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Old 29th July 2012, 02:33 AM   #41
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Be sure to check out the First Watt F6 build thread that's just getting started. I'm thinking that it might take care of your needs quite well. The full schematic hasn't hit the floor yet, so patience is required.

Don't worry about the heat, and the sound is worth the extra juice you have to put into them.
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Old 29th July 2012, 03:16 AM   #42
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Quote:
Originally Posted by tvrgeek View Post
If you have any details on the PA5 issues, I would love to cache them away. I will chew about a few more days. They come up for sale every now and again.

Replacement transistors. Funny man. That is what started the Hafler rebuild. I tested the limits after the power supply upgrade. Found them. That led to the Exicons and total revamping of compensation and feedback. In trying to fix an old Kenwood 9100 for a friend, NOTHING is available. Seems good Fets are hard to find. Even good fast BJT's are all gone or counterfeit. I still have an DH-220 on the shelf, but it is a pain just like the 120 in space.

I even got 2N2222's that I think were counterfeit and even Sanyo would not make a gain of 4. I have seen a comment that more than one current high end producer is working off a cache of NOS and is not sure what happens when that is gone. If a transistor is not needed for a cell tower or car, it is dead. Seems industry has decided chip-amps are good enough for us.

Looking in the 535, it has TONS of space for working compared to the DH-120. You can't always make a silk purse out of a sow's ear, but pigskin can be nice. I don't have a specific bias BJT or FET. They are different. Both need to be understood. An F5T looks attractive, but heat and cost may keep me in class b.
ive got a hand full of 2n2222's that ive pulled from stuff bound for the trash if u need them.
i dont know why i kept them.....but i did. i know they are real.
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Old 29th July 2012, 11:02 AM   #43
tvrgeek is offline tvrgeek  United States
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sak,
I appreciate the offer, but I got a bag from Mouser that are fine. They are handy to keep. Coil driver, led driver, power supply. Handy to have a "transistor" on hand. I keep a few 2970A's too. At 7 cents, you can have a few around. I just don't mistake them for an "audio" transistor even though Erno used one for the bias separator.

Coc,
F6, OK, I'll watch. It looks like one has to make up their mind early to get in on any group buys. I'll save the cash I might have spent on an PA-5. That means you have to put up with me while I watch these threads. In the mean time, I ordered another O-Audio plate for my little background 30 to 60 Hz "helper" sub only to find out they shut down for a month and won't ship till mid August. I understand a small company and actually getting a vacation. I just wish they had let me know in the order process. I'll have to dummy up an old car crossover until then. I am not a terribly patient person.
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Old 29th July 2012, 12:14 PM   #44
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Quote:
Originally Posted by tvrgeek View Post
If you have any details on the PA5 issues, I would love to cache them away. I will chew about a few more days. They come up for sale every now and again.

... I even got 2N2222's that I think were counterfeit.
Thanks for the heads up about counterfeit transistors - yikes !

Here is a previous discussion concerning the PA-5
http://www.diyaudio.com/forums/pass-...hi-pa-5-a.html

It seems there was the original PA-5 and a MkII
AudiogoN Forums: nakamichi pa5 or 7
.
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Old 29th July 2012, 03:14 PM   #45
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TVR,

cool, i wondered why they where used so much on the cir i took them from. i never stopped to look them up.
i'm glad i kept them then. could come in handy.
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Old 29th July 2012, 03:27 PM   #46
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Originally Posted by Uunderhill View Post
My modded B&W 603's drop down to Z = |3.9| ohms - I have no idea what the phase angle is like.

Do you think an F5 could drive these ?


Low efficiency B&W Nautilus speakers drop down to Z = |2.9| and I suspect the phase angle is hell.

These need Current.

Do you think an amp with a huge power supply - low Zout - but only 50 watts could drive these ?

Have you tried lowering the bias current on your class A amps ?



Also, do your Aleph amps thump when switched on ?


Thanks,
.
At the time of my F5 I has some B&W 683's the F5 couldn't cope with them.

I've just won a pair of YELLOW (that's another story) B&W 802D's, the F5 certainly wouldn't like them.

The Aleph 4 copes well with both the 683s and the 802D's
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Old 29th July 2012, 03:38 PM   #47
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i have 3-way scan-speak (88db 6ohm) wich is much harder load. and my F5 drive them very well
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Old 29th July 2012, 03:42 PM   #48
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It all depends on what you listen to and what you expect out of an amplifier. It is a subjective subject so you will have to build one and try one for yourself.

The F5 is relatively cheap to build.
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Old 29th July 2012, 03:46 PM   #49
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and listening level, room size++
from my F5 to your aleph4, you only gain about 3db on same speakers(8ohm) and room.
on 4ohm speakers, you don't gain anything
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Old 29th July 2012, 03:49 PM   #50
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Yes but try pushing the F5 at 100W into a 10m x 10m lounge with 83dB speakers.

This is why I say it is such a subjective subject.

When you have the luxury of comparing the various amps to each other one will naturally choose the one that he/she likes the best.

The F5 is an easy and pleasant build. The Aleph 4 was a complex and expensive build.

I'm not saying that one is better than the other but I love the A4.

If Nelson himself had produced the Nirvana of amps he wouldn't keep on trying to improve on his designs !!!!

I'm looking at the F6 and thinking, why is he going back to transformers.

Last edited by KatieandDad; 29th July 2012 at 03:55 PM.
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