Driver tube listening test results:
Some people may prefer the "tube-like" soft sound of the 6N1P, but it's not for me. It would be best suited to systems where only the midrange is critical. It does not have any hard edge to the sound at all. The poorly defined bass and very poor sub-bass totally rule it out for my use.
As for the slightly hard edge that I am hearing on 6N1 and 6N1P-EV, I suspect upstream causes, not the tubes themselves.
Of the three tube options I tested, the Chinese 6N1 sounds the most "transistor-like" of the three. I hear no flaws with it that would rule it out for normal use.
I conducted these tests using Russian 6P14P output tubes. I have new 6P16P-ER (10,000 hr rated) output tubes on hand for a Dynakit ST-35 build, but I have not tested them in this amplifier yet.
- Included Chinese 6N1
- Deep, controlled sub-bass
- Overall neutral sound
- "Bouncy" presentation
- Compelling to listen to
- Slightly hard edge
- Russian 6N1P
- Warmer presentation than Chinese 6N1
- Poorly defined bass
- Poorly controlled and very poorly defined sub-bass
- Not open sounding or transparent
- Somewhat 2-dimensional sound
- Not compelling to listen to
- No hard edge at all
- Russian 6N1P-EV
- Deep, controlled sub-bass
- Well-defined bass
- Overall "dark" sound with muted top octave
- Open and transparent sound
- Compelling to listen to
- Slight hard edge similar to the Chinese 6N1
Some people may prefer the "tube-like" soft sound of the 6N1P, but it's not for me. It would be best suited to systems where only the midrange is critical. It does not have any hard edge to the sound at all. The poorly defined bass and very poor sub-bass totally rule it out for my use.
As for the slightly hard edge that I am hearing on 6N1 and 6N1P-EV, I suspect upstream causes, not the tubes themselves.
Of the three tube options I tested, the Chinese 6N1 sounds the most "transistor-like" of the three. I hear no flaws with it that would rule it out for normal use.
I conducted these tests using Russian 6P14P output tubes. I have new 6P16P-ER (10,000 hr rated) output tubes on hand for a Dynakit ST-35 build, but I have not tested them in this amplifier yet.
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Update:
Hi everyone, I am still enjoying this little miracle amplifier. I have ordered a second kit that I plan to build with top quality components and upgraded transformers this time.
Anyone who wants to buy a kit for the little "Huaji Audio" amplifier can get it today for only $312.81 with United States tax and shipping included. This price is possible because of AliExpress' 11.11 sale ($4 off each $20 = $16 off) plus you can apply promo code AEUS15 at checkout to get an additional $15 off. Use this link for an AliExpress seller who is allowing both the sale discount and the promo code at the same time:
https://www.aliexpress.us/item/3256802532801472.html
I translated and updated the detailed assembly manual earlier this year, which is posted earlier in this thread. If you use the included power transformer and you have US 120 volts at your wall outlet, BE SURE to follow the modifications in this thread to reduce your internal voltages! The included transformer is designed for 110 volts, even if it is labeled 115 volts as some are.
Right now I'm using 6P14P-ER long life (10,000 hr) output tubes, and they are great for only $80 per quad. 6N1P-EV long life drivers (5,000 hours) also are working great.
It should be an interesting build when the second kit arrives and I can locate better transformers. It sounds fantastic as I built it in this thread, but I think it can be even better. Even without any upgrades, it at least equals the sound quality of the upgraded $1,400 Dynakit ST-35 that I just built, which hasn't turned out to be as good as I had expected. I expected the upgraded ST-35 to easily defeat this little Chinese "Huaji Audio" kit amp, but it has not. If I upgrade this build, I think there are a lot of possibilities. Plus, it doesn't heat up the whole room like the ST-35, which generates a whole lot of heat and drives the output tubes extremely hard. It's like a miniature fireplace. ST-35 build thread for anyone interested in that one: https://www.diyaudio.com/community/threads/new-dynakitparts-st-35-build.399961/page-14
Hi everyone, I am still enjoying this little miracle amplifier. I have ordered a second kit that I plan to build with top quality components and upgraded transformers this time.
Anyone who wants to buy a kit for the little "Huaji Audio" amplifier can get it today for only $312.81 with United States tax and shipping included. This price is possible because of AliExpress' 11.11 sale ($4 off each $20 = $16 off) plus you can apply promo code AEUS15 at checkout to get an additional $15 off. Use this link for an AliExpress seller who is allowing both the sale discount and the promo code at the same time:
https://www.aliexpress.us/item/3256802532801472.html
I translated and updated the detailed assembly manual earlier this year, which is posted earlier in this thread. If you use the included power transformer and you have US 120 volts at your wall outlet, BE SURE to follow the modifications in this thread to reduce your internal voltages! The included transformer is designed for 110 volts, even if it is labeled 115 volts as some are.
