| mik |
Hi all !
I'm following this forum for a while,and like someone said before in this forum I decided to stop reading and start building something.My choice is Aleph 30 and before I start I have two questions.I'm buying parts mostly in Germany because where I live(Yugoslavia) it is imposible to find heatsinks that big but also searching shops where I usually buying(Conrad,Reichelt and other) the biggest I found was rated 0.4c/w so I'm wondering:
If putting together three peaces rated 0,7K/W( ) would be enough for one chanel and second question is about mosfets, how meny i should buy to get 12 matched.
Thans in advance!
P.S
Sorry for my bad english! |
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| oliverniekamp |
If you take 3x0,4 c/w for one channel it will be working fine, if you take less it will get to hot.
You must not buy to many mosfets because you need 4 groups of 3 matched mosfet and that is much easier than matching 12 for the same value, so i guess 20 will be enough even in the worst case. |
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| HarryHaller |
One channel of an Aleph 30 generates 75 watts at idle. 25 watts
for one of the three heatsinks is 0.7 times 25 or 17.5 degrees C over ambient. This is fine and three of the 0.7 heatsinks will be adequate.
H.H. |
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| oliverniekamp |
| Sorry Harry, but i think you are wrong and one channel iddles about 100 Watt. 25V 2 amp for one rail. Nelson pass also mentioned 100 watt iddle somewhere in the manual. |
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| UrSv |
I second the 100 W but still 3 times 0.4 is too much (unless that is what you want of course) and the 3 times 0.7 will do just great adding another 6 C to the 17.5 Harry had ( 33 % more dissipation is 33 % more temp rise..) giving a total of 23.5 C rise which is hot but not too hot (IMHO). My Zen R is running 1 sink at 0.3 per side ( Austerlitz KS300.6 @ 100 mm height) and gets rather hot but not too hot (with about the same dissipation at 43 V and 2.4 A roughly).
/UrSv |
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| AudioFreak |
100W it is....
I plan to start construction on a modified XA later this year and given that we commonly have 35 degrees C in summer here i find myself having to take even more extreme measures to ensure that my expensive hardware does not self destruct during operation. I'm also trying desperately to rationalise the purchase of a AUD$900 Dot Matrix Vacumn Fluorescent Display for the multichannel control unit I plan to build (it will control the dd/dts/ac3 etc decoder, all the dacs and the preamps).
Good luck with your project.
Regards,
Daniel. |
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| HarryHaller |
| I took my numbers from the bias current on the schematic (0.5 amps per device in stead of about 1 amp as it should be). Looking at the bias circuit on the Aleph 3 and factoring the increase in number of output devices is probably more like 125 to 150 watts a channel. 50 watts times 0.7 is 35 degrees above ambient or about 60 degrees which is about 5 to ten degrees above the stated temperature for the Aleph 30 which is stiill aceptable in my eyes. I feel fine running my amps at these temperatures. |
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| oliverniekamp |
I have heatsinks 4 X 0,4 c/w for both channels together and it gets to hot to touch, but the aleph 30 didnīt break for two years and i dont switch it off very often.
The sinks are from conrad and it could be that the 0,4 c/w are just wrong because i found the same heatsink(20x15x4) at schuro and they say 5,5 c/w . |
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| oliverniekamp |
How did you get 125 or 150 watt?
Is it more than 2 ampere per rail? Than my calculation must be wrong. But i remember 2 ampere 100 watt from the manual. But Nelson Pass doesnt care for the dissipation values in the manuals too much, acording to the manuls the aleph 3 must have more output (4 ohm) with less bias than the aleph 30... |
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| cyclotronguy |
I just measured an Aleph 30..... 200 watts is correct.
Cyclotronguy |
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| HarryHaller |
I concede on 100 Watts and promise not to believe any bias currents shown on Passlabs schematics in the future. I based my numbers on .5 volts across 0.47 ohms from the Aleph 3 manual which uses the same bias scheme and source resistor values as the Aleph 30 but 4 instead of 6 output mosfets per channel. Any other differences in the A30 schematic we should know about?
