Hi Rodd,
yes something like that (Aleph2). There won´t be that many changes to the circuit. R19/21, the negative clipper and the amount of output resistors. I think I´ll leave the source resistors at 1 ohm although 0,5 would increase efficiency a bit.
william
BTW I see the new "4-letter word remover" does funny things with you sir name😛
yes something like that (Aleph2). There won´t be that many changes to the circuit. R19/21, the negative clipper and the amount of output resistors. I think I´ll leave the source resistors at 1 ohm although 0,5 would increase efficiency a bit.
william
BTW I see the new "4-letter word remover" does funny things with you sir name😛
Re: it still works,but better now
Hi,
I am considering Black Gates. But I can decided which and were to put them. Which Black Gates did you use at which places in the circuit?
Thanks,
Edwin
wuffwaff said:
Hi,
I am considering Black Gates. But I can decided which and were to put them. Which Black Gates did you use at which places in the circuit?
Thanks,
Edwin
Hello Edwin,
at the moment they´re BG FK 220micro/16V for input and ac-current gain and a BG FK 220/50V for the bootstrap cap.
I will change the input to a BG NX 220/6,3 as soon as it arrives (ordered at audionote but has to come from Japan). I´ve chosen this one cause I don´t really like the idea of a polar cap in this position (personal opinion🙄 )
william
at the moment they´re BG FK 220micro/16V for input and ac-current gain and a BG FK 220/50V for the bootstrap cap.
I will change the input to a BG NX 220/6,3 as soon as it arrives (ordered at audionote but has to come from Japan). I´ve chosen this one cause I don´t really like the idea of a polar cap in this position (personal opinion🙄 )
william
Try screwing around with the gain setting of the
current source. It is my experience that the bottom
end gets a bit punchier when you up the gain.
current source. It is my experience that the bottom
end gets a bit punchier when you up the gain.
Nelson,
I´ve raised the ac-current gain to 54% wich in my case means 60watts@4ohms for 2.35A bias. Bass has already improved and the slight forwardness at higher frequencies dissappeared.
I will try 60% for 7A peak and about 90-100 watts@4ohms and see what this does to the music.
In any case the sound has improved to a level where I think it´s worth the risk of building monos with the existing power-supplies and 3-3.2A bias spread over 5 or 6 fets. This should cure any power problems and improve bass likewise.
william
I´ve raised the ac-current gain to 54% wich in my case means 60watts@4ohms for 2.35A bias. Bass has already improved and the slight forwardness at higher frequencies dissappeared.
I will try 60% for 7A peak and about 90-100 watts@4ohms and see what this does to the music.
In any case the sound has improved to a level where I think it´s worth the risk of building monos with the existing power-supplies and 3-3.2A bias spread over 5 or 6 fets. This should cure any power problems and improve bass likewise.
william
🙂 I had little bass problems with my Aleph 4 and finally got to change the speakers cables.I now run home made multistrand wires with 4 pairs twisted together.first twisted the 4 pairs individually,and heatshrink.I used different each;one clckwise,the other cntrclckwise,etc.
Then joining them,two by two,and twist(here again the rule of clckwise/cntrclckwise.then heatshrink.
then the 2 last ones,huge snakes,twist again and final heatshrink.then join the different pairs and solder them and proper terminate the cable.
With this I get a little more capacitance,but the resistance and inductance are lowered.
I have now no bass problems any more 😉
Each sigle wire is 0.75 mm2
Regards
Anael
Then joining them,two by two,and twist(here again the rule of clckwise/cntrclckwise.then heatshrink.
then the 2 last ones,huge snakes,twist again and final heatshrink.then join the different pairs and solder them and proper terminate the cable.
With this I get a little more capacitance,but the resistance and inductance are lowered.
I have now no bass problems any more 😉
Each sigle wire is 0.75 mm2
Regards
Anael
Hello Nar,
thanks for the tip but that's not the problem. I think I know the problem now (and the sollution).
I did a few mods after the last mail:
changed the input to Aleph60 (didn't change the sound but didn't hurt either)
upped the ac current gain a bit to get approx 75 watts into 4 ohms
This made the amp sound more relaxed with more bass.
At the moment it's at my fathers home delivering current to a pair of Thiel CS3.6 (yes I know but somehow I don't know peaple with ampfriendly speakers🙄 ) fed by an ML 38S.
