To me, those are all gimmics that look good on paper.
Adcom GFA -565se
- Thread starter Frank Wong
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Frank Wong
Member
OK that's what I thought too! Designer of Benchmark said Pass designs covers up fine details!
BTW, none of the Nelson Pass's design is low THD. The Threshold Stasis is not low THD as I measured 0.04% across the audio frequencies. I simulated his famous Aleph, it's even higher THD.
Remember, I mention the biggest difference between my amp and the Nelson Pass's Nakamichi Stasis is the lack of detail of the Stasis. I can hear more with my amp, small little sound that you miss with the Stasis show up with my amp. Just more separation, more 3D.
Acurus ( very similar to Aragon in design) is even worst and the THD measurement shows.
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Are you buying new or used. I thought you go for used, but sounds like you are looking at new ones.
If you can take the heat.........literally, this might be nice:http://www.ebay.com/itm/272698837543?ul_noapp=true
KSA250 is a HUGE amp, it's a good stove( beyond heater).
I just got the schematic of the Krell FPB300C, it's a completely different design from the KSA. The KSA is like Acurus/Aragon except it's class A( that makes the difference in the world). I have no opinion on the FPB, I need to spend time to study the schematic. They are newer and a lot more expensive. I don't know whether this is out of your price range.....even as used.
https://www.ebay.com/sch/i.html?_od...0.Xkrell+fpb.TRS2&_nkw=krell+fpb&_sacat=32852
If you can take the heat.........literally, this might be nice:http://www.ebay.com/itm/272698837543?ul_noapp=true
KSA250 is a HUGE amp, it's a good stove( beyond heater).
I just got the schematic of the Krell FPB300C, it's a completely different design from the KSA. The KSA is like Acurus/Aragon except it's class A( that makes the difference in the world). I have no opinion on the FPB, I need to spend time to study the schematic. They are newer and a lot more expensive. I don't know whether this is out of your price range.....even as used.
https://www.ebay.com/sch/i.html?_od...0.Xkrell+fpb.TRS2&_nkw=krell+fpb&_sacat=32852
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Frank Wong
Member
Thanks Alan for helping g me choose my last amp! I am applying for PayPal credit so I might be able to swing a Coda S12.5 new ($3800)or a used Mark Levinson 532H under 4k 2 hrs old or new Bryston 4b3 ($4000) and lastly Adcom 565se. Looking no more than 2 yes old as probably need to recap. Krell and Pass too heavy and bulky. I want to stay under 60 lbs. I can really only afford $2 k. I have a few things to sell like my Prima Luna tube amp & maybe my Nad!
I don't know how comfortable are you to do some work like recap etc. if necessaery. I would buy used to save money.
Recap might be a little over rated. I don't recall I heard any difference after I recap the Nakamichi Stasis even though from the waveform that two of the caps are going. I never recap the Acurus after 19 years and of that 17 years of 4+hour a day, 7 days a week used ( I watch tv with it). I looked at the waveform, they still looked good to me.
Unless the cap show physical sign of problem....like leaking or swelling, I would listen to it first. Filter cap is not going to make or break the sound. I can tell you with the old caps in the Acurus, it gave the Nakamichi a good run for the money when I did the comparison test. Of cause the Nakamichi is better, The Acurus is a relative cheap amp, the Nakamichi is Stasis by Nelson Pass!!!
People here tends to do things unnecessary like pulling transistors and resistors out to measure and then put it back, I absolutely disagree with this practice. Far as I concern, if it is not broken, don't fix it. AND I am telling you as EE with 30 years in the field. You might fix it broken!!! Then you'll be in deep $hit. It's just an amp, don't put your emotion into it. I guess I've been in this field for too long, I don't get attach to this. Just an amp and I won't blink an eye dumping it if I find something better. The Nakamichi is now sitting in the garage with all the junk since I finished my amp. I won't blink an eye if I designed and build a better amp to put the current one in the shed outside the yard!!!
But, this is my opinion. You save half the cost buying used. $2K buy you a very good used amp. $2k don't get you far with new amps. Hell, my cheap Acurus was close to $1000. Hell, you buy used, you don't like it, you can sell it without much loss, you buy new, you'll loss 1/2 selling it.
