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post #31 of 500

I love reading this thread, please keep up the good work!

post #32 of 500
Thread Starter 


Eighth A / B comparison:  Beta 22 & Bijou


Same everything as above. THIS IS NOT A SCIENTIFIC (I.e., blind / statistically analyzed )  TEST.


Note: The Bijou is a DIY tube amp  designed by Alex Cavali and with some evolution by Regal and others on the boards. It is an OTL amp of unique design, being similar in topology to the Futterman OTL design.  In this case, all the complications the Futterman amps use to maintain zero volts DC on the output is forgone and a capacitor is used on the output to block the DC.The amp is also unique in having a continuously variable global negative feedback pot. The power supply is regulated, supplying 250 volts to the output tube plates. A neat feature of the power supply is the use of a rectifier tube rather than diode bridge- the advantage here is that the heater of the rectifier tube is elegantly used as a delay timer, and full B+ is not applied to the output tubes until the rectifier filament heats up- saving the output tubes from the wear and tear of applying high voltage to them before their filaments are heated.


My Bijou uses "Regal's mod," and I am using Bugle Boy 6DJ8 input stage tubes and ECC99's as the output tubes.  For this test, I kept the NFB pot at minimum. (Which is also how I listen.)


LCD-2: A little tricky setting matched levels here again. Matching levels between the two amps at 1000 Hz did not result in the same apparent loudness from each amp. Nor did trying to set matching levels using a 100 Hz tone.  I ended up using pink noise and a 'scope set to a 2 second sweep to act as an integrator.  This got me levels that sounded identical between the two amps.  Right away, this told me that one of these two amps is not ruler flat when driving the LCD-2.  (Guess which one had slight frequency response variations-  I'll give you a hint:  it wasn't the Beta-22)   SO: listening-  The Bijou emphasized the bass and lower mids just a little, but also rolled off a bit at the lowest extreme of the bass range. This could be related to the 50 ohm impedance of the LCD-2, maybe the Bijou couldn't quite provide the current down low while at the same time having a higher source impedance resulting in lower damping factor.  So the bass, while not "wooly" was a little more "full" but not as deep or tight. Lower mids were also just a little emphasized, making the sound a tiny bit "warm" - this lower midrange emphasis was not as strong as the slightly raised bass level, but it was audible.  Highs on the Bijou sounded slightly "sweetened," the typical harmonic character of a tube amp.  However, the very upper extreme treble was a little lower in level from the Bijou, and the Bijou also seemed to blunt transients just a little on the LCD-2's.  There was something more going on the midrange that I can't grasp- certain sounds seemed to be brought out a little from the mix by the Bijou, while other sounds seemed to recede a little. However this did not seem like a simple  frequency response artifact- rather, it seemed like the harmonic content of the sound was being changed a little at certain frequencies, which was audible at times, and at other times this change in timbre was masked when the music  was "busy" in terms of lots of sounds happening at once. This isn't really a satisfactory description of the differences in midrange I heard between the two amps, but it's as close as I can get.  In simpler terms: the midrange sounded a little different between the two amps.  Overall, on the LCD-2's, I liked the Beta-22 more. 


It should be noted that the Bijou drove the LCD-2s to a normal level without having to resort to increasing the NFB. I would say that the Bijou had no real problems driving the LCD-2, but the match was less than ideal.


HD800:  Setting matched levels was easier, although for consistency I used the same pink noise method as with the LCD-2.  Again, the bass and lower midrange were a little "warmed up" on the Bijou, with ultimate low bass a little rolled off.  However, this was not as pronounced as on the LCD-2.  Also, the midrange timbral changes I heard using the LCD-2 were not evident.  The midrange on the Bijou sounded just a little warmer and that's it, no other hard-to-describe difference. Highs from the Bijou were "sweetened" a little, again the signature of tubes, but the transients and upper treble did not seem very much different between the Beta-22 and Bijou; on the LCD-2 I could hear differences.  Overall, it was clear that the Bijou "liked" the HD800 more than the 50 ohm LCD-2.   Even so, I preferred the Beta-22 to the Bijou on the HD800's, because I liked the more neutral bass balance of the Beta-22.


Conclusion: There were easily audible differences between these amps, especially on the LCD-2's. 



