applebook said:
This is a centre-tapped transformer (12VAC CT : 6-0-6 )
so you may end up with less than 8 volts on each + and - rail.
This is a bit low. You can use a pair or look for
something along the line of 24VCT with an adequate
current rating.
Sorry to hear you're having some problem with Antek.
Which transformer did you order from them?
I heard good things about Antek on this forum and
was looking to order a transformer. However,
they haven't given me the shipping quote I requested...
Cheers,
Dennis
Hi, I shouldn't say anything bad about them because nothing has happened yet --except for some miscommunication and slow response, nothing major.
I ordered a 16V 300Va toroid that's pretty much ideal for the Mini without going overboard.
8V per rail is actually OK with me because this Mini will be used to drive my AKG K1000. I'll build an A30 later with toroids for a speaker rig.
I ordered a 16V 300Va toroid that's pretty much ideal for the Mini without going overboard.
8V per rail is actually OK with me because this Mini will be used to drive my AKG K1000. I'll build an A30 later with toroids for a speaker rig.
applebook said:
Hi
I am in the process of building a surface mount mini to drive my k1000's with. I have started building it, but need a few more parts before I can finish it, that I have not got around to ordering yet.
I was going to use a 18-0-18 transformer, and then make a CRC type power supply. I was planning to make the resistor big enough to drop the voltage down to around 12 vdc. Only problem with this is that I need to get some pretty big power resistors to drop the voltage down. I may look for a little lower voltage transformers, but I already have the 18-0-18's. I guess I could unwind them too, but that might be a pain.
Randy
I do not like CLC at all if the coil used is not fully encapsuleted in core material. If you use core material you have to take in account the maximum flux @ peek current.
If u ues air core, you generate very nasty magnetic pulses that show up in your amp circuit.
If you want to drop the voltage then also use a series resistor between the rectifier and the first cap. This also will extend the life of the first cap. You do not need a large resistor at all.
I would recommend to use PSU designer II (Duncan Amp tools) to have a look at the PSU. I found it is pretty accurate.
The best way to do that IMO, is to use a regulated supply, which can be made pretty easily. Here is all you want to know about it:
http://www.passdiy.com/pdf/zen-ver3.pdf
An added bonus is that the regulator cleans up the supplyrails very well, so you can relaxe a bit about the big psu-caps
I have often made those regulators on a small piece of perfboard, or "Dead bug" style. Works like a charm
Steen
Zen Mod said:
Because I want to drop the voltage down, so I need a resistor.
Tarasque said:
Thanks, I will take a look at a RC configuration.
BTW, I always use PSU designer to model my power supplies, it is a nice tool.
steenoe said:The best way to do that IMO, is to use a regulated supply, which can be made pretty easily. Here is all you want to know about it:
http://www.passdiy.com/pdf/zen-ver3.pdf
An added bonus is that the regulator cleans up the supplyrails very well, so you can relaxe a bit about the big psu-caps
I have often made those regulators on a small piece of perfboard, or "Dead bug" style. Works like a charm
Steen
Hi Steen
I have seen the paper before, but I really was not thinking regulated. But, it does look easy to do, just a handful of parts.
Have you compared the sound of a regulated supply to a linear supply, either CRC or CLC, in an aleph type amp?
I guess I am worried that a regulated supply might have trouble supplying current surges, and could limit dynamics.
Thanks for the comments,
Randy
As Brian points out, it wont be a problem. Since the Aleph amps are true Class A with a constant current draw, a regulated supply will do nicely. Its also the most convenient way to get rid of excessive voltage with added advantages as mentioned. Dont worry, it works really sweet
Regarding the sound, the difference is very small. Hard pressed I find a CLC supply best sounding, but only marginal. (I am probably just being sentimental ) Do mount the regulating mosfets on the heatsink.Steen
Since Randy and applebook intend on using mini-A's
with headphones and low rail voltages, what do
you guys think of using smaller mosfets (eg IRF610)
instead? I was looking at Mr. Pass' article on
mosfet testing and the IRFP240, for example, shows
somewhat higher distortion at low voltage levels.
Cheers,
Dennis
with headphones and low rail voltages, what do
you guys think of using smaller mosfets (eg IRF610)
instead? I was looking at Mr. Pass' article on
mosfet testing and the IRFP240, for example, shows
somewhat higher distortion at low voltage levels.
Cheers,
Dennis
Thats a good idea. I think Metalman made a headphone amp from these boards earlier in this thread. Some adjustments to the circuit is needed, to not exceed the powerdissipating of the smaller devices.(or fry your phones) IRF610's work perfectly well in the Zen Headphoneamp which uses low supply voltages and higher r source resistors. Take a look at the Zen headphoneamp :
http://headwize.com/projects/showfile.php?file=pellerano_prj.htm
Steen
This is very vague, but MOSFET 6 doesn't get warm, so I assume that it's not connected properly or is broken. I get very faint sound at very low volume despite turning my pre-amp all the way up.
