To DIY, or OEM PASS?

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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. :D
 
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.
 
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.
 
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-labs/163741-improve-sound-nakamichi-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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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,
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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
 
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.
 
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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

K & D,

Thanks for this info - its very useful.

The 683's drop down to Z = |3.0| - I don't think an F5 is designed for this.

My preference with B&W's is tubes in the preamp and MOSFET's in the power amp.
- and solid core copper speaker cables.
- something to look into is solid core OCC copper with teflon insulation.
there are only 3 companies licensed to make OCC copper wire and its sold under quite a few brand names.

With my N804's - I'm thinking of bi amping with a small class A MOSFET amp going to the mid/tweeter
and a Bi polar push - pull amp going to the bass.

B&W has really improved the crossovers with their Diamond series.

In my 603 s2's and N804's they used Bennic resistors and MKP caps.
What were they thinking ?
I rebuilt the tweeter crossover section in my 603's and it was a huge improvement.

I suspect an Aleph 4 can drive the 802D's because of a very low Zout
and they can deliver lots of current.
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K & D,

Thanks for this info - its very useful.

The 683's drop down to Z = |3.0| - I don't think an F5 is designed for this.

My preference with B&W's is tubes in the preamp and MOSFET's in the power amp.
- and solid core copper speaker cables.
- something to look into is solid core OCC copper with teflon insulation.
there are only 3 companies licensed to make OCC copper wire and its sold under quite a few brand names.

With my N804's - I'm thinking of bi amping with a small class A MOSFET amp going to the mid/tweeter
and a Bi polar push - pull amp going to the bass.

B&W has really improved the crossovers with their Diamond series.

In my 603 s2's and N804's they used Bennic resistors and MKP caps.
What were they thinking ?
I rebuilt the tweeter crossover section in my 603's and it was a huge improvement.
.

Uunderhill,
Have you read the F5 article? HAve you read the F5T article? K&D may not like the f5, but he is simply wrong about its abilities. If the standard F5 is not suited for your speakers, the F5T V2 or V3 will EASILY drive your speakers. You may not like it, but it isnt because it is having trouble doing the job. Be careful that you check what others say. BTW, he is comparing a 25W F5 to a 100W A4.
 
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i have 3-way scan-speak (88db 6ohm) wich is much harder load. and my F5 drive them very well:)

AudioSam,

I think what makes a speaker an easy load is the magnitude of the impedance curve and its phase angles.

Speakers with mostly a real impedance where Z >= |4 | ohms are a reasonable load to drive.

Speakers that have large phase angles - where there is a large rate of change in the phase angle
combined with a low Z magnitude - can be hell for an amp.

IMO an amp with a very low Zout - combined with a huge power supply - is needed for speakers like these.

I don't know which 3 way Scan Speak speakers you have,
but from what I've seen from Seas and Scan Speak designs,
the real and imaginary components of the impedance, provide a reasonable load.
Have is Troels Gravesen's builds of Scan Speak's - bless this person.
ScanSpeak Projects
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Uunderhill,
Have you read the F5 article? HAve you read the F5T article? K&D may not like the f5, but he is simply wrong about its abilities. If the standard F5 is not suited for your speakers, the F5T V2 or V3 will EASILY drive your speakers. You may not like it, but it isnt because it is having trouble doing the job. Be careful that you check what others say. BTW, he is comparing a 25W F5 to a 100W A4.

I've tinkered modding the F5 for a few weeks now.

Mr. Pass, Juma and Zen Mod have been very kind to help me with the mods.

The F5 has some great advantages
- its dead quiet
- there is no thump with switch on and off
- Beethoven piano Trios and Mozart piano concerti sound great with it.
- sonically I really like this amp

From a Zout point of view, the F5 has a parallel common source output stage.
So I think its really intended for speakers that are reasonable load.
It drives my 10" 2528 DC Tannoys beautifully.


K&D has B&W's where the Z =< |3.0| , with difficult phase angles - these speakers put huge demands on an amp.

The aleph 4 has a follower output - so I suspect its Zout is very low.
Plus the power supply could run a fork lift.
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