  • Both amps sounded "clean" and highs were never harsh from either amp on either set of 'phones.
  • LOUD levels were attainable with both amps, although the Beta-22 could not only play LOUD it could produce RIDICULOUS levels. (Hearing-harmful levels, levels at which I would never actually listen.)
  • I may revisit this test with some other headphones, like AKG-701's or maybe Beyer DT880.  I want to see if the Bijou might have a better synergy with other phones.


My compact Bijou 





Orange tubes and blue LEDs inside





Space-saving layout inside Hammond case.



post #33 of 500

Nice looking forward to even more comparisons. 

post #34 of 500
Thread Starter 

I am glad that Head-Fi members have said they enjoy reading this.  That's a really nice compliment, for sure!  Thanks!


I took a break today, but there is more to come: Beta vs. Little Dot MK III tomorrow, and then the Bottlehead Crack. Then maybe a revisit of the Bijou vs. Beta, using some other headphones besides the HD800 and LCD-2.  And then maybe a revisit of the Bottlehead vs. Beta using different 'phones.    The LCD-2's low impedance and moderately low efficiency makes them less than ideal for some of these tube amps, so I'll try those amp with some other 'phones.


And if I find a headphone that really suits the Bijou, maybe I'll do  Bijou vs. Little Dot and Bijou vs. Bottlehead comparisons. 


And then of course I will do one or two tests with some other listeners- including some professional musicians. I think the Beta-22 vs. M³  test would be a good one, not sure what other one to do, logistics of having a bunch of people over for this make me want to limit how much of this I do.  But I recognize the importance of having someone other than me repeat some comparisons in this series.


I'm also thinking about building an automated A/B/X system driven by a notebook PC for the switching and data recording, with modules to compare amps, headphone cables, and RCA interconnects.  My thinking here is to drag it to some Head-Fi meets and let people take tests and see what their listening  judgement stats look like. Gotta see if I still remember any C++ or even Visual Basic.....

post #35 of 500
Thread Starter 


Ninth A / B comparison:  Beta 22 & Little Dot Mk III


Same everything as above. THIS IS NOT A SCIENTIFIC (I.e., blind / statistically analyzed )  TEST.


The Little Dot is a pretty conventional OTL tube amp, a cathode follower I think. Build and parts quality is good but not fanatical.  Cosmetics are very nice, however, a really nice finish and good overall layout make the Little Dot MK III a pretty nice little desktop amp. It's an attractive looking component. Also, it can be used as a line stage preamp, which is pretty nice.


My Little Dot MK III uses stock tubes.  I have used it about 200 hours, so I would say that it is "burned in" sufficiently.


HD800:  OK, this amp was hard to get matched levels with the Beta-22. This is getting to be a habit with these tube amps.  Matching SPL for a 1000 Hz tone did NOT give an impression of equal loudness- the Beta-22 sounded louder / fuller.  So, back to white noise and the 'scope as with the Bijou.  This resulted in a much closer perceived match in loudness with music.  Again, this tells me that the frequency response of the Little Dot is not ruler flat in the audio range.  What I heard on the HD800's was a little extra midrange and low treble from the Little Dot. Also, the highs were "sweetened" a bit - that tube harmonic character at work, I think. The very upper upper highs were a little lacking in comparison to the Beta-22.  Bass from the Little Dot was very good, on the HD800 I could not hear any difference between Little Dot and Beta-22 on the lows.  Transients were a little blurred by the Little Dot (or one could say they sounded a bit "etched" on the Beta-22, depends on your point of view.) So, overall, this gave the Little Dot a somewhat romantic, ever-so-slightly lush sound on the HD800s. A little less "open" sound, those upper highs and transients give the Beta-22 a more "open" sound, but I have to say that on the HD800s  I could really get to like the slightly more "present" or "romantic" sound from the Little Dot.  I wouldn't say that the Little Dot "tamed" the HD800's highs, it was more that the sound of the Little Dot just suited the HD800 in a certain way.  If you are listening for the last bit of detail and resolution, the Little Dot doesn't seem to go as far as the Beta-22. But that doesn't mean the Little Dot didn't portray detail and offer resolution, what I mean is the Little Dot doesn't go AS FAR down Resolution Road as the Beta-22 does. Like I said, I could really like the Little Dot on the HD800.  And I was glad that the bass wasn't warmed up as some tube amps tend to do.


