is there any way you can squeeze more power out of an aleph5? - diyAudio
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Old 20th September 2003, 05:36 AM   #1
cowanrg is offline cowanrg  United States
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Default is there any way you can squeeze more power out of an aleph5?

im looking to get a bit more umph out of an aleph5, is there a way to get it over 100 watts per channel @ 4ohm?
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Old 20th September 2003, 07:29 AM   #2
Netlist is offline Netlist  Belgium
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Don't know if the Aleph5 is capable of decently driving 4 ohm.
According to the Aleph2 service manual, which says 100W/8ohm
and 160W/4ohm, I wouldn't be surprised that the Aleph5 already gives you close to 100W/4ohm.
Other Aleph5 owners can probably confirm this (or not)
If you really want more power I guess youíll have to convert them into Aleph2ís.

/Hugo
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Old 20th September 2003, 09:24 AM   #3
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Hello cowanrg,
the better way to proceed, IMHO, is to build a bigger Aleph, as Netlist pointed out.
Original Aleph 5 s rated 90W/4ohm, so a difference between this at the 100W target is not so big, at least in SPL.
But the A5 doesn't fell at its ease with "difficult" loads...
If you want to give a try to your Aleph, you can rise the bias current as much as you can (Hexfet dissipation, power supply an heatsinks must be suitable to the heavier job, of course).
As a last attempt, you may try to increase the gain of the current source, respect the active side: this practice has his cost against the sound, on the contrary of the previous one.

Marcello
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Old 20th September 2003, 09:31 AM   #4
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Wasn't there somewhere a post which suggested to add more output devices?

Jan
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Old 20th September 2003, 10:20 AM   #5
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Yes, you can add more fets to get more bias and output current capability, but they need to be matched like the others, you need the current capacity in your psu, and the heat sinks to dissapate the added heat. All of these changes acn be made with no adjustment to the rest of the circuit.
I built (still in progress, but playing beautifully) my Aleph 2s with 8 fets per side instead of 6 and used lower source resistors to almost double the bias for 4 ohm speakers.
Adding output devices is the way to get more current without degrading sonics by some other compromise. With the extra current avalible, you should have double the wattage @ 8 ohms into a 4 ohm load.
I have pots in mine for R19 and R21 (bias and current gain). The amps sounded better with less current gain and more bias than vice vera.
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Old 20th September 2003, 04:04 PM   #6
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Brian is correct. Up the bias. As a bonus the amp will sound better, too. You may or may not have to add more output devices, depending on what you chose to put into your amp and how much you increase the bias. More output devices will--all things being equal--give you more current capability, but it will also tend to 'darken' the sound of the amp due to increased cumulative Gate capacitance presented to the front end. Watch your heat sinking. When in doubt, add more. No one ever ran a class A amp too cool. Running one too hot, however, can cause a problem or two.
Somewhere in the bowels of the Aleph-X thread I gave a recipe for calculating the wattage/bias for Alephs and Aleph-Xs. I know it's a tough slog to wade through all that, but it's there.

Grey
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Old 20th September 2003, 04:48 PM   #7
cowanrg is offline cowanrg  United States
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the plan was over-heatsinking anyways. i always thought that the alephs were ok with a 4 ohm load. the speakers will be maggies. i know these are difficult to drive, but ive read a lot about these amps commercially, and it suggests that maggies arent a problem for them.
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Old 20th September 2003, 08:30 PM   #8
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Hi Cowanrg,

With Maggies you might consider building these versions or a modified version of the Aleph 2 instead...

http://www.passlabs.com/pdf/aleph/a0_serv_4-6.pdf
or
http://www.passlabs.com/pdf/aleph/a1serv.pdf

I run Apogees at this end and they too are known for being very hard to drive. About a year ago, I remember Nelson mentioning that I might consider looking at building these versions of the Aleph because they handle low impedances so much better.

I borrowed a 0s from a friend and was blown away by how much control it had over a pair of Apogee Stages. We hooked it up thinking that because of its low power there was no way it would drive the Apogees well...

We were very wrong!

That little amp blew away amps that cost 5 times as much and the difference wasn't subtle...

You might consider building an Aleph 2 version with the three gain stages instead... They will handle the low impedance loads much better...

By far the best sounding amp that I've ever heard drive the Apogees....

For what it's worth...
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Old 20th September 2003, 08:54 PM   #9
cowanrg is offline cowanrg  United States
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hum. i was trying to keep it cheap :-)

my main amps will be the aleph 2's im building, the other amps are for bi-amping, and the rears/center. not as important, but still should be nice.

where is this three gain stage aleph2? i would love to build another aleph2, but i need 4 channels of it to complete my theatre, and not only would the cost be prohibitive, but i wont want that much heat/space.
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Old 20th September 2003, 09:08 PM   #10
Apogee is online now Apogee  United States
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Pass never built a 3 gain stage Aleph 2. You would need to wing it a bit and combine the Alephs 0 & 1 and come up with something between the two. Shouldn't be very hard actually because the power supply voltages etc should be close to the 2 gain stage models... The output stage could be the same as the 2 gain stage models it's only the front end that you would need to change...

Also had a question for you. What are you planning to use for the meters? I too am building cases and need something similar...

You've done a very nice job thus far by the way!!!!
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