Right now I'm using 6P14P-ER long life (10,000 hr) output tubes, and they are great for only $80 per quad. 6N1P-EV long life drivers (5,000 hours) also are working great.
It should be an interesting build when the second kit arrives and I can locate better transformers. It sounds fantastic as I built it in this thread, but I think it can be even better. Even without any upgrades, it at least equals the sound quality of the upgraded $1,400 Dynakit ST-35 that I just built, which hasn't turned out to be as good as I had expected. I expected the upgraded ST-35 to easily defeat this little Chinese "Huaji Audio" kit amp, but it has not. If I upgrade this build, I think there are a lot of possibilities. Plus, it doesn't heat up the whole room like the ST-35, which generates a whole lot of heat and drives the output tubes extremely hard. It's like a miniature fireplace. ST-35 build thread for anyone interested in that one: https://www.diyaudio.com/community/threads/new-dynakitparts-st-35-build.399961/page-14
I am very curious about how your second kit turns out. I have one of these kits sitting on my shelf and now that I am in retirement (hopefully) I will be able to make time to build it. I am most interested in what transformers you decide to use as I think that will make the most difference in sound quality of anything you can do. Please keep us updated in this thread!
-david BTW
-david BTW
I am consulting with someone who custom winds transformers. I want to get rid of the metal box that covers the transformers this time and get ones that have nice end bells. Stay tuned!
@Never Get Old
Interesting sonic observations. Comparing the schematics of the ST-35 you built and Huaji amplifier also show some differences. Although the input/driver stage topology are very similar (common cathode gain stage direct coupled to a tube phase splitter), there are differences in the type of input/driver tube and also the power supply. The Huaji amplifier has a regulated B+ supply. The ST-35 you built, does not, it’s just a CLC with some extra capacitance filtering.
As you already know, the achilles heel in all these tube designs is the output transformer, so spending money there would be best especially if you like the electrical part of the circuit. It’s doubtful that the Huaji amplifier has transformers that cost more than $20 each, so an obvious area of improvement. Other areas include the power supply (for both your ST-35 and even this Huaji model). Consider designs from Neurochrome 21st century Maida v3, and also Jan Didden’s T-Reg v5.
It’s a deep deep worm hole. Enjoy it!
Best,
Anand.
Interesting sonic observations. Comparing the schematics of the ST-35 you built and Huaji amplifier also show some differences. Although the input/driver stage topology are very similar (common cathode gain stage direct coupled to a tube phase splitter), there are differences in the type of input/driver tube and also the power supply. The Huaji amplifier has a regulated B+ supply. The ST-35 you built, does not, it’s just a CLC with some extra capacitance filtering.
As you already know, the achilles heel in all these tube designs is the output transformer, so spending money there would be best especially if you like the electrical part of the circuit. It’s doubtful that the Huaji amplifier has transformers that cost more than $20 each, so an obvious area of improvement. Other areas include the power supply (for both your ST-35 and even this Huaji model). Consider designs from Neurochrome 21st century Maida v3, and also Jan Didden’s T-Reg v5.
It’s a deep deep worm hole. Enjoy it!
Best,
Anand.
If I were building one of the Chinese kits (I'm not, I have enough EL84 amps now) I'd ditch the 6N1P tubes and replace them with 12AT7s then use the parts values associated with this tube from the Tubelab SPP schematic.
Don't know if it has been mentioned on this thread but XRAYTONYB on YouTube did a full build series on this amp.
S.
Don't know if it has been mentioned on this thread but XRAYTONYB on YouTube did a full build series on this amp.
S.
Only the screen voltage is regulated though. Apparently that was done to accomodate the Chinese 6P14, which absolutely cannot tolerate over 300 volts there without self-destructing.
Yes, the output transformers will be the primary target of the upgrade. The included output transformers sound great, but if you look at XrayTonyB's bench tests on YouTube, they distort heavily below 30 Hz when you put more than about 6 watts through them. I suppose this is why the amp is rated 30Hz to 20kHz.
The power transformer also will be replaced/upgraded because, 1) I want one that actually puts out the specified 275V with a 120V input. 2) I want end bells and wire leads so I can get rid of the metal box that covers the Chinese transformers, which have solder tabs and no end bells.
