How many FET's ?
Simon,
How many FET"s ?
Assuming you go for 100W output (8A bias), do not have hugh hestsinks, and stick to 25W dissipation per FET, then you need 16 FET's per channel, which means 32 for stereo, or 80 for surround.
I would then order at least double or three times for matching. You loose about 1/3 during matching (depending on how tight you want to match), and you want some spares just in case. Unless you buy together and group match; then you might get better utilisation.
Don't save on transisotrs. It is the one single most important element that determines the end result. And the IRFP's cost less than 1 pound per piece.
Or you might want to bulid a small one (15W) first, like I did, just to convince yourself.
I was lucky. Matched 25, put 4 (not the best ones) in, worked first time, no swap, nothing burnt. Differential DC offset 2mV.
Patrick
Simon,
How many FET"s ?
Assuming you go for 100W output (8A bias), do not have hugh hestsinks, and stick to 25W dissipation per FET, then you need 16 FET's per channel, which means 32 for stereo, or 80 for surround.
I would then order at least double or three times for matching. You loose about 1/3 during matching (depending on how tight you want to match), and you want some spares just in case. Unless you buy together and group match; then you might get better utilisation.
Don't save on transisotrs. It is the one single most important element that determines the end result. And the IRFP's cost less than 1 pound per piece.
Or you might want to bulid a small one (15W) first, like I did, just to convince yourself.
I was lucky. Matched 25, put 4 (not the best ones) in, worked first time, no swap, nothing burnt. Differential DC offset 2mV.
Patrick
BIG CAPACITOR ORDER
Hi....all just to let you know that I have found a new cunning
supplier of 68,000 50v capacitors........working out at approx £3.80 each inc shipping....could be slightly more....depends on import duties....
I am liaising with BigParsnip on this one.........as far as I am aware the order stands as follows..........please post for any alterations.............I hope to get this order placed within the next ten days or so...............
D3 14
Kram 12
Jason 30
Jon 8
Bigparsnip ~44 (BP.....please confirm)
Regards
D3.................😎 😎 😎
😎 😎 😎
Hi....all just to let you know that I have found a new cunning
supplier of 68,000 50v capacitors........working out at approx £3.80 each inc shipping....could be slightly more....depends on import duties....
I am liaising with BigParsnip on this one.........as far as I am aware the order stands as follows..........please post for any alterations.............I hope to get this order placed within the next ten days or so...............
D3 14
Kram 12
Jason 30
Jon 8
Bigparsnip ~44 (BP.....please confirm)
Regards
D3.................😎 😎 😎


caps
Please note price on this add .... is not correct we are using a different supplier....BGmicro are out of caps....
d3
Please note price on this add .... is not correct we are using a different supplier....BGmicro are out of caps....
d3
Hi All,
my attemps to secure parts through a broker were thwarted because of the small numbers involved........
But, and just out of interest at the moment, I have added the BYW99W-200 to the UK Reichelt WIKI.
http://www.diyaudio.com/wiki/index.php?page=UK+Reichelt+Group+Order
Looking at the Digikey price breaks, 100 or 250 units seem to be where the biggest savings are to be made in the quantities we want.
Any thoughts???
Jon 🙂
my attemps to secure parts through a broker were thwarted because of the small numbers involved........
But, and just out of interest at the moment, I have added the BYW99W-200 to the UK Reichelt WIKI.
http://www.diyaudio.com/wiki/index.php?page=UK+Reichelt+Group+Order
Looking at the Digikey price breaks, 100 or 250 units seem to be where the biggest savings are to be made in the quantities we want.
Any thoughts???
Jon 🙂
CONRAD HEATSINKS
BP & Kram
Have packed up your sinks.....phew!!! will send tham via parcel post on either Monday or Tuesday.............
ps they look gooood......hmmm hmm..........
D3...............
........are you happy with std parcel post?
😉 😉 😉 😉 😉 😉
BP & Kram
Have packed up your sinks.....phew!!! will send tham via parcel post on either Monday or Tuesday.............
ps they look gooood......hmmm hmm..........
D3...............
........are you happy with std parcel post?
😉 😉 😉 😉 😉 😉
Patrick
For the Fets numbers still havent decided, only just got into this late on as my daughter has been ill since I ordered the boards, though ok now
My current speakers are definitely a 4ohm load The speaker I have in mind for the Aleph is an avalon eidolon/ceramic clone which would be an estimated nominal 6 ohm load.
