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.
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.
An externally hosted image should be here but it was not working when we last tested it.
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
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
GRollins said:
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.
Netlist said: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.
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
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
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 pcb’s 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.
I have some X pcb’s 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.
GRollins said:
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)?
An externally hosted image should be here but it was not working when we last tested it.
I would like to do the same, but first I'm making myself finish my Aleph 2+, APOX Preamp with built in active crossover, and Constant Current Mini Aleph headphone amp.
I have a huge heatsink that is like a honeycomb (but rectangular) for forced air that I'm thinking would make a great worlds most ugly AX. My new listening room front wall backs up to attic space that I was considering putting the worlds uglyest frankenamps in. I haven't suggested it to the wife yet because I'm sure she'll insist I do to. I was thinking about building shelves in the attic for the equipment so I didn't ever have to truely finish any of it. The only problem is 120 deg attic in the summer. I'll have make it all liquid cooled and pull the front end from a front wheel drive car for the radiator and electric fan to cool it all.
I have a huge heatsink that is like a honeycomb (but rectangular) for forced air that I'm thinking would make a great worlds most ugly AX. My new listening room front wall backs up to attic space that I was considering putting the worlds uglyest frankenamps in. I haven't suggested it to the wife yet because I'm sure she'll insist I do to. I was thinking about building shelves in the attic for the equipment so I didn't ever have to truely finish any of it. The only problem is 120 deg attic in the summer. I'll have make it all liquid cooled and pull the front end from a front wheel drive car for the radiator and electric fan to cool it all.
The numbers on the spreadsheet still look funny to me.
If you're looking for 1W into 120 ohms, you're only going to need roughly .1A and around 12V. In other words, you could build an original Aleph-X and be pretty much in the ball park. If you want to put a little extra into the circuit, 25V rails and 1A bias would be serious overkill for your headphones.
Grey
If you're looking for 1W into 120 ohms, you're only going to need roughly .1A and around 12V. In other words, you could build an original Aleph-X and be pretty much in the ball park. If you want to put a little extra into the circuit, 25V rails and 1A bias would be serious overkill for your headphones.
Grey
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