| Alain Dupont |
The first images of my A-70...
Just received my new digital camera PowerShot A70 ...
Alain.:cheerful: |
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| Alain Dupont |
| The left channel... |
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| Alain Dupont |
Nelson and Grey,
Do I qualify for DIYer ?
Regards.
Alain. |
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| trigon |
Bravo, but I can't see the PS capacitors.
Nice job. ;)
Trigon |
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| roddyama |
Very nice job Alain,
Now that you have the camera, keep the pictures coming.:) |
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| Nelson Pass |
| quote: | Originally posted by Alain Dupont
Do I qualify for DIYer ? |
Of course. Kurt Vonnegut would say, "You are what you
pretend to be."
:cool: |
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| Alain Dupont |
trigon,
The 2 battery of caps by channel will go under the rails CRC with 5 * 5600micro F - 0.5ohm and 5 * 5600micro F, i will send an other photo for that soon... so for the preamp part fixed on the back pannel, using Peter Daniel's idea ; pot's on the back of the PCb for easy adjust.
Nelson,
Thanks, always funny... :smash:
Regards for all precious comments.
Alain.
PS: Still drilling the right channel heatsinks, a lot of holes... :bawling: |
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| Alain Dupont |
| The caps in CRC schema... |
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| Alain Dupont |
| The pre, without the fets.... :eek: |
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| Alain Dupont |
The fan...:redhot:
The little pcb on the right is for 20 volts regulation + a differential
with a temp device to regulate the fan speed between 7 and 12 volts.
A+
Alain.
Still drilling...:dead: |
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| Alain Dupont |
Still drilling the heatsinks, I have 12 pieces from Thermaflo Model# EH 1126b. it's 10 holes in 10-24 plus 2 * 10 mm for the ventilation...
At least it remains only 4 to drill...:clown: :clown: |
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| Drafance007 |
| HOLLLYYY COW.....What is this amp ment to drive??? Looks like it has more power than a local electro-distribution can support??? |
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| Alain Dupont |
Drafance007,
Only to drive my 2 Martin Logan Aerius i
At that time there is only 1 transfo Plitron 750 VA; but if it works well
I could add an other 750VA ... The goal is 2*100 Watts "pure class A"
The A75 will replace my C350 NAD
:smash:
There is also the subwoofer with a 12" Shiva MK III from Adire with a 270 Watts amplifier inside...
I plan to build after that a Aleph-X at 2*60 Watts to try biamping...
Regards.:cool:
Alain. |
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| trigon |
Alain, absolutely perfect job. A+
You may want to experiment later with different rectifiers like IXYS
My experience with IXYS is marvelous. Just my two cents. ;)
Trigon.:) |
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| djk |
So how are you going to duct airflow through the main heatsinks?
In natural convection they will be inadequate for the heat involved, the fins are spaced for heavy forced air. |
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| Bricolo |
Wonderfull job!
BTW, drilling and tapping is such a nightmare |
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| Alain Dupont |
Djk,
The Heatsinks are dissipating 25watts for a 8" length in natural convection
and there are 12 pieces (6* by channel)
So in Natural convection that is roughtly 300 watts...:hot:
for a 50 centigrade rize over ambiant....
But the two 10 mm holes in the lower part of the sinks
will receive an air flux of 200 to 400 LFM to cool them down... :cool:
The idea is to deviate the flux passing through the sink horizontaly
and deviate it verticaly ; and the trick is a serie of little sheets (plates)
placed at a 45 degree angle right inside the sinks ; see the shema.
To be able to acheive a temperature rise of only 30 to 35 degrees over ambiant... :cold: :cold: |
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| Alain Dupont |
Bricolo,
Yesterday I broke a tap inside the last heatsink (Murphy's law applies also to DIYer's), I will have to by a new 10-32 tap this morning :bawling:
and try to remove the broken one, a nightmare :xeye:
Overall dimensions ot the amplifier are 17" length by 17" deep and 8" height
Well, I have to go buy my new tap...
Nice day to all, and thanks so much for you wonderful comments.
