[James Romeyn]

I am posting this amplifier comparison here because, well, who cares what they sound like on speakers other than VMPS Neo ribbons?  Spectron is $3500ea list, Ampzillas $5000pr.  I had not listened to music in a serious way for about two weeks.  I hooked up the Spectron, which was a previously burned in amp.  After several hours I was very pleasantly surprised how good the Spectron Musican II sounded.  It seemed to be close to the 2000s.  Upon plugging in the 2000s, it was clear the 2000s were one or two big steps above the II.  In every  parameter I could discern the 2000s were better.  The funny thing is that even the power seemed greater on the 2000s, though the II is rated higher.   For anyone considering a great midpriced SS amp, you might want to wait for the arrival of the stereo Ampzilla, estimated price $3000.  Even though it will be rated well below the II in power, it would appear to be something worh considering once it arrives, especially in the case of moderate-sized speakers, moderate to small rooms, or both.  After 1-1/2 years of listening, I still have not latched onto any repetivtive sonic signature atributable to the 2000s, a remarkable feet.  There would likley be pleasant sonic results if biamping with a nice tube deHavilland 845 monblock on the ribbons with SS 2000s on the bass.  But the cost, complexity, & heat generated are not enough to yet entice me to try it.

[rkapadia@ROOP]

Hey Jim,

Thanks for your notes on the comparison.  Though I have not yet auditioned the Ampzillas, the Spectron Musician II performed well when briefly auditioned with the RM40.2.  I thought it an excellent match, and this makes me all the more eager to listen with the Ampzillas.  I thought the Spectron handled the RM40.2's bass quality beautifully, and really couldn't find any fault overall.

I'll be pairing the RM/X biamped with deHavilland 845G monoblocks and the Spectron II for the bass - I'm finalizing wire selections soon, but it looks as though the combination will be ideal.

Kind Regards,

Rup

[James Romeyn]

I can think of only two alternatives offering truly serious competition for the 2000s:

1. Upper end Halcro amps (Bongiorno gets a kick out of the fact that Halcro is using circuits he invented years ago)

&
 
2. A biamp rig as follows: 845 tube SET monos (25W or more, Rup's deHavillands would by my first choice) on RM40 HET or RMX ribbons, w/ the Ampzilla 2000s on the bass.

The Parasound JC1 sounded great at CES, but I prefer the 2000s smaller size, Star Trek cosmetics, lower price, & much much cooler temperatures.  The McCormack DNA500 is appealing but it too costs more, plus I am kinda hooked on monos now.  Beyond that, there are many other amps out there, but none that I know of with Bongiorno's pedigree, mono architecture, & price.   Just for the record Rup, till the A2Ks replaced the Spectron, I thought the Spectron was very very satisfying, musical, & easy on the ears.  But you would be shocked, I believe, how much better the A2K is even just in the bass range on the RM40s.  It was not subtle in any way.

I have been around tube nuts for a long time. For many years my reference was a very fine 25w push-pull tube amp on the high-end (a hand-me-down from Big B), with SS bass monos.  A degreed/professional electronics engineer I know owns the JBL K2 beryllium-diaphragmed horns (sold only overseas) and builds exotic tube amps as often as you & I get haircuts. One mono pair weighs several hundred lbs. & has way lethal voltages inside (BTW he heard & recommends the deHavilland 845s).  I have had enlightening conversations with Jack Elliano of Electra-Print Audio, maker of some of the finest custom tube amp transformers, circuits, amps, & preamps.

Though this may come as no surprise to you, it was a surprise to me to find out recently that if bass frequencies are fed to the input of a tube amp, there must be woofers hooked up at the amp's ouputs.  

What the heck is he talking about?  Put simply, you may NOT feed a fullrange music signal to your tube amp input, then have no woofers at the output.  I am describing what I thought was a common & acceptable practice for tube biampers: feed a fullrange signal to the tube amp input, then the tube amp drives only upper range drivers.  The tube amp drives a passive high-pass crossover, which filters the bass frequencies, then that filtered signal feeds only the upper range drivers.  In the case of VMPS, that would be the ribbon mids & tweeters from 166Hz up.  The above described scenario is a no-no.  

Here is what results: the tube is fed the bass signals & attempts to multiply the voltage, but there is no correponding woofer load for the tube to drive.  If the input signal is increased to a certain point, the tube could actually arc across its filaments & could eventually burn up.

