New Aleph 5 (finally )finished

Status
Not open for further replies.
Jump to Latest
#61
I think Mark has the clue regarding one rail draining faster than the other which usualy is the + rail which is connected to the CCS.

A PI filter on the rails could help as well as the use of the thermistor (at startup) as a current limiter on the trafo primary.

There are a number of other possibilities such as one cap having excessive current leakage. I'm just guessing here but a not well match front end pair may well produce some problems.

I'm almost certain that if you don't have a PI filter on the rails you may have hum with a 90dB speaker sensitivity.

You might have already said this but what is the total cap capacity at the rails?

Do you have two secondaries with two diode bridges? One set of rails for both channels?

Just for the record, in my case (A4) I have some moderate cone movement at start and shutoff of the amps but is at very low frequency so there is no noise produced with a similar speaker sensitivity. Before the PI filter was implemented the cone movement was much higher but didn't have a sound coming from the speakers.
 
#63
Pedro,

One of the easy routes to solve part or most of the problem is to add a CRC Pi with the added benefit of reducing almost any hum you may have. Though you will loose some volts on the rails depending on resistor value.

A typical value for the first cap would be 50% of the main caps but I think you can lower this to some 10 or 15K.

I suggest you test first with a simple connection to one of your monos before doing the mod.

In my setup I use 4x 3.3 Ohms in parallel and lost 4 volts of rail, a tradeoff I gladly accept.
 
#66
Hi Pedro,

Great job on your Aleph 5.:up: The heatsinks worked out pretty nice I see.

What is your actual rail voltage at idle? I didn't see any inductors so I'm assuming your using straight capacitor filtering on the PSU.

Rodd Yamashita
 
#69
PedroPO said:
ok. At home now!

The Trafo is a 300VA 220V->25V+25V and the rail are at 33.6V with 2*47000uF.
Click to expand...
Hi Pedro,

It's interesting to see the voltage drop. I plan on running a CLC filter so the L will drop 2V or so. I think I'll go with 28V secondaries on my Aleph5.

Thanks,
Rodd Yamashita
 
#70
PedroPO said:
ok. At home now!

The Trafo is a 300VA 220V->25V+25V and the rail are at 33.6V with 2*47000uF.
Click to expand...


roddyama said:

Hi Pedro,

It's interesting to see the voltage drop. I plan on running a CLC filter so the L will drop 2V or so. I think I'll go with 28V secondaries on my Aleph5.

Thanks,
Rodd Yamashita
Click to expand...

Hello Pedro, your 33.6 VDC is very close to the theoretical 35VDC from rectification.

And Roddy your 2 x 28VAC should rectify to 39VDC, let me know how close it comes.

Both these measurments are based on Idle current and the Transfomers ability to hold output voltage. Plitron for example quotes 4% on thier big toroids.

Anthony
 
#71
Anthony,

I'm included in the wiki buy from VM for a pair of 500VA (a little over kill for an A5). I'm thinking ~1V for the rectifiers, ~2V for the inductor, and another ~1V secondary sag and I should be at 35V rails, but I'll make sure the first set of cap are rated for >40V just to be safe.

We'll see.

Rodd Yamashita
 
#72
roddyama said:
Anthony,

I'm included in the wiki buy from VM for a pair of 500VA (a little over kill for an A5). I'm thinking ~1V for the rectifiers, ~2V for the inductor, and another ~1V secondary sag and I should be at 35V rails, but I'll make sure the first set of cap are rated for >40V just to be safe.

We'll see.

Rodd Yamashita
Click to expand...

Even lees drop if you use FRED's instead of a bridge rectifier!

Anthony
 
Status
Not open for further replies.
Top Bottom