So am aiming for a doubling at 4 ohms. After reviewing the Aleph x spreadsheet, I am a little confused 😕 Would like around 50w into 8 Ohms (100 into 4) This comes in at around 16V 9A bias. which is not where the Fets work best, as soon as I put 25V 9A the power is more than I really need and the heat output is vast. (nearly a full XA160) am I missing something? Changing the number of fets only affects their individual dissipation.
For your 15W what did you use, and do you think athat it is necessary to have 25V.
TIA Simon
For the Fets numbers still havent decided, only just got into this late on as my daughter has been ill since I ordered the boards, though ok now
My current speakers are definitely a 4ohm load The speaker I have in mind for the Aleph is an avalon eidolon/ceramic clone which would be an estimated nominal 6 ohm load.
So am aiming for a doubling at 4 ohms. After reviewing the Aleph x spreadsheet, I am a little confused 😕 Would like around 50w into 8 Ohms (100 into 4) This comes in at around 16V 9A bias. which is not where the Fets work best, as soon as I put 25V 9A the power is more than I really need and the heat output is vast. (nearly a full XA160) am I missing something? Changing the number of fets only affects their individual dissipation.
For your 15W what did you use, and do you think athat it is necessary to have 25V.
TIA Simon
Configuration
Simon,
Just from a power's point of view, 8A bias will give you your 100W at 4 ohms. What you get at 8 ohms is determined by the rail voltage. 25 ~ 27 V rail will guarantee you above 100W at 8 ohms, depending on how close you what to operate near rail voltage. This is a very simplified statement, but is about true at the power level we are discussing.
In practice, you never use the full 100W, so it is all academic.
However, the level of bias current and rail voltage both have effects on the operating characterisitcs of power mosfets under linear operation. Have a look at the reference I suggested.
You can operate at a lower voltage, just use a transistor that is specified for that (e.g. the 044, as in Grey's schematic). But 1A bias is a bit too low for the 044, and pushes it further down into the non-linear region. Please rad Nelson's Mosfet matching article for more details. I am just one of you hobbist. Listen to the professionals.
Increasing the number of FET's for the same output power changes not only their individual heat dissipation, but also changes the operating point (say from 2A to 1A if you double the number of transistors). But as I mentioned, you can compensate for that by choosing the transistor with the right characteristics.
I use IRFP044 (without N) for my 15W, +/- 15V rails, exactly as the original circuit. It is not necessary to have 25V rail, if you are happy with 15W. But if you want at least 60W at 8 ohm, 18V secondary is what I consider to be minimum -- rails operating then at around +/- 21V. But again, don't just take my word. Do some very simple maths for yourself, or use the spreadsheet from the Aleph-X thread.
Patrick
Simon,
Just from a power's point of view, 8A bias will give you your 100W at 4 ohms. What you get at 8 ohms is determined by the rail voltage. 25 ~ 27 V rail will guarantee you above 100W at 8 ohms, depending on how close you what to operate near rail voltage. This is a very simplified statement, but is about true at the power level we are discussing.
In practice, you never use the full 100W, so it is all academic.
However, the level of bias current and rail voltage both have effects on the operating characterisitcs of power mosfets under linear operation. Have a look at the reference I suggested.
You can operate at a lower voltage, just use a transistor that is specified for that (e.g. the 044, as in Grey's schematic). But 1A bias is a bit too low for the 044, and pushes it further down into the non-linear region. Please rad Nelson's Mosfet matching article for more details. I am just one of you hobbist. Listen to the professionals.
Increasing the number of FET's for the same output power changes not only their individual heat dissipation, but also changes the operating point (say from 2A to 1A if you double the number of transistors). But as I mentioned, you can compensate for that by choosing the transistor with the right characteristics.
I use IRFP044 (without N) for my 15W, +/- 15V rails, exactly as the original circuit. It is not necessary to have 25V rail, if you are happy with 15W. But if you want at least 60W at 8 ohm, 18V secondary is what I consider to be minimum -- rails operating then at around +/- 21V. But again, don't just take my word. Do some very simple maths for yourself, or use the spreadsheet from the Aleph-X thread.
