| Peter Daniel |
I just started modifying one of my A75 into Aleph 2 today.;)
Since it's A75 I have available 50V regulated power supply for the input stage. I was thinking about using it for differencial pair current source and somehow improving it as well. Any suggestions?
Any improvements when current increased? What would be recommended value then?
The drain resistors (392 ohm) would be connected to output stage supply. |
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| Peter Daniel |
He's talking about output current sources and I'm talking about input.
It's a shame that something so nice has to be dismantled, but some people do anything for better sound.;) This might well be the first DIY Aleph with TO3 output devices. I'm also playing with idea of turning it into Aleph X instead of Aleph2, don't know yet.
I like the way the transformer is isolated from the rest of the circuitry. I also used special damping materal for vibration reducing. Also I used Panasonic HFQ capasitors for PS (quite a lot of them). |
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| Peter Daniel |
It's been my best work so far and it looks like it still remains with an upgraded interior.
Checking other threads I noticed that Harry placed 5 green LEDs instead of zener with a small bypass cap. Is that the best that can be done?;)
The heat sink are removed. This allows for easy access in case of repair, modification. As you see mounting TO3 devices is not as easy as those plastic ones and special bars had to be used. |
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| stefanobilliani |
It has something as a coffee machine !
Very big, and what a good job! |
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| leroy |
| Mmmmm, I love those 'capacitor-fields'!:D |
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| Peter Daniel |
| That's the detail of AC connection circuit. I got special circuit from ML 23.5 which supposedly removes DC component from AC. I'm using triak for switching and some people expressed concern it might introduce some noise. Is it true? |
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| Peter Daniel |
That's the way front end board is mounted. The input jacks are directly connected from the other side.
I wonder how it all gonna look when I start my p2p, in those days I was firm believer that PCBs are better.;) |
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| Peter Daniel |
And now everything is apart. Time to do some mods.;)
I only hope that my questions in the beginning is still drawing attention. |
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| HarryHaller |
No......... By the way do not power the front end current source from a seperate supply from the output stage or you can end up with the turn on/off thump from hell if the supplies come up or down at different rates!
H.H. |
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| UrSv |
As always, wonderful craftmanship...
Switching with triac I would say is just fine provided you mean that it is used only for switching on and off (like A75). The concern about it causing noise I would expect to be from when used as a mains regulator which will cause huge amounts of noice as the cutting of the sinusoidal mains creates massive overtone spectra. On the other hand I could have misunderstood what you use it for. If it is for on and off then of course it will create noise at switch on or off , if you have not provided for zero-crossing switching, but only for a period or so (20 ms). That is not for long and goes away til the next time you switch something...
/UrSv |
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| Peter Daniel |
UrSv,
The triac here is used according to A75 original article, so I guess it's OK then.
Those regulated supplies are so nice. What am I gonna do with them if not using here, Harry?;) |
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| roddyama |
Hi Peter,
Look at HH's suggestion about half way through this thread about LM129 voltage references.
http://www.diyaudio.com/forums/show...15&pagenumber=2
It looks like a neat device. I think I'm going to give it a try for the differential pair current source.
Rodd Yamas***a |
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| Peter Daniel |
| Neat device indeed. I might give it a try too. |
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| HarryHaller |
Post pictures of it to give the rest of us P.S. envy..... You know when you say that out loud it sounds like a bad pun.
Moderator please don't put me in the SIN BIN!
H.H.
P.S. I bet you loved show and tell in school when you were a kid....... |
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| HarryHaller |
| Something like this maybe......... |
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| Peter Daniel |
| quote: | Originally posted by HarryHaller
P.S. I bet you loved show and tell in school when you were a kid....... |
Quite the opposite, maybe that's why I'm doing it now.;)
What's the reason for Pass Gallery? Didn't you noticed that since I started posting my pictures the overall quality of DIY work from other members improved as well. Some people even mentioned something about competition going on. I also received requests to post more pix.
I personally would like to see as many good quality, innovative and inspiring projects as possible. The latest Cello pictures were good example. It's a great source of useful ideas. It's not about how it looks, but what it's about.
P.S.
I learned quite a lot from your pix of Tex-X BTW.;)
And thanx for your last suggestion:) |
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| HarryHaller |
Yes and those of us that build ugly circuits are embarrassed to post them........ I actually had to go out and buy nicer looking protoboard......
Thanks Martha.....
H.H. |
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| HarryHaller |
| I hope your happy..... |
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| Petter |
The LM329 needs a capactitor across it. Select anything good looking ... I usually go with about 1uF bypassed by about .01uF, all film of course.
However, the proposed design is not optimal. You could use an additional bipolar transistor to act as a feedback device to increase impedance of the current source. I think NP posted something on that a few months back in response to my suggestion of using an op-amp (for maximal output impedance and minimum power loss).
If your sense resistor is large (you drop several volts), your current source will be fine. If it it small, you might want to replace the MOSFET with a BJT, use a small BJT in a feedback configuration, switch to an op-amp (something tells me you don't want that) ...
BTW, beautiful work. Your mechanical skills are out of this world!