H.H. |
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| Nelson Pass |
The service manuals are not DIY projects. You
will get an extra merit badge for navigating the
treacherous waters of any service schematic drawn
by Pass. |
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| HarryHaller |
It never stopped anyone else and I am damn happy to have them. Besides, what an amp or two of bias current in the grand scheme of things. I will read the DIY articals for more exact theory on bias current. Back to work on the Tex-X. Thanks for being a good sport Nelson.
H.H. |
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| LBHajdu |
| Would it throw the numbers off a lot of I used .5ohm resistors in my Aleph 30 and not .47ohm resistors. .5 ohms is about 7% off the original value. They are easier to get, so I have a wider range of types to choose from. |
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| swede |
I think I'll build an Aleph 30.
Not that I have any really good reasons, but it seems fairly simple to build (not my first project) and it has attracted my attention a couple of times.
So, if the service manual is not a good start, where should I start? I would like to design the PCB myself, just for the fun of it. I like TO3's.
Or is the service manual the only way to do it?
(or should I go for another aleph instead?)
//magnus |
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| HarryHaller |
The service manual is fine. I was giving Mr. Pass a hard time over the bias voltages shown across the source resistors being incorrect on the schematic. Lot's of people have built home made Aleph 5s and you should get plenty of support with questions posted on the forum. I thinks the TO247 output devices will be MUCH easier to find.
H.H. |
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| swede |
I'll try and find the TO3's first, but if I can't get them I'll go for the TO247.
Thanks a lot,
//magnus |
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| Freddie |
In case anyone is interested.
I have about 0,33V across the 0,47R source resistors on my Aleph 30... So the bias current is aprox. 2,1A
/Freddie |
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| oliverniekamp |
Thank you Mr. Pass, i appreciate the little miracles in your service manuals and take them as a grant support for my learning.
And what should i have done after severel zen amps, the aleph manuals attracted me to much and they sound so nice. |
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| swede |
Hi,
I tried to find more information on the forum about the transformer, but I couldn't find any.
Will I be home safe if I build an Aleph30 using a 300VA transformer with two secondary bindings of 18V for both channels? (=> sqrt(2)*18 - 0,5 v = +/- 25 volts)
Best regards,
//magnus |
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| Freddie |
swede,
The Aleph 30 draws about 200W so one 300VA transformer for both channels is a little bit to small for my liking. I would use a >=500VA transformer. 2*18V secondary windings is good.
I use one 2*18V 600VA transformer per channel in my Aleph 30, the rails are at +/-25V. However one 600VA per channel is overkill.
I bought my toroid transformers at www.elfa.se
/Freddie |
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| swede |
I can go for a 500VA instead, but what is a good theoretical value? Or should I go for two 200VA (one per channel) instead, or 300VA per channel?
//magnus |
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| Freddie |
swede,
Perhaps these articles about power supplies is interesting to you.
http://www.passlabs.com/pdf/powersupply.pdf
http://sound.westhost.com/power-supplies.htm
From Rod Elliot's article.
"VA Rating - Class-A
The minimum VA rating suggested is 5 times the amplifier power. A 20W Class-A amp therefore needs an 100VA transformer, or 200VA for stereo 20W Class-A amps. Larger transformers will again provide a "stiffer" power supply, and this will be beneficial. Nelson Pass suggests the ratio should be 7.5 times the amp power [2]."
/Freddie |
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| swede |
Phew, that calls for a really expensive piece of hardware...
No wonder hifi equipment is really expensive. The transformer cost more than anything else in the amplifier.
Thanks a lot for the links!
Best regards,
//magnus |
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| swede |
I decided to build two monoblocks with a 300VA transformer each. Hope it is enough.
Best regards,
//magnus |
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| Freddie |
swede,
300VA per channel is enough.
Good luck with the project.
/Freddie |
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| swede |
Hi,
I'm just about to power up one channel for my Aleph30 for the very first time. Mostly to get some measurements.
Wish me luck! I'll post pictures in a couple of days.
