Hi Prasi
First of all thank you for the offer
You can read it hear
Jlh-2003-amplifier | adolfo martinez - Academia.edu
It advised to use metal can power transistors, I don't know ON semi and Sanken has some high power not metal can transistor if those can deal with the heat..
I hope some other people interested to build these amp not just me. We could do a small GB in that case, Otherwise only home brew PC boards.
It would be the best if you could make it about 32Cm long
Thanks
Hi Gabor,
You are welcome
.Whats the supply voltage and how much heat its gonna dissipate? In my view 320mm long PCB would be too big and will have very very long trace lengths and may not be an optimized design.
Like the F5 layout that I did based on people's suggestions, would be more than sufficient to dissipate for this amp also.
Have a look here http://www.diyaudio.com/forums/pass-labs/307664-f5-layout-4.html#post5083531
It more or less emulates the DIYA store PCB dimensions. Ofcourse its single sided and with its limitations unlike the DIYA store 2 sided PCB's.
my2c, however, if you still like to go with 320mm PCB, I am ok with it.
reg
Prasi
Hi Gabor,
if you think carefully the class A draws constant average current and even if the output transistors are relatively closely spaced the whole heat sink will reach equilibrium in several minutes and stabilize.
I consider it unnecessary and unwise to use long track lengths to each transistor.
I use several JHLs which are both PNP and NPN dual transistor output versions and works well for me on moderate heat sinks and reasonable spacing between transistors.
Here is a snatch view of my single sided PCB and I will e-mail my schematic and layout to you if your are interested. The PDF is 1:1 and you can cut it out to see how well it suits your heat sink.
if you think carefully the class A draws constant average current and even if the output transistors are relatively closely spaced the whole heat sink will reach equilibrium in several minutes and stabilize.
I consider it unnecessary and unwise to use long track lengths to each transistor.
I use several JHLs which are both PNP and NPN dual transistor output versions and works well for me on moderate heat sinks and reasonable spacing between transistors.
Here is a snatch view of my single sided PCB and I will e-mail my schematic and layout to you if your are interested. The PDF is 1:1 and you can cut it out to see how well it suits your heat sink.
Hi Gabor,
You are welcome
Whats the supply voltage and how much heat its gonna dissipate? In my view 320mm long PCB would be too big and will have very very long trace lengths and may not be an optimized design.
Like the F5 layout that I did based on people's suggestions, would be more than sufficient to dissipate for this amp also.
Have a look here http://www.diyaudio.com/forums/pass-labs/307664-f5-layout-4.html#post5083531
It more or less emulates the DIYA store PCB dimensions. Ofcourse its single sided and with its limitations unlike the DIYA store 2 sided PCB's.
my2c, however, if you still like to go with 320mm PCB, I am ok with it.
reg
Prasi
Hi
I attached the circuit my previous post. Dissipate - depend on the rail voltage one chose. I attache it again
That F5 you designed it look nice but these has 2 pair power transistor and if we stick to the TO-3 type (metal can) that takes up a lot of room.
I would still prefer long PC board like the original First Watt amps. If we must use wires to connect the transistors we can get that type of PC boards on Ebay very cheap ($12 pair free shipping) and already tested and built several by people.
What is in my mind something like these (see the attach) if is not to difficult
These way we could use some heavy duty L or T shape aluminium bracket for the TO-3 transistors
Only if is not to difficult to lay it out
Thanks one more time
Attachments
Sorry attachment did not attach....
Hi
That is a very nice layout for lower power a la 18 to 22 DCV rail voltage and that is readily available some nice PC board at Ebay.
I have a 28VAC 800VA transformer which give around 33-34V rail voltage biased into Class A.
I attached some pictures from my heatsink and the best would be a long (32 or so Cm) type of PC board layout .
If one must use wires to connect the power transistors for better dissipation no need for a new design.
One pair JLH2003 version HOOD class A single-ended power amplifier board PCB | eBay
For the smallest transistor, the 9015 isn't availabel here, so these are the ones I can choose from:
https://www.ic-elect.si/polprevodni...sistor_type=32387&cat=2310&manufacturer=22957
Which one to choose?
https://www.ic-elect.si/polprevodni...sistor_type=32387&cat=2310&manufacturer=22957
Which one to choose?
So sorry for littering the tread so much...
I reassembled the amp with new 2n3055s and the bd139/16 then measured quiescent current. The repaired one measures exactly 1,5A, but the healthy channel measures only 0,7A It is confusing me more and more each day
The only difference between the channels is the tr3.
I reassembled the amp with new 2n3055s and the bd139/16 then measured quiescent current. The repaired one measures exactly 1,5A, but the healthy channel measures only 0,7A
It is confusing me more and more each dayThe only difference between the channels is the tr3.
Peroz, the current will depend on the gain of the output transistors. If you bought from different manufacturers they will most definitely be different. You need to adjust the 560 ohm bias resistor the achieve the bias current that you want.
1.5 Amp I feel is too much, but it depends if you want to drive 4 ohm, or 8 ohm and to what power. If you are happy with the 0.7A and it was not distorting before expected, then adjust the repaired one down so that they are equal.
If you feel you need a little more power, adjust both amps for say 1 A, this should be good for about 8 watt per channel.
There is no point in over biasing the class A amplifier, all you do is wasting energy, set it to where you need it to be for normal listening to music.
Some people ask to have a switch installed for low and high bias so (listening/party mode) this is maybe a nice solution for 0.7A and 1.5A bias with a switch on the front panel.
