August 2001

The DIY Hi-fi Supply
"Billie" 300B
Single-Ended Monoblock
Amplifier Kit

Review by Thorsten Loesch
Click here to e-mail reviewer

  A while ago I used to be subscribed to the now defunct "Lowther" E-Mail list run by Bert Doppenberg of Lowther Holland. In the context of a discussion about fairly inexpensive Amplifiers for Lowther speakers someone then unknown to me, by the name of Brian Cherry, mentioned he had a 300B Monoblock Amplifier Kit which sold for much less than 1,000 Bucks, direct out of Hong Kong from his Company - DIY Hi-fi Supply. His website showed a nice looking pair of Amps, so I bounced a quick e-mail back, saying half in jest along the lines of - "If you really think your Amp's are as good as you make them out to be, how about sending me a pair for review?".

As it turned out, the Amp is actually a unassembled Kit version of the Consonance M500 Amplifier manufactured by Opera Audio in Beijing. Now I know, reviews in other mag's should not influence me, but the one review I had read, from the German "Image hi-fi" was by one the few people in the game I still take serious (Roland Kraft) and very complementary. So I was quite looking forward to the possibility to evaluate these Amplifiers myself.

Well, Brian took the challenge and we soon had agreed on a review. My first shock came on delivery of the kits. No, it was NOT the fact that our receptionist at work (where I had them delivered) promptly refused to touch these heavy boxes and lug them around. My shock came from the time scale. I had read the e-mail confirming dispatch from Hong Kong only the previous day! Overall the Kit's reached me in less than 48 Hours! I know plenty of fairly large UK companies that cannot manage a similar delivery time scale within the UK, never mind from a place on the other side of the world, some 12,000 or so miles distant.

I figured that if kind of speed in filling orders was anything to go by, these guys meant Business, seriously. With most DIY Kit Vendors one is used to delays, long delivery times and such and even happy to except them. But boy is it refreshing if just for a change the reverse happens. Shipping was via Fed-Ex Express, something that for the UK and US adds around 220 Dollar. So normally the shipped price for any private customer would be $ 1,000 or less if you chose a slower shipping method.

Anyway, the English Manual seemed to have been fallen out at the customs or something and her Majesties Customs and Excise decided to hit with a nice Import Tax and Viciously Added Tax Bill DESPITE the explicit statement on the papers for the Kit's as "Product Samples for evaluation only, no commercial value". But that happened on British soil and cannot be held against DIY Hi-Fi Supply. Brian send a replacement English assembly manual (25 Xeroxed pages with plenty of photos) and also included the wire upgrade which normally adds $ 20 to the cost of the Amp.

If you purchase the Kit's from Hong Kong import duties and tax may be levied, please check with your local customs and excise before ordering. One other possible snag in ordering these kit's is that DIY Hi-fi Supply currently accepts credit cards only via "PayPal". Other options for payment include money orders and bank transfer. Our local Hi-fi Club has recently purchased a substantial number of valves from DIY Hi-fi Supply using Bank Transfer, no problems and excellent service. Others who have recently dealt with DIY Hi-fi Supply also reported excellent service, so I think the excellent service I had was not an isolated case or to impress a reviewer, but the normal mode of business for DIY Hi-fi Supply.

Unpacking the "kit" revealed essentially two almost fully assembled Amplifiers, very different in feel to the usual large "mixed bag" or chassis and electronic tidbits. I'd think to less experienced DIY'ers and those new to kit building this simple fact together with the excellent manual will likely generate a considerable degree of confidence that the completed Amplifiers will look nice and that they will be able to build them.

The components supplied are of a wide variety, including funky looking Chinese resistors (which nevertheless have a reputation for good sound in the Chinese DIY community), Black Gate and Solen capacitors. The overall passive component quality is quite good, but nothing overly special, excluding perhaps the Black Gate capacitors. The Valves supplied are the quite respected Valve Art Nickel Anode 300B's and generic Chinese 6SL7 equivalent Driver Vales and generic Chinese 5U4 equivalent rectifiers. The wire from the wire upgrade is continuous cast, oxygen free, enameled wire with high temperature plastic sleeving. All in all a good basic platform.