Best regards,
//magnus |
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| swede |
...and it seems to work. Runs VERY hot, due to my small heatsink. I'll change it tomorrow, to another small heatsink (though a little better). Now I have to make friends with someone at a junkyard, so I can get heatsinks cheap.
I got -0.078 volts on my output post. Is that way off, or within margin?
Best regards,
//magnus |
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| Freddie |
Referring to the servicemanual the DC offset should be <100mV.
So it's ok. I have a DC offset around 10mV after an hour or so, on my Aleph 30. When the amplifier is cold it's a little bit higher.
/Freddie |
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| mefinnis |
| quote: | Originally posted by Nelson Pass
The service manuals are not DIY projects. You
will get an extra merit badge for navigating the
treacherous waters of any service schematic drawn
by Pass. |
With the greatest respect to Nelson, where's my badge ????
Cheers, Mark ;) |
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| till |
question to you who built aleph 3 or 30:
how many caps did you use? the manual aleph 3 says 8*22000u , for aleph 2 its only 4. How much will i need? because it looks like these large caps are the most expensive part of the projekt. |
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| Freddie |
till,
The Aleph 30 uses 6*10000uF per channel. I wouldn't use less capacitance than that. I use 24*10000uF per channel in my Aleph 30. Capacitors are indeed quite expensive.
/Freddie |
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| till |
thank you Freddi. the cheapest way is instead of 8*22000u for example 36*4700u. or instead of 6*10000u 14*4700u
Are there disadvantages for such a solution? |
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| fcel |
http://www.apexjr.com/capacitorsR.html
I have bought computer grade Phillip brand 26,000uf/75V at only $6.95 each from the above link. I have not used it yet, so I don't know how well it'll perform ... but it's CHEAP! |
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| swede |
Hi again!
Now I have tried the first board on my Aleph30. It works! Thanks a lot to all of you! Especially to Panos (panos29) and (of course) Mr Pass.
How much bigger heatsinks should I get for each channel?
I didn't get it to go very loud (fairly loud, but not VERY), but I think that has more to do with me using an attenuator instead of a pre amp. I measured the input (from the attenuator) to be +/- 2 volts max.
It runs very hot, so I don't think the heatsink vill do. It gets almost too hot to touch after just 5 minutes.
Well, now I have to build a really nice enclosure.
See ya!
//magnus |
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| swede |
Hi all,
Now I got my monster heatsinks (big, huge, fat *** heatsinks), but my Aleph 30 still runs pretty hot. Actually I found them in a dumpster!
I read somewhere that 55 degrees C is the limit where it is no longer comfortable to touch a heatsink. Well I believe I run it hotter than that. I'll do some measurements on my amp, but I'm in the middle of packing all my stuff down in boxes. The next month or so will be amp-less, since I'm moving to Schwizerland on tuesday.
Isn't it so, that oscillations can heat up the output FET's pretty much? I'll scope my amp and see what happens.
I finally got two pieces of 300VA transformers (2x18 V). Will post pictures as soon as I can.
Best regards,
//magnus |
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| swede |
By the way,
Should I put heatsinks on the IRF9620 FET's as well?
//magnus |
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| Asen |
| BTW how much voltage do you have on your PSU? I'm not sure but I think the voltage must be +/- 20V (not 25 as in the manual). May be this is the reason for the big heat dissipation. |
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| swede |
Hi again,
Couldn't resist... The amp was there, waiting for me.
I read the thread on biasing an Aleph 2:
http://www.diyaudio.com/forums/show...h+bias+resistor
Marijan had measured his amp in a number of places.
On one channel I got the following readings:
Rails: +/- 22.5 V
Current on positive rail: 2.6 amps
Hmmm... that gives 117 W idle(?).
R11 (221 ohm) 5.60 V
R14 (392 ohm) 4.11 V
Vce Q5 4.06 V
Source resistors:
+chan (R34 - R36) 0.39 0.45 0.54 [V]
-chan (R37 - R39) 0.51 0.42 0.47 [V]
Well, that seems to be pretty high on the source resistors... And the FET's are not that very well matched. (I could almost tell that by touching the FET's earlier today. Two of them seemed to be cooler than the others).