Alain. |
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| PassFan |
| quote: | Originally posted by Alain Dupont
Bricolo,
Yesterday I broke a tap inside the last heatsink (Murphy's law applies also to DIYer's), I will have to by a new 10-32 tap this morning :bawling:
and try to remove the broken one, a nightmare :xeye:
Overall dimensions ot the amplifier are 17" length by 17" deep and 8" height
Well, I have to go buy my new tap...
Nice day to all, and thanks so much for you wonderful comments.
Alain. |
Almost impossible unless you have some left hanging out. Easier to redrill the hole elsewhere and hide the old one. A professional is one who can hide his mistakes. We all do it. Next time use parrafin to lubricate your taps. Good luck with your cooling plan, I hope it works.
:hot: |
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| Bricolo |
| quote: | Originally posted by Alain Dupont
Bricolo,
Yesterday I broke a tap inside the last heatsink (Murphy's law applies also to DIYer's), I will have to by a new 10-32 tap this morning :bawling:
and try to remove the broken one, a nightmare :xeye:
Overall dimensions ot the amplifier are 17" length by 17" deep and 8" height
Well, I have to go buy my new tap...
Nice day to all, and thanks so much for you wonderful comments.
Alain. |
Guess what... exatly the same thing happend to me with my gainclone
In the last hole :xeye:
I was tapping a 20mm deep plate, absolutely impossible to remove the broken tap in this situation.
In your case, if you're tapping the heatsinks or a thin metal sheet (not 20mm!) maybe you can remove the broken tap. But it won't be easy.
There are 2 solutions (in fact 3, but the last one isn't for DIYers...)
-find or make a tool with 3 "tooths", and try to turn the tap out of the hole. Something with 2 'tooths" sometimes work, like a big pair of compasses.
-punch it out of the hole. But this will destroy the tapping, you'll have to do another hole or a bigger tapping in this one
-the last solution is to burn the tap. they are made of a special alloy that burns and turns into powder. This is done by connecting the tap and the piece of metal to high voltage. But not a diyer friendly solution. Don't try this without the stuff specially made for this! |
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| Bricolo |
| And I'd advice you to use rounded reflectors (1/4th circle) flat ones will orient the air flux 45° and it will go out of the heatsink |
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| crown300 |
You might also try using a 'dremel' tool with a 'cut-off' wheel (the fiberglass ones are better than the'sand' ones) and cut a slot into the broken tap.
Then use a screwdriver to rotate the tap out. |
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| Alain Dupont |
trigon,
thanks could you tell me what type and model you are using ?
I have a 750 VA transfo with 2*45 amps rectifiers..
And thanks for the compliment, hope it will work fine too. :rolleyes:
crown300,
I have tried to make the cut for a screwdriver, but the tap has 2 failures inside so it will stay inside for a very long time....:angel:
Bricolo,
Could you precise your point, please. I don't know anythig about fluid dynamics. I am interested in your idea.
Regards.
Its could this morning in Montreal -20 celsius, The A75 could have helped
keep the house warmer...
Alain. |
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| Bricolo |
| quote: | Originally posted by Alain Dupont
Bricolo,
Could you precise your point, please. I don't know anythig about fluid dynamics. I am interested in your idea.
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The air will keep the direction that the reflectors give to it.
So with 45° reflectors, the air will run out of the heatsinks
with a 1/4th round reflector, the air flux will be oriented to run the long of the heatsink |
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| Alain Dupont |
Bricolo,
Some thing like that... |
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| eeka chu |
Alain,
In the piccy with the fan in it, are there four hex nuts attached to the chassis to hold that platform up over the fan? I'm just curious to know how they're attached to the chassis if they are. I know it's not really a major question, it just annoys me when I see something and can't work out how it's being done! :D
As to the broken tap... phone some local machine shops and see if they have a plunge EDM machine, or an EDM centre that will plunge as well as perform wire EDM.
EDM stands for Electrical Discharge Machining. It will easily cut through high carbon steels since it doesn't involve physical tool contact.
In your case, they'd attach the heatsink to one pole and then a long, thin electrode to the other. The part would then be submerged in some form of recirculating coolant, come charge conveying fluid, and the electrode moved down onto the tap. Lots and lots of high power sparks later, the tap will have been cut out and you should be able to reuse the original hole to some degree, depending on how well the tap has been cut out.
The electrode is usually about 1 - 2mm in diameter.
