aleph 5 CLC filter

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Hello Tyimo!

1. You can use 2 paralel, but I recommend the 5ohm type
"...TH1 is a power thermistor used to connect the circuit and chassis ground to the AC outlet
ground. It will normally operate at 5 ohms, suppressing ground loops in the system, but will
drop to a low impedance if significant current is passed through it...."
2. Yes, you can put between AC fuse and switch
3. From service manual:
"...The voltage rails of the supply are at 34 volts, and each channel draws approximately 150
watts.
...
F1 is a slow blow fuse, set at 4 amps for 100-120 volt operation, and 2 amps for 220-240
volt operation."
4. In my opinion CLC, check out kristijan's homepage (link above)

BR,
 
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Re: Thermistor?

Tyimo said:
-Should I use 2 pieces 22R 3W thermistors paralel instead of the 1 10R5W-er?
If you are going to use them for current limiting, you should take a look at this thread about the thermistor that Pass Labs uses. Assuming you have 220VAC, you might think about 2 - 10ohm in series to get the inrush current down.
Tyimo said:
-Should I put them between AC fuse and switch?
I think either way will work.
Tyimo said:
-How many Amps draw the stereo Aleph5 from the AC socket?
The manual says 300W, so it's 300/VAC = Amps.
-What is the best PSU-caps arrangement-conection? [/B][/QUOTE]
I like the CLC, but most any other arrangments will work.
 
Hi Rodd-
Thanks. In the reference was a comment that most of the capacitance should be after the inductor. Is that mandatory? I have some 50v 68000 caps which I was planning on using two per channel with the inductor between them. Duncan's PSU indicates a voltage of +/- 31.9 v. This would seem to be in the hunt (yes?).

I also have some 75 v 22000 caps but they're big as Buicks.

Steve
 
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SteveA said:
Hi Rodd-
Thanks. In the reference was a comment that most of the capacitance should be after the inductor. Is that mandatory? I have some 50v 68000 caps which I was planning on using two per channel with the inductor between them. Duncan's PSU indicates a voltage of +/- 31.9 v. This would seem to be in the hunt (yes?).

I also have some 75 v 22000 caps but they're big as Buicks.

Steve
I know the 50X68kuf. Those are pretty good caps. There are a few recent projects using them. I'll probably use them myself in my up coming amp.
 
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Paid Member
SteveA said:
In the reference was a comment that most of the capacitance should be after the inductor. Is that mandatory

No, but as a practical matter, we usually get a batch of the
same kinds of caps, so we tend to put the same capacitance
before the inductor as after. The only danger is in putting
way too little on either side, but once you have at least, say,
10,000 uF before and after, you're on your way. You have to
insure that the "before" caps meet the ripple current rating,
and after that, it's pretty arbitrary, as increasing capacitance
on either side reduces the noise that the circuit sees by
inverse proportion.

Having too much capacitance on either side can be a problem
with regard to initial turn-on inrush currents, but there are
plenty of ways to deal with that, thermistors being one popular
approach.

:cool:
 
Additional clarification

I am interested in this thread as I hope to begin the PS on an Aleph project soon as well.

When modeling the PS in PSUD2, trying both a CRC and a CLC arrangement, the CRC seems to have less ripple. If this is correct, then is the only reason a CLC is more often recommended (it seems) because of the lower power loss? If I am doing the simulation correctly, then it seems that the difference between a 2.2mH and a 4.4mH inductor would be around 1/2 a volt. I was always under the impression that it was more.

Are the above observations consistent with the group's experiences? My real concern is that I too am hoping to use the 68000uf 50V caps, but was planning on an Aleph 2. It seems that I’m on the edge if I use a standard Avel 40-0-40, which modeled 44.5VRMS at the rails with a 7.5A (est 300W/40V) constant current draw. However, the peak on C1 is 49.8V, which seems a bit too close for comfort with my knowledge and the fact that they are 50V surplus caps. Should I consider getting some 63V caps for the first set of caps or just play it conservative and go for a 35 or 37V torroid? Finally, with low/no load conditions, the caps are way over their limits (around 57V). Is this an issue, since it is my understanding that a class A amp always draws constant current due to the constant dissipation across the transistors (the bias current) regardless of signal? It seems that the only time I could get in trouble would be during the trimming of the amp during the initial testing.

The above is how I understand these items from all the reading here about amp design. Please point out anything I have misunderstood, as I don’t want to build on a false foundation.

Sandy.
 
