URSV,
you won´t find a 600VA transformer with 15 or 18v secondaries so easy.
But thats´s not a problem cause you can have them made at order for a few euros more.
Peter,
of course I already have the caps (63/50 and 35volts) so these must do.
Another small problem will be power dissipation in the chokes I was planing to use (1.8mH air core 0,38 Ohms) wich (at 8A) will probably melt
I´ve heard people using ferrit core chokes so I think I´ll have to look that way.
I´ve played around with PSUDesigner and for 17-18V rails the transformer will have to have aprox. 18V secondaries.
2V to rail are 16watts you dissipate more for the same power output as a normal Aleph wich will be about 5% or so.
william
you won´t find a 600VA transformer with 15 or 18v secondaries so easy.
But thats´s not a problem cause you can have them made at order for a few euros more.
Peter,
of course I already have the caps (63/50 and 35volts) so these must do.
Another small problem will be power dissipation in the chokes I was planing to use (1.8mH air core 0,38 Ohms) wich (at 8A) will probably melt
I´ve heard people using ferrit core chokes so I think I´ll have to look that way.
I´ve played around with PSUDesigner and for 17-18V rails the transformer will have to have aprox. 18V secondaries.
2V to rail are 16watts you dissipate more for the same power output as a normal Aleph wich will be about 5% or so.
william
The alternative to chokes might be fixed resistors or thermistors. I used thermistors and they work pretty well. I like their inrush supression capabilites at start up too. I used 120,000u in my PS (per channel), but I think it might be not enough. I can hear no hum right after turn on, and then it slowly goes up. Probably because thermistors warm up.😉 But it is still very little.
Oh, that's why. I thought several suppliers had 12, 15, 18 V as standard outputs to fairly high ratings. At least the Swedish popular Toroid does for 500 VA and it is kind of "default" here.
http://www.elfa.se/elfa/produkter/se/18/185981.htm
Sorry to hear that. Obviously there's nothing wrong with custom transformers.
/UrSv
http://www.elfa.se/elfa/produkter/se/18/185981.htm
Sorry to hear that. Obviously there's nothing wrong with custom transformers.
/UrSv
Peter,
I´ll have a look at resistors if I can´t get a fitting choke. With 33000-1.8mH-100000 I will get about 20mV of ripple with 8A current but the choke is dissipating 8x8x0,4 = 26watts wich I don´t think it´ll do for very long (and with two per channel it´s a nice heatsource for the rest of the amp.
I probably have to look chokes with lower dc resistance wich is a bit of a problem with (fitting) aircores. I´m not shure how ferrit core chokes will work in a PI filter because of saturation. Maybe someone can help out here?
Somewhere a few pages ago was a question concerning why Alephs don´t need an input cap. It´s because there´s no DC gain with a cap in the feedback path (220uF).
With the x I will probably use input caps to avoid problems with my (dc-coupled) preamp.
Looking at the latest revision Beta circuit the input impedance is something like 20k diff and 10k single ended so the cap will have to be quite big for a low -3dB point.
Peter, did you also use this input configuration or did you change the resistor values?
william
I´ll have a look at resistors if I can´t get a fitting choke. With 33000-1.8mH-100000 I will get about 20mV of ripple with 8A current but the choke is dissipating 8x8x0,4 = 26watts wich I don´t think it´ll do for very long (and with two per channel it´s a nice heatsource for the rest of the amp.
I probably have to look chokes with lower dc resistance wich is a bit of a problem with (fitting) aircores. I´m not shure how ferrit core chokes will work in a PI filter because of saturation. Maybe someone can help out here?
Somewhere a few pages ago was a question concerning why Alephs don´t need an input cap. It´s because there´s no DC gain with a cap in the feedback path (220uF).
With the x I will probably use input caps to avoid problems with my (dc-coupled) preamp.
Looking at the latest revision Beta circuit the input impedance is something like 20k diff and 10k single ended so the cap will have to be quite big for a low -3dB point.
Peter, did you also use this input configuration or did you change the resistor values?
william
Wuffwaff,
I have simulated 100mF-1ohm-100mF starting from 14VAC to 15VDC for a ripple of ~5 and 5 amps. I also noticed that the 1st cap is the one that has to deal with the bulk ripple current, therefore it needs to have as low ESR as possible to heat-up less and last longer. I am going with batteries of 4700uF 25 V.
The 1 ohm will dissipate 25W that's just life I guess.
