Modding Antique Sound Labs Wave-8 Tube Amp
Yeap, it is a tube amp. The Amps are push-pull mono design and are approx 11 years old. They were introduced as “best bang for the buck” for $99. They became an instant hit especially with the diy/modder crowd. Unfortunately, many off the documented mods have disappeared from the web. That was before the time of free blogging :-). The last known troubleshoot/mod report is from 2009 [link]
They also got great reviews such as this:
At an entry-level price of only $99 per side, few power amps compare to the amazing rendition of high-end audio that these charmers give. If there is an entry level tube amp out there for neophyte audiophiles, or simply some one who wants the most “tube bang for their audio buck” with their above average efficiency speakers, these have got to be the ticket. They certainly punched mine. [link]
Let me begin by talking about the amp these replaced. I previously had a stock Phase Linear 400 II. 200watts/ch. I kept the Phase Linear in my rack to compare but I liked the Waves so much I didn’t even bother to check the Phase Linear for a month. For me, audiophile nervosa is a powerful force and the fact that I didn’t do a “reality check” back with my old amp for a month speaks volumes about the difference. [link]
Straight from the box these amplifiers (given of course proper burn in) will impress you. They will never impress those with thousands of dollars invested because hey how could something that cheap be any good? Just keep it your little secrete so all the other folks who love sound but not high prices can enjoy them. We don’t want Antique Sound Lab to start selling them for what they are really worth now do we? [link]
At this price the company was probably just breaking-even. And anything that had little to do with the sound was spared. For example, the power and output transformers covers are just raw steel without any kind of finish. But even so, if you were to buy these transformers in the retail market, they would probably set you back $40 a piece, so likely they manufactured their own transformers and probably everything else for the absolutely minimum cost.
I have been using them in their original factory-stock configuration for my bedroom system connected to a Sony SACD player through a passive volume control and powering KEF bookshelf speakers. No complains so far but having been presented with the opportunity to get expert advise in modding this amp, I couldn’t pass the chance. That expert advice came from Scott [Scott17 at diyaudio].
After a few conversations with Scott, I realized that he was selling tube kits. So I asked him for a few modding tips for my amp. Scott was extremely generous with his time and knowledge and after a few exchanges where I described the innards and measurements of the amps, he developed a complete plan for me. In a way he was even more excited about this project than I was, often expressing his excitement and anticipation for the results. I can only imagine the level of support and care he gives to the people who buy his kits.
I have also scanned the full factory documentation and posted it here: [Wave8 Manual]
Here are the innards of the Wave-8 fully stock from the factory:
Fairly good components: film resistors, name brand capacitors, spacious PCB, ready for modding. The tall blue power supply capacitors are high voltage Nichicon VX electrolytic capacitors. I think those models have been discontinued as the current configuration for VX capacitors are axial rather than radial. According to this document [link], the VX have been replaced by the VR capacitors. The ones used are Nichicon 450V 47 uF and are good standard capacitors at $2.58 each [link] (the equivalent from the new series).
The high voltage DC is provided by the 4 diodes and a CRC filter of C9, R17 and C8. C9=C8=47 uF, R17=100 ohm
MODDING THE POWER SUPPLY
Scott suggested that the most noticeable improvements would come from modifying the power supply section. The following mods were recommended (in order of importance):
- Replace R17 with 4-Henry DC choke: [link], making a CLC filter which provides better filtering than a CRC filter
- Replace C9 with 630V 47 uF film capacitor (used 400V 40uF instead): [link]
- Replace C8 with 450V 220 uF Nichicon KX electrolytic capacitor (used 400V 180 uF KX instead): [link]
- Replace the diodes with ultrafast recovery types (UF4007) [link], further reducing noise
Why use a choke? Why not just a big series resistor?
A choke is used in place of a series resistor because the choke allows better filtering (less residual AC ripple on the supply, which means less hum in the output of the amp) and less voltage drop. An “ideal” inductor would have zero DC resistance. If you just used a larger resistor, you would quickly come to a point where the voltage drop would be too large, and, in addition, the supply “sag” would be too great, because the current difference between full power output and idle can be large, especially in a class AB amplifier [link].
The first thing you realize, is that film capacitors are “gigantic” in size. DC chockes are also large in size and even the higher value electrolytic capacitors would be difficult to fit. So before you embark in buying the components, it would be wise to figure out where to put the components and whether they will fit inside the case. After doing some mockups and measurement, and based on stock availability from the different supplies, I ended up with the components specified above. The clearance from the bottom of the PC board to the edge of the chassis is 40 mm. So most components would have to be 40 mm or less in one of their dimensions.
I did several mockups to see if the components would fit. here is an earlier mockup. Eventually ended with a single 40 uF film capacitor instead of two 20-uF capacitors by doing some “clean-up” on the PC board.
“CLEARING THE PCB”
I notice that there is a lot of space in the PCB board and that the layout can be made more efficient. The 40 uF film cap I selected would fit well in the back of the board by moving some components. The first thing I did was to move the fuse, switch and associated wiring to a small board and the resistors I re-installed in the backside of the board.