It can be insanely expensive or cost nothing depending on how the guys are feeling who work there. Small EDM machines take forever to burn a broken tap out. The bigger ones can do it much more quickly.
As the machine cuts, it rotates the electrode around the diameter of the tap and very slowly moves down into it.
You probably already know about EDM, if so, I appologise. If not, check it out! :)
John |
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| Alain Dupont |
eeka,
At this time there are only 4* 10-32 by 1" long bolts to hold the bottom pannel, the future feets will be round aluminium 42 mm diameter and 24 mm height.
the fan is a very silent model with ball bearings ; that will work between 7 to 10 volts (its a 12/15 volts DC model)
Regards. |
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| Mark A. Gulbrandsen |
"BTW, drilling and tapping is such a nightmare"
___________________________________________________
Not so if one uses the correct ype of taps. If you work with alot of alumnium...who here doesn't.....then the use of either spiral or two flute taps makes that chore ALOT easier. ALso the use of a tapping lubricant such as TAPMATIC FOR ALUMNIUM makes the job so easy you would be amazed. Never try to tap alumnium dry!!!!! Also do not to try to tap a bling hole in one tapping step...do it in three or four steps by backing the tap out every couple of turns to clean off the chips.
For more technical info about different typs of taps see this web site!
http://www.tapmatic.com/tech_manual...mendations.html
Info on LPS cutting fluids can be found here.....
http://www.lpsdirect.co.uk/tapmatic/index.htm |
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| Alain Dupont |
Mark,
Thanks for your advises.
Just a look when it will be finished, with precious wood inserts in the facade
(these are simple oak) I was thinking of Birds eye Mapple for the final touch.
Regards to all.
Alain. |
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| GRollins |
Alain,
Yep, I'd say that you qualify as a DIYer.
I've had good results removing dead taps with a Dremel bit. They make several with small diameters; one's sort of ball-shaped, at least two cones, etc. Patience and a steady hand are the key. If you can buzz out the center, the flutes will be no problem. Start very, very gently. Get a dimple in the center before applying pressure. Once you've got the dimple as a guide, you're in good shape.
I can sympathize with your frustration. I have an extensive selection of tools, but it's weighted heavily towards wood working. The amount of stuff I have on hand for metal working is limited.
Grey |
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| Magura |
A bit of echo.....
To get the broken tap out you can use edm as someone pointed out. It is slow and most likely expensive!!
A more DIY friendly solution is to get the tap out with acid. I cant remember what type of acid we used (havnt broken a tap since college), but its possible to do with little or no damage done to the aluminium.
To avoid the broken tap problem in the first place is not all that hard.
To use spiral flute taps is not correct. Such taps are much more fragile than a straight flute tap. A spiral flute tap is for tapping holes that dont go all the way through.....and exclusively for tapping by machine. No hand tapping should be done with such.
Instead you must use alcohol as lubricant. It will leave your thread perfect and shiny.
Another important factor is that the tap used for aluminium must never be used for any other metal. If used just once for steel....its never gonna make a good thread in aluminium again....the same goes for tapping copper. You need a set of tools for each material.
Cheers
Magura |
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| Mark A. Gulbrandsen |
I really disagree with your assessment of using spiral flute taps in alumnium. Even the tap manufacturers reccomend using them on alumnium either by hand or by machine. the get much more stress in a machine environment too. Alumnium is not a hard metal as is steel or stainless steel. There is extra clearance for the chips when using a spiral tap, especially when tapping holes larger than 1/4 inch. Alumnium generally creates large continous chips when tapping. I can't remember when I last broke off a tap in alumnium using a spiral tap.
Also while alcohol may be satisfactory for tapping alumnium, the use of a fine tapping fluid such as Tapmatic for Alumnium or several others made specifically for that material will give you an even better finish and the tap will last far longer than it would with just alcohol.
I completely agree though with keeping a set of taps for differing metals. Fomr a metalurcical standpoint that is very proper to do. I think the majority of DIY'ers here work with alumnium though.
Mark |
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| eeka chu |
I quite like using taps! :) It's something quiet to do for a while instead of having to hold onto a mill's swarf covered dials.