Let's see here:
I = U / R
R34 0.39 / 0.47 = 0.83
R35 0.45 / 0.47 = 0.96
R36 0.54 / 0.47 = 1.15
-----------------------------
2.94 Amps
R37 0.51 / 0.47 = 1.08
R38 0.42 / 0.47 = 0.89
R39 0.47 / 0.47 = 1.00
-----------------------------
2.97 Amps
My output FET's are IRFP240 which I got from Fairchild. They are TO247 packages and I use silicone pads to mount them on the heatsink.
I find it strange that my humongus heatsink get so warm. I have to take a couple of pictures and post them here, so you'll see what I mean.
Freddie wrote earlier in this thread that his bias current was about 2.1 amps. Mine is close to 3 Amps... Weird...
Can I do anything about this? How hot can the heatsink/transistors get before they get ruined? If I'm fine with almost 3 amps bias current, I won't to anything.
Best regards,
//magnus |
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| swede |
Hi again...
I believe Mr Kirchoff is not on my side today (
I1 + I2 + ... + In= 0) ...
If I have 2.6 amps on the positive rail, it can't be possible for me to have almost 3 amps bias current...
Must be my multimeter that isn't correct enough. It's a CalTek Instrument CM4200. It cost me $100 so I hope it is not that bad after all... ;=)
Well, what I believe is that it is out of calibration between current measurement and voltage measurement. |
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| dieringe |
Could anyone tell me what an Aleph 30 is?
It's not an Aleph 3 as described in a3srvr0.pdf, or is it? I only count 4 output FETs in that schematic.
martin |
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| JasonL |
| look like a simple enough amp to build any one fab the boards around here .. i might try this project.. |
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| Nelson Pass |
It's an updated Aleph 3 with 6 outputs and a cheaper
heat sink / chassis and a few front end improvements. |
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| swede |
Hi,
The Aleph 30 is really simple to build. Make a search on "Aleph30 PCB" and you'll find a couple of PCB layouts. I did mine based on panos29's design.
Though I already (after a couple of hours of listening) believe 30 Watts is not really enough for me. I think I'll build an Aleph 60 shortly. That will probably do fine. But for Jazz and Classical music, 30 Watts is more than enough.
Best regards,
//magnus |
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| JasonL |
hey swead you should post a pic of your new heat sinks that yuor using i would like to see i might have some forsale that will do yo well they hold them to-3 ill take apic and post and yuo tell me what yuo think i think it will be perfect for you ..
J |
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| JasonL |
( hehe ) i twill also hold the other types too.. the pic will say a 1000 words..
J' |
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| dieringe |
thanks, just reading the article...
yes this sounds interesting. As the Zen seems to be too weak either for me or for my 4ohm speakers, I probably should try it...
swede, did you match the transistors? how many did you have to buy? the IRF240s are 10 euros each here...
martin |
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| transducer |
JasonL,
Can you tell me the dimensions of your heatsinks, including the depth of the fins? How much do you want for them, in Canadian $. I'm in Toronto. I'm leaving for vacation tomorrow back on the 6th.
Thanks,
RonS |
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| JasonL |
3/4 from back of base to tip of fins and the initial heatsink ie flat back is 7" x 12" and the l's on the base are 2 " aand the base thickness is 1/4 " and the l's are the same if yuo need any more info let me know and i dont know what to charge i know i cant use them and i want to get 2 heat sinks for my aleph 5's im making mono blocks and need 2 heat sinks one per block ..
J' |
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| wuffwaff |
Dieringe,
you can get IRFP240 for about 2,5 euro each from http//www.schuro.de. This will save you quite a bit and you donīt have to mount TO3īs
william |
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| dieringe |
thanks wuffwaff it's a pain ordering from schuro but if they are that cheap...
But: what are the values of R1 and the two (!?) R8s?
Could a voltage regulator like in the zen revision 3 be possible and helpful?
m. |
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| swede |
Hi again...