Yes, the output transformers will be the primary target of the upgrade. The included output transformers sound great, but if you look at XrayTonyB's bench tests on YouTube, they distort heavily below 30 Hz when you put more than about 6 watts through them. I suppose this is why the amp is rated 30Hz to 20kHz.
The power transformer also will be replaced/upgraded because, 1) I want one that actually puts out the specified 275V with a 120V input. 2) I want end bells and wire leads so I can get rid of the metal box that covers the Chinese transformers, which have solder tabs and no end bells.
I will start a new thread for questions like that whenever I start this build. However, I am extremely reluctant to change the design at all since I know exactly how this sounds, and I love it. If I have questions like that, I'll address them in the build thread whenever I start. I will be replacing every single one of the Chinese resistors, capacitors, etc.
I'm trying to get the transformers made now. I spent all morning doing scale drawings because the new OPTs are bigger than the included ones, necessarily so. It will take 2 weeks for the kit to get here and I suspect a month or two for the custom transformers.
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I have been intrigued by this company and have corresponded with them about my rebuild. Have you contacted them? They have several EL84 type parts both power and audio output. Any comments on this company?
https://www.thermioniclab.com/en/push-pull-output-transformers/
-david BTW
https://www.thermioniclab.com/en/push-pull-output-transformers/
-david BTW
Thanks for pointing that out, yes, I see now it is the screen voltages. I bet there could be benefit with the plate voltages as well. Looks easy enough to implement.
Best,
Anand.
I did contact them a few months ago to discuss ST-35 transformers. They were nice, and they seem to have a good reputation. They are located in Greece. Their products seemed expensive compared to other vendors, and their ST-35 transformers will not fit the standard ST-35 chassis if I remember correctly.
One more note on this little amplifier kit. Unlike the ST-35 that I built, this amplifier gets the "timing" of the music right. I'm not sure how else to describe it. Imagine a band where the players aren't all playing well together and their timing is a little off from each other. So many amplifiers that I have tried over the years, both tube and solid state, seem to have that problem. This little amplifier kit, as inexpensive as it is, does not have the problem. It's great. The "timing" of the music is right.
I'm not going to discuss the ST-35 here except to say that it seems to be one of the many amplifiers that suffers from what I describe as the "timing" problem. The ST-35 is a great little amplifier, but the timing is off.
With the cover off today so I can measure the transformers. I'm glad I did the all-black paint scheme. The silver hurts my eyes!
I'm not going to discuss the ST-35 here except to say that it seems to be one of the many amplifiers that suffers from what I describe as the "timing" problem. The ST-35 is a great little amplifier, but the timing is off.
With the cover off today so I can measure the transformers. I'm glad I did the all-black paint scheme. The silver hurts my eyes!
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It is easy to get confused with the Russian lettering on the tube vs. English translations. For anyone looking for the exact meaning and labeling of the Russian tubes that I am using in this amplifier with excellent results:
Russian driver tubes
--------------------------------
6N1P-EV (6H1П-ЕВ on the tube)
6 means 6.3V
N (cyrillic H) means dual triode
1 means first type in a series of dual triodes
P (cyrillic П) means housed in a glass tube with noval socket
after the dash - these are quality indicators
nothing means 3000 hour life
E means extended life
V (cyrillic B) means 5000 hour life
Russian output tubes
-------------------------------
These Russian tubes have the identical electrical characteristics but different lifespans and mechanical attributes:
6P14P-V / 6П14П-B = 1000 hr
6P14P / 6П14П = 3000 hr
6P14P-K / 6П14П-K = 3000 hr, vibration resistant
6P14P-EV / 6П14П-ЕB
6P14P-ER / 6П14П-ЕР
6 means 6.3V
P (cyrillic П) means power pentode
14 means fourteenth type in a series of power pentodes
P (cyrillic П) means housed in a glass tube with noval socket
after the dash - these are quality indicators
nothing indicates 3000 hour life (14 watt anode dissipation)
E means extended life (life depends on the character following it)
V (cyrillic B) means a higher degree of mechanical quality with 5000 hour life (14 watt anode dissipation)
R (cyrillic P) means a higher degree of mechanical quality with >10000 hour life (gold used in the grid, 14 watt anode dissipation)
I am using 6P14P-ER (6П14П-ЕР on the tube).
Note that the included Chinese 6P14 has an unknown lifespan and only 12 watt anode dissipation (like EL84) instead of 14 watts like the Russian tubes. They sound ok and will at least get you started. If you blow one like I did (my fault), no great loss because they were "free" with the kit.
