Newbie Aleph2 PSU Questions

[rcdaniel]

Hi all

Before getting into my first post proper, I would like to thank Nelson, Grey and the other regulars for their generosity in supporting this forum. From the perspective of a person who is new to DIY, it is refreshing to find people who generously devote their time to activities with little or no direct monetary benefit.

I have been lurking here for a while and although I have some doubts re my ability (this will be my first project), I am planning (with some anxiety) to build an Aleph2. As they say, an ounce of participation is worth more than a pound of procrastination. Also, that Nelson considers the Aleph2 a good project is enough for me.

Apologies in advance if I am covering old ground – I have performed and absorbed so many searches that I may have a brain-explosion! So, to the questions: 1) Do I understand correctly that the Alephs draw pretty much predictable current, therefore reducing the need for large and fast energy storage, with the main purpose of the PSU being filtration? 2) Would a dual rectifier CLC filter PSU with 1x ~22000mF (C), 2-4 mH (L) and 3x ~22000mF bypassed with a 4.7 film or metallised cap per rail will be adequate – is more necessary? 3) Is there an audible benefit to bypassing each e-cap with 1.0+mF film caps as some builders have done? I know they are different beasts, but many respected builders of valve amps are claiming that cap bypasses do more harm than good. 4) Is there any sonic value in using “better” quality e-caps? And 5) Apart from generic computer grade caps, what have other builders used – any comparisons?

As a general question, has anyone located outside the US, specifically Australia, had difficulty ordering components from Digikey? I would like to know, as some components may be difficulty to source down here.

Thanx in advance to all who are willing help

Ray

[skaara]

1. Alephs draw constant current, you need a lot of capacity in psu for them.

2. I think it will be ok.

3. There is audible benefit, at least i noticed it - highs are more defined and distinguished..

4. Havent thested that, but i think it doesnt mean too much what electrolytic caps you use in psu.

[rcdaniel]

Thanx Skaara

I will go for the configuration discussed, with each generic e-cap following the inductor bypassed with a ~ 1mF film cap.

Cheers
Ray

[grimberg]

Since we are talking about PSU, is there any benefit in adding Magnetic Shield and/or Electrostatic Screen to the transformer used in the Aleph?

[rcdaniel]

Grimberg

I am no EE, but if you are referring to an electrostatic screen between your primary and secondary windings, read on. If not, don’t. I can’t comment about magnetic screening, however.

I spent some time a while back researcing this topic when I was considering a valve amp build - specifically in relation to a heater supply. It is my understanding that it has some relevance to SS amps, though I am not yet sure to what degree - you may wish to take my advice with caution.

In short, an electrostatic screen should reduce some A/C line noise making its way into your amp via the PS. An electrostatically screened transformer may be especially beneficial if you are not intending to implement a CLC filter in your PS. Considering the cost of such screens is minimal, I would go for it. Personally, I am intending to use a CLC filter in my Aleph build and will still be using an electrostatically screened transformer. Even a small reduction in noise with only a minimal financial trade-off seems worthwhile to me. As always – your money may vary.

Cheers
Ray

[grimberg]

Ray,

Thank you for the answer. I agree with what you said that, since the additional cost is manageable, it makes sense to add both to the transformer.

Grimberg

[rcdaniel]

Grimberg

By the way, what are you intending to build?

I was planning to build an Aleph2, though I will probably end up opting for an Aleph5.

We are only into our first week of summer over here and already the temperature is hitting the ~35degC point at very high humidity. I am not sure that I want the extra heat dissipation of an Aleph2...

All the best for your project
Ray

[grimberg]

Ray,

My situation is exactly the same. I wanted to build a pair of Aleph 2 but decided to build the Aleph 5 as monoblocks instead. I too am concerned about the heat dissipation in the room, since it can get pretty hot here in the Summer months.

I wish you success with your project.

Grimberg.