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Old 31st July 2004, 08:22 AM   #1
Thunau is offline Thunau  United States
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Default Aleph-X. Will it work?

I hacked the AXE-1 preadsheet a bit to allow me to input any load (sorry , didn't mean no disrespect to the creator) It's in the column on the left with 120 Ohm power highlighted in yellow. This is what I'm getting when I'm trying to optimise the circuit for a 120 Ohm load of my new AKG K-1000 headphones. Will this setting of bias/voltage work? Any chance of it actually sounding good? Can someone with a SPICE model of the Aleph X confirm it? Thanks in advance.

I realise they (K-1000) can only take about 1-2W tops before crapping out, but I like to have some headroom and I'll not pump the volume anyway. Just trying to find a good class A design that is optimised for this load. I still have a couple of the circuit boards and FETs from the group buy, so why not use them?
The closest thing I found so far is a German KVR tube amp that goes for over $1k. Can't swing it right now, but really love the sound of these headphones. I'm using an Adcom GFA-555 right now and a chinese tube preamp. It sounds pretty good, but I know I'm not even close to maximizing the potential.

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Old 31st July 2004, 11:59 AM   #2
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Perhaps I'm misreading the spreadsheet, but the numbers look wonky to me.
If you're using a .5 ohm Source resistor for the output MOSFETs (and assuming a .5V drop across that resistor), you're going to get 1A bias per vertical pair of MOSFETs, or 2A total for the channel.
If it's a .33 ohm per Source resistor (I'm not clear on how to read this spreadsheet), then the bias will be even higher.
At 37V rails and 1A bias per MOSFET, the Pd for the MOSFETs will be considerably higher than 11W. Etc.
Maybe it's just me.

Grey
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Old 31st July 2004, 12:59 PM   #3
Netlist is offline Netlist  Belgium
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How the hack did you hack that spreadsheet?

Could you post it instead of a picture using another name to avoid confusion?

/Hugo
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Old 31st July 2004, 04:16 PM   #4
Thunau is offline Thunau  United States
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Quote:
Originally posted by GRollins
Perhaps I'm misreading the spreadsheet, but the numbers look wonky to me.
If you're using a .5 ohm Source resistor for the output MOSFETs (and assuming a .5V drop across that resistor), you're going to get 1A bias per vertical pair of MOSFETs, or 2A total for the channel.
If it's a .33 ohm per Source resistor (I'm not clear on how to read this spreadsheet), then the bias will be even higher.
At 37V rails and 1A bias per MOSFET, the Pd for the MOSFETs will be considerably higher than 11W. Etc.
Maybe it's just me.

Grey
No it's not you. My bad. By mistake I overtyped a formula field. I fixed it back to the original state. See attachment below.


Quote:
Originally posted by Netlist
How the hack did you hack that spreadsheet?

Could you post it instead of a picture using another name to avoid confusion?

/Hugo
It's not really a hack- I didn't have to guess passwords or anything like that. I just copied the whole spreadsheet into a new, unprotected worksheet and rearranged the load series. I had to make the chart from scratch because it didn't copy over, so that's why it looks a bit different.
Attached Files
File Type: zip aleph-x_any_load.zip (16.2 KB, 99 views)
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Old 31st July 2004, 08:34 PM   #5
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Also beware thatyou'll have to hack your headphone jack because 2 Aleph-X 's cann't use a common speaker ground. The Aleph-X is a bridged amp. This means thet each headphone speaker will need an independant ground wire.
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Old 31st July 2004, 09:59 PM   #6
Thunau is offline Thunau  United States
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Quote:
Originally posted by Brian Donaldson
Also beware thatyou'll have to hack your headphone jack because 2 Aleph-X 's cann't use a common speaker ground. The Aleph-X is a bridged amp. This means thet each headphone speaker will need an independant ground wire.

That won't be a problem. The K-1000 uses regular speaker cables. A normal heaphone amp can't drive them anyway, so no need for TRS type jack.
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Old 31st July 2004, 10:29 PM   #7
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I've never bothered to post the spreadsheet I use to do such things because it's ugly (it will, however, take any load, any rail, any number of output devices, etc.). I have no intention of spending the time and energy to make the thing pretty. Let others worry about such things.
I have been known to do the calculations by hand...
To wit--recently, I find myself fiddling a new Aleph-X. Higher powered (lots higher), and with a few refinements over the Version 1.0. Frequently, it's just me and my trusty scrap paper calculations. Life could be worse...much worse. In some parallel universe, they never invented the calculator.

Grey
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Old 1st August 2004, 02:22 AM   #8
moe29 is offline moe29  United States
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OK Grey... you've been hinting at this... is it time for a new
Aleph X post? Aleph XXX (for higher power!)

I still have some heatsinks left over. Lets see a schematic!
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Old 1st August 2004, 04:05 AM   #9
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Was there a high powered X Aleph thread a while back? I remember asking some questions, however they were never answered.

I have some X pcbs but I am really not interested in building a low powered X amp. I mean 150 watts is about the power I am looking for.

Also, has any one compared this amp to the standard red book Aleph?

Moe,
Yea I have a couple of boxes of heat sinks and PS caps, my wife wants me to toss them.
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Old 1st August 2004, 04:37 AM   #10
Thunau is offline Thunau  United States
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Quote:
Originally posted by GRollins
I've never bothered to post the spreadsheet I use to do such things because it's ugly (it will, however, take any load, any rail, any number of output devices, etc.). I have no intention of spending the time and energy to make the thing pretty. Let others worry about such things.
I have been known to do the calculations by hand...
To wit--recently, I find myself fiddling a new Aleph-X. Higher powered (lots higher), and with a few refinements over the Version 1.0. Frequently, it's just me and my trusty scrap paper calculations. Life could be worse...much worse. In some parallel universe, they never invented the calculator.

Grey

So Grey,
Will it work with 120 Ohm load at 37V rail with 0.59A bias per channel? Or is there something in the circuit that isn't going to like this particular setting (like the output FETs)?

Click the image to open in full size.
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