Aleph 4 Transformer

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Hi everyone,
My name is Nicolas and I am new to this forum. I am a local chinese from Sabah, formally known as North Borneo.

I intend to built Aleph 4, but I have very limited knowledge in microelectronics.

1. My AC supply is 240AC. Can I use 35V+35V 230AC transfromer from Piltron?
According to my hifi repair friend, I can use 230AC transformer. He says, our current here fluatuate between 235 to 245AC. But I will have higher rail voltage. He wonders if it is too high for Aleph 4.
If I can use 230AC transformer, how high will the rail voltage be and will it be suitable for Aleph4?

2. Is it better to use 1W resistors for Aleph4, since it is not mentioned in the circuit diagram?
Is there any online store whereby I can purchase Dale resistors?
I have problem getting a response from Michael Percy.

3. Is 60 pcs of IRFP240 sufficient for matching, or should I go for 80 pcs from Digikey?

4. Does higher input impedence for Aleph 4 improve the efficiency of a preamp and what advantages does it offers?

I hope my questions doesn't sound silly and any answers offered is very much appreciated.


Thank you
 
Hope this helps....
1. 35V sec will be fine
2. Browse thru www.vishay.com, you might find a local supplier for your 1 watt Dales
3. 80 pieces seems a lot to me, you might want to start with 60 as mentioned. If the price is right it won't hurt getting 80 or more....
4. I really can't tell, but personally I prefer the good ol' 10K
 
Thanks alot, cp642.

Will contact distributers if they supply to individual.
Yes, I also prefer old than new, old habits die hard, maybe bad for me.

Finally Avel reply me with quote. Hope that things will go smoothly that I might be able to purchase from Avel and not worry about 230AC primary, for my country is 240AC.
Having problem dealing with Avel......... maybe I am too far from US.
 
Nicolas:

A couple of points for you:

1) if Transformer is designed for 230 primary voltage, and you have 240 then the output will be higher proportionately. So a secondary rated at 35V will be at 35*(240/230). 36.5V.
2) Above situation will not be a problem with the Aleph designs. I know this from reading this forum (too much) over the past month.
3) The resistors you need will not generally need to be 1W. 1/4 watt (RN60D type) will work fine for most of the resistors. Reading this forum about the operation of the amplifiers will give you the info to be able to calculate which ones need to be higher power. Also, one source is to review the work of Mark Finnis at PassDiy.com - under the Gallery listing, is info on his Aleph 4. It includes links to his website where he gives a parts list and lots of information about what he did and why.
4) If you don't know about it, use the Search function at the top of the forum page to search for threads about Aleph AND Power, Aleph AND resistors, etc. You will have plenty to read.

Good luck
 
I'll get 80 pcs of IRFP240, hoping to get 4 sets of 12 devices ea.
This is the first time I am building an amp. Hope I won't burn down my house. My friend advice me not to built but to buy.

Avel finally took my order. Thank God! ... Michael Percy finally responded after a loooong time. It's really an experience buying things from the net. I almost have to beg.... ha ha ha......... and nightmare....I fax my credit card particulars to Avel, and suddenly fear strike my heart. "what if I have faxed to the wrong place?"

Can Aleph 4 be setup without output transistors/stage?
Just in case there is something wrong with the gain stage. My friend says I need the output stage connected or else the components in the gain stage will be fried. He advice me to connect just 2 mosfet for setting up.

I attach a power supply pic for single stage diff preamp.
Will this power supply work?
Do I need to also change the 2nd last electrolytic rail cap to solen 47uf like the last cap on the rail which is also solen?
the first 2 caps will be 1000uf electrolytic cap.

I am using 60v sec transformer and slow start fred diodes for rectifying. The capacitor filtering the diodes is 0.001 uf. 2 low pass capacitors are 0.22uf wima and 10uf electrolytic. The resistors value and the regulator is the same as Aleph L power supply for + regulated voltage. For - voltage I will be using irf9610. Pic is only for + voltage.

I modify the powersupply from Aleph L preamp. I hope I won't be seeing fire works display on my preamp. Gain stage will be modified version of David Broadhurst, New Zealand.