This explains the several problems I had over the years blowing up a power resistor near a tube, & the blue glowing which would occur within my tubes during certain enthusiastic listening sessions.  When Mr. Elliano explained this to your humble correspondent, I was reminded of an ancient proverb heard years ago: never short a SS amp, always load a tube amp.  

I often wonderd about this proverb, & now after all these years, the wisdom appears.  I never remembered reading in any of Bascom King's reviews any warnings about tube amp loads, but now it makes sense.  Yes, if you have the ribbons hooked up, you do have a load, but you don't have a load in the bass range.  If you feed the amp a bass signal, you gotta have a bass load.  Simple, yes?  

Anyway, I spent a long time listing all the many methods I could think of to fix the problem & if anyone wants it, send an email.  If enough of you want it, I'll post it here.  It's kinda long.  The most obvious fix is to use an active XO, but this has drawbacks realtive to fidelity, plus there are complications.  Peace to all.

[Horsehead]

Hi Jim,

I may be a little biased here  , but I think a Pass Labs X250/350/600s work extremely well with the RM40 and would give the Ampzillas some competiton except for price.  I would put Nelson Pass up there with James Bongiorno for "legend" status. This is a combo that just works very well together.  The design and construction of the X series is one of the best on the market.  Pass customer service is beyond reproach in the industry.  If you ever have a problem with one of their products, they don't even ask questions- it is just taken care of.  The RM40s driven by my Pass Dac/Placette Audio RVC/Pass X350 is one of the best sounds I have ever heard.  It still blows my mind how some publications still don't recognize VMPS as one of the best speakers available!  I mean you have the Perfect Vision recommending $96,000 worth of Krell speakers for their "ultimate" system.  
 
From what I have read on the Halcros they are not that powerful and you have be careful of lower impedance speakers with them.  I would love to hear the Ampzillas with the RM40, but unfortunately it's pretty hard just to find a pair to try out.  I'm hoping Rup will be carrying the Ampzillas so I can shoot over to his place for an audition with the RM/Xs-

[James Romeyn]

I'd love  to hear the Pass Labs amps.  From what Marty deWulf & other reputable VMPS owners including Horsehead say, they appear to be amongst the best SS available.  Maybe someone with A2Ks nearby Rup can bring them over for him to hear.  Again, I'd bet the coming stereo Ampzilla will be amongst the best amps available in its price range (estimated $3000ea).

[tkp]

Last year I was looking for mono block amp that can drive the RM40s in place of the Audire Otez.  The Otez is a wonderful amp but I coud not use it because I cannot place it in an enclosed cabinet (the wife wanted every thing to be in this cabinet) where as the small size of the ampzilla2000 allows me to put them behind the speaker and out of sight.

I absolutely dislike the look of the Ampzilla2000 but decided to get them for the sound.  I bought them un-heard but purely base on the design and Bongiorno reputation.  I am glad that the gamble paid off.  

The Ampzilla2000 is the best amp that I have heard to date for the money.  The Audire Otez sounded almost as good as the Ampzilla2000 and there were areas it was a bit better than the Ampzilla2000.  The catch is that it has to be modded (minor mod with zero cost in material).  I am willing to bet a modded Audire Parlando would equal the Ampzilla2000 (might be even beat it) for the cost of $ 3700.00 list price.  The only caveat here is that the Parlando is a 100 Watts class A so it will run fairly hot compare to the Ampzilla2000.

I looked at the Passlab X250 and X350 but decided to pass on them because

a)  The input impedance is quite low for passive preamp. (22K balance and 11K SE).  The Ampzilla2000 has an input impedance of 50K for SE and 70K for balance.

b)  The gain for the X250 is 30 db and the X350 is 26 db.  Once again this is not very passive preamp friendly.  The Ampzilla2000 has a gain of 32db.

Passlabs amp would work great with active preamp or a DAC with strong output and passive preamp.  Unfortunately, I don't have either setup.  I really like the look of Passlabs amp.

[meilankev]

tkp,

I was fortunate to have an Audire Parlando hooked into my system over three weekends.  According to the owner, it had been "tweaked by Julian".  It drove my RM40s much better than either of the other two Solid State amps I've had in my system (Classe' Audio 300W and McIntosh 225W).

Alas, those are the only Solid State amps I've had the opportunity to hear with RM40s.  Based upon owners' posts here, it seems there's a number of other amps that work very well.  Well, if they sound better than the Parlando, they sound very nice indeed.