Nobody seemed to notice my last question... I have to be persistent then. ;=)
| quote: |
I = U / R
R34 0.39 / 0.47 = 0.83
R35 0.45 / 0.47 = 0.96
R36 0.54 / 0.47 = 1.15
-----------------------------
2.94 Amps
|
Isn't almost 3 amps bias current a little bit high for an Aleph 30, or should I just leave it like that?
Best regards,
//magnus |
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| JasonL |
| crank er up to 50 amps then buy a stinger and a clip and start wledin .. |
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| fcel |
Magnus,
Just for comparison and to give you some reference figures, I'm pretty sure it's 2.5A for the Aleph 2. So, 3A for Aleph 30 is definitely too high. But it could till work, I guess, if you have adequate heatsinks, add some additional components etc. |
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| fcel |
Magnus,
I just looked at the service manuals .... it says 2A rms for Aleph 3 and for Aleph 2, it's 2.5A rms. I hope we're talking about the same thing.
I understand that Aleph 3 is a little different from Aleph 30 but I don't remember what's the difference .... may be higher current for Aleph 30? |
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| JasonL |
Any one want them heat sinks. ??
im looking to sell them or trade them for ones for my aleph 5 |
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| wuffwaff |
Magnus,
2.94A really is quite a lot for a 30 but if your heatsinks are big enough and the power supply hasnīt got any problems I would leave it this way.
If not you can reduce the bias by lowering the value of the bias resistor. I also had 2.8A from when first firing up my Aleph 5 and lowerde R19 to about 38k. The cause for this higher bias is probably the lower hfe value of the BC550 I used instead of the ztx450.
william |
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| Koy |
Swede: I have A3 (modif. 30) too. It runs on 2.5A per rail. As have no possibility to match IRFs best as possible, I adjusted the current by different values of resistors ( from 0.33 to 0.68), bias current is about 0.87A ( +- 0.05) per T0247. I have much better heatsinks and it works (cools) good.I am afraid you heatsinks are too small for you current. I advise to go down.
Did you perform any measurements ( distorsion, etc.)? I noticed strage thing - high distorsion and different ration of harmonics - one channel with prevailing 2nd and second with 3rd. harmonics.
http://www.diyaudio.com/forums/show...p?threadid=4499
Your experience? |
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| swede |
Hi,
I'm using BC550 as well, which probably is the cause of the higher bias current. I'll change R19 to a better value.
//magnus |
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| swede |
Hi,
I finally got to it and took some pictures: |
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| swede |
Hi again,
Here's another one.
The sinks I got are 29 cm x 21 cm at the base. The fins are 7.5 cm tall.
But still... ;=) They get pretty hot.
//magnus |
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| dieringe |
swede, you should probably place the transistors more in the center...?
BC550: i tried to replace the ztx450 by bc637 in the pearl phono. they didn't match at all, but the ztx653 worked very well. maybe it's better if you try these?
hope the guitar doesn't get hurt... |
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| JasonL |
THOse are fat
didnt you say you did some dumpster diving to get them
where is that dumpster Located i would like some too..
J' |
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| swede |
Hi,
It was quite some time ago I did my initial measurements. Now when I have some real speakers to play on (finished my ProAc 2.5 clone project the other day) I had to assemble the second channel. No pictures yet, but I found out that one of the channels were a lot hotter than the other one. Both gets really hot, but I got the answer from Mr. Pass a couple of months ago, pointing towards the "BC550 transistor instead of ZTX450"-direction.
Here are the measurements:
Well I believe I dissipate 127W on the left channel and 93W if my calculations are right. I'd like to keep myself in the 100W playfield. I know I have quite a bad matching of the Q's on the left channel. (I wonder how bad it can be?)
So, my question (for which the answer I've been searching for on the forum for a while today) is:
Is it correct to lower the value of R19 to decrease the bias? Should I tamper with any other resistors?
Best regards,
//magnus |
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| UrSv |
Yes, lowering R19 will decrease the bias. Try connecting a resistor in parallell with R19, say 470K, and see what happens (you can do that with alligator clips for easy removal). Remember that you may have to adjust R21 for the current source gain gain.
/UrSv |
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| swede |
Why is that?