I can appreciate the fact the DIY Hi-fi Supply avoided to include much in terms of fancy audiophile boutique components, as such are not only quite expensive but also very much subject to taste. For example I'm not greatly fond of Paper in Oil Capacitors while others love them. Equally some people intensely dislike my favorite foil & film capacitors. So, if you do have any specific liking for certain parts or wire buy the "Billie" kit plain and replace during building what you don't like with your favorite bits, this is one of the great benefits of kit building. If you are not sure what you like, the complete upgrade kits offered by DIY Hi-fi Supply will give a notable upgrade of sound quality and are very much worth having.

I have compiled a separate little builders log web page (click here) from pictures taken during the assembly, so I spare you details. In general assembly was easy and straightforward. I hit two major snags, one being a VA 300B which had obviously suffered a shift of the internal structures due to rough handling during transit, shorting out grid and cathode and thus making the valve unusable. The other was that all voltages where much too high. The high voltages (which would severely prejudice valve life) where the result of the rather high mains voltage in the UK. After discussions with DIY Hi-fi Supply and the factory I fitted a dropper resistor to reduce voltages, current kits should have gotten a new Mains transformer allowing for a wider range of voltages to be matched.

I changed two things. First the kit fits the Inputs to the side of the Amplifier. Good for a short signal path but seriously unusable in most Hi-fi Systems. I fitted the input to the back, giving up the option to have the 4 and 8 Ohm taps of the output transformer directly. If I need to change it now requires the take the transformer hood off and change the connection on the transformer. Secondly I used my own cable for the input wiring, exactly the same as what I'm using in my own interconnects.

I mention these issues here not to scare potential kit builders, but make clear that even a well designed and tested kit might under certain conditions cause problems. I have perhaps one or two more issues with the "Billie" Kit in general. The monoblocks are not laid out mirror symmetric. The result is that if the Amplifiers stand next to each other the visual appearance is not very pleasing. Also, the small toggle switches mounted on the back of the Amp's are not only fiddley and not very confidence inspiring, but being located on the back of fairly large amplifiers they are a major PITA (Pain In The A…) to operate, especially switching off when the amplifiers are hot.

Okay, so these gripes are only about appearance and ergonomics and one should not forget that we are talking about a major piece of kit which due to self assembly only costs about $ 1,000, so perhaps I should go easy, but hey I'm a "Hi-fi Critic", so criticizing is what I do…. One more note, the Gain of these Amplifiers is rather low, in almost all systems an active line stage ideally with pretty high gain will be required. Both the 5687 equipped line stage of my Arthur Loesch Preamplifier and the ECC81 toting line stage from the DIY copy of Shindo Laboratories "Claret" have high gain, so no problems here.

While assembling the Kit I was of course aching to replace all these cheap components with my own favorite "boutique" parts, however I felt that this was a review that should be done strictly according to Hoyle. No fancy footwork and crooked backdoor tricks. As you will see, I did not quite succeed, but much of the audition was done with the amplifiers using the components as they came out of the box.

As the pair of VA 300B's with the defective Valve where replaced I up fired the Amplifier in my system first using Svetlana 300B's, my long-standing 300B reference. Dropping the brand-new amplifier into the system instead of my "Legacy" Amp while repeating whatever was just playing (Eric Clapton Unplugged in this case). While I could immediately notice that the "Billie" had a number of small deficiencies (though remember the amp was in no way burned in), in general I was positively surprised by the sound I heard. Very natural, open and generally pleasant. I noticed that the slaps against the body of the acoustic guitar lacked a little impact, the general tone was slightly rough and the final degree of "air" and treble detail was missing. This general perception remained even after a considerable burn-in.

But hey, I am comparing an Amplifier kit costing $ 1,000 to an Amplifier I designed and build as an exercise in going "all out". This Amp has faced a lot of competition over time, matching or exceeding the performance of such excellent units as the Art Audio Jota and the Border Patrol 300B amplifier in my system. So given that the "Billie" managed to keep me captivated with music and no "take it away it's awful" impulse was triggered (I get this quite often in my system) the "Billie" sung very well indeed. Given especially the prosaic passive components and the quite lowly Valves equipping the stock kit it sounded much better than it had any right to.

