One of my viewers offered to drop ship one of these made in china HiFi 300B amplifiers me to review and make a DIY video series on how to modify them to improve the sound and power output. Given this popular amp uses the same basic schematic I found to be problematic on my own DIY 300B build, I suspect it will respond well to the same changes I made to my own build.
I haven't see anyone do a real technical review on these, just a "I plugged it into my system as a solid state amplifier user and it sounds like XYZ" kind of thing, so I hope this will be informative and helpful for folks that either own one or plan to buy one.
The first video is a basic unboxing, and I will be adding more content as I test and dive into this thing!
Boyuurange A50 Tube Amp Unboxing + Full Review - YouTube
I haven't see anyone do a real technical review on these, just a "I plugged it into my system as a solid state amplifier user and it sounds like XYZ" kind of thing, so I hope this will be informative and helpful for folks that either own one or plan to buy one.
The first video is a basic unboxing, and I will be adding more content as I test and dive into this thing!
Boyuurange A50 Tube Amp Unboxing + Full Review - YouTube
stephe,
Since you will be doing all the work of reviewing, and then designing improvements to their circuit . . .
I hope they are giving you the amplifier for free (you should not have to return it).
You should have the rights to keep or sell it.
I look forward to your review and re-design.
Just my opinions.
P.S. I mis-read your post, now I understand it was a reader that sent you the amplifier. That was nice of him.
But I bet when you get done, China will re-do the PCBs, and sell the "New and Improved" version.
Since you will be doing all the work of reviewing, and then designing improvements to their circuit . . .
I hope they are giving you the amplifier for free (you should not have to return it).
You should have the rights to keep or sell it.
I look forward to your review and re-design.
Just my opinions.
P.S. I mis-read your post, now I understand it was a reader that sent you the amplifier. That was nice of him.
But I bet when you get done, China will re-do the PCBs, and sell the "New and Improved" version.
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Assuming the negative - that had occurred to me too - however china focuses on cost. So if Stephe decided to improve it with high cost options I would suspect that you'll see copies of the high cost components made and used rather than real Mundorf etc. Additionally it allows a company to understand the general preference of that countries' ear too.
Yes it's PR on a influencer's YT channel, almost endorsement of the brand as legit and the insides are 'good' etc even though non-recognised brands. Issue here is there's no contract to ensure that they don't cheap the amp in the manufacturer post review.
Assuming the positive - I don't think it's been the first time that an amp has been sent to specialist/consultancy for measurable improvement.
I noted that the PSVANE seemed to be non-PSVANE tubes so perhaps PSVANE can confirm if they're real PSVANE..
Personally I find the design style of the amp garish, way too much gold and the shape doesn't look nice when loaded with a whole load of stuff on the front with switches and panel meters.
Rip out the VU meters and replace with mA and voltage, simplify the front end by perhaps moving the meters to the top at the back. Also the switch knobs looks way out of proportion. Lastly the case with the pillars in the corners to simplify manufacture and to hide the bad corner joins. Seriously the case is an affront to my sensibilities.. Nope. Visually it hit every branch of the ugly tree when it fell out. If they made the base in bamboo and left the top it would look both stylishly different and differentiated itself from the other Chinese amps (with a little reference to china in the form of bamboo).
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I watched; it was interesting and engaging video! It was nice to put a face and a voice to a valued contributor here.
The product looked quite impressive I thought! Bearing in mind how hard the presentation part of building an amp is (chassis, cage and other hardware), buying a cheap, well built amp, and optimising some of the electronics, would seem to be an excellent path to take! I'll be subscribng for updates.
The product looked quite impressive I thought! Bearing in mind how hard the presentation part of building an amp is (chassis, cage and other hardware), buying a cheap, well built amp, and optimising some of the electronics, would seem to be an excellent path to take! I'll be subscribng for updates.
NickKUK,
I did not expect the China designers and marketing to use boutique parts (part$).
What I expect that China designers and Marketing might do:
When they use up the stock of PCBs, they re-layout the PCB, and use the Cascode 6SN7 circuit that stephe created, significantly increasing the undistorted power.
A Marketing person would be proud to announce: New Improved Version II, Higher Undistorted Power Output.
Right?
I did not expect the China designers and marketing to use boutique parts (part$).