Just put some tapping fluid on it and work very slowly. I use a quarter of a turn in the cutting direction, then run it back out about two quarters, then back down and move forwards another quarter. If you try to do it any faster, broken taps are waiting for you! :D |
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| Magura |
| quote: | Originally posted by Mark A. Gulbrandsen
I really disagree with your assessment of using spiral flute taps in alumnium. Even the tap manufacturers reccomend using them on alumnium either by hand or by machine. the get much more stress in a machine environment too. Alumnium is not a hard metal as is steel or stainless steel. There is extra clearance for the chips when using a spiral tap, especially when tapping holes larger than 1/4 inch. Alumnium generally creates large continous chips when tapping. I can't remember when I last broke off a tap in alumnium using a spiral tap.
Mark |
The statement i made was intended for the DIY people. I am perfectly aware of the manufacturers recommendations. It is though a fact that a spiral flute tap is only half the strenght of a straight flute tap, and since the main problem for a DIY'er is not to speed up the thousands of threads he have to cut, but to cut those few threads in an amp or so...without breaking the tap. A straight flute tap is lots better for the purpose.
As well with the cutting fluid. A diy'er will cut 20 threads a year....and sure dont have the correct cutting fluid around for aluminium. In that case alcohol does just fine. I agree that the tool life is shortened.....but how many DIY'ers would ever wear out a tap by cutting aluminium ??
Cheers
Magura |
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| Magura |
ohhh....and besides that, a straight flute tap of reasonable quality will break the chips and push them in front of the tap.
Magura :) |
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| Mark A. Gulbrandsen |
"ohhh....and besides that, a straight flute tap of reasonable quality will break the chips and push them in front of the tap."
____________________________________________________
Yes they sure do, and thats what causes taps to get jammed in a blind hole and break off! As for the fluid it is very common over here. Gee, 20 holes a year.....I'm a DIY'er and I've tapped several hundred holes in the last year just for my home audio projects..... I doubt there is a single Aleph 2 out ther that has less than 25 tapped holes in it and 50 might be more common...and then there are two for a stereo system. There are 12 power devices alone to mount with tapped holes.
Mark |
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| Magura |
| quote: | Originally posted by Mark A. Gulbrandsen
[B
Yes they sure do, and thats what causes taps to get jammed in a blind hole and break off! As for the fluid it is very common over here. Gee, 20 holes a year.....I'm a DIY'er and I've tapped several hundred holes in the last year just for my home audio projects..... I doubt there is a single Aleph 2 out ther that has less than 25 tapped holes in it and 50 might be more common...and then there are two for a stereo system. There are 12 power devices alone to mount with tapped holes.
Mark [/B] |
No matter how you put it...a tap lubricated with alcohol will do thousands of threads....not 50 or 100 :)
For blind holes a spiral tap can be used with care by hand...but ideal is to make the hole deep enough to make room for the chips.
Magura :) |
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| Peter Daniel |
| quote: | Originally posted by eeka chu
I quite like using taps! :) It's something quiet to do for a while instead of having to hold onto a mill's swarf covered dials.
Just put some tapping fluid on it and work very slowly. I use a quarter of a turn in the cutting direction, then run it back out about two quarters, then back down and move forwards another quarter. If you try to do it any faster, broken taps are waiting for you! :D |
Tapping seems like a touching subject, everybody has his own ideas.
But if you do it by hand, you must be kidding yourself. I simply use a cordless drill gun with clutch (and reverse) and then I can say I really enjoy tapping. Never used spiral taps and regular ones work fine for me. With a drill gun I can tap 60 #4 holes in 15 minutes.:) Never broke a tap either.
http://www.diyaudio.com/forums/show...69414#post69414 |
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| Alain Dupont |
Ok,
I will not tap for a long time now....:cool:
All the major heatsinks are done, let me finish the enclosure.
Thanks for all those ideas.
Best regards to all.
Alain. |
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| Mark A. Gulbrandsen |
Peter,
That method is a great way to go and I do repeated through holes that way as long as squareness of the threads is not an issue. If a tapped hole needs to be perfectly square though I use my tapping jig or start in on the verticle mill and then finish by hand. Tha majority of my tapping is done with two flute taps for sizes under 1/4" and sprial flute taps for over 1/4". 4-40 and 2-56 only come in three or four flute taps.
