My life with the Reisong Boyuu A10 EL34 tube amplifier...so far...

I knew I couldn't expect much out of it, but after watching a favorable online review of the Reisong A10 amp and reading a few others, I bit the bullet and found one available with two desired options: 1) no tubes, and 2) point-to-point wired. My thinking is that the cheap tubes that ship with these amps usually aren't good, and I could provide my own. And, with it being point-to-point wired, it would make future upgrades and repairs easier. I was into it for $160 plus shipping from the far east.

I use this in my computer desktop system attached to an older DACMagic DAC (which needs replacing--it's woefully out of date) and a newer pair of KEF LS50s. Part of my reason for "overkill" on the speakers was that I sometimes need to do some audio or video editing, or analyze something closely, and the previous pair of speakers I used came with an awful resonance at 125Hz that made them tubby sounding. (I had to use a really deep notch filter to get rid of some of it.) The LS50s were a killer deal at the time, so I didn't pay anywhere near list price for them. I pair them with a small subwoofer beneath the desk.

The A10 does sound good, but I felt the KEF LS50s sounded too bright in my main system. (I normally listen to stats.) On the desktop, though, the more relaxed sound of the A10 worked in their favor. Maybe you can see where this is leading.

Only last week did I get a chance to try the A10 in my main system. And let me just put it politely--I lasted three tunes and had to yank the A10 out. It was that bad. The nearest equivalent was the garbage I used to buy from Radio Shack in the late 70s (I had that SA-1000A integrated amp which, surprisingly, sounds very similar to this.) What did I hear? Three things. 1) The highs feel as though I had cotton stuffed in my head; this amp is quite rolled off. Much of the detail was missing. 2) The sound was a bit grainy. 3) While the left-to-right spread was about the same, the soundstage was flat. No depth at all.

Was it fair to pit it against an amp that was probably 15 times the cost when new? Maybe not, but if you read the hyperbole from others who own it, it makes you wonder what it is they're hearing that's so special about this A10.

For the record, I'm using Electroharmonix 6CA7 and Voshkod 6N2 tubes (which supposedly are well-regarded). The rectifier I bought was a Tung-Sol 5AR4, as the 5Z4 Mullard I'd ordered was in the bowels of USPS for several weeks before it finally arrived. (The 5AR4 is electrically close enough to the 5Z4 to work properly.) I can rewire the 6N2 sockets for 12AX7s quite easily, and may do that if I decide to keep the amp.

As it stands, the A10 has been an interesting experiment but I don't have the time or patience right now to see if it can be improved on. (Without a schematic, that would be a bit difficult anyways.) I'm probably going to get a Sprout for the desktop instead, as it's a cleaner and more neutral amp, and the built-in DAC is more capable than what I'm using now. (Plus, it will use less space.) The KEFs deserve better.

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To be continued...
 
You paired it with Martin Logans?
What better way to hear how bad it sounds? 🤣 But really, I wanted a fair assessment of what it actually sounded like, vs. the online praise I've read about it. It surprised me how quickly I heard the difference. I've gotten so used to the sound of my main system now that I can better hear when something changes. It's the first time in my life after four decades of playing with this stuff that I can listen to a system for hours and never tire of it, and never have anything about it annoy me.

Could the A10 be improved under the hood? Most certainly, I'm sure. At any rate, it's a decent chassis and the transformers may be adequate enough to sound respectable. I have a feeling it's the no-name components and maybe a few circuit tweaks away from being a nice amp for casual listening. I figure I don't have the time, resources or patience to even start considering making my own chassis for anything, so this at least gives me something to start with. That is why I bought the point-to-point wired version, as I figured I'd be making changes at some point.
 
@Rudy
The way I read your report, your sonic description of the very poor resulting sound quality appears to point to a very poor amp/speaker mismatch (impedance mismatch, lack of power, etc.) - between A10 and your chosen speaker - as opposed to criticism of the A10 amp in general.
Have I understood your report correctly?
 

paulbottlehead

Active Member
Looking at some build photos on the internet, this amp operates the EL34s in ultra-linear mode but does not use any global feedback. In the point-to-point wired version, it's also obvious that there's no local feedback. Consequently the damping factor will be very low, bass will be very boomy indeed, and the output of the amplifier will be incredibly sensitive to the impedance curve of the speaker used. I would suspect that the damping factor will be a bit under 1. This is a sub-par amplifier design.

This situation could indeed be improved with a different circuit design. Even the Chinese amp I got that I wasn't a huge fan of had a feedback loop and low damping (2), but there was at least some attempt to address the issue.
 
@Rudy
The way I read your report, your sonic description of the very poor resulting sound quality appears to point to a very poor amp/speaker mismatch (impedance mismatch, lack of power, etc.) - between A10 and your chosen speaker - as opposed to criticism of the A10 amp in general.
Have I understood your report correctly?
No, the KEF LS50s are too bright in my main system, but a bit soft in the desktop system, which is what I tried to point out in my first post (and not too well):
On the desktop, though, the more relaxed sound of the A10 worked in their favor. Maybe you can see where this is leading.

If I apply EQ in Roon on the desktop (and I hate EQ), I can get some semblance of life into them, but then when I have to use other software, I'm back to the dulled sound (which is somewhat compensated for by the bright KEFs). Putting the amp into my main system only reinforced how poor this amp is...only it was worse than I thought. (It went beyond just a rolled-off high end, in other words.)

I will say that the A10 sounded more powerful than I thought it would in my main system--the speakers are 91dB/2.83V sensitivity and have a powered woofer section. I didn't have to push it much to get plenty of volume, and never reached clipping. (I had that in my first post but I think I edited it out by mistake.) Handled some orchestral crescendos just fine.

At any rate, I just wanted to offer this as a cautionary tale, and can revisit this thread when I can get a chance to look it over and see where some mods might help. As I said, it's a nice enough chassis to work with, so it might be a good project for when things slow down here. I already have a couple of leads on a replacement--they'll cost more but for some upcoming projects, I need to get this addressed.
 

paulbottlehead

Active Member
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This is doable in the chassis you have. It won't oscillate if the output transformers you have are marginal, which would otherwise be an issue. You can disregard the power supply and just use what you have. You can disregard the cathode biasing block in this schematic for the EL34 and just use what you have.
 

adaug

Awaiting Updated Member Status.
@Rudy
The way I read your report, your sonic description of the very poor resulting sound quality appears to point to a very poor amp/speaker mismatch (impedance mismatch, lack of power, etc.) - between A10 and your chosen speaker - as opposed to criticism of the A10 amp in general.
Have I understood your report correctly?
agree - martin logans dont seem like a fair way to evaluate a small tube amp.
 
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