Actually, it is way better to have the input AC wiring off to another board. You move a lot of wires out of the way.
Although not recommended in the mods, I replaced the IEC socket with one with built-in EMI filter.
C8 and C9 would also be replaced, so we can remove those too. Now we have a nice empty space where we can install the large film capacitor.
The diameter of the film cap is 40 mm. Any larger would not fit in this location.
Replacing the diodes with ultra fast recovery diodes and installing C8. C8 is installed in position C9 (to free up space for the large film cap, which is C9). This requires that we cut the + trace and find a place to connect the + terminal of C8.
The KX series are designed for audio use.
C8 is in position C9. We need to cut the trace as shown and connect to the + connection of C8 (short orange jumper – you can see the trace goes around and connects to + of C8 position)). The long orange jumper connects the + connection of C9 to the large film capacitor which replaces C9 (not in the picture).
Installing C9. The 47 uF electrolytic capacitor is replaced with a film capacitor. Because of the size, I used a smaller-sized 40 uF 400V film capacitor. The + connection of C9 connects the + connection of the 4-diode bridge rectifier.
According to this article [link]:
One of the best amplifier power supply grounding schemes is a “star” ground system, where all the local grounds for each stage are connected together, and a wire is run from that point to a single ground point on the chassis, back at the power supply ground. Even better is a two-point star, where the power supply grounds (PT center tap, first filter cap ground) and output stage grounds (output tube cathodes for fixed bias, or cathode resistors for cathode biased, and output transformer secondary ground) are connected together and to the chassis at a single point, right at the ground of the first filter capacitor. The ground of the second filter capacitor, after the choke or filter resistor, is the star ground point for the preamp stage grounds. Use a local common point for each preamp stage ground, and run a wire from this common point back to the second star point. If two stages are out of phase with each other, the can share a common local ground, but don’t use more than two stages per local common ground. This concept can even be taken further, with multiple star points for various amplifier stages.
I used a single star ground approach (since the ground of the second filter capacitor is right next to ground of the first filter capacitor) with the negative lead of the film capacitor as the star ground. To this ground connects the negative output of the 4-diode bridge rectifier, the speaker GND connection and the GND from the “front-end” where the input signal ground is connected. From here, there is a single cable that connects to the chassis.
It is important that you pay close attention to grounding. This means good solder contacts, good contact to chassis (scrape the paint off) and good wiring. Make sure you measure continuity and resistance from all the ground points.
The choke is installed to the side of the chassis. The choke replaces the 100 ohm power resistor.
“This is the most common 90mA DC rated Fender* type choke used in many of their amplifier applications. Provided with shields for extra protection. Paper layer wound choke like vintage era originals!”
A bit of “Made in USA” in a Chinese Amp 🙂
The choke, the film cap and the electrolytic capacitors are near flush with the edge of the chassis.
REPLACING THE COUPLING CAPACITORS
After the PS mod, the coupling capacitors will also make a big difference.
Scott recommended the use of ERSE caps as an economical upgrade of the coupling capacitors.
The ERSE replaces the BENNIC capacitors.
Change R14 and R15 with lower noise versions. The cathode bypass caps C6 & C7 should be changed to 220uF. The stock configuration of 390R/100uF yields a -3dB corner frequency of 4Hz. As a general rule, the -3dB corner frequency should be 1/10th of the desired low-end response of 20Hz, which is 2Hz. This mod will achieve just that.
THE COMPLETED BOARD
Before and After
More bypass capacitor options:
There are so many choices and reviews. According to reviewers, their performance also depends on their application.
Capacitor review links
According to Joseph Lau, the designer of the amp, the calculated value of the bypass capacitor is 0.1 uF. 0.22 uF is already overdesiged. [link]
|Bennic XPP 400V||~18×10||<$1|
|Erse MPX 630V||20×11||$1.37|
|AmpOhm tin foil 630V||54×25||$20.55|
|AudioCap Tin Foil PPT Theta||30×17||$8.06|
|ClarityCap SA 630V||21×20(.47 uf)||$3.70|
|ClarityCap ESA 630V||20×24||$7.90|
|Multicap PPFX 400V||28×15||$6.45|
|Russian Teflon FT-3 600V||72×31||$5.50|
|Jantzen Z-Superior 1200V||43×22||$8.64|
|Audyn Plus 1200V||43×25||$6.50|
Even more mods [link]
Don’t use the cage as it makes things sound worse however the IEC allows you to use a quality after market power core and that is well worth the few extra dollars.
The parts count inside is very good and I did not feel that replacing caps and resistors would yield a big enough difference to justified the expense. The amp can and does respond to bypass caps and these are most cost effective and easy to install. Bypass the power supply caps with 1000 Volt ceramic disk caps.
