I am in the process of buying parts for my Aleph 1.2 project. Apart from the apparent heatsink issues (this is not a new thread on this issue), there is the issue of capasitors. As I'm quite new to the DIY arena, I have some questions regarding capasitors:
Is 63v sufficient for the Aleph 1.2, or is it better (as in safer) to have 100v. Isn't 63v pushing the limits a bit? As in; will the 63v do for my Aleph 1.2 or not? I have seen several projects with 63v. The cost of quality caps with 100v is much higher than 63v.
If I'm not mistaken the original has 4x25000uF 75V capasitors. Why then has almost every Aleph 1.2 (and even 2) have over twice this amount? What is the "just right" value to go for?
Is 63v sufficient for the Aleph 1.2, or is it better (as in safer) to have 100v. Isn't 63v pushing the limits a bit? As in; will the 63v do for my Aleph 1.2 or not? I have seen several projects with 63v. The cost of quality caps with 100v is much higher than 63v.
If I'm not mistaken the original has 4x25000uF 75V capasitors. Why then has almost every Aleph 1.2 (and even 2) have over twice this amount? What is the "just right" value to go for?
folkeb said:
As much as you can afford.
Dropping ripple is the most important on the Aleph powersupplies.
Volume and cost of capacitors is a prominent issue with commercial amplifiers, for DIY it generally is not.
If you are investing so much in all other parts of a 1.2 it's better not to be to economical on the capacitors.
Even 200kuF per channel for an Aleph 1.2 is squeemish in my book.
The voltage rating depends on which transformer voltage you pick. If you use a 50Vac toroid i'd go for at least 75V for the capacitors.
Using 100 volt capacitors is blowing cash for nothing. Sensible practice is to use a CRC or CLC powersupply. The high bias of the 1.2 will make the nominal rated voltage of the transformer drop.
A CLC or CRC configuration will drop the voltage even further for the second capacitor bank. You will not even get near 100 volts, and 100V capacitors are relatively very expensive.
Up to 80volts capacitors there is a reasonable linearity between price and the product of capacity times voltage rating.
Above 80 volts they become more expensive, spend that money on more capacitance.
If the rail voltage never reaches 100V, 100 volt capacitors will behave like lower rated capacitors after some time, only advantage remaining is the voltage safety but the current rating wil be the same.
The problem I face is that the caps I'm after, either the Evox-Rifa or the Fischer and Tauche, are only supplied for 63v or 100v.
I think 63v is running a bit close, and 100v is overkill! Are there any other recommended capasitors that have 75v and that can compare both with regard to price and performance?
I think 63v is running a bit close, and 100v is overkill! Are there any other recommended capasitors that have 75v and that can compare both with regard to price and performance?
A number of people here share the view that you can't get better than Rifa.
An option would be to use lower transformer voltage, you may get away with 45Vac on 63 Volts Rifa169.
If you desire to stick to higher transformer voltage, order a load of NOS capacitors from a surplus store in the US. As economical as you can get and you end up with the same capacitor brand as the original ones use.
In these amplifiers a big can is worth more than a fancy weeny one.
(they stick a US engine in a Volvo, not the other way around)
An option would be to use lower transformer voltage, you may get away with 45Vac on 63 Volts Rifa169.
If you desire to stick to higher transformer voltage, order a load of NOS capacitors from a surplus store in the US. As economical as you can get and you end up with the same capacitor brand as the original ones use.
In these amplifiers a big can is worth more than a fancy weeny one.
(they stick a US engine in a Volvo, not the other way around)
imho, the Rifa PEH169 has been the top notch capacitor.
And the most expensive of the 2, to obtain them i had to pay silly prices overhere 15 years ago.
But the PEH169 is being dumped, i got me 20 NOS 33KuF/63V for a lot less than the MSRP.
If you use inrush protection and CRC/CLC, no risk.
Under constant load the regulation factor of the transformer is of no consequence.
The bias load will drop the nominal secondary transformer voltage well below sqrt2*45.
A CRC/CLC drops the voltage even more for the second capacitor bank.
Both effects are large enough so compensate for voltage surge.
With a 45Vac transformer the voltage after the rectifier is likely not to go above 55Vdc.