Recap might be a little over rated. I don't recall I heard any difference after I recap the Nakamichi Stasis even though from the waveform that two of the caps are going. I never recap the Acurus after 19 years and of that 17 years of 4+hour a day, 7 days a week used ( I watch tv with it). I looked at the waveform, they still looked good to me.
Unless the cap show physical sign of problem....like leaking or swelling, I would listen to it first. Filter cap is not going to make or break the sound. I can tell you with the old caps in the Acurus, it gave the Nakamichi a good run for the money when I did the comparison test. Of cause the Nakamichi is better, The Acurus is a relative cheap amp, the Nakamichi is Stasis by Nelson Pass!!!
People here tends to do things unnecessary like pulling transistors and resistors out to measure and then put it back, I absolutely disagree with this practice. Far as I concern, if it is not broken, don't fix it. AND I am telling you as EE with 30 years in the field. You might fix it broken!!! Then you'll be in deep $hit. It's just an amp, don't put your emotion into it. I guess I've been in this field for too long, I don't get attach to this. Just an amp and I won't blink an eye dumping it if I find something better. The Nakamichi is now sitting in the garage with all the junk since I finished my amp. I won't blink an eye if I designed and build a better amp to put the current one in the shed outside the yard!!!
But, this is my opinion. You save half the cost buying used. $2K buy you a very good used amp. $2k don't get you far with new amps. Hell, my cheap Acurus was close to $1000. Hell, you buy used, you don't like it, you can sell it without much loss, you buy new, you'll loss 1/2 selling it.
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Frank Wong
Member
OK let me look through it! I like coda as not too bulky!
That, I hope you can change your mind. There is a lot of truth that the amp worth it's weight in gold. Heavy and bulky amp does not guaranty a good amp, BUT a light and small amp almost guaranty you it's not. But I know what you mean. I am setting up my second system in the family room, cabinet is small, I can't fit the Nakamichi, particular not a pray to fit my amp as it's even bigger. I have to resort to use the Acurus. It really doesn't matter much as I only have a pair of Monitor Audio speakers, best amp in the world would not make it an audiophile system.
Ha ha, I was disappointed when my amp weight in at only 52lbs. Sooooo,........this time on my second amp, I bought a bigger transformer, more filter caps to stuff it up!!!!!
Now you make me want to buy a nicer amp. I bought the Nakamichi to serve as a reference amp against my designs, it got shot down on my first try. I can use a better amp as reference.
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Frank Wong
Member
Re-read some white papers! Going back with Adcom or Bryston!
Frank Wong
Member
I need high power so I never clip at my low listening levels, low output impedance low thd and no interfering protection circuitry!
nyhifihead
Well-Known Member
for 2k used have you considered threshold? Some of the smaller S series shouldn't be hard to find under 2k. SA series/pass aleph will be a little bit more if you have room
Most threshold are class AB, you will find it difficult to find a formidable class A for under $2k, only first watt comes to mind if you don't have demanding speakers..
Most threshold are class AB, you will find it difficult to find a formidable class A for under $2k, only first watt comes to mind if you don't have demanding speakers..
I think 100W is plenty. All the ones you mentioned are over that.
I think Frank want better than the Threshold. My Nakamichi PA-7 is almost the same as Threshold S300 designed by Nelson Pass, I don't think it's particularly good, That's why it's in the garage now. Even the Threshold S300 and my PA-7 are about $1100 on ebay only. The smaller ones like S150 is in $700 to $800 range.
I am thinking about buying the pcb kit of Aleph, build it and see how it sound. I have the platform and heatsink to put it in. I'll cost me only about $200 to $300 to build one and try. I always curious about his famous Aleph.
nyhifihead
Well-Known Member
I would look into the SA/1 monos from threshold, they are rare but they are out there reasonably priced. Best from threshold
FootFungus
Super Member
The Nakamichi PA-7 isn't on par with the actual Threshold S/300. The Nakamichi is under-biased. The design goal for the Stasis was to eliminate the global NFB loop. The extra bias helps compensate for the lack of NFB loop.
