Dan's Aleph Build Thread

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Hello Everyone,

I am about to start my Aleph project and this will be the thread where I document my progress.

I'd first like to start by thanking James Dumesnil, a fellow member, for sending me some surplus PCBs to get me moving. Mind you, he drives a hard bargain - I quote from a message from him to me, "if you are certain that you will BUILD one and post pictures. I will part with them free of charge." Now that's dedication to supporting fellow members. He posted PCBs across the world within days - thank you James!

Now the question is, what am I going to build? I'm hoping to get some good feedback from you guys to help me work this out. The original plan was to build an Aleph 5 stereo amp as a rehearsal for building a high powered Aleph X down the track. I'm now considering building Aleph 2 monoblocks after much reading on the Aleph amps.

The amps will be driving the Acorn from ER Audio, a full range electrostatic speaker:

http://www.eraudio.com.au/

They're not a particularly difficult load to drive (I'll see if I can get more info on the speaker impedance curve). Let me say that my NAD C320BEE drives them with no trouble at all, which really surprised me.

I've read mixed opinions about pairing Alephs with ESLs - please, make you comments heard here as I'm most interested! Negative opinions are not going to stop me building the Alephs for two reasons - 1) The Alephs can alway be re-purposed, driving other speakers, or acting a a boat anchor. 2) If I don't, James will hunt me down.

I'll see if Rob Mackinlay from ER Audio wants to chime in as he planned to build Aleph 4's once upon a time. I wonder if he ever got round to it.

Anyway, I'm likely to take a while to ramp this up, sourcing time, money and parts.

Cheers,

Dan
 
It's decided - I going to build Aleph 2 monoblocks.

I will be increasing the bias to help drive the difficult electrostatic load. I have a couple of questions about this:

1) If I remove R19 altogether, what will the bias current be (I've read that it approaches 3A), and what does this mean to heatsinking requirements over the original Aleph 2 design?

2) Has anyone experimented with the effect of varying the AC current gain when driving reactive loads like electrostatic speakers?

3) Will the removal of R19 give a high enough bias, or should I lower the value source resistors too?

I've settled on Conrad heatsinks as all feedback I can find is positive and they're prices are very reasonable. Now I just need to settle on a bias setting to work out how much heat I'm going to be dissipating.

I'm looking into transformers now - can anyone recommend an Australian manufacturer? Even better if they're Perth based!

Cheers,

Dan
 
Try varying R19 first to get a >3A bias; increasing its value increases the npn ref voltage by a fraction -as it approaches >>high resistance or infinity the ref voltage nears a Silicon device's G-S voltage drop value of about 0.6V.

Doing this has the advantage of not messing with the original AC current gain set by NP at 50% (best sound), as opposed to lowering the Source resistances.
 
Keeping it cool

I've been thinking about forced air cooling - fans! Here's my maths transfered from the back of a napkin...

I'll assume that I'll need to dissipate around 400W as heat once I raise the bias and that I'm shooting for a 25 degree temperature rise above ambient. This leads to heatsinks that have a thermal resistance of 0.0625 deg/W.

Conrad have a suitable heatsink, the MF18-151.5 in their Fine Fin Spacing range:

http://www.conradheatsinks.com/products/flat_hd.html

Lets assume I can quitely push 27 cfm of air over two of them, I'm down to 0.077deg/W (0.11*1.4/2.0 = 0.077). This includes the correction factor of 1.4 to get 25 deg rise, not 80 as quoted on the Conrad site.

Working backwards, that'll take me to 31 degrees rise above ambient. Close enough for me.

If you put two of those heatsinks face-to-face, you'll end up with a 124mmx125mm tunnel, ready to mount a 120mm fan. Which fan? This one (NF-S12-800 from Noctua):

http://www.noctua.at/main.php?show=productview&products_id=4&lng=en

It pushes 19 cfm at <5dB(A) and 34 cfm at 8dB(A). Bingo! Quite and powerful.