1.5 Amp I feel is too much, but it depends if you want to drive 4 ohm, or 8 ohm and to what power. If you are happy with the 0.7A and it was not distorting before expected, then adjust the repaired one down so that they are equal.
If you feel you need a little more power, adjust both amps for say 1 A, this should be good for about 8 watt per channel.
There is no point in over biasing the class A amplifier, all you do is wasting energy, set it to where you need it to be for normal listening to music.
Some people ask to have a switch installed for low and high bias so (listening/party mode)
this is maybe a nice solution for 0.7A and 1.5A bias with a switch on the front panel.
Dear all,
Here is a very rough draft; can someone tell me about wattages of resistors ? also whether TO-220 type heatsinks will be sufficient for Q8/Q3 ?
As I was afraid some traces that go to the base are too long. what can be done about it?
Any comments on layout welcome.
regards
Prasi
Here is a very rough draft; can someone tell me about wattages of resistors ? also whether TO-220 type heatsinks will be sufficient for Q8/Q3 ?
As I was afraid some traces that go to the base are too long. what can be done about it?
Any comments on layout welcome.
regards
Prasi
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The heat sinks should be fine. I am curious why you selected the2Sc3421 instead of BD 139-16. Both works but in my opinion BD 139 sounds "nicer".
Regarding the length of traces, I don't think they will be a problem unless there is a big transformer in close proximity radiating large magnetic field. If it is a toroidal then you may need to wind a mu-metal screen, but don't worry about it until it becomes problematic.
Regarding the length of traces, I don't think they will be a problem unless there is a big transformer in close proximity radiating large magnetic field. If it is a toroidal then you may need to wind a mu-metal screen, but don't worry about it until it becomes problematic.
Nice Prasi!
Just a suggestion from me...
Give the opportunity putting footprint for MPC74 non inductance resistors in emitter resistors position .
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Hi Prasi
It is definitely a great start, just waited to see if other people interested on the PC boards...
I have a couple request
Please keep the emitter resistors as long how it is now and if you can make it somehow so those who prefer the non inductive plate type of resistor they can use it. I would like to use these. I read some feedback they are great resistors..
10 X DALE LVR-5 0.1R 0.1 OHM 5W +/-1% NON-INDUCTIVE RESISTOR | eBay
The other think if you can make some more room for the input capacitor, some exotic caps are large for example these in in my mind.. But any 100V 2.2uF decent MKP caps has some size to.. 2 X 2.2 uf 450VDC MUNDORF M-CAP® EVO OIL Capacitors 2.2 uf (1 pair) | eBay
If is not possible we can mount the capacitor on the RCA connector. Not always the best idea but most of the time acceptable.
The other think and these in totally my fault, I went after the size of the heatsink.. Hard to get 320mm clad board. Can you reduce it to 300mm. Usually they sell it 300mm or 12 inches.
You can leave the two in the two power transistor on center where they are now just move the one each side (the first and forth) 10mm toward the center.
Thank you very much!!!
About the small resistor sizes it look like all 1/2W types.
Dale or PRP are 10mm the half Watt type.
JLH Class-A Amplifier
Please someone who already built the amp and have other opinion let us know.
Thank you!
Dale or PRP are 10mm the half Watt type.
JLH Class-A Amplifier
Please someone who already built the amp and have other opinion let us know.
Thank you!
Calculate the current through each and then multiply by the voltage across each.
Hi Andrew
He does us a huge favor by designing the PC board layout that more than enough... We can not ask him to do more work you know what I mean. There are several guy in these tread who already built these amp, it just take a sentence or so to inform us.
Based on the original (looking at the pictures) he used 1/2W resistors.
I have a question to you If you would be so kind
I have 3 at hand transformer for these project
1 2X28V 800VA
2 2x24V 500VA
3 2X20V 500VA
Which transformer would be the best.. The reason I ask because the amp biased into full Class A and here we no longer calculate based on the usual 1/3 rating..
Please if you would be so kind let me know your opinion...
Greetings
Thanks guys for your suggestions,
here is how the fine tuned current version looks like (both type resistors can be fitted). Next question is how high can one go for rail decoupling caps? I have 7.5mm p x 18mm dia cap there right now. If 220uf is mandatory, I can put additional pads. Vishay RN60D can be fitted easily in the current version.
PCB sized to 300mm x 75mm, by only moving extreme transistors by 10mm. I have tried to fill it by copper as much as possible.
One related question, I didnt get answer by searching google. How thick the 4 traces connecting the ground pour to the pad should be, for high current traces?
regards
Prasi
Edit: regarding the mundorf cap, fitting that on PCB itself may lead to compromises in i/p section and grounding. Could check the possibility of fitting it in the same pads but somewhat hanging outside of PCB?
I prefer to use Wima / Epcos film caps in that position. barrel sized polyprops go in xover in my builds.
here is how the fine tuned current version looks like (both type resistors can be fitted). Next question is how high can one go for rail decoupling caps? I have 7.5mm p x 18mm dia cap there right now. If 220uf is mandatory, I can put additional pads. Vishay RN60D can be fitted easily in the current version.
PCB sized to 300mm x 75mm, by only moving extreme transistors by 10mm. I have tried to fill it by copper as much as possible.
One related question, I didnt get answer by searching google. How thick the 4 traces connecting the ground pour to the pad should be, for high current traces?
regards
Prasi
Edit: regarding the mundorf cap, fitting that on PCB itself may lead to compromises in i/p section and grounding. Could check the possibility of fitting it in the same pads but somewhat hanging outside of PCB?
I prefer to use Wima / Epcos film caps in that position. barrel sized polyprops go in xover in my builds.
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