Since I also do most of my stuff as countersunk and flush head allens a perfectly square tapped hole is important to me most of the time. When I make a chassis I like to keep things to at least plus or minus .01 or better most of the time. I admit it is nice having access at work to a verticle mill and a lathe to do my work on.
To dissolve a broken or stuck tap from Alumnium immerse the piece in into a well saturated solution of Aluminum Sulfate at 120+ deg F. Let it work for a number of hours.and it will literally dissolve the remains of the tap. You must make absolutely sure there are no other ferrous patrts on the piece you want to do or they will also be dissolved. This method only works on alumnium!! Another route is to simply have the part anodized as that process will also dissolve anything ferrous in the alumnium part. When you get the part back simply finish tapping that hole.
Mark
Added: If you do the Alumnium Sulfate solution be sure to only use glass or plastic containers!! It would dissolve a steel container! |
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| Peter Daniel |
| quote: | Originally posted by Mark A. Gulbrandsen
Peter,
That method is a great way to go and I do repeated through holes that way as long as squareness of the threads is not an issue. If a tapped hole needs to be perfectly square though I use my tapping jig or start in on the verticle mill and then finish by hand. Tha majority of my tapping is done with two flute taps for sizes under 1/4" and sprial flute taps for over 1/4". 4-40 and 2-56 only come in three or four flute taps.
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I can't really imagine how your thread won't be square, if the hole is drilled properly.
But since you use all those fancy taps it may be an issue. You see, older taps were shaped in such a way, that tapping action was self guiding and the tap couldn't be not square in a hole. That's why I prefer to use those older type and using drill gun helps further to start tapping properly. I remember when I used to do it by hand, the smaller holes where always hard to start.
I never used jigs or mills for tapping and all my work was always very accurate. But I'm also pretty skilled with hand drills (not exaggerating I have at least 20 different types of them) ;)
PS: I remember when in 80's I was playing with those things, taps where available in sets of 3 (for manual work). First one had barely any threads ( and was intended to start a hole), then was an intermediate one (to do the real tapping work) and finally the finishing tap, to make the final thread. |
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| Alain Dupont |
Finished taping... ;)
See the last pictures.
Regards. |
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| Alain Dupont |
| Picture two. |
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| Alain Dupont |
The two channels...
For today that's enough...:bawling:
See you tomorow.
Alain. |
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| moe29 |
First i want to preface this comment - your work is absolutely top
notch! ...and i knew the minute the "tapping" subject came up
we were in for some heart felt serious posts! Tapping brings out
the beast in DIY'ers (for some strange reason)
But, at this point in time, why build an A75 instead of an Aleph 2?
Parts on hand? asthetics? ability to drive low-impedance loads?
Works better in your bi-amp/tri-amp setup?
I'm not trying to slagg you off, was just wondering. The Aleph 2
seems to follow the PassLabs ideal of simpler circuits - better sound.
Please don't take this wrong... it was worth it for you to build this
amp, just for the lovely pictures!
m. (who uses the Peter Daniel method for tapping... and it works!) ;) |
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| Peter Daniel |
Yes, the work is indeed top notch, on equal level with best that we've seen here. So you qualify for DIYer.;)
Building A75 brings slightly different pleasure than Aleph. Whoever never did it, don't know what I'm talking about: all those TO-3 devices mounted in rows and there are 24 of them per channel ;). I'm still using my A75 amp for subwoofers. |
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| lgreen |
| Just wanted to let you know that in 10 minutes I broke off a 4-40 and a 6-32 tap in the hole when I was tapping by hand into heat sinks for my GC. After one broke I just switched to the other wich then broke. They were getting tough to spin, so I should have known. But it was after many beers so not really my fault. Your stuff looks very good. Nice work. Keep us updated. |
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| Variac |
| I drilled the heatsinks and used self tapping sheet metal screws to install my aluminum power resistors. Maybe they'll loosen up maybe they won't......:rolleyes: |
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| Alain Dupont |
moe29,
> work is absolutely top notch!
Thanks I realy apreciate.
>why build an A75
Because the Aleph X was not created at the time of choice, second I wanted Power!