I tried also the Sovtek 300B Output Valves I had at hand, both the standard bakelite base and the new (Electro Hamonix) ceramic base one. Once I received the replacement Valve Arts I tried these also.

While my extensive audition results including almost all currently available 300B's will have to wait till next month, I found the stock VA 300B to give a fairly bright tone, a very open sound with rather more of an edge to it than I like. A friend commented that the harmonic balance of brass instruments seemed to be altered to a rather tilted up sound. I found this Valve to work well with the Beauhorn B-2 Speakers I reviewed in last month issue. These speakers have a very soft top end, also found often as a matter of voicing on modern smaller stand mounting speakers. The extra brightness of the Valve Art Output Valve will work well here.

With my own Speakers (Tannoy 15" Monitor Red Dual Concentric's in corner York enclosures and the "Magnificat" Speakers based on antique Goodmans Drivers) I found the Sovtek to give a much better overall balance with more detail and refinement, making the VA sound positively rough edged and a bit aggressive. The considerably more expensive Svetlana 300B turned in a much more evenhanded and refined performance than either VA or Sovtek. However, leaving aside concerns about reliability and availability of the Svetlana 300B,

I got even better sound from the "Billie" Kits using some new Chinese made 300B's also supplied by DIY Hi-Fi Supply. Made in a factory in the Tianjin Province near Beijing these have been sold so far under a number of labels, the ones supplied to me by DIY Hi-fi Supply are dubbed TJ, short for TianJin. While my absolute champion is the Globe Type one with a mesh Anode (pictured above), the other TJ 300B Valves available have much of the magic and sound of the Mesh Anode ones and are available from only $150 the pair. They are definitely worth having, in my tests I preferred the basic Coke Bottle TJ to new production WE's.

I did some more Valve "rolling" with rectifiers and driver valves. The fabled RCA "Red" 5691 sounded muddy and closed in, pairing this with the Valve Art 300B gave a reasonable balance to the sound, but lacked openness and detail. Some Philips 6188 sounded nicely balanced, much better than the Chinese 6N9. My favorites so far are fairly old Sylvania and Ken-Rad 6SL7/VT-229. At any extend, I think all of the old stock 6SL7 improved the sound of this amp, so go out and get some. No need to go for the highly regarded money sinks, get some decent Philips or Tung Sol, they'll hugely improve the sound of the Amp for only a few bucks.

When I experimented with the rectifier valves I was in for another shock. Replacing the Chinese 5Z3 with RCA 5R4GY gave a great improvement in tonality, giving a slightly lightweight, but very evenly balanced and ethereal performance. The music filled the room very well, also the behind the wall! Some Mullard GZ34 (a.k.a. 5AR4) gave great power, impact and pace, I got a similar sound from some Sovtek and EI 5AR4/GZ34. The downside of the GZ34 was a slight edginess to the sound. I recently got a second Mullard GZ32 to make up a pair and found this to lie deliciously just in-between the GZ34 and 5R4GY. Lacking the slight edge but with most of the pace and bass impact retained this is my current preferred combination.

I compared the Amp over time repeatedly against my "Legacy" and also against a pair of highly regarded monoblock amplifiers from "Heart" Holland. As the "Heart" amplifiers cost a similar amount as finished products as the fully assembled units from Opera/Consonance I felt this to be an especially worthwhile comparison. Previously the "Heart" units had shown themselves very capable, neatly outperforming both Cary and Canary Audio 300B monoblock amplifiers. The units I had available where very recent production and supposedly even better than the older units I tested a while back.

Well, using the TJ Mesh Anode 300B in either amplifier (also using other 300B's) the "Billie" not only showed off a much lower noise floor (the Hearts had notable hum with my high sensitivity speakers) but offered with the stock Chinese 5Z3 rectifiers a much better and lower reaching bass, more detail in the midrange and a slightly deeper and wider soundscape.