Kevin

[audionoob]

Hey can someone tell me whether ampzilla2000 is a class A/B amp or a class A amp? And whether the amp is consider high current?

[Horsehead]

Not sure about all passive combos with the X series, but the Placette Audio passive devices work extremely well with them.  You are correct to mention the source must be up to the task.  I reach very satisfying levels at only half of the Remote Volume Control's 125 steps- which is ideal according to Guy at Placette Audio.  I am in total agreement with Guy that a volume control may be one of the most important "components" of a system.  One of the nice things about the RVC is with the remote, you can place the unit very close to your amplifier and then use short, low capacitance interconnects from the RVC to the amp.  It may not work in every situation, but at least with the Placette you have 30 days to check system compatibility.  According to the X series manual, I am running a combo that they say themselves will work quite well with their amps:

"The amplifier does not care what the source impedance is, although its gain will drop a bit with high source impedances. Since we have 30 dB of gain (26 dB in the X350), we can afford to throw a little bit away, since the quality is unaffected. Using a balanced source attenuated through a balanced passive attenuator is perfectly OK, and we often use this approach ourselves to minimize components in the signal path and also to reduce bit loss in CD players with digital volume controls.
The differential input impedance of the amplifier is 22000 ohms, although this drops to 2000 ohms when the amplifier is in stand-by mode. 22000 ohms is not a problem for any balanced source circuit we ever heard of, and will not be a problem for you."

www.placetteaudio.com

[tkp]

Hey can someone tell me whether ampzilla2000 is a class A/B amp or a class A amp? And whether the amp is consider high current?

The Ampzilla2000 is class AB and to my ears it is high current.  

The Audire Otez is a true dual mono 250 Watts amp with

-  1 KW transformer per side
-  16  Motorola MJ 15022/23 output transistor per side.  
-  108,000 uF of capacitance per side.  These caps are computer rated so they will last for ever.  As of this writing, I have a 22 years old Audire Forte still playing strong and kicking a$$.

The ampzilla2000 rated at 200 watts with
-  2.5 KW transformer.
-  12 Motorola output transistor.  These are the lastest version of the MJ15022/23 family so they are a bit better.
-  100,000 uF of capacitance per side.

Sound wise, the Ampzilla2000 beat the Otez in the bass area with a pair of RM40.  The Otez is no slouch in the bass but the Ampzilla2000 is really special in this area.  One of the trade mark of high current amplifier is its ability to control the woofer for low bass.

[JoshK]

Jim,

Not to defend the II in anyway b/c some like it, some don't but what kind of retuning did you do for the RM40's?   I ask because it took me a while to get the tuning just right with the Spectron.  The spectron seems to not overly damp the bass like many SS amps do, but still yielding much cleaner bass than tube amps I have tried making it somewhat deceptive to my ears when it came to tuning.   Also, due to the laid back soundstage of the Spectron its tuning was much different then the couple of SS amps I have on my RM40's.   Just wondered if you tuned each to their best perf or if you compared to how you had your RM40's already tuned.  

I am very interested in trying the A2000s in my system, although I think I will stick with my Spectron long term b/c of so many other reasons, incl'ing efficiency.

[James Romeyn]

This is a great question, sorry I did not address it earlier.  

If I gave the impression there was anyting wrong with the II I apologize.  Like I said, till I plugged in the A2K it appeared the II was in a similar league.  There was a very strong, detailed presentation to the II, yet it sounded smooth & musical.  I'd like to say I did optimized the 40s tuning for the II, but I did no tuning at all.  

The 40s were pretty well tuned to the A2K, I plugged in the II & let her warm up, then plugged back in the A2K.  It may have been more fair to adjust the 40s to match the II.  The reason I did no tuning is that there was really nothing wrong with the II, it was that there was just so much more realism with the A2K throughout, from top to bottom.  The A2K left less sonic footprint, removed a veil & got me closer to the music in every way.  Keep in mind that till I plugged back in the A2K, I felt the II was its equal, so my mental expectation was different than what was later perceived.  

Though tuning may have minimized this difference, it seemed to be an inherent difference between the two pieces.  I totally admit this is all just a hypohesis, but I stand by it unless someone showed me different.  

