser parts.
I myself cannot terminate molex (no tools) so may use screw terminals instead if they fit.
I will say the ExtremeA is extremely expensive due to those current regulating diodes.
Great, looks like there are only a few of us making this, lets keep in touch on this thread.
My parts list should be up soon. I never have been able to figure out those molex connectors so appreciate the help on 'connectors' section vs. mouser parts.
I myself cannot terminate molex (no tools) so may use screw terminals instead if they fit.
I will say the ExtremeA is extremely expensive due to those current regulating diodes.
Lgreen,
Not sure where you bought your CRDs, but there's several sources that carry these with pricing less than $5 a piece. Siliconix/Vishay discontinued them, but Linear Systems still manufactures them and also sell direct to end users.
http://www.linearsystems.com/datasheets/J500.pdf
Cheers,
Sander.
Not sure where you bought your CRDs, but there's several sources that carry these with pricing less than $5 a piece. Siliconix/Vishay discontinued them, but Linear Systems still manufactures them and also sell direct to end users.
http://www.linearsystems.com/datasheets/J500.pdf
Cheers,
Sander.
thanks for the info.
EDIT - that is interesting- those look like they actually fit the board.
Here is J511 from mouser- J511
Unlike those linear systems ones, which look like they fit the profile on the board, these come in a TO-35 diode glass package and will have to mount vertical. Do you think the diode leads will fit into the boards?
I don't mean to be negative, full speed ahead!!!
EDIT - that is interesting- those look like they actually fit the board.
Here is J511 from mouser- J511
Unlike those linear systems ones, which look like they fit the profile on the board, these come in a TO-35 diode glass package and will have to mount vertical. Do you think the diode leads will fit into the boards?
I don't mean to be negative, full speed ahead!!!
ExtremA Parts List ver. 1
Here it is- ExtremeA parts list ver 1.xls in Excel spreadsheet with handy hyperlinks.
I was told in email that resistors should be 1/4W and 1%, but this means that many resistors listed are not available, since for example you cannot get a 47K in 1%, you need to get a 47.5K and so on.
I figured that the values are close enough to not make a difference.
For transistors there are multiple options so I kind of blindly picked the ones I thought were correct.
CRDs are DO-35 glass case, but should fit.
No idea about the connectors.
Can someone check?
I measured the package dimensions and lead distances on the boards but not the lead size, some of the diodes may have thick leads that will not fit...but I'm not sure.
I have none of these parts and just went from the data sheet dimensions and rough estimate of the board dimensions using a micrometer.
The total price is wrong since the channel $ is added two times (oopsie) and some of the items are not included in the total. Have been working all night on this and will fix in next revision.
Please comment and edit!!
Here it is- ExtremeA parts list ver 1.xls in Excel spreadsheet with handy hyperlinks.
I was told in email that resistors should be 1/4W and 1%, but this means that many resistors listed are not available, since for example you cannot get a 47K in 1%, you need to get a 47.5K and so on.
I figured that the values are close enough to not make a difference.
For transistors there are multiple options so I kind of blindly picked the ones I thought were correct.
CRDs are DO-35 glass case, but should fit.
No idea about the connectors.
Can someone check?
I measured the package dimensions and lead distances on the boards but not the lead size, some of the diodes may have thick leads that will not fit...but I'm not sure.
I have none of these parts and just went from the data sheet dimensions and rough estimate of the board dimensions using a micrometer.
The total price is wrong since the channel $ is added two times (oopsie) and some of the items are not included in the total. Have been working all night on this and will fix in next revision.
Please comment and edit!!
Here in Toronto, there is a small manufacturer of toroidal transformers. They do custom work. I had my transformer made with 4 sets of secondaries. One section of 2x22 V at 500 VA and one sections of 2x25 V at 50 VA used for the lower power circuit. THis way you end up with one transformer that has everything you need for this project. Naturally the output voltage can be specified as need it. THe price was in line with the market. Here is the link http://www.sumr.com
Vadim
Vadim
I think you meant to write 'second' rather than 'third' as it needs two transformers at most, or a single one with seperate windings (2x 0-18V and 2x 0-25V).