Include therm-control of the fan speed and we're done. Fast warm up time, extra cooling capacity, small and light heat sinks. All this and the heatsink/fan assembly will be about 12x12x17.5cm overall in size.

Cost wise, this will be very cheap, saving on heatsink and shipping costs!

Now, am I dreaming, or does that all sound right?
 
monarodan,

Just a piece of advise....

I tryed 3 different fans in my A75
and it's difficult not to get noise, even with silicon suspensions
thermo regulation etc ; even lowering the speed {1/3 rd}.

It has been very difficult to shut-up the fan noise...
It induces vibrations into the chassis, think special suspension plate
isolated from the chassis to fix the heatsinks and fan.
Avoid open air in and output for the air ; otherwise the noise will be there...

Fans are noisy by nature... so search and find the right fan before
starting anything!

I pushed 2*80 watts with 2*6 pieces of Therma Flo, EH 1126 B long 8"
and the temp reached 53 degrees about 0.06deg/W

http://www.passdiy.com/gallery/a75-p11.htm

Good luck with your project.

Regards.

Alain.
 
Points taken - these fans are very, very quiet and would run at 500 to 800 RPM to achieve the desired air flow. Not to mention their 150,000 hour MTBF! Very reliable.

I might shell out for one fan and play with it first. I can always stick it in a computer (the intended use for it anyway).

Cosidering that a bog standard 12cm computer case fan will emmit around 28dB, and these run at around 5dB, that's pretty quiet.

From their marketing blurb:

http://www.noctua.at/main.php?show=straight_blade_design&setlng=en

"Sound-optimised blade geometry and profile: The NF-S12 is the first fan employing a novel rotor which was developed by the Austrian Institute for Heat-Transmission and Fan Technology (Österreichisches Institut für Wärmeübertragung und Ventilatorentechnik, ÖIWV). Thanks to the special optimisation of the blade geometry towards ultra low noise application, the NF-S12 is up to 10% more quiet than current high-end fans at the same flow rate."

I've only read good reviews about these fans. There is a local supplier who has these in stock, so I should be able to get hold of one quickly and let you know how it goes!
 
I got a few of the fans. Boy are they quiet. On the "high speed" setting, which is only 800RPM, you can not hear them unless you're ear is practically in the blades. I put a couple in my computer and it's made it a lot quieter! They really do push a lot of air, so I'm willing to trust the manufacturers specs at this point and expect that a single fan will be more than adequate for one monoblock.

So, I'm going to go down the fan assisted cooling route. Heatsinks and fan come out to AU$200 to do both monoblocks! I costed the passive route at AU$333 for Conrad heatsinks.

The plan is to get the heatsinks, assemble them as a tunnel, attach a fan to one end and burn some heat to test the cooling capacity. Does onyone have any comments on the easiest way to do this? I guess the simplest way a few power resistors and some thermal paste...
 
Nuvotem toroidals and Erse Inductors

Hi All,

Progress is being made. I have MOSFETs, heatsinks, fans, PCBs, power supply capacitors (in the post) and a mate that does metal work (now that's handy).

Does anyone know anything about Nuvotem toroids (http://www.nuvotem.com/)? RS Components sell the 1000VA 2x40V toroidal for AU$161 and qualifies for free shipping. That is the best price on toroidals that I've found.

I'll be using a CLC filter in the power supply. PSU designer shows that I should hit very close to 45V with the Nuvotem toroid, the caps on order and Erse 2.2mH air core inductors (0.328 DCR). There is no Erse distributor in Australia - where is best to buy from? From those that advertise price on their web site, Zalytron has the best price.

Alternatively, I found these listed on eBay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=9727797592

I would have gone for 14ga. Would 16ga suffice for an Aleph 2 power supply? If so, I will find out more about these inductors.

Cheers,

Dan
 
Formerly "jh6you". R.I.P.
Joined 2006
Re: Nuvotem toroidals and Erse Inductors

monarodan said:
I would have gone for 14ga. Would 16ga suffice for an Aleph 2 power supply? If so, I will find out more about these inductors.


