Solid State Confessions

[garylkoh]

I would have to disagree here, headroom is what a power amp is all about, thats why we call it a power amp.

I'll have to throw in my hat with Tom and Tim here - headroom is everything to music. However, to a sine wave, headroom does not matter as much. When you look at the spectra of music playing (even the highly-compressed, volume at 11 stuff) there is tremendous difference between the highest peak and lowest trough at ALL frequencies.

Headroom, however, is not solely the domain of the power amp. The power amp swings current to the loudspeaker. This is controlled or regulated by the preamp which swings voltage to the power amp.

If the improvement in the power supply of the Counterpoint now allows it to command the power amp better, that may be where the improvement in the Phase Linear may have come from. Some power amps can sound anemic and undynamic if the preamp used cannot make it sing because it has too low an input impedance or the preamp cannot deliver the current (which most preamps are not designed to do anyway).

 

[mep]

Yes, with the VU meters. The Auto Correlator was awful, but of course it could be switched in or out. That pre-amp only lasted a couple of months, I traded it in on a modified AR-3a which I kept for many years.

Never mind the Auto Correlator circuit, the basic preamp just never sounded very good. After being shamed by the NAD 3020A, my friend sold his C-4000.

 

[mep]

And I agree with everyone who thinks you can never have enough power. My speakers are very efficient at 92dB. I can barely turn my volume knob past 9:30. It would be rare to hear any sounds of clipping or amplifier distress at my house. As Tom likes to point out, most modern amps don’t have clipping indicators built into them or meters. Now the mighty little 400 Series Two does have the cute little LED meters. If nothing else, the little LED meters will give you an idea of how much dynamic range is on the recording you are listening too just like my meters do on my Otari MX-55 and my Ampex 350s. Another thing I believe the LED meters would tell you would be if you were driving the amps too hard and the meters were staying buried at the right. That never happens here. When I had the Pass Labs X-250, I used to bury that current meter all the time. All things being equal, you really do want lots of power.

Gary-I really needed my power supply refreshed in my 5.1. The power transformer was ready to give up the ghost and it was running super hot. Right before I sent it back the filament supply did go out. All of the power supply filter caps were over 20 years old. So now it has a Plitron power transformer and all new caps and other upgraded passive parts.

 

[FrantzM]

Hi

From memory the Phase Linear was a decent soudning amplifer for its time that was when SS regularly sounded worse than tubes.. and that was consistently no golden ears needed.. Things have changed and there are now better, much better SS amps..
What surprised me in this thread is that the 400 was almost on a par with the Defy 7 which to my recollection was a wonderful amplifer (I owned one and for some reasons was one of the best amps for the ESL 63 with the Crosby mod) ... In my estimation they would not be in the same league but here they are close and here mep finds digital through foobar (which is what I also use) very interesting ...

Now it would be interesting to look into the speakers more profoundly. efficiency is just one of the parameters one should look at when matching speaker and amp .. You can have 105 dB 1/w/1m efficient , yet impossible-to-drive loudspeaker... (Not that I know any )... So I would look at the impedance curve ... by the way I wasn't able to find and impedance curve on their (Definitive Technology) web site .. They simply state " Compatible with 8 Ohms outputs" whatever that really means...
My recommendation in all this would be to try another SS , a modern one and report to us .. Oh and while you're at it , a serious SS preamp may be a consideration ... I would think that you should be prepared to be shocked as well .. SS has gotten that much better and also, yes!, digital properly done can be shockingly good, in fact as realistic and good (and to me better) than what the best of analogue has been able to provide ..

Welcome to the future mep .. it's not as sterile as you may have been thinking ..

 

[mep]

Frantz-Good to hear from you as always. The latest generation SS amp that I owned farily recently was the Pass Labs X-250 which I have already said I disliked immensely. Trust me, I'm as shocked as anyone that I like the way this old SS amp sounds. I wish I had that Symphonic Line amp back now so I could hear it again. I had different speakers when I had the Symphonic Line amp in house. It's hard to believe that I have a perfectly working Jadis sitting in my room and it's not currently connected to my system. Maybe I feel during the night last week and whacked my head and I don't know it.

 

[rbbert]

Hi

From memory the Phase Linear was a decent soudning amplifer for its time that was when SS regularly sounded worse than tubes.. and that was consistently no golden ears needed.. ..

Back in the mid-70's Bascom King and Geoff Cook modified Phase Linear 700's were often thought to be sonically very close to the Macintosh 275 tube amps (but with gobs more power, of course).

I wouldn't be surprised if a member here is currently in touch with Bascom King. It would be interesting to hear more about that.

