There's really nothing special to them, most are taken during the growing pain's and assembly stage. You'll find the more significant ones in this thread and also at the PassDiy site.rwagter said:
I'll send what I have to Ralph. If he wants to make a selection and put them on line, it's fine with me.
/Hugo
Hugo ea
I kept it really simple, you can view all pictures as long as my provider doesn't cut me off
Netlists Aleph-X
Ralph
I kept it really simple, you can view all pictures as long as my provider doesn't cut me off
Netlists Aleph-X
Ralph
Relevant modifications??
I have been reading trough this thread, and most of the original Aleph-X thread ....
There is a lot of posts about different modifications etc.etc. and I can no longer sort out what was valid and what not...
Are there any mods to Greys original schematic, in the versions being built ?? Any relevant changes in component values, except for stuff related to voltage/wattage level??
I have been reading trough this thread, and most of the original Aleph-X thread
....There is a lot of posts about different modifications etc.etc. and I can no longer sort out what was valid and what not...
Are there any mods to Greys original schematic, in the versions being built ?? Any relevant changes in component values, except for stuff related to voltage/wattage level??
I'll see if I can scrounge up enough time to post a Ver. 1.1 or something. Got something I want to breadboard first, just for fun. The unfortunate thing is that I'm trapped in carpenter mode at the moment, hanging a door and doing molding. Hope to knock that out in the next couple of days. Then I'll try to get to the Aleph-X thing.
Grey
Grey
The DC offset and the Absolute DC offet adjustment using VR1 to VR3 is quite a challenge! I also found out that browsing through all the Aleph X is also quite a challenge, too! I have spent hours on the thread and, honestly speaking, did not quite get all the DC offet info I need (even though I know that generally DC offset is OK as long as it is < 100 mv and Absolute DC offset is normally OK even upto 1 - 2V).
Can I suggest to put this DC offset and Absolute DC offset adjustment in the wiki page? I viewed this as the trickest part in making Aleph X to work (assuming we have good matched mosfet already)!
Just my suggestion!
Thomas
Can I suggest to put this DC offset and Absolute DC offset adjustment in the wiki page? I viewed this as the trickest part in making Aleph X to work (assuming we have good matched mosfet already)!
Just my suggestion!
Thomas
Gracious me, I know I'm silly, but I fail to see why people find this difficult.
1) Assuming that you use the output current adjustments at all. Set them such that you have the same voltage drop across the Source resistors on the output MOSFETs comparing one side to the other.
2) Set the front end current source adjustment so that the absolute DC offset (DC offset measured from the outputs to ground) is as close to zero as possible. As long as you're close, you're okay. The speaker does not see the absolute DC offset. The only reason you fiddle with it at all is that it will cut into your potential output voltage swing to either positive or negative, causing premature clipping. It will drift a bit, particularly with heat variations. Don't worry about it.
3) Let the amp cook for a while and readjust if necessary. Thirty minutes to an hour should be enough to get the amp nice and warm. The output current adjustments can help with small relative DC adjustments at the output.
4) Listen.
It's that simple.
Grey
1) Assuming that you use the output current adjustments at all. Set them such that you have the same voltage drop across the Source resistors on the output MOSFETs comparing one side to the other.
2) Set the front end current source adjustment so that the absolute DC offset (DC offset measured from the outputs to ground) is as close to zero as possible. As long as you're close, you're okay. The speaker does not see the absolute DC offset. The only reason you fiddle with it at all is that it will cut into your potential output voltage swing to either positive or negative, causing premature clipping. It will drift a bit, particularly with heat variations. Don't worry about it.
3) Let the amp cook for a while and readjust if necessary. Thirty minutes to an hour should be enough to get the amp nice and warm. The output current adjustments can help with small relative DC adjustments at the output.
4) Listen.
It's that simple.
Grey
Grey:
Thanks for the wonderful info. After so many hours of reading, that is almost the info I got. These steps is pretty easy, but it is hard for a new DIYer to know what is acceptable (such as Absolute DC offset) or else.
If these info are in wiki page, it will saved me more that 10 hours of reading time.
Many thanks, Grey!
Thomas
Thanks for the wonderful info. After so many hours of reading, that is almost the info I got. These steps is pretty easy, but it is hard for a new DIYer to know what is acceptable (such as Absolute DC offset) or else.
If these info are in wiki page, it will saved me more that 10 hours of reading time.
Many thanks, Grey!
Thomas
Very close matching of the differential pair also helps a lot,
in fact it's almost mandatory. Also, mount them back to back
(electrically isolated) on a small heatsink - so that they'll thermally
track better.
Not to mention closely matching the FETS for each channel.
I found I could only get very close matches by taking readings
off the devices in circuit after 30 minutes to 1 hour warm up time.
Matches i had made out of circuit just weren't close enough.
(i don't mount FETS on a heatsink when matching)
((if you're going to do that might as well measure in circuit))
...i thought there was DC offset info in the WIKI.
in fact it's almost mandatory. Also, mount them back to back
(electrically isolated) on a small heatsink - so that they'll thermally
track better.
Not to mention closely matching the FETS for each channel.
I found I could only get very close matches by taking readings
off the devices in circuit after 30 minutes to 1 hour warm up time.
Matches i had made out of circuit just weren't close enough.
(i don't mount FETS on a heatsink when matching)
((if you're going to do that might as well measure in circuit))
...i thought there was DC offset info in the WIKI.
GRollins said:
This worked for me, but I've another question. After using my Aleph-X for almost 1 year, one channel has some 50Hz hum after warming up. The dc off-set looks oke, it's in the same leage as when I built these amps. The problem also occurs without a preamp connected. Everything is fine, when the amp is cold, in the first 10 minutes or so. Then slowly the amounth of hum increases.
Is this due my settings are changed overtime (bias etc), or are there other components to check?
and Grey thanks for this great amplifier!
in my Aleph X case, I use 18V trans (PSU out is 25V) with 12 mosfets for each channel. For 1st ch, I am able to adjust to 66mv on the relative DC offset. The other channel, there is no voltage drop when I connect the board and the heat sink stay cold after 5, 10 minutes. I thought it might due to Q6 (I use IRF9610) failure, but I replaced it with the same result. I tried to find out if I had miss placed any part or have cold-soldering, but I have none!
On the working channel, R23 and R25 is about 4.7V; but the one that is not working is only about 3.3V.
What might be the cause of it? Anyone had similar problem?
Thomas
On the working channel, R23 and R25 is about 4.7V; but the one that is not working is only about 3.3V.
What might be the cause of it? Anyone had similar problem?
Thomas
As usual, I'm on the run, but I'll toss in one quick observation.
That low frequency hum is almost certainly either a grounding or power supply problem. Possibly an old electrolytic cap drying out.
I swear I thought I covered the setting of the pots a dozen times (more like three dozen) during the course of the main Aleph-X thread. My mind must be going.
Grey
That low frequency hum is almost certainly either a grounding or power supply problem. Possibly an old electrolytic cap drying out.
I swear I thought I covered the setting of the pots a dozen times (more like three dozen) during the course of the main Aleph-X thread. My mind must be going.
Grey