I adjust the bias myself. Nelson Pass talked about adjusting bias for the Nakamichi.....adjust so you can still hold on to the heatsink with your hands!!!
I have both schematic and compare. They are both Stasis design, in fact you really have to look to tell the difference. The S300 has cascode VAS, BUT Nakamichi has newer 30MHz transistors rather than the old 4MHz power transistors in the S300. Only thing S300 is better is it has 8 pair of output transistors, Nakamichi has 7 pairs. As an EE, I take the Nakamichi PA-7 any time of the day because of the 30MHz big power transistors.
It is so important to have fast transistors, my amp uses 150V transistors that limit the rail voltage to about 55V just to get higher speed transistors. It is that important.
This is PA-7
This is Sxxx that includes S150, S200, S300 and higher depends on how many pairs of output transistors.On top, Nakamichi use separate filter section for each channel, that is a plus also to eliminate crosstalk between channels.
At the time, I would be ok to buy either one, just happened no S300 available and there's a PA-7 that was not fully functioning for cheaper price, so I got it. If you look on ebay, the PA-7 price is not much lower than S300, only difference is the name, Threshold has a big name.
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FootFungus
Super Member
The construction of the Threshold is significantly better. That's likely the reason the Nakamichi is biased lower.
You are paying for more than a brand name in the case of a Threshold and Nakamichi wasn't exactly bargain basement stuff. The fact that they sell for similar amounts despite the flimsier BOM on the Nak is testament to that.
The S/300 has 6 pairs of outputs. The PA-7 has an extra pair, likely to compensate for the lower dissipation capability of the plastic outputs.
The Sanken outputs on the Nakamichi are actually faster than 30Mhz (35 for the pnp, 60 for the npn). They are better parts, but the beta linearity and lack of droop is probably more important than the Ft in this situation.
BTW, I own several variants of the S and SA series. I've had the Nak too. They aren't my favorite amps, but don't discount the value of the extra bias. It makes a huge difference when it comes to depth and tonal quality.
You are paying for more than a brand name in the case of a Threshold and Nakamichi wasn't exactly bargain basement stuff. The fact that they sell for similar amounts despite the flimsier BOM on the Nak is testament to that.
The S/300 has 6 pairs of outputs. The PA-7 has an extra pair, likely to compensate for the lower dissipation capability of the plastic outputs.
The Sanken outputs on the Nakamichi are actually faster than 30Mhz (35 for the pnp, 60 for the npn). They are better parts, but the beta linearity and lack of droop is probably more important than the Ft in this situation.
BTW, I own several variants of the S and SA series. I've had the Nak too. They aren't my favorite amps, but don't discount the value of the extra bias. It makes a huge difference when it comes to depth and tonal quality.
Oh no, we all know that the bias is too low. Pass talked about it. That's why there was a discussion and he suggested to adjust differently. The heatsink of PA-7 is huge also, it can take the heat. I adjust to a little over 50mA each pair to get a little over 350mA of bias current. For a normal amp, it is quite high. The amp is not even that hot, I can adjust even higher if I want to.
Beta droop is not that important if you have 7 stages output. That's why people put so many output stages for. Just calculate for driving 4ohm to 70V, peak current is 70/4=17.5A. So peak current of each transistor is 17.5/7= 2.5A. That's very low for big transistor. You never get into beta droop, not even close.
PA-7 was designed after the S300, faster transistors came out in the late 80s and Pass used the newer faster transistors. That's a big big plus.
I use 9 stage for my amp and use lower voltage to avoid beta droop, I can afford to use TTC5200 and TTA1943 that has the lowest Cob to put less load on the drivers. They are not the highest power transistors, but difference is made up with more pairs.
All that said, I don't think the Stasis are the best design. I think my amp sounds better, with more separation and clarity. My amp is a lot quieter. The PA-7 is in the garage shelf now. That's the reason I never suggest Frank to buy the PA-7 nor the Threshold. I believe the SA series is just class A version of the Sxxx series by halving the rail voltage and double the bias current.