LCD-2: First off, I noticed that the Little Dot had no problem driving the 50 ohm, fairly inefficient LCD-2. The attainable volume level was way louder than I would ever use, but still clean. Second, I heard SOME of the same frequency-emphasis differences as I heard on the HD800.  The midrange and lower treble was a little emphasized by the Little Dot.  However, the rest of the highs did not sound much different between the Beta-22 and the Little Dot.  Except MAYBE a little less upper-top treble and not quite the transient ability from the Little Dot, but then again maybe this was just my brain expecting less upper treble and less transient ability because that's what I heard on the HD800.  The sound of the treble between the Little Dot and the Beta 22 was so close that I'm not really sure there was much - or any - difference.  There WAS a little more midrange and low treble, but the additional midrange seemed not as pronounced as with the HD800.  The lower treble - the "presence" range around 2 kHz- sounded just as it did on the HD800.  This was not unwelcome, really, on the LCD-2's; the amount of extra lower treble was quite modest and added a little something nice to the sound.  Bass, however, was a different story.  Here again I think the OTL tube amp is running out of driving current at the lowest audio extreme. Bass was GOOD from the Little Dot on the LCD-2's, while from the Beta-22 it was GREAT.  There is a little less deep bass level from the Little Dot and also bass did not sound as well controlled on the Little Dot - fast very low frequency bass synth runs tended to kind of blur together on the Little Dot but these low notes sounded sharp and distinct on the Beta 22. Whereas I liked the Little Dot with the HD800's pretty well, it didn't do that much for me on the LCD-2's.  It was OK on the LCD-2's but I'm a man who likes my bass so really I wouldn't choose to use the Little Dot with the LCD-2's.


Stereophile's Sam Tellig liked the Little Dot MK III quite well, and said it gave him what he wanted from tubes- he called it "rich, warm, spacious..."  and while I would say that it changed the sound to make it A LITTLE more "tubey" in the mids and treble on the HD800's, I don't know that I'd represent the amp's ability to add euphonious sonic presentation as strongly as Tellig did. 


CONCLUSION: Noticeable difference in sound between this amp and the Beta-22. I like the way this amp is "voiced"  when using the HD800. Was it  better than the Beta-22? Well, no probably not really as detailed, as accurate. But it does offer a DIFFERENT listening experience which has some strong points and which I will  continue to enjoy IN ADDITION TO having the Beta-22. Really, the Little Dot Mk III seems to offer very good value for money in a tube amp.  Note that I did not like it on the LCD-2. If I couldn't afford a Beta-22 for the LCD-2, of all the amps I've compared, I'd go with the M³ for the LCD-2.




MK III Tube Sockets.jpg

Edited by milosz - 11/25/10 at 3:00am
post #36 of 500

 Nice thread, thx

post #37 of 500
Originally Posted by milosz View Post
Really, the Little Dot Mk III seems to offer very good value for money in a tube amp.  Note that I did not like it on the LCD-2. If I couldn't afford a Beta-22 for the LCD-2, of all the amps I've compared, I'd go with the M³ for the LCD-2.


First off: what a wonderful thread! I'm loving all these comparisons, very informative. I'm very glad you enjoyed the LD MKIII as I have just ordered one for my DT990/600 Ohms. I really hope I get that slightly sweetened highs you got with the HD800s. Also like the fact that they easy drive the LCD-2 since the DT990/600 Ohm are quite difficult to drive to get to their full potential.


Thank you for these comparisons and keep them coming.


PS: I don't know if you mentioned this earlier in the thread, but was is the price for the Beta-22 and M3?

post #38 of 500
Thread Starter 


Tenth A / B comparison:  Beta 22 & Little Bottlehead Crack


Same everything as above. THIS IS NOT A SCIENTIFIC (I.e., blind / statistically analyzed )  TEST.


My Bottlehead Crack has the Speedball upgrade. In addition, I have Dayton 100 uF film capacitors as the output DC blocking (or coupling, if you will-) caps. They are the least expensive 100uF film caps you can get.  When I built the Crack, and added the Speedball, I also wired a DPDT switch that let me select wither the stock electrolytic output caps or the Dayton metalized polypropylene caps.  But I didn't pay attention to the way I wired the switch- when I sat down to listen, I did not know which switch position was electrolytic and which was film.  In a way this was a semi-blind A/B test of the two capacitors.  It was pretty immediately apparent that there was a difference in the way the highs sounded between the two switch positions. It turns out the direction I preferred was the film cap.  To me, I feel I showed myself that I really could hear a difference between these caps.  Of course more rigor and large number of samples would be needed to "prove" this hypothesis, but this simple test satisfied my curiosity. Anyway, that's a digression.....