Okay, now perhaps some more listening observations from my little black book. Some of my regular test records for natural tonality and detail contain Baroque music, played on original instruments, especially a range of pieces by Haendel on the Hamonia Mundi label and on the L'oiseau-Lyre Decca sub label. On Vivaldi's Gloria in D Major I noticed for the stock Amplifier "Good soundscape, voices a little too aggressive and edgy, strings have a little edge". Switching the valve complement around to TJ 300B's, Ken Rad Drivers and Mallard Rectifiers produced the following rave: "Wow, never knew there was so much space on this recording, the voices are just so real." The supposed critical listening session quickly degraded in pure indulgence. Well, I guess the upshot is that stock kit is pretty good with natural classical music, with better valves it is amazing.

While auditioning the "Billie's" with Mussorski's Pictures at an Exhibition (Reference Recordings CD, Eji Ojie directing) I noticed that in stock condition the "Billie's" had notable lack of impact in the nether regions and that strings sounded slightly rough and edgy. That aside the sound was very open and natural. Overall I found the result very listenable and had I not gotten used to a much higher performance level over the years I might be now raving how this is the "best amplifier I ever heard".

Well, even with the best available valves fitted the "Billie's" fall slightly, very slightly short. Yet listening to the "Billie's" with my preferred set of Valves and playing again Eric Clapton's Unplugged set I find now the impact on the guitar body rendered with the right kind of impact and within the limitations of the recording vocals are intimate, detailed and smooth. The detail rendered on such items like percussion is breathtaking.

If any sonic complaints remain it is perhaps an ever so slightly overly warm midrange. Saxophones sound just a tiny tic too creamy, vocals perhaps a little warmer than in reality. At any extend, here is an Amplifier that can, if fitted with suitably high quality valves offer way more than a glimpse of the true High End. Indeed, among the commercially available 300B SE Amplifiers I had the chance to hear, the "Billie", a.k.a. Consonance M500 Kit (and obviously also the Consonance M500 assembled unit) rates easily in the top 5. The Border Patrol Amplifier, relying here on my sonic memory betters it in pure bass impact and pace a little, the Art Audio Jota has more power, but both loose out in terms of transparency and palpability.

The Audio Note Japan Baransu is I think better through the bank (while not often in my system as I can't afford it and must beg for having it over for an hour, it remains my 100 points reference but only if fitted with NOS pre 1988 WE 300B's or STC 4300B's). Clearly Heart, Cary and Canary audio slot in below the Billie/M500. In fact, I'd say even if equipped with the stock Chinese valves (and using identical 300B's on the others) the Billie/M500 would make sure work out of the competition.

Given the price of the Kit and the performance both stock and the potential for performance if fitted with the best valves available I can only call it a huge bargain. Value for money if I ever saw it. Even the assembled units at around $2,500 to $3,000 the pair (depending on valve complement and who you ask - prices from Germany, UK and US) are excellent value for money.

The Kit's are pretty simple to assemble and hence suited as a project for 1^st time DIY'ers (but please observe electrical safety). The assembled units solid and high performance, if a lot more money. So for anyone who wants a pair of good quality, affordable 300B monoblocks the Billie Kits or assembled M500 should be high on the list. If you already have say a Cary or Canary or similar Amp, I think some internal upgrades and TJ Output Valves will give better value for money than buying a finished pair of M500's, but if you can build a kit have a go at the Billie's.

Actually, did I make quite clear that this Amplifier/Kit comes from mainland china? Yup, from the same place that supposedly only turns out low grade, unreliable, poor sounding gear! Well, I had my bad experiences with products "Made in PRC". So it is very encouraging and a nice break from the usual prejudices and perceptions about Chinese products to see that these Amp's are as well designed and made as any I came across.

Okay, perhaps the litmus test is to ask me what is playing in my system at the moment. Well, the Billie's of course, fully loaded with the best valves I can get my hands on, some passive parts replaced (especially the coupling cap - at the moment Jensen PIO and the 300B Cathode Cap - Black Gate). I am just playing through all my ABBA records (okay - I have now ousted myself as individual without taste). Playing now is "Lay all your love on me" from the "Super Trouper" Album. I'm swaying in front of the keyboard, sing along with the chorus and can barely keep typing (but Steve will kill me if miss the deadline again). Any Stereo that can do that to me is great. And the Billie's are a major part of it. So go and listen for yourself. I need to get up and dance, see you later.