At this stage, I believe in low THD and GNFB. I designed my amp to be ultra low THD with tons of GNFB, it has more clarity, separation than the PA-7 that has no GNFB. I explained in post #62 in detail why I think low THD is the key, that people that claim low THD is not important need to look at their speaker cable because the cable creates so much distortion that it drown out all the good a low THD amp can offer.
I want to try the Aleph, it is highly regarded but very high THD. Pass does not seem to worry about THD. I want to give it the benefit of the doubt and try one more time.
Beta droop is not that important if you have 7 stages output. That's why people put so many output stages for. Just calculate for driving 4ohm to 70V, peak current is 70/4=17.5A. So peak current of each transistor is 17.5/7= 2.5A. That's very low for big transistor. You never get into beta droop, not even close.
PA-7 was designed after the S300, faster transistors came out in the late 80s and Pass used the newer faster transistors. That's a big big plus.
I use 9 stage for my amp and use lower voltage to avoid beta droop, I can afford to use TTC5200 and TTA1943 that has the lowest Cob to put less load on the drivers. They are not the highest power transistors, but difference is made up with more pairs.
All that said, I don't think the Stasis are the best design. I think my amp sounds better, with more separation and clarity. My amp is a lot quieter. The PA-7 is in the garage shelf now. That's the reason I never suggest Frank to buy the PA-7 nor the Threshold. I believe the SA series is just class A version of the Sxxx series by halving the rail voltage and double the bias current.
At this stage, I believe in low THD and GNFB. I designed my amp to be ultra low THD with tons of GNFB, it has more clarity, separation than the PA-7 that has no GNFB. I explained in post #62 in detail why I think low THD is the key, that people that claim low THD is not important need to look at their speaker cable because the cable creates so much distortion that it drown out all the good a low THD amp can offer.
I want to try the Aleph, it is highly regarded but very high THD. Pass does not seem to worry about THD. I want to give it the benefit of the doubt and try one more time.
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FootFungus
Super Member
If your beta starts drooping at 1 amp, like a the Motorola parts used the S/300, it makes a difference. The S/300 opto versions ran with about 1 amp per side of bias.
The S/300 Opto and S/350E came out around the same time as the Nak. Pass still used 4 mhz transistors. Only in the Forte line did you see anything faster. Then he moved to Mosfets.
I agree that the Stasis isn't the best design out there anymore. But on a hard load they will likely outperform a lot of stuff out ther. Low THD or otherwise.
Low THD is a pretty low bar since then end of the 70's. Being able to render spatial depth in a sound stage? Being able to convincingly reproduce brass, strings, percussion and piano? That's actually still pretty hard for most electronics. THD measurements alone aren't going to convey those abilities. That is not meant to be a disparagement on your design or engineering achievements. What you've done with your amp design in in my opinion is quite phenomenal in my opinion. However, I think you've still got a long ways to go on the listening side. The more experienced your ears are, the more you will be able to notice and appreciate the other stuff.
The S/300 Opto and S/350E came out around the same time as the Nak. Pass still used 4 mhz transistors. Only in the Forte line did you see anything faster. Then he moved to Mosfets.
I agree that the Stasis isn't the best design out there anymore. But on a hard load they will likely outperform a lot of stuff out ther. Low THD or otherwise.
Low THD is a pretty low bar since then end of the 70's. Being able to render spatial depth in a sound stage? Being able to convincingly reproduce brass, strings, percussion and piano? That's actually still pretty hard for most electronics. THD measurements alone aren't going to convey those abilities. That is not meant to be a disparagement on your design or engineering achievements. What you've done with your amp design in in my opinion is quite phenomenal in my opinion. However, I think you've still got a long ways to go on the listening side. The more experienced your ears are, the more you will be able to notice and appreciate the other stuff.
The 2SC3263 and 2SA1294 used in PA-7 definitely can provide 2.5A without droop. If you talk about transistors used in S/300 start to droop at 1A, the S300 really has problem not the Nakamichi. I did not look up those transistors. I thought S300 has 8 pairs, you said it only has 6? That would be not as good as the Nakamichi.