The second transformer needs to supply the front stage of the amplifier with power. The power supply PCB has two dedicated discrete voltage regulators to handle this task. The output voltage is +30V and -30V. Hence the non rectified voltage from that second transformer should be at least:
30V / square root of 2 ~ 21V, hence 21V is right on the limit leaving no room for the discrete regulator itself, so 25V is a typical value. A little higher shouldn't be an issue, hence 28V is acceptable.
Cheers,
Sander.
I have been working on it. Slowly. So far completed-
- chassis obtained
- AC wiring including soft start to xformers is complete and working.
- PS boards are almost done; regulators are complete and tested/ working.
- high current PS done and wired with big 60,000 uF caps x 4. This is off - board.
I fear that I have emailed Sander too many stupid questions about parts substitutions and he is not going to answer them. Sorry, but a lot of those parts cannot be gotten in USA and I like to confirm maybe too much for my own good.
In the meantime- open up my parts list above (Post 168) and help by answering the questions therein!! Oh, and the CRDs from Mouser turn out to fit and work.
I cannot find fuse holders in USA that fit these boards;
I need help specifying the molex type connectors, pins and headers.
Need advice on the other questions in the parts list.
Also FYI, the big PS caps on the board are 40mm diameter with 22.5 mm lead spacing and 4 prongs. In the USA these are almost unobtanium (and >$10 each even for small values). I have a lead on some but may have to wire in leaded caps instead of using the snap ins that fit. Not an issue for me but just fyi for US builders.
- chassis obtained
- AC wiring including soft start to xformers is complete and working.
- PS boards are almost done; regulators are complete and tested/ working.
- high current PS done and wired with big 60,000 uF caps x 4. This is off - board.
I fear that I have emailed Sander too many stupid questions about parts substitutions and he is not going to answer them. Sorry, but a lot of those parts cannot be gotten in USA and I like to confirm maybe too much for my own good.
In the meantime- open up my parts list above (Post 168) and help by answering the questions therein!! Oh, and the CRDs from Mouser turn out to fit and work.
I cannot find fuse holders in USA that fit these boards;
I need help specifying the molex type connectors, pins and headers.
Need advice on the other questions in the parts list.
Also FYI, the big PS caps on the board are 40mm diameter with 22.5 mm lead spacing and 4 prongs. In the USA these are almost unobtanium (and >$10 each even for small values). I have a lead on some but may have to wire in leaded caps instead of using the snap ins that fit. Not an issue for me but just fyi for US builders.
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Amp Board
For what its worth, I think there is an error on the parts list for the amp board. The parts list says-
Diodes
D1/D2/D5/D8/D11/D12 (6) = 1N4148
D3/D4/D6/D7 (4) = BAT85
LD1/LD2/LD3/LD4 (4) = LED (green)
D9/D10 (2) = BZX79C12V (12V zener)
U1 (1) = J511/J510 (4.7/3.6mA CRD)
The problem is that two parts are listed for U1 (J511 and J510), according to the schematic it is J511 not J510. So this is what I am using on the assumption that the parts from the PS board got put in by mistake.
For what its worth, I think there is an error on the parts list for the amp board. The parts list says-
Diodes
D1/D2/D5/D8/D11/D12 (6) = 1N4148
D3/D4/D6/D7 (4) = BAT85
LD1/LD2/LD3/LD4 (4) = LED (green)
D9/D10 (2) = BZX79C12V (12V zener)
U1 (1) = J511/J510 (4.7/3.6mA CRD)
The problem is that two parts are listed for U1 (J511 and J510), according to the schematic it is J511 not J510. So this is what I am using on the assumption that the parts from the PS board got put in by mistake.
Lgreen, it seems youve really struggled to get a BOM together for this project. Do you not get one supplied with the pcb that includes vendor part numbers? Dont you have a farnell or RS that sells everything you need for this project. Im pretty sure I can get all these parts in NZ so they must be available in USA?
Good luck
Good luck
parts
Luke, I wish!