And remember - Enjoy the Music Dudettes and Dudes!

 

Note: I considered it necessary to include two sets of scores, one covering the stock Amplifiers made from the contents of the Kit and one set allowing for the use of the Valves I found to give best sound. This way both the actual performance of the kit and the potential performance of the amplifier is fairly assessed.

The Geek Files -
Technology and Measurements:

This is the section that tells you about all the technical details, in case you should care about them or want to know about them.

 

Some technical notes on the M500 Monoblock Amplifiers

The M500 monoblocks are build into very substantial steel enclosures, the case is painted in gray hammer tone lacquer. The Finished M500 uses a natural color stainless steel enclosure. All transformers are covered with substantial covers, made again from steel, this time lacquered black. A safety cover for the valves is provided, but requires modifications to fit the Amp with the physically very large Tianjin Valves. The Quality of paint work and fitting in general is high, though the use of self tapping chassis screws for the bottom panel and the slightly non ideal fir of them distracts from the general feeling of quality. The Transformer covers are secured with real machine screws, requiring a hex key for removal.

The Kit comes with most of the hardware, the transformers, sockets etc. already installed, making the assembly mostly a question of fitting parts and wiring up the circuit, a doodle to build really. The English manual is detailed and very comprehensive. Assembly is pretty quick, but all components are hardwired around the Sockets, sonically one of the better solution but a little messy. I suggest you follow the manual step by step accurately, it ensures you get it all together reasonably neatly.

The Circuit is as classic as it is simple. A 6SL7 or equivalent operates as SRPP, the lower cathode is bypassed with a black gate capacitor. The output from the SRPP is coupled to the Grid of the 300B, which operates in selfbias mode with around 380 - 400V Anode Voltage and around 80mA Anode current. This operating point maximizes power and gives good subjective sound, but it will shorten the lifespan of the output valves compared to more conservative operating conditions. While this is not really an issue with modern, current production 300B equivalents, if you are using rare pre 1988 WE 300B's or the like you might consider not using them in this Amplifier. That said, most other commonly available 300B Amplifiers (Cary, Canary, Border Patrol, Wavelength Audio, Audio Note UK etc.) use similar operating conditions, so don't worry too much.

The Powersupply is Valve rectified using a standard 8 Pin Base rectifier. Fitted as stock from the factory are 5Z3 which is essentially Chinese for 5U4. Other Rectifiers that can be used (all tested by me) include GZ34/5AR4, GZ32 and 5R4 in the various incarnations. Following on from the rectifier is a simple Pi Filter using four 220uF/450V Electrolytic Capacitors from Rubycon (two each series connected) and a very substantial choke. A further RC filter circuit supplies the driver stage. The 300B Heater is supplied with DC, for noise reasons. This is unregulated and produced by a bridge rectifier and a Rubycon 10,000uF Low Impedance long life Electrolytic Capacitor.

The Output Transformer is a very antique looking EI Unit, made according to old traditions, a lot like the transformers found in classic and highly regarded vintage Amplifiers. This goes from core material all the way to the use of oil paper rather than plastic for insulation. True, I'd have liked to see permalloy or amphorous dual C-Core with Teflon insulation and so on, but such not only costs a lot, in many cases people find antique transformers to sound subjectively preferable. At any extend, the Output Transformers seem to work very well, so why change a formula that has been a winning one for 70 odd years? The mains transformer is a hugely over dimensioned toroidal unit, very modern and looking perfectly likely to be found in any High End 150W per channel solid state amplifier. Here it supplies only about 60W to a simple Class A Amplifier of around 10W Output. The filter choke for the high voltage supply is a VERY substantial double C-Core unit, rated at 8H. No doubt this very substantial filter choke contributes a good deal to the excellent signal/noise ratio of this amplifier. All in all a very unusual and motley assortment of Transformers and other Iron compared to the usual approach in the industry, but one that undeniably works very well in practice.

