I was wondering if the aleph 1 would be able to handle larger voltage. I'm looking at running it with +-80 Vdc.
The schmatics of the Proximity amplifier are unavailable. So i was looking at pressing the dual transformers mounted in a 19" rackmount to good use.
The schmatics of the Proximity amplifier are unavailable. So i was looking at pressing the dual transformers mounted in a 19" rackmount to good use.
Well, I think IRFP240's can handle 80 volts.
But what are you going to do with the bias?
Aleph 1.2 runs on 4 Amps @ 60 Volts.
Can you imagine the size of the heatsinks you
are going to need if you keep the bias at 4 Amps?
And I don't think it would be wise to lower the bias.
In the original Aleph 1.2 each mosfet (of the 12 used) draws about 330 mAmps (330 x 12 = 3.96 Amps).
When I built mine I used 10 mosfets and placed a 100K trimmer in place of R19 just to see what happens with bias trimming.
With 300 mAmps per mosfet the amplifier sounded harsh and aggressive.
With 400 mAmps per mosfet it really sings.
Good luck anyway!
Nick
But what are you going to do with the bias?
Aleph 1.2 runs on 4 Amps @ 60 Volts.
Can you imagine the size of the heatsinks you
are going to need if you keep the bias at 4 Amps?
And I don't think it would be wise to lower the bias.
In the original Aleph 1.2 each mosfet (of the 12 used) draws about 330 mAmps (330 x 12 = 3.96 Amps).
When I built mine I used 10 mosfets and placed a 100K trimmer in place of R19 just to see what happens with bias trimming.
With 300 mAmps per mosfet the amplifier sounded harsh and aggressive.
With 400 mAmps per mosfet it really sings.
Good luck anyway!
Nick
Nelson Pass said:
Thanks for the quick response. The heat won’t be a big problem, the proximity was forced air.
Now on to building this animal... Whats the differance between the 1 and 1.2 ??
Anyone know of a supplier of PCB's? groveling will accompany if required. 🙂
Big difference between 1 and 1.2. The 1 has 3 gain stages and lower distortion and higher output into low impedances.
The 1.2 has 2 gain stages, and is the more familiar Aleph design. I recommend this, particularly as you will find more support for it here.
The 1.2 has 2 gain stages, and is the more familiar Aleph design. I recommend this, particularly as you will find more support for it here.
Nelson Pass said:
The main reason i picked the 1 over the 1.2 was because of the lower distortion and higher voltage supplies. I thought that modification of the 67Vdc supplies to 75-80Vdc would be less troublesome then the 60Vdc. The Horns are going to be a complex load for this amp so it should be interesting.
I plan on running this amp on a pair of klipschorns with 120db+ sensitivity. I've been looking for a nice clean amp to run on these speakers. The reveiws said that a well designed single ended tube amp sounds nice on these speakers. Seeing as fets and tubes are "simular" in the way they handle sound, i thought i'd give this a try.
Any assistance would be great.. Thanks everyone.
I agree that 200watts from the aleph 1.2 would be to much. The aleph 1 was only rated at 150w and i prefer to run just a little more then speakers can handle.
I've always done this, and i've never blown a amp and never smoked a woofer. I still currently run speakers i designed 15years ago. Although the new klipschorn replicas should be a nice change.
The speakers will handle 100Wrms with a peak of 400w.. So the match sould be really good.
I've always done this, and i've never blown a amp and never smoked a woofer. I still currently run speakers i designed 15years ago. Although the new klipschorn replicas should be a nice change.
The speakers will handle 100Wrms with a peak of 400w.. So the match sould be really good.
Hey!
please don´t feel offended but 120 dB /1W sensivity means much more than 100 % efficiency !!! 100 % equals 112 dB/1W1m
Although I know what al Khorn is capable of, I recomend to stay on the ground with any ratings!
I also feel that it´s senseless to specify sensivity at a single frequency which might just coincide with a strong resonance as it´s often done.
Franz
please don´t feel offended but 120 dB /1W sensivity means much more than 100 % efficiency !!! 100 % equals 112 dB/1W1m
Although I know what al Khorn is capable of, I recomend to stay on the ground with any ratings!
I also feel that it´s senseless to specify sensivity at a single frequency which might just coincide with a strong resonance as it´s often done.
Franz
you were correct.. the rating i gave was wrong... the correct rating is.
SENSITIVITY: 104dB @ 1watt/1meter
SENSITIVITY: 104dB @ 1watt/1meter
Well,
Regardless of power handling capacities and loudspeaker sensitivities the 1.2 is a very fine amplifier with more than enough power.
I think it would be wise to forget these transformers you already have and get yourself a pair of new ones rated @ 45-0-45 Volts @ >= 2 KVA.
Go for the 1.2 and you won't regret it.
I hope the attached files will help you.
Nick
P.S.
A friend of mine is driving his Klipschorns with a Crown Macro Reference, but then he is practically deaf.
Regardless of power handling capacities and loudspeaker sensitivities the 1.2 is a very fine amplifier with more than enough power.
I think it would be wise to forget these transformers you already have and get yourself a pair of new ones rated @ 45-0-45 Volts @ >= 2 KVA.
Go for the 1.2 and you won't regret it.
I hope the attached files will help you.
Nick
P.S.
A friend of mine is driving his Klipschorns with a Crown Macro Reference, but then he is practically deaf.
You could series the primaries of the existing transformers
to halve the 80 volt secondaries to 40 volts. Then bias
the hell out of it...
Recommended only for Class A circuits, as they offer more
constant draw.
to halve the 80 volt secondaries to 40 volts. Then bias
the hell out of it...
Recommended only for Class A circuits, as they offer more
constant draw.
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