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Old 28th July 2012, 09:03 PM   #31
tvrgeek is offline tvrgeek  United States
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My Seas ER18RNX is about typical and it just makes 88 dB before any network is put in. A typical 6 inch 2 way you can put in a real living room or office is going to be 86 or so when done. Wish it were better. 50W may not cut it in a big room ( but I used RB951's for years just fine), but in my office at less than concert levels, just fine. We are still talking a couple hundred watts of idle power to get rid of. I guess I had better not go that route just yet.
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Old 28th July 2012, 09:29 PM   #32
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i'm not talking about smal bookshelp speakers here they are normaly 84-87db.
and not for use with low wattage amps.
86db with 50W in = around 103db peak at one meter. and with 10W it's 96db peak.
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Old 28th July 2012, 10:23 PM   #33
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Originally Posted by KatieandDad View Post
The F5 likes easy high efficiency loads.

Couple it with a decent pair of British low efficiency speakers and it just lacks the power to drive them fully.

Hence my B-I-L went for the Aleph 4, it's 100W/Channel of Class A and copes beautifully with low efficiency loads, but it comes at a price. 2 x 100W of Class A power gives about 400W of heat to the living room.

The F5 is only 25W/Channel which should be more than enough with reasonably efficient speakers.
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,
.

Last edited by Uunderhill; 28th July 2012 at 10:27 PM.
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Old 28th July 2012, 10:26 PM   #34
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Originally Posted by tvrgeek View Post
Would some DIY SOP work to clean up an Adcom 535 have decent results, or is that just trying to make a mass market cheap amp something it isn't?
Not a good starting point, as 535 is BJT throughout (and not much space). Maybe certain 5xxx series (all-mosfet) with more PS and much more bias, but then you might as well DIY....

Go with an F5 variant with your favorite parts.
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Old 28th July 2012, 10:39 PM   #35
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Originally Posted by tvrgeek View Post
So what's the word over here in Pass-land; used, modded, or scratch? I'm partly fishing for word on how good the PA-5 was. The Hafler is several steps above it's original design, and I could always use one of my many slightly cleaned up Rotel 951's as they are beguine, if not very detailed. I want more.
Well if you rebuild a classic amp

You get the case - heat sinks - power transformer - and the silicon - plus all the hardware bits.

and proven design - Sounds pretty good to me.

Over time - any of the electrolytics will be cooked.

I'd say if you intend to re build any classic amp make sure you can get a schematic and can get replacement transistors.

I've read the PA-5 feedback loop needs correcting - to be the same as the Statis Amp.

.
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Old 28th July 2012, 11:46 PM   #36
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Originally Posted by KatieandDad View Post
All nice amps. Pass is the only amp that has it's designers DIY backing. The F5 is a nice amp but it does have its limitations.

The commercial designs ? you will need to listen to them or rely upon reviews to know what they might sound like.

My family had a clone of one of ML designs (not an original), it was OK but was surpassed in EVERY detail by the Pass Aleph 4 built by my Brother-in-Law.
The only limitation of the F5 has been addressed with the F5T. It may be a somewhat expensive build, but much cheaper than anything of equal quality.
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Old 29th July 2012, 01:08 AM   #37
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Originally Posted by Uunderhill View Post
...

I'd say if you intend to re build any classic amp make sure you can get a schematic and can get replacement transistors.

I've read the PA-5 feedback loop needs correcting - to be the same as the Statis Amp.

.
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.
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Old 29th July 2012, 01:27 AM   #38
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Originally Posted by AudioSan View Post
i'm not talking about smal bookshelp speakers here they are normaly 84-87db.
and not for use with low wattage amps.
86db with 50W in = around 103db peak at one meter. and with 10W it's 96db peak.
Unfortunately, bookshelf (with subs) is what fits in real houses. I don't even have room for floor-standers on any of my systems. That's part of the challenge. Designing with constraints. In my office, I listen at only a little over conversation. The 6W tube ( when stock) ran out of steam, but all of my 50W or so amps are fine. Even the 40W Creek was OK power-wise. Just did not love it. Then I need the better tuner and started down the NAK path, just to fine the footprints of the good Mr. Pass.

I guess the definition of low wattage has changed. I know when my dad had the "monster" 30 Watt Knight it could drive the AR-2. My "high end" HK 300 Elite was about typical at 12W. My RLD, when done will be about 6W I consider 50 to be pretty robust. I only have the big Parasound on my living room because they are the smallest Curl designed ones, rather than "inspired" by, which means cheapened. I switched back to an RB-951 because the HCA-1200 was vastly better than the DH-220 on the subs. Hard to describe. It should not have been.

Gonna think a bit. Read all the threads again. Price it out. I don't know what an F5T would run me if I had to start from scratch.
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Old 29th July 2012, 01:38 AM   #39
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Don't know anything about 5xxx or 6xxx series. The do seem to be Fet.
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Old 29th July 2012, 02:07 AM   #40
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Originally Posted by tvrgeek View Post
So what's the word over here in Pass-land;
used, modded, or scratch?
Pick your poison. I recommend scratch as the most entertainment
for the buck.

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