First comments were that the highs didn't sound as free as he's used to but bass and mids sounded nice (normally a ML 331 is used). So I upped the current gain a bit more (R21 from 420 to 385 ohms, no scope so no gain values) and wouldn't you know.....the highs were not sounding "compressed" annymore 😀
So I think that when I will have rebuild the amps my "problems" will disappear🙂
william
thanks for the tip but that's not the problem. I think I know the problem now (and the sollution).
I did a few mods after the last mail:
changed the input to Aleph60 (didn't change the sound but didn't hurt either)
upped the ac current gain a bit to get approx 75 watts into 4 ohms
This made the amp sound more relaxed with more bass.
At the moment it's at my fathers home delivering current to a pair of Thiel CS3.6 (yes I know but somehow I don't know peaple with ampfriendly speakers🙄 ) fed by an ML 38S.
First comments were that the highs didn't sound as free as he's used to but bass and mids sounded nice (normally a ML 331 is used). So I upped the current gain a bit more (R21 from 420 to 385 ohms, no scope so no gain values) and wouldn't you know.....the highs were not sounding "compressed" annymore 😀
So I think that when I will have rebuild the amps my "problems" will disappear🙂
william
William,
It has been an interesting journey. It has been enlightening to see the changes you've made and the results of those changes. Please keep us informed on future changes in your project.
Happy Listening,
Rodd Yamas***a
It has been an interesting journey. It has been enlightening to see the changes you've made and the results of those changes. Please keep us informed on future changes in your project.
Happy Listening,
Rodd Yamas***a
warm up time
Hi all,
amp sounds quite good now but the next problem is on it´s way.... It takes about 1.5 hours to warm up and doesn´t sound very nice from cold.
Since I don´t always know beforehand if I want to listen and don´t like like leaving it powered up all of the time I would like to try some kind of standby, i.e. leaving input powered up all of the time and only power up/off the power fets.
I´ve used this on my last amp and this really helped a lot to reduce warmup time and make the amp sound better from cold.
Now I´ve read some remarks that using two power supplies on the Aleph can produce some nice turn on thumps.
Question1: is this also the case when one of them (input) is on all of the time (I have no problem doing this with my crescendo at all) ?
Question2: will it help to reduce warmup time/ better sound from cold?
william
Hi all,
amp sounds quite good now but the next problem is on it´s way.... It takes about 1.5 hours to warm up and doesn´t sound very nice from cold.
Since I don´t always know beforehand if I want to listen and don´t like like leaving it powered up all of the time I would like to try some kind of standby, i.e. leaving input powered up all of the time and only power up/off the power fets.
I´ve used this on my last amp and this really helped a lot to reduce warmup time and make the amp sound better from cold.
Now I´ve read some remarks that using two power supplies on the Aleph can produce some nice turn on thumps.
Question1: is this also the case when one of them (input) is on all of the time (I have no problem doing this with my crescendo at all) ?
Question2: will it help to reduce warmup time/ better sound from cold?
william
William,
I can't answer your question but I thought I throw in my obervations when I was building my Aleph 2.
I noticed that it'll take at least half an hour for the source current to stablize at the output fets. That is at turn on, it'll show a slightly higher current than say half an hour later. By following this logic, it appears that the amp tend to sound better after the fets has been taken some time to settle in (sort of like after the fet has been stabilize & in harmony with the whole system temperature).
So, instead of answering your question, I have to ask you a question. It seems like the output fets should be left ON at all time for it to sound good right away and something else (don't know what) should be turn off. I was thinking, may be provide some kind of lower rail voltage at the "sleep mode" (which is when the amp is off but NOT completely off) and when you are ready to listen to the amp, you turn on another switch to ramp up the rail voltage to spec.
Just my 2 cents. I would also like to hear more feedback on this matter.
I can't answer your question but I thought I throw in my obervations when I was building my Aleph 2.
I noticed that it'll take at least half an hour for the source current to stablize at the output fets. That is at turn on, it'll show a slightly higher current than say half an hour later. By following this logic, it appears that the amp tend to sound better after the fets has been taken some time to settle in (sort of like after the fet has been stabilize & in harmony with the whole system temperature).
So, instead of answering your question, I have to ask you a question. It seems like the output fets should be left ON at all time for it to sound good right away and something else (don't know what) should be turn off. I was thinking, may be provide some kind of lower rail voltage at the "sleep mode" (which is when the amp is off but NOT completely off) and when you are ready to listen to the amp, you turn on another switch to ramp up the rail voltage to spec.