Also I needed to drive my electrostatics speakers, Martin Logan Aerius i go low at 1.7 Ohm >15kHz
This A-75 is built for 80/100 watts pure class A.
Peter,
>Equal level with best that we've seen here
Thanks so much, I have made plans for 1 month before starting the project,
so many nights, not hard work, but pleasure and delight...
lgreen,
I will keep posting... :D
Special thanks: to Peter Daniel who sold me the cap's and 750 Plitron transfo's
to Norman Chow who sold me the 48 TO-3 Mosfets lost in his closet !
Great thanks: to Norman Thagard and Nelson Pass to make such things happen !
Special reward: My girlfriend Danielle, because hi-fi is not a girls thing, she is giving me great support.
To be done: install the PCb for regulation and temperature security (2 big 24DC relays 30 Amps for standby ) and fan supply
Install the mosfet's on the pre PCb, work the cabling...
Then the fun will start :clown: , put the scope on and finish the tests....
Future projects: One X-BOSOZ with CCS and Phono Pre. integrated
with separated power supplies ; 6/7 input's with 2 balanced and Tape in/Tape Out
+ 2 output 1 balanced + 1 for subwoofer...
I want to get reed of my NAD C350... |
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| Alain Dupont |
The power supply for the pre. is running at 2*49 volts, I expected 2*50 volts
and the alim for the finals is 2* 39 volts with no load...
I think its correct for the first run.
PS: The blue light is shinning prety good !
Alain. |
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| JOE DIRT® |
| Alain ...nice work!!!...perhaps you know Silvain (local to you).... |
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| Alain Dupont |
Joe,
Thanks, I don't know Sylvain, is he in Montreal ?
regards.
Alain. |
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| JOE DIRT® |
| yes...and a fellow active audio guy from the island.......I saw your location as I lived in Lasalle for a few years |
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| Alain Dupont |
Joe,
That's 7 years I live in Lasalle.
Could you give me the email of Sylvain, I will contact him.
Good fellows of DIYAudio.
A+
Alain. |
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| grataku |
Alain,
Great job!
Alain and all:
the carbon steel of the broken tap dissolves over the course of 24hrs using a mixture of readily available acids that leaves the Al absolutely untouched. It's a trick an old machine shop guy taught me and which I have readily forgotten. I will ask the guy for the correct proportion af acids again if anyone is interested. As I said it takes a little patience. You can use the 24hrs to cool off and go buy more taps. |
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| Alain Dupont |
grataku,
Thanks,
I am interested in this acid to disolve the taps.
All taping's are finished ; I bought a new tap, comming from Vermint tools
but not top quality...
The power supplies are already working.
So tomorrow I will install the mosfet on the pre pcb and will see...
Regards.
Alain. |
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| Jean |
| Wow, thats simply awesome ! Keep it up ! |
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| CheffDeGaar |
Alain.
Just...
Wooooooooowwwwwwwwww !
Amazing work ! All is so neat, clear and straight... Really really impressed ! Hope you will be finished soon, to enjoy both the view and the sound... Keep the photos coming.
And... congrats to Danielle ;)
You lucky lucky guy :) |
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| Alain Dupont |
CheffDeGaar,
Thanks,
I hope to finish by the end of this week... :drink:
Regards.
Alain. |
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| SY |
| quote: | | Added: If you do the Alumnium Sulfate solution be sure to only use glass or plastic containers!! It would dissolve a steel container! |
:att'n: Safety warning! If you do this, wear goggles and rubber gloves. Dispose of the aluminum sulfate solution in a safe and ecological manner. And, do use a corrosion and heat-resistant container. Pyrex is ideal. |
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| Alain Dupont |
SY,
Thanks, I will try this one day, as I can remove each part of the sinks without dismanteling all the amplifier.
I have one more question for Nelson:
The output voltage for the finals are 2* 39 volts, no load.
The output voltage of my circuit is only 2*49 volts for the preamp ;
I would need a few more
ie :52.0 volts
in the A75 Power supply schema here after
I read that the differential amplifier had 5.5 gain so 9.1 zener diode gives
5.5 * 9.1 = 50.05 volts
How could I simply modify the circuit gain built with the original values to reach 52 volts ? :smash:
I don't know any thing about diff's
Alain. |
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| Sandy H. |
Looks like a lot of good info on tapping did arise. My experience is similar to others: Good fluid, use a tap only in the same type of metal, the first time you feel it even have a hint of a bind, throw it away. $5 on a tap is much better than the 10 minutes of profanity after it breaks!!!!