//magnus |
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| UrSv |
I think that adjusting R19 may affect the current source gain which then needs to be adjusted to the optimal value (which should be 50% I think).
/UrSv |
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| swede |
Well...
We'll se how it turns out with R21. I did that aligatorclip thingie...
It turned out pretty good... Cool, I never thought of using a large value resistor in parallell with R19. R19//470k = 43.1k
It looks a lot better now.
UrSv, bring something nice for dinner when you get to my place tonight! I'm starving. ;=)
Best,
//magnus |
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| UrSv |
Great news.
I'll bring something. You may need to increase the bias as the food might be cold when I get there though :yuck:
/UrSv |
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| wuffwaff |
Hello Swede,
I've just replaced the trimmers for R19 and R21 on my Aleph 5 and they were quite different for left and right channel.
On the left R19 is 47k and on the right it`s 100k. Both values lead to 2.4A bias. The main influence is the difference in the source fets where the "sence resistor" is connected so when matching it would be intelligent to use values in the same range for left and right channel current source fets (I will do this for my upcoming monos).
R21 turned out to be 390R for both channels as an optimum value for sound quality with my speakers (about 2.5 ohms all the way). This means a ac current gain of a bit over 60% for 6.8A peak current (still 1A shy of the original Aleph5 spec wich was 8A). This value gives 52watts/8ohms and 90watts/4 Ohms
It is true what URSV said that the current gain is also affected by R19. When upping the bias from 2 to 2.4A, ac-current gain went from 50% to 43%. I think this is caused by the changed "input impedance" of the BC550/ZTX450 in combination with 19.
william |
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| Tony D. |
Hi wuffwaff, do you measure the ac-current gain accross R21? And what kind of reading are you looking for?
If I am reading your post correctly you are judging the current gain quality by ear, no?
Thanks for any info.
Tony D. |
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| swede |
Hmm...
I'm still not with you (yet). Can we take this slooow so even I can understand it.
Start with "what is it for, the R21?".
And what do you mean with the gain? I'm really interested, but have not yet got the grip of R21. I hope you don't think I'm stupid and uneducateable. ;=)
How do you calculate those 60% and the 6.8 amp.
I believe I know how you calculate the current though, but not the 60% (since I don't understand the figure/number).
Best,
//magnus |
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| UrSv |
Hi Swede,
Actual calculations are somewhat complicated it seems but implementation is easier. I think that essentially R21 measures the AC current in the negative part of the output stage and feeds that back to the current source which is then driven to share the work for the output current. Nelson replied in a previous thread:
"When you parallel devices in an Aleph but want to
vary the bias per device, you look to the value
of the Source resistances on the current source
(the bank on the positive half), and also (referring
to the Aleph 60 schematic) resistor R19.
After you get the DC figure you are looking for, you
want to adjust the AC gain of the current source so
that the current source provides about 50% of the
output AC current.
The easiest way to do this is to build the circuit
without R21 and operate it at 10 watts or so into a
load while measuring the AC voltage across R46-51
which are the Source resistors on the negative half
of the amp. Put in a value for R21 which halves
the AC voltage across R46-51, and you'll know that
the current source is doing half the work."
Hope this helps
/UrSv
Try:
http://www.diyaudio.com/forums/sear...rder=descending |
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| wuffwaff |
Tony D., Swede,
current gain can be calculated by measuring the maximum output current.
For a current gain of 50% half of the output current is delivered by the current source so max. peak output current is twice the bias current.
So if the max. peak current is 6.7A and the bias is 2.4 A then the ac current gain is (6.7-2.4)/6.7x100%=64%
I came to this value by raising the current gain (lowering R21) until the sound coming out of the speakers didnīt sound "compressed" anymore. Iīm still not shure what the actual effect is cause normally I donīt listen at these power levels. So at "normal" listening levels the current source wonīt turn of but it will take a larger part of the current, leaving the bias current through the other fets more constant.
As soon as Iīm able to set the bias to 4A I will know if itīs only the power that counts or if there are other effects too.
