Mini-A Boards for Aleph 2?
I just received two new sets of Mini-A boards. Can't say enough about the nice boatds, great service and fast shipping! Anyway, I have enough matched IRFP240s for an Aleph 2. I've gone through the schematics and I know what I need to change, but I am wondering if the boards can handle the output current/rail voltage of an Aleph 2. My main cocern is the pads connected to the output. Does anyone have any experience with 45-50 Volt rails on these mini-A boards?
Thanks in advance for your time.
Paul
I just received two new sets of Mini-A boards. Can't say enough about the nice boatds, great service and fast shipping! Anyway, I have enough matched IRFP240s for an Aleph 2. I've gone through the schematics and I know what I need to change, but I am wondering if the boards can handle the output current/rail voltage of an Aleph 2. My main cocern is the pads connected to the output. Does anyone have any experience with 45-50 Volt rails on these mini-A boards?
Thanks in advance for your time.
Paul
Re: Mini-A Boards for Aleph 2?
I have been running Brian's boards with doubled up FET's in an Aleph 2 configuration for a few years now. Just used the values (including higher voltage rails) in the now hard to find service manual for the Aleph 2. No problems at all. They are visible in the pictures from our 2007 DIY get together at my house.
http://www.lonesaguaro.com/speakers/DIY2007/Index.htm
pdrie said:
I have been running Brian's boards with doubled up FET's in an Aleph 2 configuration for a few years now. Just used the values (including higher voltage rails) in the now hard to find service manual for the Aleph 2. No problems at all. They are visible in the pictures from our 2007 DIY get together at my house.
http://www.lonesaguaro.com/speakers/DIY2007/Index.htm
They are also item 10 in the pictures from our 2006 get together.
http://www.lonesaguaro.com/speakers/azdiy05/AZ2006Pix.htm
http://www.lonesaguaro.com/speakers/azdiy05/AZ2006Pix.htm
Thanks for the replies and the pictures. I think that I'll go for it. I understand that Aleph 2s are better suited to my MG-IIIas than a pair of Aleph-Xs would be.
I plan to use two forced convextion towers per monoblock, with 2 Conrad MF18-151.5s for each tower. I bout two Mini-Aleph board sets, so I have 4 output boards for each monblock. Should be a great adventure!
Paul
I plan to use two forced convextion towers per monoblock, with 2 Conrad MF18-151.5s for each tower. I bout two Mini-Aleph board sets, so I have 4 output boards for each monblock. Should be a great adventure!
Paul
Hi,
@Brian: Managed to recover the original diyamps pages via archive.org If you want, I could send you the archive.
Read a lot, confused now. What I want to do:
Build a Mini-Aleph based on Brians boards with the input-section of the Aleph-J which is not that difficult to realize. The only thing not that nice is that R5 in the original schematic has to be tied to V- instead of gnd. All the other changes fit the board.
But the output is a little more difficult. At least for me at the moment - perhaps I read too much about Alephs. I have a toroid with approx. 500Va and dual 15V secondaries, my heatsinks seem big enough. So I want to bias my output with two transistors at approx 2A. If I am right, I have to increase R13 to at least 220k (or leave it out completely. But what about R16 then? And which value to choose for R27/R28?
After all those threads about Alephs I am a bit confused.
Thanks in advance
Flo
@Brian: Managed to recover the original diyamps pages via archive.org If you want, I could send you the archive.
Read a lot, confused now. What I want to do:
Build a Mini-Aleph based on Brians boards with the input-section of the Aleph-J which is not that difficult to realize. The only thing not that nice is that R5 in the original schematic has to be tied to V- instead of gnd. All the other changes fit the board.
But the output is a little more difficult. At least for me at the moment - perhaps I read too much about Alephs. I have a toroid with approx. 500Va and dual 15V secondaries, my heatsinks seem big enough. So I want to bias my output with two transistors at approx 2A. If I am right, I have to increase R13 to at least 220k (or leave it out completely. But what about R16 then? And which value to choose for R27/R28?
After all those threads about Alephs I am a bit confused.
Thanks in advance
Flo
On the verge.
O.K.
I've spent a couple of weeks reading every post in this thread and most of the posts in other threads referenced in this one, pored over multiple schematics, including Algar_emi's very helpful one, and am ready to order parts. Before I do, however...
I'd like to build a pair of Aleph 30 monos with Brian GT's latest (black) boards, and start out with both amps running at maximum bias, so I'll omit R13. I'll substitute a rheostat at R12 so that I can adjust AC gain, and another one at R8 so that I can adjust DC offset.
