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

[Rudy]

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I use this in my computer desktop system attached to an older DACMagic DAC (which needs replacing--it's woefully out of date) and a newer pair of KEF LS50s.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.



To be continued...

 

[paul_b]

Wanna mail it to me and I'll do a write-up like I did here?
This isn't about cheap Asian-sourced amps/preamps -- but it IS about economics and value :)

 

[Rudy]

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.

 

[paul_b]

the transformers may be adequate enough to sound respectable.

This is usually the biggest problem, and a soft top end would suggest that the transformers aren't so great. Putting fancy caps in is unlikely to fix anything besides the weight of your wallet.

 

[paul_b]

Would the ML 1 ohm treble impedance explain the rolloff?

This with poor damping could make the stats sound very rolled off and a dynamic speaker with rising impedance up top sound unbearably bright. What is the speaker model in question?

 

[SONDEKNZ]

@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?

 

[paul_b]

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]

@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.

 

[paul_b]

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]

@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.

 

[iix23]

Hi, I new here and to HIFI.
I bought this amp and kind of have regrets. I paired them with my Klipsch RF-35 8homs thinking that it would be softer with my speakers already driving high frequencies and it's not what happened. The amp is distorting the high frequencies and make everything sound like mud without any depth. I run solid shielded RCA expensive one way cable (that can't remember the name). I had a proper (expensive) power cable made for the amp and still no bingo for me. It's all mud, distortion and a (physical) headache.
There is no sound staging. Everything is a mess. Sarah Brightman is giving me an ear bleed. Ah, also, the left channel plays louder than the right.
I borrowed a Nobsound 6p1 6.8W to see if my speakers, my TT (Rega p3) or my DAC were the problem and,, they aren't. I am now looking at new tubes?? or other mods but also asking myself, "How deep do I want to get in this amp?" I don't have the knowledge or the skills to open it up and start welding stuff inside.
I bought this based on reviews and didn't listen to it before buying as it wasn't possible.
For my first steps in Hifi, it's a little depressing as my budget doesn't permit me to buy an MC1502

Oh, I forgot. I was playing the TT on line 1 and my DAC on line 2 at the same time to run tests. When I unplugged the DAC (line2) to try an other DAC (thinking that all these problems were due to the DAC) I could hear the TT on line 1 playing in channel 2 (10% volume).

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[paul_b]

The amp is distorting the high frequencies and make everything sound like mud without any depth.

The design is crap. You could try triode strapping the output tubes to patch things up a bit, and with your speakers you'd probably still have enough power.

 

[Wntrmute2]

Well, it looks nice!

 

[iix23]

I Plugged in a Burson Funk 35W 8homs in my RF-35 and it was night and day. Steve Vai came to life. Sarah Brightman didn't give me an ear bleed and felt I was in space when listening to Vangelis.
For a newbee like me that don't have the skills or knowledge to tweak things like this, it put a major hold on the idea of owning a tube amp (although I own an Orange TH 100 with 4x12 cab guitar amp).
This one is getting returned to the sender.

 

[Andy Bergstrom]

Bought one based off the hype and online reviews. Very disappointed. There are some mod ideas going on Audiokarma and DIY audio. Thinking the OT transformers are the limiting factor.

 

[paul_b]

it put a major hold on the idea of owning a tube amp

You own something that's pretty close to what I would expect in a cheap old tube table radio.

Try finding an old ST-70/ST-35 or something locally to get a better idea of what a decent tube amp sounds like.

To triode wire the finals in this amp, you'd just need a pair of 100-500 ohm 1/4W resistors, some heat shrink tubing, and a soldering iron.

 

[iix23]

Hello Paul and thank you for your reply.

-"You own something that's pretty close to what I would expect in a cheap old tube table radio."
It's not how it its reviewed on the interweb. Even "Steve Guttenberg" praises this amp. I then think that if this gets praised, how good are tube amp really?

-"Try finding an old ST-70/ST-35 or something locally to get a better idea of what a decent tube amp sounds like."
Thanks for the suggestion.

-"To triode wire the finals in this amp, you'd just need a pair of 100-500 ohm 1/4W resistors, some heat shrink tubing, and a soldering iron."
So, it's not a finished product? In the reviews I based my purchase from, it wasn't "advertised" as an unfinished product. It would be like buying a house that is 70% finished and being told that " All you need is a hammer, some lumber and nails to make it work for you."