The bass difference was most interesting.  I certainly expected less differnce between good SS amps.  I played bass, worked at the Record Plant in Sausalito years ago, & play a nice Gibson acoustic which took about 6 months to find.  It was a surprise to hear so much more realism in the bass harmonic integrity, transient attack, depth & dynamic bloom with the A2K.  Please forgive me for the overstatment, but in comparison the II leaned toward a jukebox type effect.  I suppose this might be one range which could be improved wth tuning, plus possibly there was a room mode interaction.  

Member TKP is one incredibly picky audiophile.  If memory serves he uses a transformer based silver-wired passive preamp.  The fact that he bought & liked the A2Ks says volumes to me.  I am really glad he jumped in, took a chance, & tried them.

[James Romeyn]

tkp
Hey, how the heck did you find out which outputs JB used?  Did you crack it open, or did he tell you up front?  I've been around a lot of designers & they are more paranoid than OBL when it comes to trade secrets!  What the heck makes the A2K sound so good anyway?  If anyone can tell us I know you can!  What is so special or unique about JB's new proprietary bridging circuit (SE to balanced)?

[JoshK]

Fair enough.

[tkp]

tkp
Hey, how the heck did you find out which outputs JB used?  Did you crack it open, or did he tell you up front?  I've been around a lot of designers & they are more paranoid than OBL when it comes to trade secrets!  What the heck makes the A2K sound so good anyway?  If anyone can tell us I know you can!  What is so special or unique about JB's new proprietary bridging circuit (SE to balanced)?

Jim,

I have not openned the Ampzilla2000 to see what was inside.  JB actually told me to open it up to check out the quality of the parts inside but I have not have time yet.  JB posted the device that he uses on the Ampzilla2000 output stage at the SAE newsgroup.  Here is the exact post.

"Dear Ryan,
I have been using the 21193/94 devices for a couple of years now and have
never had one go bad. Evidently, Motorola got their act together. Also, I use
these same devices in my new Ampzilla2000 (over 3000 devices so far) and have
not had a single failure. FWIW.
James
"

The rest of the information I got from several phone call to JB prior to making my purchase.  

The output stage of the Ampzilla2K is a true push-pull and it is the same as the ouput stage of the Sumo amp.  Push-pull output stage has great control on the woofer but trying to match all 12 transistors is going to be hell.  

I was a bit nervous when I found out that the Ampzilla2K output is in push-pull mode because my pass experience with push-pull amp was not that great.  However, JB assured me that no one can do the push-pull output like he can.  I did not believe him 100% but took a chance and found out that JB was not pulling my chains.

In addition, the Ampzilla2K has DC servo.  Once again, I questioned JB on this one also because all amp with DC servo that I listenned to sound lifeless.  Powerful but lifeless.  The Ampzilla2K is the first amp that I could not detect any hint of servo DC or DC blocking cap.

JB was extremely tight lips about the input stage where he convert the SE signal to balance.  The Ampzilla2000 should sound better with balance input since the input conversion circuitry is bypassed.

[bboplive]

Is there a big difference between the two sonically when used with the RM-40.2's?  One poster remarked that the VMPS TRT cap really required the 2.5 kvolts in the X-350 and another remarked that the X-250 was more "musical" and less "analytical" than the X-350.  What gives?

On a side note, I don't know anyone but VMPS dealers who have used/purchased the Ampzilla 2K's and they just raised the price on these due to "lack of sales".  (Inverse logic at work here.)  I'm sure they are wonderful, however, as a consumer, this makes it hard(er) to justify a purchase, especially when put against the good name and warranty of a Pass.

[JoshK]

I certainly expected less differnce between good SS amps.

Are digital amps still considered SS?

[bkwiram]

bbop,

What's the new price for the A2Ks?

I'm surprised and impressed that JB is so contrary he would raise the price and leave the cosmetics unchanged. I bet I could design a faceplate in about 45 minutes that would "enhance" sales!

Maybe he doesn't actually want to sell amplifiers. I've heard of more surprising things.

-Brandt

[Horsehead]

bboplive- here is a discussion on Audio Asylum about the X250 and X350

http://www.audioasylum.com/forums/amp/messages/25151.html

[bboplive]

Thanks Horsehead.  Kind of confusing, but did shed some light on the question.  BTW, what the devil   are those cup-like things holding your cables?

http://www.audiocircle.com/circles/modules.php?set_albumName=Always-looking-to-improve&id=10_G&op=modload&name=gallery&file=index&include=view_photo.php