All large value caps were bypassed with 0.1 uf plastic caps (despite what people say Mylar sound fantastic). All the small value caps were bypassed with 0.01 uf plastic caps.
I removed the “bell” or “end” caps from the output and power transformers. I then installed an electrostatic copper wrap shield around both of the transformers and in my case turned the output transformer 90 degrees to the power transformer and re mounted both transformers on rubber grommets to reduce vibration to the chassis. Removal of the “Bell” caps really opened up the sound and gave a sense of life and new dynamics. I have found this to be true on other amplifiers also. I did not do a direct before and after comparison with the physical orientation of the two transformers however with two chokes you want them aligned this way to place one in the exact electrical/magnetic “null” of the other an so minimize coupling between the two. This makes sense so I decided to do it with the two transformers even though it did involved making some of the lead wires longer.
The second last change that I made was to replace the input interconnect and to shield the power on/off wires which run to and from the front of the chassis to the back to the chassis. This one is up to you to do as you see fit.
Last but by no means least I froze the tubes down to liquid nitrogen temperature. If you haven’t tried this do so as it is a great upgrade all on it’s own. Sound is smoother and there is more detail with greater resolution and an apparent increase in dynamics. I can assure you that once bit (frozen) you will never go back to non frozen tubes or other parts for that matter.
Next go to Elliott Sound Products and read his article on a passive volume control “project 01” build one to use with your “Wave” amplifiers and then you will enjoy a level of performance you probably have never dreamed you even reach. The price of entry is a laugh. You will now be able to make your “Audiophile” friends so sick with what they own and with what they paid for it that they will in the words of J C Morrison “want to go and find a high place from which to throw off their gear”.
And more mods [link]
(These recommended by Joseph Lau, the designer of the amp)
I then started thinking about resistors. Joseph Lau recommended replacing 4 resistors in the signal path per unit. R4, R7, R10 and R11. Those are a 33k, 390k, and 2 1ks. I thought, what the hell and I ordered full compliments of Rikens, AN Tants, Holcos and Roederstein Resistas from Angela.com, Michael Percy, and Audio Note North America.
I began by replacing one amp with all Rikens. The bass response increased dramatically and I liked that (Tom Waits never sounded more gravel-ly and unshaven), but after closer examination I felt the highs were rolled off and there was way too much of a “tubey” or “hollow” sonic characteristic. Also some low end distortion.
I switched out the Rikens for all Holcos, but that didn’t seem exactly right either. It swung the other direction and I found it was too lean for my taste and lacked deep dynamic punch. Tom Petty whined too much.
I then put in all AN Tants which were very musically satisfying in the bass but the top end was restrained, or oddly veiled, but better overall than the other pure attempts. Ry Cooder had post nasal drip. hahaha
I then started thinking that I should try combinations, looking for the optimal blend. I put in the 33k and 390k Rikens for bass, with 1k Holcos in R10 and R11 and wow. Very nice highs, not too bright, but “there” with deep bass. I decided to try a variation on the other amp which was AN Tants in the 33k/390k positions and Holcos in the 1k positions and then duel the two off, A-B.
Upon extended HEAVY DUTY listening, there was more bass with the Rikens, but the Rikens were muddying or smearing the bass somehow, while the Tants were producing very slightly less bass, but it was a VERY well defined and musical bass. There was no comparision. The more I listened, the more I got goosebumps, and the more I loved this combination. AN Tants in the 33/390 positions and Holcos in the 1k positions created tonal characteristics nothing short of spectacular IMHO.
All the music I tried sounded “just right” in tight bass and extended yet not overly bright highs. Sampled music included Tom Petty Wildflowers, Ry Cooder Bop ‘Till You Drop, Les Nubians Princesses Nubiennes, Sheila Chandra Roots and Wings, Tom Waits’ Foreign Affairs, Eric Truffaz The Mask.
I did pop in 1k Roederstein Resistas in the 1k positions in one amp to test that possibility that they would increase dynamics, but they were a bit dry and substantially less dynamic than with the Holcos in the 1k slots.
There certainly are other combinations I didn’t try, but I think I’ve found a real winning combination that bring these little Wave-citos up a few big notches that have them competing sonically with my Zen Select amp for tonal character, but they’ve got muscle behind them.
I did find that when I put in Caddock TF020Rs in my volume shunt on my Foreplay Preamp, it made a huge difference and was the best I had tried (over Rikens, AN Tants, Holcos and Resistas). I may go ahead and get some Caddocks for the 1k slots, but I’m pretty certain that the AN Tants are the bomb in the 33/390k positions as they seem to tame the other stock metal film resistors which tend to be so bright, while the 1k slots keep the sound open and let in the high dynamics.
I’m no expert and I’m using “down home” language to try to explain my experiments and what I’m hearing. My Waves are singing beautifully.
I’d love to hear what anyone else has done to these fun little amps.
Overall, a very fun project. At about $50 per amp (and free guidance from Scott), it is a heck of a good deal…
Additional reading: [link]
Part II of the mods here: [link]