The parts are just provided generically- like this
[Parts list amplifier PCB]
Resistors
R1/R2/R29/R30 (4) = 2K2
R3/R4 (2) = 47K
**
P1 (1) = 10K (multiturn)
L1 (1) = 10uH
Capacitors
C1/C2/C5/C6/C10/C11 (6) = 33pF
C3 (1) = 10nF PP
C4/C9 (2) = 1nF PP
**
**
Connectors
Faston printconnector 6.35-mm 5x
4-pole Molex 2.54-mm pitch 1x
3-pole Molex 2.54-mm pitch 1x
Faston printconnector 6.35-mm 11x
**
Fuseholder PCB 22.5-mm 2x
Fuse 22.5-mm 6.3A slow 2x
No actual part numbers from farnell/ etc are given.
The sizes pinouts and ratings are for the most part left out.
And some, like the L1 = 10uH are really hard to figure out. This is a tiny part on the board the size of a resistor. Wind by hand? how many turns?
So you need to get the board and measure sizes and pinouts, which I have carefully done and so I ordered the parts as there was no commentary by anyone on the selected items. It turns out most of the ordered parts actually do fit with the exception of fuseholders/ fuses and of course the parts that I cannot figure out. I also made a mistake by ordering the multiturn pots in a staggered leadout vs. inline on the board, not sure how as I was aware of this.
Right now I need help figuring out these using Mouser (digikey if not at mouser) part ##s-
- molex and faston printconnector part #s (header, pins, receptacle)
- fuseholder and fuse part ##'s (these are too small for standard fuses that we have here in the US)
- inductor part #
I have found a suitable replacement relay that has 5A contacts, and am wondering if this is sufficient.
Also- the relay actuation voltage is 24V and my power supply will be about 21 volts. The article says you can size your power supply to your power requirements, giving an example of plus and minus 14V for a lower power version. But if you do this I am not certain that the DC protection will be triggered, as it uses the + supply to fire the 24V relay. I think 21v will trigger a 24v relay but if people are going to power this with lower power rails such as 14V as provided in the example it may not.
Luke, I wish!
The parts are just provided generically- like this
[Parts list amplifier PCB]
Resistors
R1/R2/R29/R30 (4) = 2K2
R3/R4 (2) = 47K
**
P1 (1) = 10K (multiturn)
L1 (1) = 10uH
Capacitors
C1/C2/C5/C6/C10/C11 (6) = 33pF
C3 (1) = 10nF PP
C4/C9 (2) = 1nF PP
**
**
Connectors
Faston printconnector 6.35-mm 5x
4-pole Molex 2.54-mm pitch 1x
3-pole Molex 2.54-mm pitch 1x
Faston printconnector 6.35-mm 11x
**
Fuseholder PCB 22.5-mm 2x
Fuse 22.5-mm 6.3A slow 2x
No actual part numbers from farnell/ etc are given.
The sizes pinouts and ratings are for the most part left out.
And some, like the L1 = 10uH are really hard to figure out. This is a tiny part on the board the size of a resistor. Wind by hand? how many turns?
So you need to get the board and measure sizes and pinouts, which I have carefully done and so I ordered the parts as there was no commentary by anyone on the selected items. It turns out most of the ordered parts actually do fit with the exception of fuseholders/ fuses and of course the parts that I cannot figure out. I also made a mistake by ordering the multiturn pots in a staggered leadout vs. inline on the board, not sure how as I was aware of this.
Right now I need help figuring out these using Mouser (digikey if not at mouser) part ##s-
- molex and faston printconnector part #s (header, pins, receptacle)
- fuseholder and fuse part ##'s (these are too small for standard fuses that we have here in the US)
- inductor part #
I have found a suitable replacement relay that has 5A contacts, and am wondering if this is sufficient.
Also- the relay actuation voltage is 24V and my power supply will be about 21 volts. The article says you can size your power supply to your power requirements, giving an example of plus and minus 14V for a lower power version. But if you do this I am not certain that the DC protection will be triggered, as it uses the + supply to fire the 24V relay. I think 21v will trigger a 24v relay but if people are going to power this with lower power rails such as 14V as provided in the example it may not.
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Either that, or go to Mouser/DK/Farnell/RS and type something like : radial drum core inductor 10uH.
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