As far as the inductors are concerned 25 w is not that much, if you take a look at your 500 VA transformer datasheet you'll see that if you add iron and cu losses you go up to a sizable number fairly close to that.
Saturation should not be a problem if the core is designed for it (ie doesn't get too hot).
I have simulated 100mF-1ohm-100mF starting from 14VAC to 15VDC for a ripple of ~5 and 5 amps. I also noticed that the 1st cap is the one that has to deal with the bulk ripple current, therefore it needs to have as low ESR as possible to heat-up less and last longer. I am going with batteries of 4700uF 25 V.
The 1 ohm will dissipate 25W that's just life I guess.
As far as the inductors are concerned 25 w is not that much, if you take a look at your 500 VA transformer datasheet you'll see that if you add iron and cu losses you go up to a sizable number fairly close to that.
Saturation should not be a problem if the core is designed for it (ie doesn't get too hot).
wuffwaff said:
I used 220k in feedback loop and 33k input to ground resistor. Initially I had 68K, but Nelson suggested that it's too high and optimally 10k should be used. Interestingly, changing input resistor's value didn't affect much low cutoff frequency when using cap. I'm using 0.12uF for 120Hz high pass filter. When I had 2uF at the input -3dB point was at 8Hz or so. I don't think thtt anything more than 10uF is required. If I go full range with my next amp I'll be using 4uF for input caps. Even though my preamp is AC coupled, when I shorted either cap, I had DC offset at the output. I also added 100k resistors to ground before caps and there is a sonic difference. They somehow clean the sound and everything becomes more focused.
With the transformer it may be easier to get say two transformers and run their independant secondaries in parrellel for double the current rating and then use each transformer output as single secondary.
This may allow the use of stock transformers to obtain the current rating we are looking for more conveniently.
cheers
macka
On the sound thing I still think the Aleph 2 will be hard to beat and is still the bench mark. But I many of us I am keen to play with my Alpha boards when they arrive.
This may allow the use of stock transformers to obtain the current rating we are looking for more conveniently.
cheers
macka
On the sound thing I still think the Aleph 2 will be hard to beat and is still the bench mark. But I many of us I am keen to play with my Alpha boards when they arrive.
Attachments
Peter,
is your input layout the same as the one published, with input-10k-68k to ground and feedback resistor connected in between? Wich resistor did you change, the 10k or the 68k one and what gain do you get (unbalanced)?
Would it be possible to put two dc blocking caps in the way they are placed in an Aleph, so (seen from the input) after the 10k (r18/28 and 68k r19/29) or is the dc connection to ground neccessary?
Macka,
it would be nice to hear of your future listening experience comparing X and 2. I´m not in a hurry so I can wait a bit and put my cases / caps / etc. together before I buy a transformer. You know, all of the automotive industry goes from 12V to 42V because of the disadvantages with low voltage high current and we are doing just the opposite
william
is your input layout the same as the one published, with input-10k-68k to ground and feedback resistor connected in between? Wich resistor did you change, the 10k or the 68k one and what gain do you get (unbalanced)?
Would it be possible to put two dc blocking caps in the way they are placed in an Aleph, so (seen from the input) after the 10k (r18/28 and 68k r19/29) or is the dc connection to ground neccessary?
Macka,
it would be nice to hear of your future listening experience comparing X and 2. I´m not in a hurry so I can wait a bit and put my cases / caps / etc. together before I buy a transformer. You know, all of the automotive industry goes from 12V to 42V because of the disadvantages with low voltage high current and we are doing just the opposite
william
This is how I did it. The gain is 26dB single ended. I used 220K for feedback, because I just had Holco resistor in that value (and not 100K). The 100K resistor before cap cleans the sonics somehow and make everything more focused. The negative side is exactly the same and input is connected to ground through 60ohm resistor (which is my DACs output imp.).
With this low input caps I have a sort of very low volume resonance at turn on, which lasts about 4 sec. When I tried bigger caps (2u), I didn't experience that.😉
With this low input caps I have a sort of very low volume resonance at turn on, which lasts about 4 sec. When I tried bigger caps (2u), I didn't experience that.😉
Attachments
Hi William,
Yes, I would be pleased to provide feedback, of course it will need to be apples vs apples so the macka Aleph X will need to be 100/100 watts @ 8 ohms.
However, I think my initial buy in on this project will be somewhat more modest so I can understand and tame the creature before I go down the road of the Forbidden Planet.
That is of course unless Peter Daniel and the others can persuade me otherwise.