If I where to build up a unit strictly for my own use, I'd be replacing all signal circuit resistors with Rohpoint non inductive precision wirewound resistors. Beware, these are from no boutique supplier with 200% margins but cost around $ 5 each from industrial suppliers. I'd also use a Mundorf M-Cap Zn or Audyn KP-SN Tinfoil & polypropylene coupling Capacitors and suitable Ansar Supersound Capacitors (47uF/450V eight pieces) for the power supply and the 300B cathode bypass Capacitor, but at around $ 30 each such an all out set of components would add a cool $ 400 or so for a pair of monoblocks at the prices paid when buying direct from the manufacturers or large trade suppliers. If the Kit came with this level of component quality it would likely double the price overall, so the choice of passive components applied by DIY Hi-fi Supply is perfectly acceptable and sensible.

All in all a simple, proven, reliable and robust circuit, I covered the sound elsewhere, but "how did it measure?" some will ask. I measured around 9V RMS on the output (equivalent to 10W RMS) before clipping set in. Even at what I considered clipping level the distortion spectrum remained low order, with dominant even harmonics, a textbook case of a single ended triode Amplifier and generally leading to a subjectively quit mildly impact despite an overall THD Level exceeding 5% at full output. To obtain the full output level an input voltage of around 1.5V RMS was required. This amplifier has very low gain and will in most systems require an active line stage, preferably with quite a bit of gain.

I also could broadly confirm the frequency response claims made by the manufacturer. Given that measurement techniques differ and my PC based Audio Lab setup only manages to measure with reasonable accuracy to 20kHz I could not fully explore the bandwidth, but the response between 20Hz and 20kHz was very flat, with only modest LF & HF rolloff.

The Output impedance on the 8 Ohm output tap was around 2 Ohm. If we take a Speaker with a nominal 8 Ohm impedance and a fairly extreme Impedance curve (5 Ohm Minimum and 50 Ohm maximum, the impact on the frequency response will be around +1.5db / -1db, something certainly audible, but hardly relevant in the bigger context, where room position introduces easily a +/10db variation of the any speakers frequency response. Moving the speaker around a little (forward/back, experiment with toe in) will easily compensate any subjectively objectionable changes in balance, if you use (like I do) a digital room/speaker response correction system, simply re-run the setup procedure.

Noise was spectacularly low, the noise floor being below 0.1mV RMS. This translates into over 100db Signal to noise ratio for full power. When related to an output voltage of 2.83V (equivalent to 1W RMS into 8 Ohm) the signal to noise ratio is still 89db! This is the quietest 300B SE Amplifier I have ever measured, including my own designs.

While measurements in general say little about the sonics of any given piece of High Fidelity Equipment, the results turned in by the M500 Kit (Billie) are extremely solid for the genre and in some instances (bandwidth, noise) way better than what I have come across in the majority of SE Amplifiers. The design again is solid, pretty conservative and proven, build quality is good, so from a standpoint of "How does it measure and how is it build" I can certify the M500 Kit a clean bill of health, thumbs up Opera Audio, well done.

Specifications

MSRP: $775 for the Basic Kit plus shipping
Power Output: 9W RMS per channel (@ 1kHz)
Frequency Response: 17 Hz - 47 kHz (-3db @ 5W)
Total Harmonic Distortion: <1% (5W @ 1kHz)
Signal to Noise ratio: 90dB
Input Sensitivity: 2V
Impedance: 100k Ohm
Output Impedance: 4 or 8 ohm selectable
Power Supply: 100 - 120V AC or 200 - 240V AC
Power Consumption: 50W each monoblock
Dimensions: 6.5" x 8.7" x 16.2" (HxWxD)
Weight: app. 32 lb. (net.) each monoblock; 72 lb. (shipping)

 

Company Information

DIY Hi-Fi Supply
Manufacturer: Opera Audio Beijing
Peoples Republic of China

Website: www.diyhifisupply.com
E-mail: sales@diyhifisupply.com