 

[microstrip]

(...) The latest generation SS amp that I owned farily recently was the Pass Labs X-250 which I have already said I disliked immensely. (...) It's hard to believe that I have a perfectly working Jadis sitting in my room and it's not currently connected to my system.

What is the input impedance of the X-250 in unbalanced mode? May be your Counterpoint preamplifier was not happy driving it - some tube preamplifiers are not happy with loads under 50 kohm.

BTW, are you sure that the Jadis is in perfect condition? Unhappily sometimes storm discharges damage components irreversibly, but not to the point a making them non-functional.

 

[mep]

What is the input impedance of the X-250 in unbalanced mode? May be your Counterpoint preamplifier was not happy driving it - some tube preamplifiers are not happy with loads under 50 kohm.

BTW, are you sure that the Jadis is in perfect condition? Unhappily sometimes storm discharges damage components irreversibly, but not to the point a making them non-functional.

Interesting question regarding the input impedance of the X-250. I can't find it listed. It only specifies the balanced input impedance which is 22k. As to whether I'm sure the Jadis is working perfectly, I don't have any test points to look at beyond the bias and I know the bias circuit is working just fine.

 

[DaveyF]

Frantz-Good to hear from you as always. The latest generation SS amp that I owned farily recently was the Pass Labs X-250 which I have already said I disliked immensely. Trust me, I'm as shocked as anyone that I like the way this old SS amp sounds. I wish I had that Symphonic Line amp back now so I could hear it again. I had different speakers when I had the Symphonic Line amp in house. It's hard to believe that I have a perfectly working Jadis sitting in my room and it's not currently connected to my system. Maybe I feel during the night last week and whacked my head and I don't know it.

Mep, looking at your speakers, don't they use a 1800 watt class D sub woofer amp built into the cabinet? Therefore, you are using your primary amp to drive the mids and tweet. Which brings me to my thought: perhaps you are preferring the synergy between the ss Phase Linear and the sub amp vs. the Jadis and the sub amp. IMO, the Phase Linear has more characteristics of the class D amp than the Jadis, Which most likely results in a better synergy between the two. Your speakers also use an aluminum dome;whenever i have listened to this type of driver it exhibits a propensity to 'ring'...which I never really noticed until I did away with my old titanium dome drivers(similar problem) ( in my old speakers) and now use silk domes. IMHO, the metal domes tend to sound 'brighter' with most ss amps and this effect can lead one to be fooled into thinking that there is more information being passed through.
I use an ARC D70 Mk2 tube amp as well as a Jeff Rowland Model 8 with choke as my ss amp. The two amps have their plusses and their minuses. Some days I prefer the tube amp, some days the ss amp. One thing for sure, I would not want to have to choose between the two. Interestingly, I think my speakers prefer the tube amp...at least on most days

 

[mep]

Davey-You are correct that my speakers have 1800 watt amps driving the subs. I have mentioned that several times. These tweeters sound very good and that's because I don't hear the tweeters being tweeters or any ringing. The designer of these speakers has done a masterful job in making these speakers speak with one voice. I have always loved the way they sounded with the Jadis. If I hadn't blown an output tube, this thread wouldn't exist. The Jadis would still be in my system and I would be perfectly content.

I too once owned the D-70 MK2 amp as we have discussed before. It is a nice sounding amp with a criminal bias scheme. The D-70 MK2 amp is dangerous to bias while the VT-100 MKII that I also owned was just insane to bias. ARC also turned the D-76 amp from a finger burner to a total pain in the ass to bias with the D-76A. They flipped the meter jacks upside down on the D-76A which requires you to remove the bottom from the amp (and there are stand-offs in there that fall out). Sheer non-sense on ARC's part and you won't convince me that this wasn't done deliberately in order to force customers to go see their dealers or send it back to ARC where of course they will always find something that needs attending to. The Jadis is just merely a pain in the ass to bias, but it sounds better to me than all of the ARC amps I just mentioned and have owned.

 

[Phelonious Ponk]

C) They have different distortion spectra

This is a metric that is starting to show up in manufacturers specs and accounts for audible differences outside of plain jane FR and output ratings

Oh they do have different distortion spectra, but if both are operating under enough headroom, distortion, regardless of spectra, shouldn't be a significant factor. Even I, SS guy that I am, like tube distortion better than solid state distortion. But what I really like is inaudible distortion.

Tim

 

[RogerD]

I find the same problem and there are similar issues I deal with. I have a pair of Vac 140's that I found has a uncanny ability to bring lot's of emotion to the music. The only problem is they use 8 pairs of 300B tubes. The quality of 300Bs available at this time leaves a lot to be desired. I have had problems,so I deided to switch to my SS monoblocks.