The effect of lower rail voltage for the amplifier is lower max output power, but you have the advantage of being able to increase the bias with the same setup.
Personally, i believe high bias on these amplifiers is far more important than having it do 150 or 200 watts.
And the most expensive of the 2, to obtain them i had to pay silly prices overhere 15 years ago.
But the PEH169 is being dumped, i got me 20 NOS 33KuF/63V for a lot less than the MSRP.
If you use inrush protection and CRC/CLC, no risk.
Under constant load the regulation factor of the transformer is of no consequence.
The bias load will drop the nominal secondary transformer voltage well below sqrt2*45.
A CRC/CLC drops the voltage even more for the second capacitor bank.
Both effects are large enough so compensate for voltage surge.
With a 45Vac transformer the voltage after the rectifier is likely not to go above 55Vdc.
The effect of lower rail voltage for the amplifier is lower max output power, but you have the advantage of being able to increase the bias with the same setup.
Personally, i believe high bias on these amplifiers is far more important than having it do 150 or 200 watts.
Another thought is to check the ripple current rating of the caps, particularly the capacitors immediately following the rectifier.
Higher voltage tends to offer higher ripple current rating as a rule.
Size is a good indicator of ripple current rating.
They should be rated 3 x the ripple current (if parrelleled with will double the total rating).
The Aleph ones were rated at 15 amps as I recall, they were large bottles.
Mr Pass did not skimp on his power supplies. I recall seeing the capacitors and transformers at the factory..greater care is taken with the power supply and the newer models feature a clever improvement to reduce noise (a secret) .
macka
Higher voltage tends to offer higher ripple current rating as a rule.
Size is a good indicator of ripple current rating.
They should be rated 3 x the ripple current (if parrelleled with will double the total rating).
The Aleph ones were rated at 15 amps as I recall, they were large bottles.
Mr Pass did not skimp on his power supplies. I recall seeing the capacitors and transformers at the factory..greater care is taken with the power supply and the newer models feature a clever improvement to reduce noise (a secret) .
macka
Attachments
I have a possible solution given to me elsewhere. If I go for transformers with secondarys at typically 45v, this would give some 63v out. If I then use resistors with high watt tolerance then I could adjust the voltage to about 58. With this it should be safe to go with the 63v. Is this a correct, or to some extent correct to asume? If so, I'll put in 8x47000uF for each channel, brand: Fischer and Tauche as these have been recommended in this forum (better values than the RIFA)
I'm sort of confused. The dealer first recommended that I should go for 50v on the secondaries, however not with 63v capasitors as he said this would be a safety issue. Also he says that "his" transformers give 1.4 x VAC. So he recommended 45v and then use resistors to bring the voltage down. As it is, I don't know anything about transistors and class A. My problem is that I would like to get within a safe operating voltage range (for 63v capasitors), but at the same time stay as close to the 60v(rails) of the original (and 200w) Aleph 1.2. Can someone explain me the details or give me a reference to a thread with more info?
I plan to use CLC (2x47mF, 2.2mH 0.1ohm, 2x47mF) if this is of any help.
Are the big differences within transformers with regard to actual secondary voltage, as in; do different transformers with the same spesifications give the same secondary in the same setup?
Thanks for your help and insight!
I plan to use CLC (2x47mF, 2.2mH 0.1ohm, 2x47mF) if this is of any help.
Are the big differences within transformers with regard to actual secondary voltage, as in; do different transformers with the same spesifications give the same secondary in the same setup?
Thanks for your help and insight!
A 50 Vac transformer gives 70.7 Vdc, 50 *sqrt2.
A rectifying diode causes a 0.6 volts drop, after rectifying you get 70 Vdc.
The voltage coming to your home can fluctuate, probably 10% higher as it can be here.
So the actual transformer voltage can be 77 volts.
Without a current load the voltage can become even higher than that, depending on the type and size of the transformer.
Average values are 5%, so for 50Vac transformers the secondary can become as high as 80 Vdc.
That is without a load. A regular amplifier is Class AB, without a signal the current through the output transistors is very low.