This Bottlehead amp has stock tubes, which are some kind of NOS stuff.


LCD-2:  The Bottlehead amp could not drive the LCD-2 properly- sound was distorted at my chosen listening level of about 83~88 dB SPL.  The Bottlehead Crack is not designed to drive low impedance phones, and although some users have reported good results on Grado, I found that the Crack could not provide sufficient drive to the low impedance and fairly low efficiency LCD-2.  Grados are generally higher than "average" efficiency, so even though they are low impedance they might have high enough efficiency to work on the Crack.  I myself do not know, I don't have any Grado headphones.  I did have a pair of GS1000's  but I did not like the way they sounded at all and sold them shortly after acquiring them.


HD800: OK, right off, it's interesting that setting SPL at 1000 Hz with my reference tone resulted in a match of apparent loudness between the Crack and the Beta-22.  The other tube amps I tested had enough frequency response difference at 1000 Hz to make this particular volume-matching procedure fail.  So, I'm guessing that the overall response of the Crack is a little flatter than the other tube amps I tried. Listening to the Crack on the HD800's was nice. The midrange sounded pretty much the same from both amps.  However, the Crack added just a little upper bass / lower mids.  In addition, the highs from the Crack sounded a bit "sweeter" as has been the case with all these tube amps. And again, the level of detail was good but the Beta-22 was better. Detail isn't exactly the right term here for what I heard; the Crack was quite detailed, but seemed to lack a little level at the very highest frequencies making transients stand out a little less. And that doesn't quite exactly describe what I heard, either... it's almost as if the slightly richer harmonic content of the highs (i.e., the "sweeter" highs) masked the very highest highs a bit.  Lowest bass notes were more solid with the Beta-22 but the Crack was not thin sounding.  In fact the bass was a little warmed up, except for the very lowest notes.  Bass resolution- "tightness" - from the Crack was not quite up to the level of the Beta-22.  However, the overall sound of the Crack on the HD800 was very enjoyable- the slight midbass emphasis gave instruments and voices a little extra "body" which went well with the slightly sweetened, but somehow not quite as "airy," highs.  It was very good, musical sound from the Crack on the HD800's.  Different from the Little Dot in that it was the midbass that was emphasized a little and there was also a little more "sweetening" from the Crack. I would have to say that I preferred the Crack on the HD800's over the Beta-22 to some degree, at least I did today.  It's a taste thing.  One, the Beta-22 is the netral /accurate but highly detailed sound, while the Crack was a little more "musical" as Kingwa would say. With the somewhat exaggerated highs of the HD800's, I kind of liked the juiced-up sound from the Crack.  Juicy, that's a good word to describe it.  A LITTLE juicy, the difference in sound was NOT like dialing in a whole bunch of EQ, it was more reserved a difference than that.


AKG K-701: Since the LCD-2's didn't really go with the Crack, I went to the K701's as a second headphone on this amp comparison.  I find the K701's to be one of the least fatiguing headphones to use, their lack of strong peaks above the 0 dB line in the highs makes them easier for me to listen to at my preferred listening levels.  The elevated highs of the HD800s  cause me a little fatigue /  pain when I listen to my preferred volume of ~85 dB in the midrange.  However, even I've broken then in for WEEKS, the K701's just don't do it for me basswise.  They HAVE bass, even some deep bass, but it's not at the level I like.  Denon-AHD7000's they are certainly not.  Still, they sound good, particularly on symphonic and small ensemble acoustic stuff like jazz quartets and string ensemble music.  So.... on the Crack I did notice the highs sounding a bit sweeter and the bass a little warmer than the Beta-22 but this was not nearly as noticeable as with the HD800's. The K701's seemed less sensitive to the amp that was driving them.  HOWEVER, the K701 is rated at 62 ohms and at louder levels the Crack sounded a bit "iffy" - the K701s apparently are efficient enough to let the Crack drive them OK as long as you didn't try to drive them hard. Classical sounded very good on the Crack though the K701s, a little nicer than through the Beta-22 due again to the slightly warmer / sweeter presentation.