Just my 2 cents. I would also like to hear more feedback on this matter.
fcel,
either a lower voltage or a reduced current. But both will reduce the temperature in the output (though not as much as a input only) so there will be changes when heating up again.
An idea would be a switchable R19 to reduce bias from 4A (250watts) to 0,5A (30watts) or so.
With my other amp (also Fet although a gain stage more) the temp difference between standby and operate is also 25° or more and the bias will change all of the time but still the effect of the standby mode is verry positive.
william
either a lower voltage or a reduced current. But both will reduce the temperature in the output (though not as much as a input only) so there will be changes when heating up again.
An idea would be a switchable R19 to reduce bias from 4A (250watts) to 0,5A (30watts) or so.
With my other amp (also Fet although a gain stage more) the temp difference between standby and operate is also 25° or more and the bias will change all of the time but still the effect of the standby mode is verry positive.
william
I really don't know how useful this comment will be, but one approach is to make the bias current "switchable". So the amp may be left on at a lower idle current then switched to "full power" prior to listening .... assuming you would like to leave it on.
This idea is not mine, it was suggested by another on this forum some time back (just can't remember who, sorry) and has been used by a number of commercial amps (Plinius has a model which does this).
Just a thought.
cheers, mark
This idea is not mine, it was suggested by another on this forum some time back (just can't remember who, sorry) and has been used by a number of commercial amps (Plinius has a model which does this).
Just a thought.
cheers, mark
Here's a wild idea.The problem is how to heat up the heatsink faster since this is where all the thermal inertia is.
How about a second set of FETs (maybe 250's) powered from the same voltage rails as the amp, but the outputs are connected to a load resistor mounted on the same heatsink. The gates of these "heater" FET's gets its voltage from a voltage divider that can be switched off and on. You could even make it automatic by using the correct value of thermistor mounted to the heatsink as well. This way the "heating" circuit does not effect the audio circuits as they are totally separate circuits except for the power source (the transformer will have to carry both loads if you run the amp while heating). Both the FET's and the load resistors will heat the heatsinks to warnup the amp faster. If you have multiple heatsinks, you can put a heater circuit on each so the idea is scalable. If you're worried about the draw on the supply caps effecting the audio, and your running a PI filter PSU, the heater can draw from the first set of caps before the inductors.
This might work
Let me know why not
Rodd Yamas***a
Correct me if my understanding of FET is incorrect in regards to heat and current ....
Here's my comment. Don't we want to heat up the output FET - from the inside by feeding it a little current during the "stand-by mode" - so that it will reach a optimal heat equilibrium quicker at turn on and thus sounding better quicker? I would think heating the FET from the outside via the heatsink is different than ....
Here's my comment. Don't we want to heat up the output FET - from the inside by feeding it a little current during the "stand-by mode" - so that it will reach a optimal heat equilibrium quicker at turn on and thus sounding better quicker? I would think heating the FET from the outside via the heatsink is different than ....
Hi Fcel,
Yes. but as the FET is trying to heat up, the cold heatsink is pulling the heat away. The FET cannot reach its operating temperature until the heatsink starts to get close to the stabilization temperature.
That's why Peter sits there with his heat shrink gun trained on his amp for 20 minutes before any critical listening.😀
Well, nobody said it wouldn't work yet.
Rodd Yamas***a
Yes. but as the FET is trying to heat up, the cold heatsink is pulling the heat away. The FET cannot reach its operating temperature until the heatsink starts to get close to the stabilization temperature.
That's why Peter sits there with his heat shrink gun trained on his amp for 20 minutes before any critical listening.😀
Well, nobody said it wouldn't work yet.
Rodd Yamas***a
Yeah it´s different of course.
but the result is the same. Heat also goes the other way around.
If the heatsinks are warmer heat runs back to the FETs. Its like changing the polarity of the current flow.
but the result is the same. Heat also goes the other way around.
If the heatsinks are warmer heat runs back to the FETs. Its like changing the polarity of the current flow.
Probably it will take a lot more power to heat the heatsink with the warm air gun, so for economy of electricity its not a good idea. But at least I think its faster....lol
What about implementing something similar to an engine block heater? You could put it on a timer ahead of time to get your amp ready for listening.
--
Brian
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Brian