For a very good explanation of the circuit it would be good to read the patent a few times (or even more often).
william |
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| swede |
Hi,
As usual, knowledge just makes you realize how little you know... ;=) Just when I thought I knew how an amp is working, this little master piece with just a handful of parts, it got back to me and demands some more investigation.
I've been reading old posts in the forum for an hour now, even though I should have gone to bed. The conclusion is that I now know that there is some really good use to change the R21 value. I also know that I will have a couple of more hours of reading the patents as well.
Thanks William and Urban. (by the way, thanks Urban for the food.)
I need (would like to have) more measuring equipment as well! Knowledge is really expensive nowdays...
Best,
//magnus |
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| swede |
By the way,
I'm either stupid or just plain tired... But which patents should I get hold of, and where do I get them? Sorry for being lazy, but my searches on the forum gave no fruit.
//magnus |
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| BrianGT |
You search on the uspto website. Here is a link to the advanced search page:
http://patft.uspto.gov/netahtml/search-adv.htm
Search for the string:
in/Nelson and in/Pass
It will bring up his Pass Labs patents. You will want to read 5,710,522 and maybe some of the others.
You will probably have to download the tif viewer to see them, which is available at:
http://www.alternatiff.com/
--
Brian |
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| swede |
... but the USPTO is charging $3 per patent. I figured I'd get the seven patents I found there, total $21. What the heck, I'll just pay for it.
Are there any copywright for the patents? Can I distribute them freely afterwards (with no charge)? I'll get them in PDF, I believe. Does anyone else have them for distribution (if legal)?
Best,
//magnus |
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| swede |
Ah, found a site...
I believe you were kind of pointing in this direction anyways...
http://www.alphapatent.com
Requires the TIFF plugin mentioned above.
//magnus |
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| UrSv |
Why not just download the images and print them?
/UrSv |
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| swede |
This is because the images didn't work on my computer at work. Some kind of restriction, maybe. Don't know.
I got it out on my printer, though.
But how does it work? If I get the PDF:s, can I redistribute them?
//magnus |
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| UrSv |
I just downloaded them and it seemed to work fine. For redistribution I have NO clue.
/UrSv |
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| swede |
Sorry guys... I wasn't smart enough... The USPatent office was smarter than me and set cookies for retrieval of patents... Bummer.
//magnus |
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| protos |
Magnus,
When you say hot have you measured your heatsink temp. ? |
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| swede |
I haven't exactly measured the teperature of the heatsinks, since I don't have the right tools for it. Though I've used my hands to feel the heat and they were not comfortable to touch. Maybe not to the point where I have to remove my hand immediately, but really warm.
//magnus |
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| protos |
Magnus,
Before getting worried about whether your heatsink temps are too hot I would think a relatively accurate measurement is necessary. For example , 45-50C might seem uncomfortable to you but is whithin the recommended range. Looking at the measurements of your heatsinks and using a very rough comparison with mine 29x21x7.5=4567.5 vs mine 25x30x4=3000 I would say that you have plenty of heatsink. Mine are rated at0.33c/w and they dissipate around 75 W at 45C. You seem to have about 50% more heatsinking so dissipating around 120W would have you at more or less the same temp.
So I don't see any problem with the higher bias since most people agree that Alephs sound better that way.
Of course I am not an expert and these are rough estimates.
I also didn't have a temp measurement device until I bought it included in a new multimeter for 40 euro altogether new. |
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| macka |
On the current share issue,
Mr Pass emailed me some time back with a useful method.
I also have the patent some where on disk is you require.
Method.
Run the amp for 1 hour to warm up. then apply a 10 watt (I K sine wave) signal to the load (ie 8ohms).
Measure the voltage across the source resistors on the negative side and then calculaterand derive the total current x the number of resisitors ie 3 , 6 pairs as the case may be.
While the signal is still applied, now measure the voltage across the bunch of resistors on the output in series with the load and again derive the total current to the load.(AC)
You then compare the current share of the negative side to the current via output, adjust R21 until you get 50% for the negative side.
This is done with removing any resisitors, and hence is convenient.