As I understand,
If we make 2mH air coil with 1.2mm dia magnetic wire
the Rdc is approximated about 0.55Ohms

Since Aleph 2 draws 3A bias per channel
3x3x0.55 = about 5W heat per coil
I don't foresee any problem with 16ga . . .
 
Disabled Account
Joined 2005
Nuvotem aren't too bad - sonic frontiers/parts connexion used their smaller potted toroids in the assemblage DAC's back last century ;)

You should also give Harbuch a call. I bought transformers from them for a pair of aleph 30 monoblocks and they seem very nicely made. They use high quality Antrim cores and will wind just about anything you need if they don't have them in stock. They have much better pricing than RS Components - but to be honest I think anywhere is cheaper than RS :eek:

http://www.harbuch.com.au/


cheers
Paul
 
Hi Paul,

Harbuch's quote for the standard Antrim range was only slightly higher than the Nuvotem from RS Components. Once shipping is factored in, RS is considerably cheaper. I know it's hard to believe - initially I didn't bother checking with RS for toroidals as I expected them to be far too expensive.

I also tried Tortech, but their quote was much higher than others.

As for RS's prices, they seem quite variable. Some items are very competitively priced while others are way over the top. The other factor to cosider is that RS is giving away a crappy remote control car if you spend over $400... I hate to admit it, but this appeals to me :rolleyes:.

I think I'll go with RS this time round to get my free remote controlled car and try Harbuch for my next project.

Dan
 
Disabled Account
Joined 2005
I stand corrected... I must admit I do use RS a fair bit because they have a reasonable range at their trade counter. However Farnell has far better stock and low volume discount points vs RS. Mind you for panasonic PSU caps etc etc it's cheaper to order from digikey (even with the obligatory fedex shipping) than either of the local "houses".

The transformer I needed wasn't a standard value anywhere except Harbuch. Tortech wanted an arm and leg to custom wind. Not sure why Mark Finnis recommends them to be honest as they seem to be _very_ pricey??


enjoy the car ;)

I'll just keep twiddling my thumbs until my parcel turns up from digikey sometime today :rolleyes:
 
Harbuch praise

Hi folks,

Just a little praise for Harbuch. The man in charge knows his work very well. You want an unusual transformer, he will make it. Describe your intended purposes and he will advise wisely. (I do not know about audio output transformers, but certainly for all power transformer needs.) They will also supply low flux designs if you are worried about transformer hum in higher current requirement designs.

And their starting prices are by way cheapest ... including Jaycar.

The postage remains a killer though. I wonder why Wes Components can mail a whole set of Orion woofers (4 Peerless XLS woofers - significant weight and volume) from Melbourne to Townsville for less than $15 (via Toll, or some similar company) and other transport companies start their fees at $25 or so.

Regards,
George.
 
Thanks for your feedback George. Your sentiments seem to be in line with all opinions I've heard about Harbuch. I couldn't dig up any dirt on them!

I'm starting to realise just how isolated Perth is given all the mail order stuff I'm doing lately... Damn shipping charges. RS Componets wins out this time with no shipping charges on this order, plus, I can grab a bunch of other small component (that aren't stocked by the like of Jaycar) at the same time.


Zen Mod - thanks for the like to Apex Jr. I've not seen that sight before!


Dan
 
monarodan said:
I got a few of the fans. Boy are they quiet. On the "high speed" setting, which is only 800RPM, you can not hear them unless you're ear is practically in the blades.

This post influenced me to buy couple of NOCTUA fans (NF-S12-800) and I can confirm what monarodan said. They are unbelievably silent and guaranteed MTBF is 150.000 hours. I put one on the back plate of my Mini Aleph and now the teperature on MOSFET cases is only 55 deg. Cels. (47 deg. on heatsinks) with 60 W dissipation per channel. With NOCTUAs I see no reason to avoid fans anymore. Amp's details are on my web site.
 

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