:confused:
 

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HPotter said:
Regarding matching the mosfets: I just went through that yesterday. Out of 100 Irfp140 I got 6 sets of 12 devices ea. matched to 0.03v without any problem. I was testing each device at 0.5A for 4 sec. Hope it helps.

Peter

I will suggest you to Matching POWER MOSFET under condition, as it will work under final circuit (the VA rating). And at lease 5 min. for each measurement (Temperature condition). and Always under same condition.

This will give you most reasonable data to Matching it.
 
While it is generally considered better to match the mosfet under the conditions that they will eventually be placed in, it can be a big pain to go to the trouble of fitting a heatsink etc... from memory Pass Labs measures them for only a matter of seconds at what i would guess to be a somewhat reduced current.... probably not ideal but should be fairly close.
 
Regarding matching MOSFETs, I bought a total of 30 from Newark and ended-up with 9 sets of 3, easily matched to 0.02 (cf 0.1 recommended). If I were trying for banks of 6, then they would have been within 0.05

Heatsink mounting is EASY. Simply use a small sink about 10cm or so, use a rubber insulating washer, use a strong bull-dog clip.

Mounting takes about 5secs per device. I measured VGS after several minutes, as it does change quite quickly immediately following power-up.

Regards

mark
 
Wow,it will take about 7 hours just to match 80 pcs for 5 mins each. How do I make sure that the temp is the same throughout the matching exercise? Do you attach a thermometer to do that? Is there a special thermometer to guage the temp of a mosfet.

I was thinking of attaching the mosfet to a computer heatsink and use the mother board software to monitor the mosfet temp. The display monitor swap every 1 sec. I wonder if the heatsink is too small. I don't know how hot will the mosfet be at 0.4A for 5 min. Actually the software can be set to beep at certain temp. It's call MP Probe, a freeware.

Just some crazy ideas.

PS. After spending some time with diyaudio, I don't find any fanatics. But I find most of those who post here offer sound advice, and are serious, knowledge filled music loving and generous people, esp NP. I thought this site is for trying out wierd extreme projects when NP directed me to this site when I ask him to help me built an Aleph 0. :D
 
Yes, It is pretty annoying work to do. But it will return better sound in my experience.
I think in PassLabs, they make/bring every device to same temperature then measurement the VGS.
But in my case, I have to apply (same) current into device to make it heat-up till the temperature is same & stable (w/heatsink). The heating of device takes some time, so I check it after 5min. Then, I think the measurement data is reliable.
Actually I take additional step to recheck my matching result. It is in Aleph circuit. I spend 2 days to doing this.
:)
 
I have received info of DynamiCap(latest improved version of infinicap) from Michael Percy in pdf fromat. I was thinking of putting it on this web site for general reading but I can't attach the file. Anyone knows how to convert it to text file?

Very tempted to use it on Aleph 4 for Cap C103, but very pricey- About USD11.

Regards
 
Regarding matching mosfets: I compared few of them for 4 sec, then run a check for 1 min, checking values every 10 sec, then checked the same devices with 2/3rds of a current and received pretty the same results ( less than 0.02V difference). Putting mosfets on a heatsink and checking the value after 30 min doesn't gurranty the same temparature for each device so the voltage values might not be accurate. The proper alternative would be measure them in actual circuit after 2 hours warm up, but with 24 devices per amp swapping them seams like a lot of hassle.
I just wonder if perfect matching of output devices really affect the sound of the amp? Also how the number of output devices affect the sound. I am building Aleph 2 but since I have so many spare mosfets (I bought a 100) I was thinking about increasing the number of output devices to at least 20 per channel. Is it a good idea? I built A75 few years back and it had 24 devices per channel. It is still working fine and although I shorted the output once I only had a single mosfet failure.
 
Stress Thermometer
Temperature updates every 2 seconds, Accuracy +/- 1.80 F, Displays Fahrenheit or Celsius Temperature. Electronic Quartz Accuracy. Temperature range 58 F to +158 F
Pricing: $19.95 each
http://www.cliving.org/sale.htm#Stress Computer

It has a little probe which I think can be mount to a heat sink.
How hot will the mosfet be if it is fed with 0.4A using a 15v dc regulator for mosfet match?

I think the temp range of product above should be sufficient. Might try using the above product for mosfet matching.
 
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