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Old 17th December 2013, 09:24 AM   #1
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Question Selection an amplifier Pass in class "A"

Hello,

I would like to ask you for advice to select the appropriate amplifier Pass for listening classical music. Now I have Electrocompaniet ECI 2, which is very good.
I'm thinking about amplifiers from Pass Labs Aleph 5, Aleph 3 ...
I listen to mostly classical orchestral music from LPs (large orchestras, symphonies, concerts, ...).
Speakers I have 2.5 band with 65 liter bass reflex, made according the project to Zaph|Audio - ZRT - Revelator Tower. Sensitivity have approx. 90 db impedance is 4 ohms (may also fall slightly below 4 ohms).
I have upgraded turntable Lenco L75 + arm Jelco SA-750D + Shelter 90X cartridge.

Which amplifier will be right for me, Aleph 5, Aleph 3, or which else? Where can I find the most complete project for its construction?

Thank you for your opinions. Milan
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Old 17th December 2013, 09:51 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

Your amplifier is 2 ohm capable (2x150W and 2x90W 4 ohms)
and you would need a massive proper class A amplifier to get
anywhere near its capabilities. As it is it matches pretty well.

Its clearly not Class A beyond a certain point, but that is no
bad thing, its better than just clipping due to low output.

All proper class A designs basically usually can only manage
about half the power into 4 ohms than they can into 8 ohms,
unless specifically built for 4 ohms, and for 4 ohms they
should be designed for maximum output into 3R*.

Also note a higher than normal amplifier output impedance
in this case won't interact much with the broad very flat
impedance of the ZRT2.5, but will interact with bass tuning.

rgds, sreten.

* A compromise for class A, for Class aB you really should
build a 4 ohm amplifier to be able to handle 2R loads well.
I suspect the ECI 2 specs are into R, not nominal ohms.
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Last edited by sreten; 17th December 2013 at 09:59 AM.
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Old 17th December 2013, 10:08 AM   #3
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Is sufficient a smaller amplifier Power Output approx. 60 watts / ch 4 ohms, I have a smaller room, ECI 2 is not working to full power.
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Old 17th December 2013, 10:23 AM   #4
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Considered an Aleph 0 ?
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Old 17th December 2013, 10:23 AM   #5
Zen Mod is offline Zen Mod  Serbia
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borrow , listen , decide
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Old 17th December 2013, 03:29 PM   #6
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ZM, don't you mean build them all, listen, decide?

ZRT 2.5 way doesn't look like it dips much below 4 ohms. I would consider an F-4 driven by a pumpkin or BA3 front end or an F5T with at least two pairs of output devices. An Aleph J with doubled up output devices should work as well.
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Old 17th December 2013, 03:43 PM   #7
PKI is offline PKI  United States
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Quote:
Originally Posted by BobEllis View Post
ZM, don't you mean build them all, listen, decide?

ZRT 2.5 way doesn't look like it dips much below 4 ohms. I would consider an F-4 driven by a pumpkin or BA3 front end or an F5T with at least two pairs of output devices. An Aleph J with doubled up output devices should work as well.
Aleph J, F5Tv2 based on sound preferences. Or BA-3/Pumpie +F4, can't comment here.
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Old 17th December 2013, 03:45 PM   #8
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I've tried the Aleph 4 and the F5, the Aleph has a far more subtle sound which to me is more pleasing to the ear. However, the Aleph 4 is a far more challenging build. The Aleph 4 is a monster at 100W Class A, it needs huge heatsinks and a huge PSU. ISTR it dumps about 400W of heat into the heatsinks.

Last edited by KatieandDad; 17th December 2013 at 03:48 PM.
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Old 17th December 2013, 03:58 PM   #9
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Quote:
Originally Posted by BobEllis View Post
An Aleph J with doubled up output devices should work as well.
400W is a lot of heat to pay for 25W of amp.
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Old 17th December 2013, 04:36 PM   #10
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Should be a bit more than 25W with a 4 ohm load, and it will help cut the heating bill.
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