Here's a thought on the fly, could the Aleph 2 be re configured to an Aleph X in the practical sense? I realise the transformer would be different as would the central board but the power fet count would be the same wouldn't it?
macka
Yes, I would be pleased to provide feedback, of course it will need to be apples vs apples so the macka Aleph X will need to be 100/100 watts @ 8 ohms.
However, I think my initial buy in on this project will be somewhat more modest so I can understand and tame the creature before I go down the road of the Forbidden Planet.
That is of course unless Peter Daniel and the others can persuade me otherwise.
Here's a thought on the fly, could the Aleph 2 be re configured to an Aleph X in the practical sense? I realise the transformer would be different as would the central board but the power fet count would be the same wouldn't it?
macka
Attachments
I converted my A75 into Aleph X, yet, it wasn't practical. Converting Aleph 2 would be easier. You just have to replace front board (which gonna cost you $5 BTW😉 ) and separate output fets bank in two halves. You have to change transformer and double capacitance (at least).
Output devices count is the same for both amps.
Output devices count is the same for both amps.
Peter,
Why bother with conversions? It's much better to build new stuff and dedicated chassis (and transformers). Weren't you sad to see the A75 go? As you said it was a think of beauty. Some things should just be preseved, maybe put in a diy audio museum....aint't that an idea? I want to be the curator.😀
Why bother with conversions? It's much better to build new stuff and dedicated chassis (and transformers). Weren't you sad to see the A75 go? As you said it was a think of beauty. Some things should just be preseved, maybe put in a diy audio museum....aint't that an idea? I want to be the curator.😀
Hmm,
Peter,
The bit about the capacitance I had not considered, a assume this is due to higher currents (x2) or the RC network.
No matter I have 54 x 15,000 63 volt still in my project stock pile.
It seems it will have to be a new one then and perhaps a square using 4 sided heatsinks for the box which would be easier to make.
By the way how big is your Aleph X?
The earthing will be interesting, given the hot +- outputs with little current through the earth on the power supply.
cheers
macka
Peter,
The bit about the capacitance I had not considered, a assume this is due to higher currents (x2) or the RC network.
No matter I have 54 x 15,000 63 volt still in my project stock pile.
It seems it will have to be a new one then and perhaps a square using 4 sided heatsinks for the box which would be easier to make.
By the way how big is your Aleph X?
The earthing will be interesting, given the hot +- outputs with little current through the earth on the power supply.
cheers
macka
grataku said:
I would have never done it, unless I had another two to spare.😉
I my case space becomes an issue as well.😉
Member
Joined 2002
well if yuo have 54 of them suckers give me some or tell me where you got them from eh.. id like to have them all for my 2 amps that are going to need them
pair of mono blocks ( av800's)
pair of aleph 2's Mono blocks.
i have to order 4 transromers now all 1kva too :" O ) B.C hydro is going to hate me when i turn on my amps. : O )
pair of mono blocks ( av800's)
pair of aleph 2's Mono blocks.
i have to order 4 transromers now all 1kva too :" O ) B.C hydro is going to hate me when i turn on my amps. : O )
Jason,
I obtained then on Ebay from a Trader in the USA, when I get a moment I will look up the invoice as he said he had boxes of the them so you can attempt to contact the guy.
They were NOS and quite cheap so no point sending them from down here.
Better build SOLAR wind mill for that turnon surge.
Cheers
macka
I obtained then on Ebay from a Trader in the USA, when I get a moment I will look up the invoice as he said he had boxes of the them so you can attempt to contact the guy.
They were NOS and quite cheap so no point sending them from down here.
Better build SOLAR wind mill for that turnon surge.
Cheers
macka
Peter.
Is your preamp or cd player cap coupled. I wonder why the cap cleans up the sonics?
Jam
P.S. Now that your Aleph-X has broken in, how do you like it and have the sonics changed much since you first powered them up?
Is your preamp or cd player cap coupled. I wonder why the cap cleans up the sonics?
Jam
P.S. Now that your Aleph-X has broken in, how do you like it and have the sonics changed much since you first powered them up?
It is difficult to say now, because I'm already used to it's sound, so my first impressions were probably most valuable insight into the sound of this amp. I can only say that it's very neutral (more than regular Aleph) with better highs and bass and more detail. It is also very revealing to what you feed it with. Every type of capacitor I connected to the input had distinctive sonic character. I can't find nothing that I don't like about it's sound.
I guess it is indeed the cross between previous X series amps and Alephs: the best of both worlds.😉
I guess it is indeed the cross between previous X series amps and Alephs: the best of both worlds.😉