Boyuurange MT34 MkII mods?

[>m0]

After all the hype and or deserved accolades re the SET only version (A10) of my new MT34, I am nonplused re the awful audio quality of this unit. It is a screech box at best. I tried it first with my modded MMGs, then purchased a set of Focal floor standers with a 91.5 DB rating, hoping that the screech box in question would be tamed...awful again. I then purchased several sets of power tubes, the Golden Lion, the EH variants, and a new set of my beloved Russian 6n1 signal tubes...after days and days of waiting for something to 'give'...nada, just a horrid heavy box of ugly sound.

Has anyone replaced any innards, caps, etc, on this particular unit?



Any help would be appreciated...

 

[s-petersen]

In the documentation they said it it push pull triode or ultralinear, yours is a single ended triode version?
Have you tried both modes?
What are you comparing it to? What amp were you using?

 

[FlaCharlie]

I just searched and the Boyuurange MT34 MkII is a push-pull EL34 amp. The A10 is a single ended EL34. SET stands for Single Ended Triode. The EL34 is not a triode and, although it can be wired in triode mode, this link to the amp says that it operates in ultralinear mode, not triode. Does your amp have a switch that allows you to choose UL or Triode.

https://www.amazon.com/dp/B07L4GL63...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

Pics of your amp and clarification would be helpful.

 

[>m0]

It has the switch:
https://www.amazon.com/BOYUU-MT-34-...l/dp/B07L3HQ425/ref=psdc_537344_t2_B07L4GL63N

I was comparing it to my old Yaqkin 10L driving modded Dalquist D8s, though at present I am using an Audio Mirror T-61 (just recapped), dual mono SX 500, 'Gunned' MMG, an electronic xover to a QSC dual mono power amp and dual 18" sealed subs. I loved the 10L for what it could do, and came to appreciate what the 6n1p did in particular, at least in the 10L and T-61.
I wanted that warm, rounded bass and euphonic mids/highs that was produced by the 10L output tubes plus the 6n1p. Sadly, my 10L is no more, it has been discontinued, and used options are priced through the roof.
The MT34 MKII has the advantage of the tube rectifier and the SET switch, and is also a lot sexier than the old 10L...but it just sounds like a Sears entry level solid state all-in-one, atm...
I was hoping that I could spot obvious caps to replace with better audio choices, but after opening it up it looks just as ugly as it sounds...

 

[>m0]

 

[GuyNoir]

I wanted that warm, rounded bass and euphonic mids/highs that was produced by the 10L output tubes plus the 6n1p. Sadly, my 10L is no more, it has been discontinued, and used options are priced through the roof

Hi-Fi Exquis has the 10T, which looks to be virtually the same amp.

 

[>m0]

Alas, the T uses different signal tubes, lacks the tube rectifier and that SET switch.
Using the switch, the MKII became barely acceptable, but the speakers I picked up for it (Focal Cobalt 816, because of availability and the purported 91.5db sensitivity) sounded overly harsh.

 

[Old Guy8]

I have the A10 model. Quite pleased with its sound for small room. Not equal to my Cronus Magnum, but looks well built. But, my expertise isn't electronics. I rolled Russian rocket and Tungsol tubes.
Your experience doesn't match the other Amazon reviews for your model. Could yours be one with an issue?

Have you tried another amp on the same electrical circuit? Looked for other sources of interference near system or on same circuit? Other possible external causes. House electrical receptical condition? Amp power cord issue? Assume like A10, it didn't come with one and you had to find one. (I see this one comes with a cord.) Any other outlier reasons.

I've read complaints of ground hum issues with model A50 mkii, that may have been cured with mkiii.

Having Maggie 1.7i, maybe MMGs are too much miss match to your MT34.
My 2 cents

Edit, this thread is puzzling to me. The A10 I have was half price of this model. Not my experience at all, after tube rolling away from stock Chinese tubes. I'd guess this unit should be a step up. Everyone's ears, systems and expectations vary.

 

[GuyNoir]

Pitty about the Reisong. I've had my eye on it, and also the A30 2A3.

 

[FlaCharlie]

Alas, the T uses different signal tubes, lacks the tube rectifier and that SET switch.
Using the switch, the MKII became barely acceptable, but the speakers I picked up for it (Focal Cobalt 816, because of availability and the purported 91.5db sensitivity) sounded overly harsh.

It's not an SET switch because SE means single-ended. That's an amp with one output tube per channel. This is a push-pull amp (two output tubes per channel) that has a switch that allows either UL (ultra-linear) or Triode operation.

It's not always easy to find a good match between any particular amp and speakers.

I was comparing it to my old Yaqkin 10L driving modded Dalquist D8s . . . I wanted that warm, rounded bass and euphonic mids/highs that was produced by the 10L output tubes plus the 6n1p. Sadly, my 10L is no more, it has been discontinued, and used options are priced through the roof.

The MT34 MKII has the advantage of the tube rectifier and the SET switch, and is also a lot sexier than the old 10L...but it just sounds like a Sears entry level solid state all-in-one, atm...
I was hoping that I could spot obvious caps to replace with better audio choices, but after opening it up it looks just as ugly as it sounds...