Puzzled about psu

I assembled the PSU (for Aleph 5). I used a 30-0-30 toroid with a 2 mH inductor "sandwiched" between two 68000 50 v caps (for each rail). Duncan's software suggested I should see +/- 32v. I measure +/- 43. I used the rectifier board (and diodes) from the Aleph 2 posted on Passdiy by Wayne Sankey. Why the difference between the predicted and observed?
Sure wish this was chemistry.
Steve
 
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Joined 2002
Re: Puzzled about psu

Sandy H. said:
I am interested in this thread as I hope to begin the PS on an Aleph project soon as well.

When modeling the PS in PSUD2, trying both a CRC and a CLC arrangement, the CRC seems to have less ripple. If this is correct, then is the only reason a CLC is more often recommended (it seems) because of the lower power loss? If I am doing the simulation correctly, then it seems that the difference between a 2.2mH and a 4.4mH inductor would be around 1/2 a volt. I was always under the impression that it was more.

Are the above observations consistent with the group's experiences? My real concern is that I too am hoping to use the 68000uf 50V caps, but was planning on an Aleph 2. It seems that I’m on the edge if I use a standard Avel 40-0-40, which modeled 44.5VRMS at the rails with a 7.5A (est 300W/40V) constant current draw. However, the peak on C1 is 49.8V, which seems a bit too close for comfort with my knowledge and the fact that they are 50V surplus caps. Should I consider getting some 63V caps for the first set of caps or just play it conservative and go for a 35 or 37V torroid? Finally, with low/no load conditions, the caps are way over their limits (around 57V). Is this an issue, since it is my understanding that a class A amp always draws constant current due to the constant dissipation across the transistors (the bias current) regardless of signal? It seems that the only time I could get in trouble would be during the trimming of the amp during the initial testing.

The above is how I understand these items from all the reading here about amp design. Please point out anything I have misunderstood, as I don’t want to build on a false foundation.

Sandy.


SteveA said:
I assembled the PSU (for Aleph 5). I used a 30-0-30 toroid with a 2 mH inductor "sandwiched" between two 68000 50 v caps (for each rail). Duncan's software suggested I should see +/- 32v. I measure +/- 43. I used the rectifier board (and diodes) from the Aleph 2 posted on Passdiy by Wayne Sankey. Why the difference between the predicted and observed?
Sure wish this was chemistry.
Steve
Sandy, Steve,

Duncans is good for a quick look to get you in the ballpark. You have to have the DCR of the inductors and the ESR of the caps set as real as possible. Same holds for the other components. Then you need to very the load as it will vary in real life. In the case of the Aleph amps where there's a large current draw, you can get away with marginal cap voltage values. However, if you use tricks like limiting the bias current during non-use, or if you use a safety disconnect on the DC rails where the load current is allowed to go to a low value or zero, the cap voltage will go to the maximum no load voltage. This value can be found by setting the load to 0A in PSU2. (Sandy, applying voltage with no-load during testing and setup is also a place where you can over voltage the caps.)

Steve,

You should see voltages in the 40+ Volt range if you're measuring the static supply. The voltage drops come in to play when you have a load current flowing. You need to attach a load resistor on the supply output to get a true picture of the "in use" Voltages. (Be sure the load resistor is of a high enough wattage.)
 
Hi Rodd-
Thanks, I inserted a 10R 22W resistor between the + and - outputs and measured ~33.5 volts. However, within seconds the resistor was starting to smoke. Is 22W not adequate?! Is it too much? I thought I would simulate an 8 ohm load but all I had available was a 10 ohm 22 Watt resistor. What should I have used?

Even though the output side of the supply seems to be providing the correct voltage I am concerned about frying the circuit boards were they to be connected at this stage.

Thanks again
Steve
 
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Steve,

The Aleph amp output sees a different load than its PSU. If you're testing the actual PSU alone you need to consider the load it sees. The total power consumption of the Aleph 5 is about 300W. Some of that will be consumed by the supply itself, but for testing the PSU, it's a good place to start.

300W delivered by 2 X 35V = 70V mean you need a total load of a little over 4 amps. That would equate to a resistor of 70V/4A ~ 18ohms @ 300W. For this you can use 2 - 10ohm resistors @ 150W, with the resistors tied to the + rail to ground and ground to the - rail.

First, you should be using a variac so you can bring the voltage up slowly. You can increase the resistance to simulate a lighter load (~2A at idle at the PSU output).
 
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