Most importantly, though, keep up the good work and get to other projects soon. I like very much the quality of what you've done.
Sandy. |
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| Alain Dupont |
Sandy,
Thanks.
The X-BOSOZ with a ONO Phono included will be my next priority,
Alain. |
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| Peter Daniel |
| quote: | Originally posted by Alain Dupont
How could I simply modify the circuit gain built with the original values to reach 52 volts ? :smash:
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Try to play with R10 (2k2). The simplest way would be adding a parallel trimpot (100K or so) and see what this does.
Also, under the load your rails might go lower than 49V so maybe what you are getting presently at front end is high enough? |
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| Alain Dupont |
Peter,
>Try to play with R10 (2k2). The simplest way would be adding a parallel trimpot >(100K or so) and see what this does.
I appreciate, my knowledge of diff's and digital circuits is near the grass!! :bawling:
I am here to learn a lot.
>Also, under the load your rails might go lower than "39Volts" so maybe what
>you are getting presently at front end is high enough?
In fact they will because of the 0.5 Ohms 20watts of the CRC's
I just wanted a little more security. and 50/52 volts sounds good to me !}
Thanks.
Alain. |
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| Alain Dupont |
Peter,
The finals 2 power supply's gives 2* 45 volts with "no load",
I had to replace the 6amp fast blow fuses ; they blew up ; but 10 amps are OK now...
I have soldered 75 K ohms in // with R5 and R10
which gives 50 volts for the pre.
Do you think it's enough ?
Regards,
Alain. |
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| Peter Daniel |
I don't remember exactly, was it 5V or 10V difference between output rails and front end supply.
As to the blowing fuse, are you using any thermistors on primary?
With such big toroids and so many capacitance it's nothing unusual. Even with thermistor, I was using 10A fuses. |
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| Peter Daniel |
I just checked: the front end should be 50V and output stage 40V.
So how much you are getting on rails under the load? I think it shoul be close to 40V, so you should be fine. |
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| Alain Dupont |
Peter,
Thanks , I go with these values. I think the voltage will drop of 4/5 volts under load.
I will install the mosfet's on the front end tomorow,
and let the fun begin...
Now I am willing to finish the cabling of the standby relays
Thanks for the fast reply.
Regards.
Alain |
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| Bricolo |
| You could use shottky diodes to get 1 more volt. |
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| Alain Dupont |
Peter,
Tested on right half channel final's power supply (positive only) 38.8 volts
on 10 ohms between positive to ground.
I think it's good. ;)
Regards.
Alain. |
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| Alain Dupont |
Bricolo,
>> You could use shottky diodes to get 1 more volt.
Thanks, I take that for the next project, at this point of the A-75 ;
my only care is for the Front end PCb, I want to listen Sunday ! :trapper:
A+
Alain. |
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| Alain Dupont |
| Front vue, without facade. |
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| Peter Daniel |
| That's what amps are all about;) |
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| Alain Dupont |
| Front end Mosfet installed. |
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| Alain Dupont |
| Temperature regulation installed and working... |
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| Alain Dupont |
| Front end ready for wiring... |
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| Alain Dupont |
| Wiring the entries... |
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| Alain Dupont |
Next episode:
Letterings on the back pannel... :bigeyes:
Alain. |
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| eeka chu |
Excellent work Alain!
How are you applying the lettering?
Thanks,
John |
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| Alain Dupont |
eeka chu,
Adhesives lettering, just position the letters and with a round tip press on.
Its easy, the letter sets come from
http://www.tubesandmore.com/
# S-M180 at 4.95$ the set.
Regards.
Alain. |
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| eeka chu |
Does it not rub off?
I have used something similar for pressing lettering onto paper, but it always comes away if it's abraided at all. Do these have some kind of sticky stuff on them?
John |
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| Alain Dupont |
First power on Front end right Channel.