Patrick
BIG UK CAP ORDER IMMINENT
BIG CAPACITOR ORDER
I WISH TO PLACE ORDERS NEXT MONDAY .......
THE CAPS COME OUT @ APPROX £4 EACH INC SHIPPING TO UK
.........PAYMENT WILL BE BY PAYPAL..........I WILL EMAIL YOU WITH THE CONFIRMED COST..............PLEASE CAN YOU ALL REPLY PROMPTLY TO MY EMAILS AND GIVE CONFIRMATION..... THAT YOU WISH TO PROCEED........AT PRICE QUOTED.......THANKS!!!
D3 14
Kram 12
Jason 30
Jon 8
Bigparsnip 12
😉 😉 😉 😉 😎 😎 😉 😉 😉
BIG CAPACITOR ORDER
I WISH TO PLACE ORDERS NEXT MONDAY .......
THE CAPS COME OUT @ APPROX £4 EACH INC SHIPPING TO UK
.........PAYMENT WILL BE BY PAYPAL..........I WILL EMAIL YOU WITH THE CONFIRMED COST..............PLEASE CAN YOU ALL REPLY PROMPTLY TO MY EMAILS AND GIVE CONFIRMATION..... THAT YOU WISH TO PROCEED........AT PRICE QUOTED.......THANKS!!!
D3 14
Kram 12
Jason 30
Jon 8
Bigparsnip 12
😉 😉 😉 😉 😎 😎 😉 😉 😉
Attachments
CAPS.......IN CASE YOU ARE WONDERING!!!
In case you are wondering BGmicro are out of caps in above picture (I think most of pass labs forum scooped up what BG had!!!)..............I have found an alternative supplier............but they are dearer........but still excellent value!!!
I am definately non profit making!!!!!!!
In case you are wondering BGmicro are out of caps in above picture (I think most of pass labs forum scooped up what BG had!!!)..............I have found an alternative supplier............but they are dearer........but still excellent value!!!
I am definately non profit making!!!!!!!
At last, have been on a client site since sunday with no Internet access Argh!
D3 in for 12 capacitors please. Could I pay directly to your bank account via my internet bank? No charges.
Patrick
From WuffWaff's last spreadsheet axe-1.xls.
Voltage 15
Bias 7.5
Ac current gain 50%
Number of fets 8
Peak current 8
Power 8 Ohms (RMS) 42
Power 4 Ohms (RMS) 85
Power 2 Ohms (RMS) 56
Dissipation for one channel 225
Dissipation per fet 28
Transformer secondaries standard 11.13
Using IRFP044's gives 1.88A per Fet, have looked at spec sheet this seems fine.
Any thoughts on whether its worth going the extra mile for IRFP240 and the 25V, better sound?
What are you all building?
Need to decide soon for tranny order.
TIA Simon 😕
D3 in for 12 capacitors please. Could I pay directly to your bank account via my internet bank? No charges.
Patrick
From WuffWaff's last spreadsheet axe-1.xls.
Voltage 15
Bias 7.5
Ac current gain 50%
Number of fets 8
Peak current 8
Power 8 Ohms (RMS) 42
Power 4 Ohms (RMS) 85
Power 2 Ohms (RMS) 56
Dissipation for one channel 225
Dissipation per fet 28
Transformer secondaries standard 11.13
Using IRFP044's gives 1.88A per Fet, have looked at spec sheet this seems fine.
Any thoughts on whether its worth going the extra mile for IRFP240 and the 25V, better sound?
What are you all building?
Need to decide soon for tranny order.
TIA Simon 😕
Richard, the heatsinks arrived this morning and they do look nice. Shame, I haven't got the rest of the bits to build any cases around them at the moment, but hopefully that can be solved soon.
The only thing is, the big one's don't seem so big in person, and I'm wishing I had another two to build mono blocks from. But, I guess there is always another project to order some more for.
The only thing is, the big one's don't seem so big in person, and I'm wishing I had another two to build mono blocks from. But, I guess there is always another project to order some more for.
Voltage & Current
Simon,
I don't quite understand why you would want to use 15V, 8A.
Being most optimisitic, and you drop 2 V across a FET, you get max. 13V at the ouput. Divide by 8A gives 1.6 ohm. What speaker are you going to use ?