One thing I notice, the wires used in the PA-7 are smaller wires, they use 14 or 16 gauges for most of the wiring. I use bigger wires through out my amp as those are very important. I double up wires inside the Nakamichi particular the speaker output and return. So the Nakamichi is as good as it gets short of going into the circuit.
I don't think getting below 0.004% into 4ohm load at 20KHz at 110W power is that common and easy. That's almost like 0.002% using 8ohm load. I admit I have no experience in different designs, all I can do is compare with the PA-7 and my amp has more separation and clarity. It is hard for me to justify spending thousands to buy another reference amp for comparison. Maybe it's a mistake to buy the Nakamichi or the Threshold. Maybe I should aim higher. I really thought the Stasis were already quite higher up at the time. I should have got a better one. BUT Nelson Pass is so famous, how can I go wrong. Now that I sunk about $800 on the Nakamichi ( including new filter caps and others), it's hard to justify spending thousands more on another better amp. That's why I am thinking about spending about $300 buying the Aleph kit and build on my proto board. I still have the proto board up and running with my first run design, so it's easy to switch the Aleph into it.
As I kept stressing, before I make better cables, I did A/B comparison using switching fixture to A/B switch between the Nakamichi and the prototype of my amp. I could not hear any difference after a day of back and fore. I was still using multiple monster 12 gauge cables at the time. BUT after I went through the experiments and build better cables, I definitely can hear the difference....granted I was using the complete version of my amp that has lower THD. My conclusion is before you say low THD is not important, look at the cable first.
All talk is cheap, I am building another amp so I can run monoblock. I want monoblock so I can shorten the speaker cable to 4ft each side. If I can hear improvement, then I can conclude my finding...that speaker cable is about the most important thing next to speaker and amp. That low THD is very important, that an inferior cable negates all the good a low THD amp does.
I can tell you for sure, when I custom built the speaker cables and replace all the monster 12 gauge cables, even with the Nakamichi, the improvement is staggering. To me, cable is everything. Mores separation, clearer, better attack, better sound stage. The improvement is at least if not more than switching from the Nakamichi to my amp.
One thing I notice, the wires used in the PA-7 are smaller wires, they use 14 or 16 gauges for most of the wiring. I use bigger wires through out my amp as those are very important. I double up wires inside the Nakamichi particular the speaker output and return. So the Nakamichi is as good as it gets short of going into the circuit.
I don't think getting below 0.004% into 4ohm load at 20KHz at 110W power is that common and easy. That's almost like 0.002% using 8ohm load. I admit I have no experience in different designs, all I can do is compare with the PA-7 and my amp has more separation and clarity. It is hard for me to justify spending thousands to buy another reference amp for comparison. Maybe it's a mistake to buy the Nakamichi or the Threshold. Maybe I should aim higher. I really thought the Stasis were already quite higher up at the time. I should have got a better one. BUT Nelson Pass is so famous, how can I go wrong. Now that I sunk about $800 on the Nakamichi ( including new filter caps and others), it's hard to justify spending thousands more on another better amp. That's why I am thinking about spending about $300 buying the Aleph kit and build on my proto board. I still have the proto board up and running with my first run design, so it's easy to switch the Aleph into it.
As I kept stressing, before I make better cables, I did A/B comparison using switching fixture to A/B switch between the Nakamichi and the prototype of my amp. I could not hear any difference after a day of back and fore. I was still using multiple monster 12 gauge cables at the time. BUT after I went through the experiments and build better cables, I definitely can hear the difference....granted I was using the complete version of my amp that has lower THD. My conclusion is before you say low THD is not important, look at the cable first.
All talk is cheap, I am building another amp so I can run monoblock. I want monoblock so I can shorten the speaker cable to 4ft each side. If I can hear improvement, then I can conclude my finding...that speaker cable is about the most important thing next to speaker and amp. That low THD is very important, that an inferior cable negates all the good a low THD amp does.
I can tell you for sure, when I custom built the speaker cables and replace all the monster 12 gauge cables, even with the Nakamichi, the improvement is staggering. To me, cable is everything. Mores separation, clearer, better attack, better sound stage. The improvement is at least if not more than switching from the Nakamichi to my amp.
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