CONCLUSION:  The Crack is pretty much my favorite amp for the HD800s at the moment. 


NOTE: I will do an A/B comparison of the Crack / Little Dot next.  I have finished comparing all the amps I have on hand to the Beta-22.


Here's my white Crack....



The guts


Edited by milosz - 11/25/10 at 4:19am
post #39 of 500
Thread Starter 
Originally Posted by Yekrut View Post

Originally Posted by milosz View Post
Really, the Little Dot Mk III seems to offer very good value for money in a tube amp.  Note that I did not like it on the LCD-2. If I couldn't afford a Beta-22 for the LCD-2, of all the amps I've compared, I'd go with the M³ for the LCD-2.


First off: what a wonderful thread! I'm loving all these comparisons, very informative. I'm very glad you enjoyed the LD MKIII as I have just ordered one for my DT990/600 Ohms. I really hope I get that slightly sweetened highs you got with the HD800s. Also like the fact that they easy drive the LCD-2 since the DT990/600 Ohm are quite difficult to drive to get to their full potential.


Thank you for these comparisons and keep them coming.


PS: I don't know if you mentioned this earlier in the thread, but was is the price for the Beta-22 and M3?

I paid $330 in 2009 for my M³ from a professional builder, with Elpac "wall wart" power supply.  I built my "single chassis / 3 channel" Beta-22, and the parts cost about $450 plus about $110 for a Par-Metal chassis.


I did not use the "Epsilon 22" backplane board for my Beta-22, my amp boards / power supply are connected to each other by wires instead of using this backplane. At the time I built the Beta, the backplane was out of stock.  I would have spent the ~$90 for the backplane, it makes assembly easier and neater. The Beta-22 was the biggest project I ever built, there are a LOT of parts in there! I wouldn't suggest it to someone who is a beginner at soldering & assembly, but if you've built one or more amps, I say go for it.  Just pay close attention to the instructions, and TRIPLE check each part as you install it, and use the parts list as a checklist- put a checkmark for each part, this helps keep track.   I've seen professionally built Beta-22's go for around $1,500~$2,000, so you can say a fair chunk of change if you build one yourself. Also, I suggest a 2-chassis version- the power transformer has one heck of a field around it and for some reason the boards in this amp is sensitive to that magnetic field from the 60 Hz power going through the transformer. Moving the transformer a few feet from the boards is one of the best ways to combat this. In my one-chassis build, I had to enclose the transformer in a steel box inside my chassis.  The steel "confines" the magnetic field from the transformer and keeps it from inducing a noise current in the amp boards.  


The gray box (lower left) is a Hammond HM305-ND steel enclosure and the transformer fits neatly inside. This steel box kept hum out of the amp.  I had to add this steel box after I built the amp; before having it, there was a quiet hum which did not vary with the volume control. Annoying. But the steel box totally eliminated the hum. I just barely had room to retrofit this box into the amp, I am really glad that a box of just the right size was available- any larger and it would not have fit, any smaller and the toroidal transformer would not have fit inside it.





The Beta-22 is one of the best amps out there, it is a true reference design.  It sounds great. It's measurements and specs are so good it's almost surreal. For example:




at 0dBV output
0Hz - 2.5MHz, +0dB -3dB      
Slew rate 100KHz square wave, at 43Vp-p output


So, it's flat from direct current into the shortwave radio band, and has a 198 volt / microsecond slew rate. I've NEVER seen any other audio amp with a slew rate like that.  I don't know that such electrical engineering overkill makes it sound better but one thing is for sure- you can bet that the quality of sound through this amp is not going to be limited by frequency response or slew rate..... and typically with an amplifier, if the amp has huge bandwidth and fast slewing, and is still stable, then you know that sources of possible nonlinearity in the amp have been minimized by careful design.  

Edited by milosz - 11/26/10 at 3:24am
post #40 of 500
Thread Starter 


Eleventh A / B comparison:  Little Dot MK III & Bottlehead Crack


Same everything as above. THIS IS NOT A SCIENTIFIC (I.e., blind / statistically analyzed )  TEST.