So low that the voltage on the capacitors may reach 80 volts, for such an amplifier you need capacitors that are rated for 80 volts minimum.
A Class A amplifier has high bias currents going through the output devices constantly. On an Aleph amplifier these currents start running the moment the voltage level is high enough to open the output devices.
With this constant load the regulation factor of the transformer is of no importance. (the 5%)
Transformers that are loaded do not deliver the nominal voltage, the voltage will drop from the 50Vac to a level that again depends on the size and type of transformer.
But even the highest load will not bring the maximum output voltage of a nominal 50Vac transformer below 63 volts, you need to use a lower voltage transformer on 63V capacitors.
The next regular series lower voltage transformer is 45Vac, loaded it will get near 60 volts dc. How well depends on the transformer you intend to use.
I tried F/T capacitors a long time ago, they were easy to buy here, not impressed by them then. I gathered the high voltage double capacitor F/Ts are good for tube amplifiers, no idea how well the current production lower voltage F/T capacitors are.
A 33.000/63V Fischer & Tausche does $30 here, i bought the PEH169 for a lot less.
A rectifying diode causes a 0.6 volts drop, after rectifying you get 70 Vdc.
The voltage coming to your home can fluctuate, probably 10% higher as it can be here.
So the actual transformer voltage can be 77 volts.
Without a current load the voltage can become even higher than that, depending on the type and size of the transformer.
Average values are 5%, so for 50Vac transformers the secondary can become as high as 80 Vdc.
That is without a load. A regular amplifier is Class AB, without a signal the current through the output transistors is very low.
So low that the voltage on the capacitors may reach 80 volts, for such an amplifier you need capacitors that are rated for 80 volts minimum.
A Class A amplifier has high bias currents going through the output devices constantly. On an Aleph amplifier these currents start running the moment the voltage level is high enough to open the output devices.
With this constant load the regulation factor of the transformer is of no importance. (the 5%)
Transformers that are loaded do not deliver the nominal voltage, the voltage will drop from the 50Vac to a level that again depends on the size and type of transformer.
But even the highest load will not bring the maximum output voltage of a nominal 50Vac transformer below 63 volts, you need to use a lower voltage transformer on 63V capacitors.
The next regular series lower voltage transformer is 45Vac, loaded it will get near 60 volts dc. How well depends on the transformer you intend to use.
I tried F/T capacitors a long time ago, they were easy to buy here, not impressed by them then. I gathered the high voltage double capacitor F/Ts are good for tube amplifiers, no idea how well the current production lower voltage F/T capacitors are.
A 33.000/63V Fischer & Tausche does $30 here, i bought the PEH169 for a lot less.
I'm thinking of two 625 VA transformers, for a total of 1250 VA with two 45v secondaries. I know that many in this forum use a lot bigger transformers, but the original (as far as I can see uses 1200 VA). Another issue with higher voltage is the increased power, and size of heatsinks.
My conclusion is that 63v capasitors will be fine with 45v secondaries, and that this voltage will after the brigde recifier and so on give something in the region of 60v on the rails, give and take some. On PassDIY 42v gave 57v, and the capasitors where in this project 63v.
If I had a good deal on the PEH169, all would be well. However, I have not and ca. 25 euros for F&T 47000uF is not too bad from what I have experienced (actually quite good in fact).
F&T were hyped in a dutch thread. If I'm not mistaken they were the same as Krummer or Mundorf to much higher prices. I'm not sure, so don't take my word for it. Unfortunately, I can't find the thread again.
Thanks for all the respons! This is a great forum!
My conclusion is that 63v capasitors will be fine with 45v secondaries, and that this voltage will after the brigde recifier and so on give something in the region of 60v on the rails, give and take some. On PassDIY 42v gave 57v, and the capasitors where in this project 63v.
If I had a good deal on the PEH169, all would be well. However, I have not and ca. 25 euros for F&T 47000uF is not too bad from what I have experienced (actually quite good in fact).
F&T were hyped in a dutch thread. If I'm not mistaken they were the same as Krummer or Mundorf to much higher prices. I'm not sure, so don't take my word for it. Unfortunately, I can't find the thread again.
Thanks for all the respons! This is a great forum!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.