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Old 4th October 2005, 07:15 PM   #1
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Default Questions for the Class A gurus! Need advice

Gentlemen,

I have just finished my first DIY speaker project and the results are amazing. I'll be posting some pictures of the completed pair in the loudspeaker forum tonight. I'm running an all active system with a DCX crossover. The drivers are all high efficiency designs Fountek JP2.0 tweeter (98db), PR170m0 midrange (98db) and 2x 12" Poly Paper woofers (93db per, 99db system).

I want to replace the mid and tweeter amplifiers with a Class A design. I don't think I need alot of power since most of the drivers are 98db+. Looking at the threads on the forum I'm thinking Aleph 3, Aleph 30, or maybe even a Pass F1? The amp would need to be able to accept balanced inputs. Any recommendations? Can you use an F1 to driver a speaker directly, I see that in the reviews Mr. Pass supplied custom filter networks to the reviewers.

Thanks in advance,

--Chris
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Old 4th October 2005, 07:21 PM   #2
PMA is offline PMA  Europe
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Try this one:

http://www.pha.inecnet.cz/macura/follower_e.html
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Old 4th October 2005, 09:11 PM   #3
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Thats interesting but I think I'll need more gain than that.

I'm leaning towards one of the lower power Alephs or trying my hand at the F1.

This will be my first amplifier project so I'd like to keep it relativly simple, but still achieve excellent results. The F1 in particular looks like a simple schematic that I could wire mostly point-to-point. I think I would probably do the powersupply on a PCB since ground shielding would probably help with noise on the supply. I've been reading Mr. Pass's comments in the F1 service manual about cross overs and which drivers are suitable for these transcoductance amplifiers. I think my mid/tweeter selection will work. I'm using a digital cross over before the amplifiers so the crossover should not be an issue.

Comments apreciated, Thanks!

--Chris
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Old 5th October 2005, 01:09 AM   #4
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As you say, F1 is easy for the p2p.
And very low noise without requiring any special care.

The sound is wonderful.

Regards
jH
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Old 5th October 2005, 01:51 AM   #5
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Quote:
Originally posted by jh6you
As you say, F1 is easy for the p2p.
And very low noise without requiring any special care.

The sound is wonderful.

Regards
jH
You've heard one in person? I would love to here your comments on how it sounded. I'm really leaning towards the F1 and trying it out with my midrange. Possible changing to an MTM in order to get somemore efficiency to help with maximum SPL.

My concern is will the sound be affected by the protection cap on the ribbon tweeter? Is it ok to drive a ribbon with this kind of amplifier? Dc offset will kill a ribbon very fast and the documentation states that the amplifier idles at 13.7V DC offset on both outputs.

--Chris
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Old 5th October 2005, 02:03 AM   #6
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Quote:
The outputs of the amplifier are balanced, and operate at a 13.8 Volt DC potential above ground, just like your car battery. Don't worry, the speaker sees only the difference between them, and not the DC, but don't expect the amplifier to operate properly if you attach either output to ground.
Its floating above ground, there should be very little DC current. They are both at 13.8V, no offset.
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Old 5th October 2005, 02:53 AM   #7
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Quote:
Originally posted by DIY_newbie


You've heard one in person? I would love to here your comments on how it sounded.

Click here

Regards
jH
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Old 5th October 2005, 05:14 AM   #8
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Read through your comments on the F1.. sounds like a good first project. I'm still hoping someone chimes in with their experience with both Aleph and F1 amplifiers? Probably unlikely that someone would have built/heard both?

Best Regards,

--Chris
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Old 5th October 2005, 07:46 AM   #9
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I think only Nelson could answer your question, but he will never do it.

Good luck!

Regards
jH
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Old 5th October 2005, 08:56 AM   #10
djk is offline djk
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Are you going to do anything with the DCX?

The 4560 is a pretty good opamp for $0.13, but not up to the quality of the other items you are talking about. Did I mention there are 17 of these things in the I/O of the DCX?

Oh, and 15 polarized electrolytics too?
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