The maxim is a work out your requirement for DC bias for the intended load and power, set up the amp accordingly, then adjust the AC current share for 50% into that load which will give best performance.
The amp is best optimised for you load impediance, and may not sound best at another impediance unless the current share is trimmed to suit.
Hope this helps as it can be confusing,
Cheers
macka |
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| wuffwaff |
Hi Macka,
Iīm afraid your confusing me a bit concerning the ac-current gain. As far as I know this is not dependent on the load the amp sees.
Senced is only the current through the output resistors and via R21 fed back to the current source. If the ac-current gain is 50% at 8 ohm it will also be 50% at 4 ohm.
So when optimising the amp for a given load the only thing you can change are bias (when possible) or ac-current gain (leaving the "ideal" 50%).
william |
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| macka |
Hi William,
I see what you mean, When I wrote this I was recalling what Mr Pass had said in a much earlier thread.
I will try and find it, I will have to read up on this but I suspect we are talking the same thing but from different angles.
I recall the matter concerned the Aleph 5 bias and current share and some issues surrounding power/distortion in to 4 ohms vs 8 ohms.
I suspect the matter concerned varying the current share to improve the 4 ohm operation for a fixed level of DC bias.
As to the purpose of R22-R27 which is a very low resistance, the small voltage drop accross them and hence current sense/shift only comes into play with a significant shift in load current and therefore load impediance, the effect of which is the AC current message sent back via R21 under heavy loads only, so the current share must shift relatively at high drive levels where this equates to an inductive load, or a drop in load impediance.
The sharing of AC current under the Pass patent, allows as we know, 2X improvment of efficiency over the traditinal passive (DC only) current source where only the negative side conducts AC current.
Forgive me if I am wrong, but I have a feeling this is the purpose of R22-R27, that is to modify the efficiency of the amp under the effect of real world speaker loads for a given level of DC bias.
Cheers
Ian |
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| JDeV |
| quote: | Originally posted by swede
[BI got -0.078 volts on my output post. Is that way off, or within margin?
Best regards,
//magnus [/B] |
Can someone please explaine to me why the reading on the output posts are negative? I just start to learn about electronics so please excuse stupid questions. |
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| swede |
Well,
The offset is less than 100mV (+ or - doesn't matter), so it is not a problem for me. When I wrote that, I wasn't very experienced with the Aleph 30.
What the negative reading could origin from is either badly matched input FET's, or differences between the positive output FET's nad negative output FET's. Could be either.
Though, the important thing here is that you usually get a (very) small amount of (prefereably) negative voltage (less than 100mV) on the ouput.
In my case it wasn't a problem, just insecurity in my own competence that made me put up the post.
//magnus |
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| Algar_emi |
My first channel of my first Aleph30 is working now. I had to reduce R19 from 47.5K to 30.2K to get o.5A on the IFR240 current sources. With 47.5K I was getting 0.8A.
My problem, if a problem it is, is that when first starting the amp, The current on the Positive side of the supply jumps to the maximum of my test supply (limited to 3A for testing), then after about 1 sec, it drops to the normal 1.5A.
Is this normal?
If not what can cause this behaviour?
Thanks in advance... |
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| Algar_emi |
Here results from my aleph30. Are my calculations Ok. The IFR240 are really hot and I don't want to destroy them...
Note: All values in Deg C/W are thermal resistances
IFR240, Rjc max:0.83 C/W, Max Tj: 150C (from Specs)
Rcs (typical): 0.2 C/W
Heatsink used: 0.45 C/W (no fan)
Temp Case=75 deg C (after 48hrs, running full power 30W)
Power dissipated per FET: Volt DS X Id = 24.7V * 0.5A=12.35W
6 FET mounted on the same heatsink:
Pd = 12.35W X 6=74W to dissipate...
Now my question, do I used Total Power for all six Fets on the same heatsink, 74W, or the power for just one fet, 12,35W,ex:
Temp Junction = Tcase + (Rjc X Pd) = 75 + (0.83X74)=136C !
Or
Temp Junction = Tcase + (Rjc X Pd) = 75 + (0.83X12.35)=85C
Thanks. |
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