Petter |
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| dice45 |
Peter,
beautiful work indeed!
| quote: | Originally posted by Peter Daniel
... The input jacks are directly connected from the other side.
I wonder how it all gonna look when I start my p2p, in those days I was firm believer that PCBs are better.;) |
Only two things i do not like: excessive abuse of PCBs and those {insert unprintable here} RCA plugs bitten right out of the full. RCA plugs are evil anyway but if you use them, use thin sheet metal stuff. You 'll find ones that sound better than any massive stuff, not kidding.
Hollow stuff, not solid stuff :)
If i catch up with my REDEL crusading a bit, maybe in 12 months the whole board uses Redel instead. :) -same as with the MKVs :)
Harry,| quote: | | Moderator please don't put me in the SIN BIN! |
next time maybe .... when you are not prepared .... ;) ... :cool: |
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| HarryHaller |
| I'm ready when you are...... |
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| HarryHaller |
Says you........
If I wanted bipolars and and feedback I would have put them in.
If you put a cap across the LM329 the current source will come up slowly and you will get the turn on thump from hell. This is the third time I have explained this but I will keep explaining and save some poor soul from killing a speaker during power up or down. I put the resistor in series to damp any resonance from the inductive output impedance of the LM329 and capacitance in the current diode or fet use to bias the LM329.
Thanks for your help though......
H.H. |
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| dice45 |
| quote: | Originally posted by HarryHaller
I'm ready when you are...... |
says Hannibal Lecter ...
Harry, you watched "Silence of the Lambs" too often ? (just kidding :) ) |
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| Petter |
Thanks Harry,
Good point. I use output protection circuitry (delayed on, DC sense, extremely fast output relay off-switching, ac-loss detect) so I don't "see" the thump, but it is a good point since this will likely be stressful on the device itself and protection circuits can fail. Perhaps I will consider going with .1uF alone in the future, but there is no way that I personally will forgo without any capacitance in that position.
Another point. If you ever need symmetrical current sources (one on top, the other on bottom), you might want to feed the two voltage sources driving that current device directly between each other instead of to the traditional ground. I have standardized on this approach. I see more and more postings indicating this type of approach, the latest by NP, but in a slightly different scenario.
Different folks, different strokes.
Petter :) |
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| HarryHaller |
The ap notes shown the noise voltage rolling off above 10kHz and the gate resistor and Mosfet capacitance are going to roll off high frequency noise.
The ap notes show no caps across reference. I believe 0.1uF will still thump a bit. I assume no blame for bent voice coils and jumpy pets and family members...... |
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| Petter |
You are right again, HH
And I had forgotten that I have been drawing RC circuits lately as well .... Thanks for reminding me!
Shown with matching negative current source to illustrate that one does not have to go to ground.
The curious 3 resistor setup is what i use in low power situations to get maximum use of each turn, while putting minimum current through the adjustable resistor. I call this "triplets" and there is an excel spreadsheet (using linear optimization) to work out "optimal" values here.
http://diyaudio.com/projects/petter
Petter |
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| HarryHaller |
| Put a J503 current fet in series with the four LM329s and you will the most over kill CCS around....... Way cool pics on your link |
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| Peter Daniel |
| That reminds me of an Alien movie.;) |
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| Peter Daniel |
So Harry,
How come after '1000s post you got "Enlightened" title and I didn't get one? And they say life is fair.;) :) :(
But then, OTOH, I have to admit I didn't practise Zen everyday.;) |
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| AudioFreak |
| The 'Enlightened' level is very new... Jason just added it recently. |
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| HarryHaller |
My caridiologist said I had better enlighten the load around my waistline if I know whats good for me.... I thought it was a hoot and I imagine Jocko is never going to let me hear the end of it. Time to go practice my yoga levitation lessons.........
H.H. |
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| hifiZen |
Man, too bad the rating's not based on total words posted... I'd probably top HH on that count. I wonder what my average post lenth is? Err, maybe I don't want to know... heh ;)
Now if only the total number of posts actually did make one enlightened.. I'd be on here every 5 minutes!
Well, good work anyway HH... keep it up! |
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| Petter |
I must admit that building the X100 version 1 (referenced here as an abstract sculpture :) ) was a bit painful, particularly after I had spent a lot of time essentially compressing the X1000 input stage into 5cm*5cm ... and realizing that I needed much more cooling than anticipated. It does look somewhat abstract and I am pleased with it, but it does rather miss that Peter Daniel touch and finish ... Even then, for being the first audio unit I ever built it is not all that bad.
I have since laid out a Eurocard sized version. I now use component footprints that include the heatsinks which is much smarter. I also learned that splitting components evenly between top and bottom was somewhat painful :)
I will use the J503 as HH suggested. However, I am wondering if I can do without the gate resistor altogether.
Petter |
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| dice45 |
Harry,
this sculpture is no Bauhaus style, definitely not.
But thanxalot for posting the Bauhaus link, very interesting. :) |
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| Freddie |
| What's the purpose of R3? |
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| HarryHaller |
Isolation of CCS output capacitance and an easy way to measure current in the circuit. the voltage across R3 is 10 times the current from the CCS.
H.H. |
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