As noted in earlier posts, my Bottlehead Crack has the Speedball upgrade in which " ...the 22k1 ohm plate loads of the 12AU7 input triodes are replaced by constant current source loads, as are the 3K ohm cathode load resistors of the 6080 triodes, " to quote the Bottlehead site.  I also have metalized polypropylene film caps instead of electrolytic output coupling caps.  Tubes are stock.


Everything in my Little Dot MK III is stock.


As the Crack is not intended for low impedance phones and won't drive my LCD-2's well at all, I only used my Sennheiser HD-800's for this test.


Due to frequency response differences between the two amps, I used the pink noise / 'scope  method to set the levels, and the apparent loudness levels of the two amps sounded like they were well matched as I began the test.


This was a very interesting test. As with all the tube amps I own, these amps both added a little euphonious signature to the sound, but each amp had a different character.


Compared to the Little Dot Mk III, the Crack added a little midbass which made the music sound a bit warmer and a little "richer" in a certain way.  However, the lowest bass notes seemed better served by the Little Dot- this gave the Little Dot a tighter bass sound, overall.  


Because of the midbass "bump" from the Crack, mids seemed to have a little more "body" than with the Little Dot, although not by a big margin.  Both amps had very nice midrange.  Separation / imaging sounded about the same with maybe a trifle better sense of space from some recordings produced by the Crack.  Operative word:  a TRIFLE.


The sound of the treble range differed between these two amps.  The Crack added a little more harmonic sweetness, while the Little Dot seemed a bit more transparent in the highs.  The Crack sounded like it had a little bit of rolloff at the highest frequencies compared to the Little Dot  This actually was OK on the Sennheisers which are a little hot in the highs. 


Overall, the Crack had a more "tubey" sound. As you may recall, I found both the Little Dot and the Crack to "sweeten" the harmonic balance of the highs a bit compared to the Beta-22, and this comparison seems to show that the Crack adds a little more treble sugar than the Little Dot. There was also a slightly "smoother" quality of the highs on the Crack, maybe what I'm hearing here is the sound of film caps in the Crack vs. electrolytic caps in the Little Dot.


They both sounded pretty nice. I liked the tighter bass from the Little Dot, but the overall sound from the Crack added a lush quality that I liked.  I would have to say I preferred the Crack overall; if I want tighter bass than the Crack I can go to my Beta 22 which is fantastic in this regard with very clean highs.  So, for me, to able to choose from the romantic sound of the Crack and the "precise" sound of the Beta-22 is a really nice option.


The Little Dot MK III, in a sense, fell between the Beta and the Crack.  If I only had one amp, I would want the Little Dot over the Crack because, to me, it sounded a bit more "accurate" - less euphonious coloration added. But having a good solid state amp like the Beta, it's nice to have the Crack which offers a greater contrast in sound quality against the Beta.  Does that make any sense? 


Here's the rear panel of the Little Dot Mk III from a stock shot, showing input connectors and the output connectors which allow using it as a line stage preamp.

MK3 Rear.jpg


Here's a stock shot of the Crack WITHOUT the Speedball constant-current load upgrade:




And here we have the Crack innards WITH the Speedball upgrade.  This builder did a neater job than I did, but his amp is all stock, without the film caps I substituted for the electrolytic coupling caps, which you can see by the photo of my amp in an earlier post in this thread.


Edited by milosz - 12/2/10 at 12:03pm
post #41 of 500

Very cool, it really affirms with my belief that when I go out and buy amp I try to buy amps of different flavor because I doubt I would hear much difference between two similar sounding amps.  For instance, I can barely tell the difference between the KICAS and Sparrow, but when put up to tube  or hybrid amps that has the particular tube flavor I do notice a difference.  Very nice comparison! 

post #42 of 500

VERY nice thread! I've been very tempted to do something like with for amps, but just never got to it. Can you think of a method to quickly switch between DACs in a similar way? Depending on how you connect to a DAC I think it might be possible.

post #43 of 500

Thanks for the nice review and taking your precious time to do all the different A/B test. Great work 

post #44 of 500

Thank you for posting your findings. Very interesting thread.  What tracks are you playing for your comparisons?

post #45 of 500

Great post and review once again. I have just recieved my LD MKIII and I am loving it so far. Working wonders with my DT990.

Thats really cool that you built the amps yourself. And by the looks of it are getting an amazing deal out of it.

Genuinely impressed!

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