The difference between the 2 is somewhat of a trade off. The SS has gobs of transparency but the Vac's are I think better. The SS amps produce a dynamic that is easy to get hooked on,very fast and to me much more realistic. I have decided until I can get better tubes for my Vac's I will stay with my Agtron monoblocks;1250 watts is hard to beat.

I have another solution that I have tried. I use a Accuphase SS C200 preamp. This preamp allows me to use my Ampex 350's to listen to my digital software. The sound through the 350's gives me everything the Vac's do and I have the benifit of using SS amps.

I have yet to use the Ampex with the Vac's,something to look foward too.

As for the power outages, I hate those,but using the SS amps,it doesn't seem as troublesome as the big tube amps, though I have never had a outage while using my Vac's and I don't want to either.

 

[Phelonious Ponk]

Davey-You are correct that my speakers have 1800 watt amps driving the subs. I have mentioned that several times. These tweeters sound very good and that's because I don't hear the tweeters being tweeters or any ringing. The designer of these speakers has done a masterful job in making these speakers speak with one voice. I have always loved the way they sounded with the Jadis. If I hadn't blown an output tube, this thread wouldn't exist. The Jadis would still be in my system and I would be perfectly content.

I too once owned the D-70 MK2 amp as we have discussed before. It is a nice sounding amp with a criminal bias scheme. The D-70 MK2 amp is dangerous to bias while the VT-100 MKII that I also owned was just insane to bias. ARC also turned the D-76 amp from a finger burner to a total pain in the ass to bias with the D-76A. They flipped the meter jacks upside down on the D-76A which requires you to remove the bottom from the amp (and there are stand-offs in there that fall out). Sheer non-sense on ARC's part and you won't convince me that this wasn't done deliberately in order to force customers to go see their dealers or send it back to ARC where of course they will always find something that needs attending to. The Jadis is just merely a pain in the ass to bias, but it sounds better to me than all of the ARC amps I just mentioned and have owned.

Mark, you have a pair of big Def Techs, right? That's an aluminum tweeter with a silk surround, a hybrid of sorts. I've heard a whole lot of Def Techs from the tiny to the mammoth. That tweeter, while pretty smooth for aluminum, is a bit bright. It may like your tube amps better, but your midrange drivers, and most of the "music range," may really be benefitting from the speed and damping of the big SS amp. Just a guess. Do you have EQ of any kind in the system? If you do, while you're still using the SS amp, fool around with a slight dip, 3 - 6 db, at around 2k - 5K. You may get ultra sweet, sell your tube amps and take a cruise.

Or not.

Tim

 

[microstrip]

Mep,
Just found that the Pass Labs X250 unbalanced input impedance is 11 kohm and a few people complain about it as it ruled out tube preamplifiers. It explains your findings.

Concerning your Jadis I would try another set of input and driver tubes. Input/driver section is separated from the output stage by coupling capacitors and any problem in the input stage would not show at the biasing section. I also find strange that your amplifier does not bias properly with the input disconnected - I never had such a problem . It could be caused by a leaky or noisy input tube, as input impedance is 100 kohm.

 

[fas42]

The only thing I can think of is my Counterpoint SA-5.1 has only been back at my house for two weeks since it came back from having the power supply rebuilt and the volume pot was replaced with a DACT attenuator

Again, it's a silly me ... . I first proposed digital interference but this, I feel, is the key to the "dilemma". You mentioned it earlier, but when I read it it didn't register properly. In a later post you mention this preamp in fact has had a major refurbish, but probably the key change has been to get rid of a lousy volume attenuator. If there's one thing that will kill digital sound it's poor connections, which the old potentiometer effectively was. I mentioned the problem with volume controls a little while ago; once your ear tunes into the effect this has on the sound it becomes easy to detect on any half reasonable system. You will get away with dodgy components with LP and tape source because the sound is intrinsically "smoother", for want of a better term, but digital takes no prisoners: everything has to be functioning at its best for the sound not to irritate the bejeezus out of you ...

Frank

 

[fas42]

headroom is everything to music.

Yes and no. It's easy to engineer headroom, the key is whether it's "clean" headroom, this directly relates to the distortion spectra mentioned in other posts. My own experience has been that a lot of, far too many, power amps are badly engineered in their ability to produce their maximum voltage swings without stress. In my early fiddling with gear days I would take a "difficult" CD to dealers and was quite amazed at hearing highly regarded and impressively built units starting to collapse well, well before reaching clipping levels. IMO, a combination of inadequate power supplies and poor circuit layout.