If you use normal speakers, and assume minimum impedance of say 3ohm, 8A x 3 ohm + 2V drop = 26V rail. No magic, just Ohm's Law. And output power = rms voltage x rms current, so 24x8/2 = 96W.
Your load and output power decides what current and voltage.
And forgive me for being too direct; I have a feeling that the AX is not the right project for you. It is definitely not for beginners. Try the Gainclone first. It costs 20 Euro per chip plus a supply and few resistors, and you get instant good sound. Can't go wrong.
Patrick
Simon,
I don't quite understand why you would want to use 15V, 8A.
Being most optimisitic, and you drop 2 V across a FET, you get max. 13V at the ouput. Divide by 8A gives 1.6 ohm. What speaker are you going to use ?
If you use normal speakers, and assume minimum impedance of say 3ohm, 8A x 3 ohm + 2V drop = 26V rail. No magic, just Ohm's Law. And output power = rms voltage x rms current, so 24x8/2 = 96W.
Your load and output power decides what current and voltage.
And forgive me for being too direct; I have a feeling that the AX is not the right project for you. It is definitely not for beginners. Try the Gainclone first. It costs 20 Euro per chip plus a supply and few resistors, and you get instant good sound. Can't go wrong.
Patrick
Output power
Patrick,
Can't argue with raw figures..........however, alot of us are going
for 18v with a beefy 1000va transformer and 130,000+ uf per
+ & - supply rail together with a decent rectifier.............
With a 8a bias this should.............be a really solid performer
...... up to 80 odd watts (being very pessismistic) into all rediculus loads....................
Even the 15V suggested by Simon should be fine for realistic sound levels with average efficiency speakers....(Is he proposing 11v tranny.....if so I am a little worried...sorry if this is the case I tend to agree with Patrick!!!)
I admit I have never heard these amps.......however....have you ever heard the little commercial Naim Nait........rated at humble 30w..........
on reasonable speakers.........
Don't forget to double the volume of a solid 25w amp you need
alot of power......can't remember now it's logerithmic.........I think you need like 100w..............or more
Patrick,
Can't argue with raw figures..........however, alot of us are going
for 18v with a beefy 1000va transformer and 130,000+ uf per
+ & - supply rail together with a decent rectifier.............
With a 8a bias this should.............be a really solid performer
...... up to 80 odd watts (being very pessismistic) into all rediculus loads....................
Even the 15V suggested by Simon should be fine for realistic sound levels with average efficiency speakers....(Is he proposing 11v tranny.....if so I am a little worried...sorry if this is the case I tend to agree with Patrick!!!)
I admit I have never heard these amps.......however....have you ever heard the little commercial Naim Nait........rated at humble 30w..........
on reasonable speakers.........
Don't forget to double the volume of a solid 25w amp you need
alot of power......can't remember now it's logerithmic.........I think you need like 100w..............or more
D3,
have you placed the cap order yet? If you have, do you have any left? If not, can you put me in for 12?
Let me know...
Thanks,
Gaz
have you placed the cap order yet? If you have, do you have any left? If not, can you put me in for 12?
Let me know...
Thanks,
Gaz
Hi, Patrick, one thing that you may nt have remembered is that the x opperates in a bridged mode, so witha +-15V supply, you effectivley get uo tp +/-30V peak at the output. So for a voltage drop of 2V, you will still have an RMS out of almost 20V. However, at 8 amp bias, this will still give a peek output power in the region of 2.5 ohms which is still rather on the low side of things.
Oh, and one other thing to consider here, runing +/-25V with an 8 amp bias will lead to 400W of heat being dissipated per channel, which would need a lot of heatsinking to stay cool (and could be used as a rather nice looking roomm heater).
Oh, and one other thing to consider here, runing +/-25V with an 8 amp bias will lead to 400W of heat being dissipated per channel, which would need a lot of heatsinking to stay cool (and could be used as a rather nice looking roomm heater).
hello gaz,
we could share the postage on the caps, would probably save us a few quid each.
Anyway we can discuss this later when we find out how much the caps weigh.
When are you getting those speakers??
See you later.
Mark.
we could share the postage on the caps, would probably save us a few quid each.
Anyway we can discuss this later when we find out how much the caps weigh.
When are you getting those speakers??
See you later.
Mark.
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