I'll never need the balanced input, so I'll substitute jumpers at R9 and R10 (to extend the ground plane a bit) and omit C1.
I'll bypass the zener at Z5 with a 1uF film cap.
I'll use Brian's PS boards with 20-0-20 trafos and 99,000uF per rail and will not permanently install the CRC resistors until I can run the completed amps under load and adjust their resistance to achieve 25 volt rails.
Some questions.
First, have I made any mistakes in trying to achieve what I want by misinterpreting what I've read?
If not, what value rheostats should I use at R8 and R12? What value CRC resistors should I start with in the power supply (I can't get PSU Designer to work correctly on my 64 bit desktop)?
Thanks for your help (and allowing me to keep five fingers on each hand).
George
O.K.
I've spent a couple of weeks reading every post in this thread and most of the posts in other threads referenced in this one, pored over multiple schematics, including Algar_emi's very helpful one, and am ready to order parts. Before I do, however...
I'd like to build a pair of Aleph 30 monos with Brian GT's latest (black) boards, and start out with both amps running at maximum bias, so I'll omit R13. I'll substitute a rheostat at R12 so that I can adjust AC gain, and another one at R8 so that I can adjust DC offset.
I'll never need the balanced input, so I'll substitute jumpers at R9 and R10 (to extend the ground plane a bit) and omit C1.
I'll bypass the zener at Z5 with a 1uF film cap.
I'll use Brian's PS boards with 20-0-20 trafos and 99,000uF per rail and will not permanently install the CRC resistors until I can run the completed amps under load and adjust their resistance to achieve 25 volt rails.
Some questions.
First, have I made any mistakes in trying to achieve what I want by misinterpreting what I've read?
If not, what value rheostats should I use at R8 and R12? What value CRC resistors should I start with in the power supply (I can't get PSU Designer to work correctly on my 64 bit desktop)?
Thanks for your help (and allowing me to keep five fingers on each hand).
George
Hi George,
I am not one of those Aleph-Experts, a beginner too. But I think:
I would not omit C1 even if the inverting input is grounded permanentely. Without C1 the amp has DC gain, without the DC-Gain is 1. Could be very healthy for your speakers depending on your sources.
C1 does not need to be an electrolytic, choose any film with C from 2-10 uF.
In my opinion R9 and R10 have to be there - if you jumper them you won't get any gain. Instead you could use one R with 8,7k and leave the other one open. But you may leave out z3 and z4.
Best regards.
Flo
I am not one of those Aleph-Experts, a beginner too. But I think:
I would not omit C1 even if the inverting input is grounded permanentely. Without C1 the amp has DC gain, without the DC-Gain is 1. Could be very healthy for your speakers depending on your sources.
C1 does not need to be an electrolytic, choose any film with C from 2-10 uF.
In my opinion R9 and R10 have to be there - if you jumper them you won't get any gain. Instead you could use one R with 8,7k and leave the other one open. But you may leave out z3 and z4.
Best regards.
Flo
Hi George,
have to correct myself: If you jumper those resistors you will get maximum gain (and maximum distortion). Don't know how this happened, I was thinking in the right direction and wrote the wrong thing down...
But the essence remains the same: The resistor(s) have to stay.
Best regards
Flo
have to correct myself: If you jumper those resistors you will get maximum gain (and maximum distortion). Don't know how this happened, I was thinking in the right direction and wrote the wrong thing down...
But the essence remains the same: The resistor(s) have to stay.
Best regards
Flo
Just noticed...
I was actually about to hit "enter" to confirm my parts order when I decided I'd better check one last time.
The Mini-A schematic of the Aleph 30 output boards appear to call for 1 ohm, 3 watt resistors at positions 35-40, and .47 ohm, 3 watt resistors at positions 23-26 (27 and 28 not used on the 30). On the other hand, the Aleph 30 BOM calls for .47 ohm, 3 watt resistors at all these positions ("24 P0.47W-3BK-ND. R23-R26.R35-R40.R47.R48"). Which value in which position is correct?
George
I was actually about to hit "enter" to confirm my parts order when I decided I'd better check one last time.
The Mini-A schematic of the Aleph 30 output boards appear to call for 1 ohm, 3 watt resistors at positions 35-40, and .47 ohm, 3 watt resistors at positions 23-26 (27 and 28 not used on the 30). On the other hand, the Aleph 30 BOM calls for .47 ohm, 3 watt resistors at all these positions ("24 P0.47W-3BK-ND. R23-R26.R35-R40.R47.R48"). Which value in which position is correct?
George
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