Voltages: correct
Input: 100 milli Volt 1000 Hz sinus from the sound channel of the Macintosh
using AudioToolbox
Alain. |
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| Alain Dupont |
eeka chu,
>> it always comes away if it's abraided at all.
Yes, a little...
>> Do these have some kind of sticky stuff on them?
They are auto adhesive, the only thing you do after applying them, is to coat with a little warnish (Chelac).
Regards.
Alain |
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| Luke |
Congratulations Alain,
Its a beautiful piece of engineering.:) |
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| Alain Dupont |
Lost all night and this morning too, a potentiometer P2 died on the left channel, took my long time to understand !!! :smash: :bawling:
Then about 3 hours to grip the drift of the 2front end... :mad:
Now about to finish the wiring... ;) OUF!
Luke,
Thanks, it's a lot of work...
Regards to all. |
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| Netlist |
Very impressive amp Alain. I really like the TO3 battery...
The pictures become better and better.
That camera is a real handy tool I see ;)
/Hugo :) |
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| moe29 |
| hmmm.... family resemblance? ;) |
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| Alain Dupont |
moe29,
>> hmmm.... family resemblance?
"Touché" ; well thanks, but I have to confess, this photo inspired me
for my A-75, thanks to Nelson for his wonderfull design. :)
It would have been easy if such heatsinks were available... :bawling:
Regards.
I hope the remaining work to fire the two channels will be easy ;
at this time I have 350 hours invested in this project.
Regards.
Alain. |
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| moe29 |
Well Alain, i bet you get more than 350 hours of listening pleasure
out of this beautiful A75! :)
The A75 must be an Uncle, or 2nd Cousin, or something like that
to the X series! ...a good bloodline for sure ;) |
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| Alain Dupont |
Almost finished, I have no more silver solder to wire the WBT's...:smash:
Time to rest before firing the finals... :clown:
1* 70 C temperature security on each channel sinks.
I will probably add a 12 volts remote standby relay ; and thats all.
Regards to all.
PS: See you when music will flow!
Alain. |
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| Alain Dupont |
"El Diablo" is heating... :mad:
PS: without load, only to stabilize the bias!
Nice in winter to have a Class A... :cool:
I will keep that name "El Diablo"
Alain. |
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| Alain Dupont |
El Diablo on the Martin Logan
with 67 mA bias, on 0.47 Ohms sources resitors
temperature Mosfet 52 degrees Heat sinks 45 degrees
and perfectly singing, wouah !!!!!!!!!!!!!!!!!!!!!!
great change from the NAD C350
I am so glad, time to rest ... :eek:
Regards.
PS: Thanks so much to Nelson and Norman.
Alain. |
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| eeka chu |
:bigeyes:
Alain, the photos from inside the amp where good... the full view of it is amazing! With it's cover on this thing is going to look incredible!
Does anyone know where I can get heatsinks that will fit a multiple of T0-220 packages on them? I have to use a few of them and using individual sinks is time consuming and looks quite messy.
John |
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| Alain Dupont |
eeka chu,
It works.... speaking od "El Diablo"
Look at these for 2 To-220
http://www.thermaflo.com/bin/stddat...um=824302b00000
But you can use watever profile you want from alu bars, angles to mount
several TO-220 in line ... there are profiles for clips mounting also.
Regards.
Alain. |
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| Alain Dupont |
I made a mistake :
>> with 67 mA bias, on 0.47 Ohms sources resitors
it was 67 milli Volts on 0.47 Ohms sources resitors
Ultimately when all will be set, I will reach 75/78 milli Volts
for 2 amp bias by channel...
I expect keeping 50 degrees max on the heatsinks...
Note the fan was at minimal speed, and 7 volts supply.
Alain. |
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| Alain Dupont |
Set the bias to 78/80 milli Volt, and listening to my favorite vinyl's
Temperature reached 50 degrees on the upper part of the heatsinks
I will let it for long time.
Let's listen to the music.
Alain. |
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| Alain Dupont |
Last picture of "El Diablo"
Working at 70 milli Volt Bias temp 51/52 degres... :devilr:
Quite finished, missing a great Logo...
Have fun DIY'in
Best regards to all.
Alain. |
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| john-china |
beautiful amp.
i want to know what your IR mosfets are. please , let me see
close picture of them.thanks |
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