My other board doesn't seem to be working at all because I get no sound, and the FETS don't warm up. Unfortunately, I have no tools to measure the voltage levels.
If anyone has had a similar experience, please share your troubleshooting tips.
My other board doesn't seem to be working at all because I get no sound, and the FETS don't warm up. Unfortunately, I have no tools to measure the voltage levels.
If anyone has had a similar experience, please share your troubleshooting tips.
Zen Mod said:
Hi Zen
When I looked at using inductors in my PS filter before, I was modeling a CLC filter, and could not get enough voltage drop. So, I ran PSUD with an LC filter.
BTW, I am not sure what “1,41” means? 1,410 uf, or 14,100 uf, or 141,000 uf? 14,100 uf seems like the most appropriate, but 1,41 would be a strange way to say that, and the other values either seem too low or high.
So, I looked at Hammond chokes for the L.
From the original mini aleph thread, they draw around 1 amp at 15VDC. So, I figured I need a choke rated for at least 1.5 amps. Best Hammond I could find was the 159ZC, it is rated at 2A, 60Mh and 0.7 ohms. This guys weighs 2.5 lbs, and costs about $20 each.
If I plug these parameters in, with a 14.1 mf cap, I get 16VDC output from the simulation. My transformer is rated for 18V at 6.25 A, 7% load regulation.
Does all this seem reasonable?
I was thinking I could lower the current, so I could use a chock with a lower current rating, but lowering the current would increase distortion, so I am not sure I want to do that. And, I am not sure I want to spend $40 on two inductors, to build a LC supply.
Dennis Hui said:
Thanks for the advice. These are not your normal headphones though, AKG 1000’s need more power than a standard can, I think they recommend at least a few watts of power, so you don’t want to use a normal headphone amp for these.
I will look at the IRF610’s, but at this point, since this is my first aleph (first class A actually), I think I should build it per the standard design, and see how it works. After I get it working, I will see if I want to tweak it further.
applebook said:
Bummer. I have not finished mine yet (need a power supply), so I don’t have any practical experience to share. I do think you at least need to get a volt meter. I think it will be hard to troubleshoot without that, as a minimum. If you are going to DIY stuff, I think a decent DVM is mandatory.
Randy
steenoe said:Thats a good idea. I think Metalman made a headphone amp from these boards earlier in this thread. Some adjustments to the circuit is needed, to not exceed the powerdissipating of the smaller devices.(or fry your phones) IRF610's work perfectly well in the Zen Headphoneamp which uses low supply voltages and higher r source resistors. Take a look at the Zen headphoneamp :
http://headwize.com/projects/showfile.php?file=pellerano_prj.htm
Steen
A 6moons review of metalman's amp is here
http://www.6moons.com/audioreviews/realitycheck1/aben.html
Interesting reading.
Randy
Is GND1 and GND2 on the PSU board not supposed to be connected together? I finally managed to get one channel running at low volume, with both FETS working (I assume), but I couldn't find any problems with the connections on the board, so I disconnected GND1 and GND2, and two of my resistors fried.
I still can't get the other board running at all. This is amusing since I actually printed out the rear on this channel so as not to make any mistakes
I guess that the lesson that I've learned from this fiasco is to leave amp building to pros...or invest in measuring equipment and not assume that new parts actually work
Anyone want to buy a heatsink and a toroid that I have coming in a week?
I still can't get the other board running at all. This is amusing since I actually printed out the rear on this channel so as not to make any mistakes
I guess that the lesson that I've learned from this fiasco is to leave amp building to pros...or invest in measuring equipment and not assume that new parts actually work
Anyone want to buy a heatsink and a toroid that I have coming in a week?
Don't give up!! Go get a simple VOM (volt Ohm Meter). You can check your FETs by measuring the resistance between pins, looking for shorts.
FETs are very sensitive to static discharge. You may have accidently fried them (really, does not take much). In that case you can probably swap them out and be fine.
You can do this... Maybe take a couple days off then come back to it.
FETs are very sensitive to static discharge. You may have accidently fried them (really, does not take much). In that case you can probably swap them out and be fine.
You can do this... Maybe take a couple days off then come back to it.
Hey Applebook,
I second what Brian has said. If you don't have
a meter, you should get one. Even a cheap one
is very useful and will help you diagnose all
sorts of problems. (In Toronto, cheap multimeters
go for $10 or so.) There are many of us who,
thanks to the help on this forum, were able
to build Alephs without more than a multimeter.
Take a little break and come back to it. Ask
some questions. You'll get it working.
Cheers,
Dennis
I second what Brian has said. If you don't have
a meter, you should get one. Even a cheap one
is very useful and will help you diagnose all
sorts of problems. (In Toronto, cheap multimeters
go for $10 or so.) There are many of us who,
thanks to the help on this forum, were able
to build Alephs without more than a multimeter.
Take a little break and come back to it. Ask
some questions. You'll get it working.
Cheers,
Dennis
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.