What happened to your 10L? Have you tried the new amp with the Dalquists?

If the new amp sounds as bad as you say changing a few caps is unlikely to solve the problem. But if you want to try, you could try replacing the coupling caps with some NOS American PIO (paper in oil) caps or, if you can't find any, try some Russian K40Y-9s. Use the same values as the stock ones.

 

[>m0]

"But if you want to try, you could try replacing the coupling caps with some NOS American PIO (paper in oil) caps or, if you can't find any, try some Russian K40Y-9s. Use the same values as the stock ones."


Where are the pesky things? I'm used to finding cylinders that stand out from the other items. I was thinking more along the lines of Mundorf silver gold oils, maybe Jupiters, depending on their size...
"What happened to your 10L? Have you tried the new amp with the Dalquists?"
The 10L had issues and after a good run decided to not power up. It was replaced by a Musical Fidelity dual mono pre and dual mono power amp. the Dalquists were an experiment: I decoupled the woofer box, gutted a set of Klipsch towers, made new baffles, used Scanspeak Woofers (incredible difference), and placed the open mid/tweeter baffle of the Dalquists on top of the 'new' woofer compartments/towers. I loved the results, but then I tried out different styles of Magnepans, and got hooked. After spending a bit on custom crossovers ('Peter Gunn' designed), the little set of new MMG sounded astounding. The Dalquists were given away...

 

[opnly bafld]

then purchased a set of Focal floor standers with a 91.5 DB rating, hoping that the screech box in question would be tamed...awful again.

A spec or two doesn't always tell the whole story, the Focals more than likely present a difficult load to the amplifier.
Every measurement of Focals that I have seen shows a very low impedance (4 ohms often lower) in the bass region.

 

[>m0]

Thanks for the info. I'll try them on the 4ohm taps.

 

[FlaCharlie]

View attachment 2075795
Where are the pesky things? I'm used to finding cylinders that stand out from the other items. I was thinking more along the lines of Mundorf silver gold oils, maybe Jupiters, depending on their size...

For some reason I thought this used point to point construction. I must have seen the wrong pic.

The grid of the EL34 is pin 5, so whatever cap is connected between your input tube and pin 5 of each EL34 would be the coupling cap. You might have to unscrew the circuit board and lift it up a bit to see. That's one of the reasons why I'm not a fan of circuit board construction.

The 10L had issues and after a good run decided to not power up.

If it was such a good amp why didn't you didn't try to repair it?

In most cases tube amps can be repaired, especially if they're wired point to point or use tag boards. But if a circuit board gets damaged and a replacement is not available . . . oh, well. And, as far as I know, nobody sells replacement boards for any of these Chinese amps. It's hard to even find an accurate schematic for many of them.

Did your 10L use circuit boards too? Did you ever figure out why it stopped powering up?

This is why I recommend vintage gear. Not only can it be repaired relatively easily, but it actually appreciates in value. So much of the current Chinese offerings seem to be throw-away items if anything goes wrong.

The only tube amp I have that uses a circuit board is the Dynaco ST70 and those were/are so popular that a wide variety of new boards are available with both stock and modified circuitry. I haven't restored mine yet but it's "on the list".

Dynaco ST-70 clones are still sold new in both fully assembled and kit form. If I were looking for a new PP EL34 amp that's the direction I'd go.

 

[>m0]

Thanks for the pin-out info. After connecting the speakers to the 4ohm taps and flipping the triode switch, the setup sounds kinda ok (listening to streaming "groove salad", Soma FM), the bass is a bit shy, but I didn't expect too much in that dept.
Regarding the pin-out, I do have a schematic that was sent with the amp. I don't have a scanner at home, but will upload it when I can.

 

[opnly bafld]

After connecting the speakers to the 4ohm taps and flipping the triode switch, the setup sounds kinda ok (listening to streaming "groove salad", Soma FM), the bass is a bit shy, but I didn't expect too much in that dept.

Have you tried U/L and the 4 ohm posts?

 

[>m0]

Just did. A bit more forceful, but not as bad as I thought it would be.

 

[>m0]

I tried everything in a different part of the room, and the rig sounded ok. I guess I would need to either find an ideal place to set this system up and add a sub or two, and/or place some deflectors, but I guess I just didn't realize how good the Maggies sounded to me,
as even using the Focals with my main rig was ultra disappointing compared to the Maggies. Ugh!
Here is a pic of the schematic, and a detailed section, sorry for the quality as they were taken with a phone:

 

[vinylkid58]

With only 25 watts/ch, I'm surprised it will drive Maggies. And that power supply is a bit of a head scratcher. A SS diode bridge for B+, into a rectifier tube for the rest. Who does that?

jeff

 

[>m0]

I tried the Maggies on this amp, and of course it wasn't my intention to use the tube integrated with them. I already have a system for the Maggies. I wanted a tube integrated to be used with higher sensitivity speakers, plus a sub if need be as a second or a more euphonic main rig.
It didn't happen. I was checking out old Klipsch boxes, etc., but the price for these crumbling pieces of classic audio (mid-fi?) are just ridiculous, and I wanted to stay away from shouty towers with pro speakers, so the trial with the Focal towers...