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Old 2nd March 2004, 02:44 AM   #111
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"I did a test with my wifes iron"


Surely this will become an industry standard test from now on, also to be adopted by the FTC and added to the power conditioning testing procedure...... To be known as the "Steam Iron Thermal Dissipation test".

Mark
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Old 2nd March 2004, 01:45 PM   #112
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Default Heat Sinks

Thanks for the info on the Ultra Stick. Looking at the data this material is far superior than the thermal grease I was going to use. I had nightmares on how I was going to neatly assemble them with grease. I make a horrible mess just mounting FETS.

I will post the drawing of the sinks and amp when I figure out how to export the file into a form that this board will accept.
Scott
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Old 2nd March 2004, 07:53 PM   #113
Eric is offline Eric  United States
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Default Aleph-X power supply

Hi Everyone,

I've been following the Aleph-X threads and making notes as I go, but I can't seem to find what I am looking for in my notes and the search turns up 9 thousand hits...

Can someone post a schematic of the Aleph-x power supply for me, please? I am starting to look at transformers and don't know how many secondaries I need. Do I need a transformer with two secondaries for each channel, like the Aleph 2 design?

Thanks for your help!
Eric
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Old 2nd March 2004, 08:05 PM   #114
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Default Calculating Power of Q6 and r48

I have been searching the associated threads for calculating power dissipation of Q6 to no avail. Considering that my philosophy for the amp is to use as quite of a CCS as I can, I have chosen the Q6b, ZVP3310A option. Seeng that the MAX dissipation of the device is .6W I need to calculate the appropriate value for r48.

Given that my rail voltage is +/- 23V
subtract (VR2,R24,R26 network) voltage (about 4V)
subtract Vgs of diff pair Q5,Q7 (about 3.5V)
Leaves 15.5 Volts Vds across Q6

Power Dissipation would be (0.02A*15.5V) = .31W

To reduce power to lets say .2W and keep it linear I need to lose 8 volts which would set r48 to around 400 ohms. This puts the Vds of Q6 at 7.5 Volts.

I assumed Zero Volts on speaker out to back calculate Vds on Q6.

Additional note, I have chosen J1b and a J509 current regulating diode to give 3mA across D1b. R17 would be 10k.

Does this seem to be reasonable thinking?

regards
Scott
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Old 2nd March 2004, 08:58 PM   #115
Netlist is offline Netlist  Belgium
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Default Re: Aleph-X power supply

Quote:
Originally posted by Eric
I am starting to look at transformers and don't know how many secondaries I need.
This is what I brewed for one monoblock: http://www.diyaudio.com/forums/showt...297#post194297

/Hugo
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Old 2nd March 2004, 10:25 PM   #116
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Eric,
A single secondary will do in a pinch. You can always create a virtual ground using resistors, since very little current flows to ground in this circuit. A center tapped secondary will be better, and dual secondaries would arguably be even better still.
Start by determining how much wattage you want, then work backwards from there, as that will give you the rail voltage and an indication of where you want your bias set. If you're buying a new transformer, then you'll very likely end up with a center tap or split secondary. If you're buying surplus/used, don't be afraid to go with a single secondary if it'll save you money.
Scott,
I'm trying to visualize the front end current source in my mind...your thermal calculations look good to me. I can't remember where the J509 would go, as that's not something I put in (Vref for the CCS, perhaps?). Perhaps someone who has a schematic at their elbow can answer that one.
Low noise is a good thing, no doubt about it, but the fact that the front end current source noise is common mode once it hits the differential, it'll cancel out for the most part. My two cents worth is that a TO-220 device (i.e. the IRF9610) can easily do a half-watt with no heat sink. If you want to use another package, then flip a coin and decide how close to the Pd limit you want to run. I tend to run things a little cooler than some people--I like being able to hold on indefinitely.

Grey
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Old 2nd March 2004, 10:26 PM   #117
Coulomb is offline Coulomb  England
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In the file Axe.zip what resistor is the spread sheet calculating the value for?

I am so confused, the Aelph X is an option nightmare compared to Aelph2 boards from Dale Havardian. I am just about ready to give up on building an Aelphx. The more I read the more I get confused.



Anthony
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Old 2nd March 2004, 10:49 PM   #118
moe29 is offline moe29  United States
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Unless you need more watts than the original schematic with 15V rails
It's actually quite an easy build. Just follow the BOM and buy
parts that match the original schematic.

Where it's not so plum easy is getting the DC Offset within working
limits. But with very good matching (.01) she'll work, and the offset
will come into line... just have patience (that's what i keep telling myself!)

I mean, if i can do it anyone can!
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Old 2nd March 2004, 11:52 PM   #119
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Default Q6 and Power cont.

Grey,

Thanks for the reply. For clarification, the J509 is Q12b which is an option on the Group purchase boards and not in your original circuit. The option actually calls for a J505 (1mA) current regulating diode but I thought it would be better to increase the current with a J509 (3mA) to operate d1b(lm329) further away from it minimum. Could have selected a j511(5mA) as well.

I failed to remember that the CCS is common mode which reduces the importance somewhat. I also agree that operating Q6 in the to92 pakage at 40% of its max capacity isn't my cup of tea either. However out of all of the devices this is probably the easiest to replace.

Lets consider this, r48=0 Q6=irf9610 using a precision reference of the type lm329 as d1. With this example I calculate that the resistor network (r24,r26, and vr2) would have to be around 130 ohms to get sufficient Vgs for linear characteristics. As you stated earlier, Q6 would be well within its power limits and vref would be much quieter than the original zener.

Maybe I am being to short sighted, I will have to search for a precision 9.1V voltage reference and these questions will become mute.


In the end I may just end up with the original version, however, I'm having fun trying to learn this stuff and satisfy my desire for improvements with the minimum amount of smoke. Not that smoke scares me mind you.

Regards
Scott.
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Old 3rd March 2004, 01:43 AM   #120
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Default CCS Calculation Spreadsheet

Attached is a spreadsheet that I have been using for calculating the CCS components for the various configurations. I am not an electrical engineer so be careful with the results until somebody on the web that is more qualified can verify it. The results seem reasonable.
Attached Files
File Type: zip ccs calculator.zip (4.1 KB, 458 views)
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