I understand that perhaps most people on this forum are highly knowledgeable and invested in these things. Something like a passion for the intricacies of getting that last once of perfection that audio related hardware can provide and I respect that. As a bow hunter, I spend hours building/ fletching my arrows and trying new setups for my bows. However, I was just looking for an amp that would deliver good sound. It was reviewed as such and even you, had to give me a work around to make it work.

I want to put the emphasis on that fact that, I am not knowledgeable and a newbee at this. I wanted to see if I was the only one who had trouble with this amp and I came across this forum who also had people with issues with it. I shared my thoughts thinking that it might help other newbees have access to a different opinion than what is propagated on the web.

I sent the amp back and went a completely different route. I got myself a Burson TK-3i. An integrated solution more adapted to my needs and more in line with the time I am willing to invest into this specialized field. A plug and play solution if you will.
My last statement made me laugh as, when I see a guy or girl getting into archery or bow hunting show up with pre-made/fletched arrows, I take a pause to remind myself that, not everyone is as invested in my passions as I am. Some people just want to have a good time without all the headaches and the investment in time needed to learn a new skill. This is where I fall here in this case.

 

[paul_b]

When you buy something like this, try to learn who designed the amp and what else they have designed. Also look for reviews that have a measurements section, as this amp is not going to measure well at all.

 

[iix23]

Follow up on this.
Yong Lee from China-hifi-audio.com.hotmail tracked down my email from a comment I left on a youtube review. He wasn't too happy with me.
He aggressively sent me a string of 6 (unsolicited) emails in 1 hours.
-"The problem is that you did not buy from me, and I sale out a lot of Reisong A10, and my buyers love it very much."
-" All the reviews are real."
-"You post it anywhere, it is not fair for me."
-"Could you open the body to take a picture? Is it a PCB version or a point to point version?"
-"I think one of your tube is bad on your Reisong.
c), Check the tubes if work normal. It is usually(75%) because of the tubes.
Please removed all the tubes, and then, plug in all, test. If the RIGHT channel still don't work, try next.
Change each of the left tubes to right, right tubes to left. If the RIGHT channel still don't work, try next.
If RIGHT channel work, that because of the tubes.
If it is because of the tubes, try to find which tube are bad. Please change only one(one single) tube from left to right, test. Test one, and then change next tube to test, one by one, when you change the tube, and the bad channel is changed too, this tube is bad.

I remember when I bought my last Playstation, Sony tracked down my email and sent me some unsolicited mail giving me an "SOP" to make it work. I had to open the playstation to unplug and plug other things and run tests on the electronics to see why it didn't work properly.
After all this, Sony then complained to me that it wasn't fair that I left a unfavorable review of their products that didn't work properly because I could not finish assembling/ fixing the brand new product I bought at full price.
Oh, wait, that never happened.

I remember when Ford tracked down my email... Oh, wait, that also never happened.

What is going on here? All I wanted was a working amp. Not an international incident with people tracking me down telling me what I can or can't say. Ha ha ha. I feel like the James bond of Amplifier.

 

[paul_b]

When you design a single ended amp, you start with the speaker you're driving. A typical speaker will be 8 ohms and if it's vented, the design will likely work best with a damping factor of at least 10. A damping factor of 10 for an 8 ohm speaker means an output impedance of 0.8 ohms. Less than this and the amp actually changes the T/S parameters used to calculate the box volume and port tuning. You can just barely scrape by with a DF of 2 in order to avoid the boomy fuzzy bass that is associated with poor damping.

We know that this amplifier is run in ultra-linear and from examining both the PCB version and point-to-point version, there is no feedback (there are only a few ways to apply feedback to an amp like this, and they are visually obvious).

From the other Chinese EL-34 SET amps I've seen, they tend to run an operating point that's about 350V P-K and 70mA. With an ultra-linear output transformer, that gives you about a ~3K plate impedance on the EL34. If you add in a few hundred ohms of copper that has to be in the transformer and aim for a damping factor of at least 2, then your transformer impedance will need to be 8-10K. The problem with landing here is that you won't get anywhere near 6W of output with such a high load. This is the crux of why you don't see successful zero feedback UL amps, as you may as well just triode wire the thing from the get go.

Instead I suspect that this amp uses either a 3K or a 5K output transformer and just rolls the dice that nobody will bother to measure it.