Frank

 

[Phelonious Ponk]

Yes and no. It's easy to engineer headroom, the key is whether it's "clean" headroom, this directly relates to the distortion spectra mentioned in other posts. My own experience has been that a lot of, far too many, power amps are badly engineered in their ability to produce their maximum voltage swings without stress. In my early fiddling with gear days I would take a "difficult" CD to dealers and was quite amazed at hearing highly regarded and impressively built units starting to collapse well, well before reaching clipping levels. IMO, a combination of inadequate power supplies and poor circuit layout.

Frank

This is semantics, Frank. I would say that if the amp is "stressed" it has exceeded its useful voltage swing, and its headroom. Therefore we agree on everything except, perhaps, the definition of headroom.

Tim

 

[JackD201]

Oh they do have different distortion spectra, but if both are operating under enough headroom, distortion, regardless of spectra, shouldn't be a significant factor. Even I, SS guy that I am, like tube distortion better than solid state distortion. But what I really like is inaudible distortion.

Tim

We do know however that distortion is present and we don't need to approach clipping to for it to be there either. The spectra is commonly associated with "texture" audio following what guitar players have known instinctively all along. What's curious to me is why there's so much focus on the output devices and not the whole circuit. Now more than ever, one can fins SS amps that sound tubey in the traditional sense and tube amps that sound very solid state again in the traditional sense even if tube types or transistor types are the same.

The convergence is also happening with source equipment as Mark also pointed out as an aside. This points to what Sean Olive and Paul Barton have found, that people regardless of experience level or training know good sound when they hear it. If this is so, then this also suggests that despite the advances, sound reproduction is really still in its infancy because there are still so many correlations to be made in order to fully map out or model human perception of sound.

If Mark is a bit shaken, then that's still a good thing. Paradigm busters are always a good thing IMO. Whatever he prefers at the end of it doesn't matter. What matters is whether he'll end up listening to music more and the sound of his equipment less

Personally, I never assess an amplifier based on its performance with just one loudspeaker, even if it is a high powered amplifier that should be able to drive anything. A case in point is my Lamm M2.2 amplifiers. I've tried them with the infamously power hungry Infinity IRS IIIs, Harbeth Super HL5s, Maggie 1.6QRs, VR-4jrs, 3 generations of SRs, VR-5s, 9s and 11s, even the 99dB sensitive semi active DB-99 SE all to very good effect. In a bookshelf shoot out done in a recent Philippine Hi-Fi Show, various other dealers asked that our room be used being "neutral" territory. The contenders were the B&W 805, Monitor Audio Platinum, Usher Tiny Dancer, and Focal (forget which model). They are now partnered with Magico Q5s at a friendly dealer's showroom. That's a lot of speakers.

I did hook them up to LSA2 Standard towers (which I carry) which were designed to work with the beastly LSA Amplifiers just 70 wpc down in output and the M2.2s made the LSA2s sound like the woofers would jump out of their spiders and the baffle would burst. Even at moderate levels the sound was boomy and chesty. Now is that an inditement on the amp or on the speaker which performs very well for the money from Marantz receivers to more exotic SS and Tube amps? I really don't know.

All I am sure of is that if you own LSA towers be they Standard or Statement, the Lamm M2.2 sucks and you should save 15 grand and get the LSA Standard amp or 11 grand and get the LSA Statement amp. Heck save 20 grand and get a Marantz receiver.

Synergy is NOT a dirty word.

 

[microstrip]

This is semantics, Frank. I would say that if the amp is "stressed" it has exceeded its useful voltage swing, and its headroom. Therefore we agree on everything except, perhaps, the definition of headroom.

Tim

It can be more than semantics - if the amplifier is current limited it will show in performance. With speakers having low impedance, many times you get limited before the theoretical voltage clipping. Surely you can consider this under the definition of "useful voltage swing" but is almost impossible to measure when playing music.

 

[mep]

Mep,
Just found that the Pass Labs X250 unbalanced input impedance is 11 kohm and a few people complain about it as it ruled out tube preamplifiers. It explains your findings.

Concerning your Jadis I would try another set of input and driver tubes. Input/driver section is separated from the output stage by coupling capacitors and any problem in the input stage would not show at the biasing section. I also find strange that your amplifier does not bias properly with the input disconnected - I never had such a problem . It could be caused by a leaky or noisy input tube, as input impedance is 100 kohm.

Microstrip-Very interesting. I called Pass Labs and asked them if it was going to be a problem driving their amp with my 5.1 and they said no. It obviously was a poor match which would explain lots of things. By the way, when I replaced the bank of 3 output tubes, I went ahead and replaced all six of the input/driver tubes as well.