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Nelson Pass amps

Sal1950

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Oh and a question for you guys. Do any of you know which First Watt amplifier might work well with my JBL 4367?
If you listened to the above video, Nelson gives some description of how he manipulates distortion bands to achieve his desired goal. I believe there's more to it than that but in any case he does try to voice his designs.
If it was me and I owned those awesome 4367's I get a Benchmark ABH2 and be set for life.
Then if you wish to voice the system get some DSP going with it. ;)
 

ahofer

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My understanding, including from a personal email exchange with Pass himself, is that he designed the original MOSFET-based 5x00 series just as he'd done the original bipolar-based 5x5 series. And as others have said, he had no part in the modifications made for the mk ii versions of some of those models.

I have a GFA-5400, Japan-made version, that I picked up used about 5-6 years ago for $150. My local tech had completely gone through my 535 and my 565 preamp and replaced tons of caps. I paid him $40 to go through the 5400 and check it out, and he said he cleaned it but it was totally fine otherwise - caps all good, performing to spec as-is.

It is on my list to get it serviced one of these days, though, as those caps will need replacing eventually.

However, I am mighty tempted by the emergence of such highly performing Hypes-Based amps now coming down below the $1500 (or I guess $750 per channel) price point, and so I might just save up for one of those. I do love that 5400, though - I don't know if it's the MOSFETs or what, but I slightly prefer it to my 535 (yes I know they have different power capabilities as well).

If you look in some other threads, you’ll see that i recently A/B’d my Adcom 5802 against a $850 two-channel Hypex Nc252mp design. In the end, I felt they were indistinguishable. Also, with a test tone, the gain was the same. The Class D design is small and cool, while the 5802 is an enormous, heavy, space heater. I think it’s probably past time to accept Class D as potentially just as good or better than AB designs. I’d love to repeat this with a current Pass design, if anyone wants to bring one over...:)
 

Sal1950

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ahofer

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Sal1950

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The distortion values on those SIT/First Watt designs are pretty outrageous. I'm curious, tho.
I belive the Pro product lines have all sort of distortion injecting stuff that you can play with for peanuts. :p
 

ahofer

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I belive the Pro product lines have all sort of distortion injecting stuff that you can play with for peanuts. :p
Is that right? Is there a second harmonic injector?

When I saw the "pleasure" dial on a Dartzeel preamp, I was wondering if that was what it did. I guess it's just volume.
(in this system - https://systems.audiogon.com/systems/615 )
 

MRC01

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...
I run 5 of his Adcom GFA 5X5 II amps in my multichl rig.
Built like tanks, 25 years old and running strong.
Transparent, that's the bottom line.
Kudos for his contributions to the DIY crowd!
I agree. I bought an Adcom 5800 in 1994 and still use it today. 25 years of near daily use and it's still going strong. I get it bench tested every few years and it's always been spot-on, no internal parts have needed replacing, still performs equal or better than specification for power & distortion. DC offset measures 3-5 mV on each channel. The only part I've ever replaced is the power switch, which fails every 10 years or so. That's a $20 part and a 15 minute repair.
It's powerful and transparent with excellent reliability. What else could an audiophile want?
If all the Nelson Pass designed gear is like this, he's earned his good reputation.
 

mitchco

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MRC01

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Not all distortion is equal. Some is easier to hear or subjectively more annoying/dissonant that others. Thus it's possible that an amp with higher overall distortion could not only sound better, but be more transparent and true to the source psychoacoustically. By this I'm not talking about adding distortion just to make it "sound better", but an engineering tradeoff. For example something like, we chose this design B over A because even though B's total distortion is slightly higher, it has lower odd order distortion and IMD. Psychoacoustics and A/B testing can provide an empirical basis to make such a decision not entirely subjective.
 

Bruce Morgen

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I owned the "entry-level" Pass-designed Adcom power amp, the original GFA-535. It was excellent and a very good value back in the day. Nowadays, my little Chinese-made TAS5613A-based mini-amp sounds every bit as good and cost me only $25 used plus another $25 for a hefty new SMPS.
 

Twitch54

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Longtime PASS enthusiast, started with Threshold in the mid-eighties and currently running a pair of X260.8's, couldn't be happier ......
 

cjfrbw

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I built this NuTube preamp unit from the DIY site with the board. It was my first beginning to end DIY project, and it worked to my shock and amazement. It's a high end sounding preamp/gain unit for something this inexpensive to make. Going beyond the 1 volt 'speed limit' into higher gains obviously increases the distortion profile.

However, it is unapologetically designed specifically to create this second order harmonic effect.
 

Batty

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I use a DIYA M2X clone as my main power amp, all 25 watts class A, actually it has been measured at 24.7 into 8 ohms and 39 into 4.
Speakers are 92dB sensitivity. It requires 2.7V for max power, I use a CD at 2V.
 

Julf

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I built this NuTube preamp unit from the DIY site with the board. It was my first beginning to end DIY project, and it worked to my shock and amazement. It's a high end sounding preamp/gain unit for something this inexpensive to make. Going beyond the 1 volt 'speed limit' into higher gains obviously increases the distortion profile.

However, it is unapologetically designed specifically to create this second order harmonic effect.

That is precisely what the nutube was developed for.
 
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