What I expect that China designers and Marketing might do:
When they use up the stock of PCBs, they re-layout the PCB, and use the Cascode 6SN7 circuit that stephe created, significantly increasing the undistorted power.
A Marketing person would be proud to announce: New Improved Version II, Higher Undistorted Power Output.
Right?
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Makes sense.
Cascoded 6SN7s would be rather nice. The Atmasphere M60 front end is basically a 6SN7 CCS followed by a 6SN7 cascode and then a 6SN7 driver for the output section. Low distortion - the tube CCS helps bucket loads, the driver then helps provide a low impedance low distortion too. I just made it a 12BH7A instead of 6SN7. Different beast but still will be interesting to see how the cascode performs in a different amp.
I suspect you're right - a new PCB based on the public domain eagle/kicad files would end up being of interest to many parties.
Looking forward to seeing the measured differences.
I finished up the next videos covering the actual testing using voltmeter and scope, as well as running the audio analyzer suite on it. As I suspected, it puts out right at 3W before it goes into heavy clipping, just like my initial 300B build did using a similar schematic. I was shocked to find the voltages on the MKII version are correct on 120V input, so a bucking transformer etc. isn't required, at least on the model I was shipped.
Boyuurange A50 Tube Amp Full Test Reisong - YouTube
This next video is about my initial impressions listening to the amp and doing some tube rolling. Again, it sound very similar to the results I got from my initial 300B build: thin bass and with the factory supplied china tubes, fairly shrill sounding to me. I honestly feel the little $300 Nobsound 6P1 sounds better, especially after the few minor mods I made to it.
Boyuurange A50 Tube Amp First Listening Impressions Reisong - YouTube
Boyuurange A50 Tube Amp Full Test Reisong - YouTube
This next video is about my initial impressions listening to the amp and doing some tube rolling. Again, it sound very similar to the results I got from my initial 300B build: thin bass and with the factory supplied china tubes, fairly shrill sounding to me. I honestly feel the little $300 Nobsound 6P1 sounds better, especially after the few minor mods I made to it.
Boyuurange A50 Tube Amp First Listening Impressions Reisong - YouTube
Got around to doing some modifications to the power supply and made a couple of videos. Raising the B+ definitely helped, more than I expected. With a 5AR4 rectifier, a piece of wire and a few caps, got a nice boost in the output and it sounds much better. I still plan to rebuild the front end into a cascode, but this simple to do mod made a nice improvement.
Boyuurange / Reisong A50 300B Tube Amp Basic Mods Part One - YouTube
Boyuurange / Reisong A50 300B Tube Amp Basic Mods Part Two - YouTube
Boyuurange / Reisong A50 300B Tube Amp Basic Mods Part One - YouTube
Boyuurange / Reisong A50 300B Tube Amp Basic Mods Part Two - YouTube
Excellent videos, as usual.
An old skool rule of thumb for gridleak resistors is that if it's 5 times (or more) larger than the preceding plate load, you don't have to worry about its loading of the preceding stage. If that helps make you feel better about changing the original - arf! Also, grid voltage distortion caused by (very non-linear) grid leakage current decreases linearly with smaller gridleak resistance.
What I'm trying to say is to trust your gut feeling here. And the Force be with you.
Always the best regards,
Chris
An old skool rule of thumb for gridleak resistors is that if it's 5 times (or more) larger than the preceding plate load, you don't have to worry about its loading of the preceding stage. If that helps make you feel better about changing the original - arf! Also, grid voltage distortion caused by (very non-linear) grid leakage current decreases linearly with smaller gridleak resistance.
What I'm trying to say is to trust your gut feeling here. And the Force be with you.
Always the best regards,
Chris
@Stephe - great videos.
I just watched - Audio Analyzer Suite / Analog Discovery 2 Review and Demo and I saw on one of your amp videos where you stated to use a 1:1 transformer when testing and needed when testing with the oscilloscope for safety.
So do you use the 1:1 transformer with the Audio Analyzer Suite as I did not see this in your connections? Thanks
I just watched - Audio Analyzer Suite / Analog Discovery 2 Review and Demo and I saw on one of your amp videos where you stated to use a 1:1 transformer when testing and needed when testing with the oscilloscope for safety.
So do you use the 1:1 transformer with the Audio Analyzer Suite as I did not see this in your connections? Thanks