The "plain" 6P14P sounds ok to me, but I prefer the 6P14P-ER and you can't beat the 10,000 hour rated life. With 14 watt max dissipation and a 10,000 hour rating, they will last a long time in this amplifier so no need to worry about changing tubes frequently.
Russian driver tubes
--------------------------------
6N1P-EV (6H1П-ЕВ on the tube)
6 means 6.3V
N (cyrillic H) means dual triode
1 means first type in a series of dual triodes
P (cyrillic П) means housed in a glass tube with noval socket
after the dash - these are quality indicators
nothing means 3000 hour life
E means extended life
V (cyrillic B) means 5000 hour life
Russian output tubes
-------------------------------
These Russian tubes have the identical electrical characteristics but different lifespans and mechanical attributes:
6P14P-V / 6П14П-B = 1000 hr
6P14P / 6П14П = 3000 hr
6P14P-K / 6П14П-K = 3000 hr, vibration resistant
6P14P-EV / 6П14П-ЕB
6P14P-ER / 6П14П-ЕР
6 means 6.3V
P (cyrillic П) means power pentode
14 means fourteenth type in a series of power pentodes
P (cyrillic П) means housed in a glass tube with noval socket
after the dash - these are quality indicators
nothing indicates 3000 hour life (14 watt anode dissipation)
E means extended life (life depends on the character following it)
V (cyrillic B) means a higher degree of mechanical quality with 5000 hour life (14 watt anode dissipation)
R (cyrillic P) means a higher degree of mechanical quality with >10000 hour life (gold used in the grid, 14 watt anode dissipation)
I am using 6P14P-ER (6П14П-ЕР on the tube).
Note that the included Chinese 6P14 has an unknown lifespan and only 12 watt anode dissipation (like EL84) instead of 14 watts like the Russian tubes. They sound ok and will at least get you started. If you blow one like I did (my fault), no great loss because they were "free" with the kit.
The "plain" 6P14P sounds ok to me, but I prefer the 6P14P-ER and you can't beat the 10,000 hour rated life. With 14 watt max dissipation and a 10,000 hour rating, they will last a long time in this amplifier so no need to worry about changing tubes frequently.
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Interesting to note that Decware chose 6N1P-EV driver tubes for their Zen Triode amplifier. They work great in this amplifier.
We ship it with Russian ... variant of the 6922 called the 6N1P-EV. This is a warmer and nearly bullet-proof tube that exemplifies the term 'liquidity'.
https://www.decwareproducts.com/se84ufo
We ship it with Russian ... variant of the 6922 called the 6N1P-EV. This is a warmer and nearly bullet-proof tube that exemplifies the term 'liquidity'.
https://www.decwareproducts.com/se84ufo
Just remember that variant doesn’t mean substitute. They are different tubes and both good, as such the circuit needs to be optimized for each tube.
Best,
Anand.
Best,
Anand.
I was just interested in the fact that Decware chose it and thinks it sounds good, not trying to put a different tube in this amp. This amplifier is designed for 6N1 / 6N1P / 6N1P-EV, and the 6N1P-EV sounds great.
I'd love to fiddle with one of Decware's 2.3 watt single-ended EL84 amplifiers to see what 2.3 watts actually can do in my living room, but I'm not willing to pay for the iron to build one and find out.
I'd love to fiddle with one of Decware's 2.3 watt single-ended EL84 amplifiers to see what 2.3 watts actually can do in my living room, but I'm not willing to pay for the iron to build one and find out.
@davebtw Discussion of possible replacement OPTs: https://www.diyaudio.com/community/...er-recommendations.405967/page-7#post-7523612
I am looking at transformers from Primary Windings in the UK if they will fit. I'll know Monday when the new power transformer arrives. The metal cover that goes over the three transformers will be left off to get more available space, requiring a set of 3 transformers with protective end bell covers.
A new build thread for the second amplifier will be coming soon. The kit arrived yesterday. My custom power transformer is arriving Monday according to USPS. I can then measure for OPTs.
New here and really tempted to make this my first build. I read through this thread yesterday but still have a couple questions. Full discloser I was nursing a sick kid while making my way through and was slightly distracted, so don't skewer me if I ask a question that was covered in here 🙂
First of all, I have some soldering experience but have never tackled a full kit like this, I've built a couple guitar fuzz pedals. Is this too much for my first build? Or is this a good place to start?
Second, I'd really love to be using EL84s as I have a couple nicer quads that are just sitting around here. Has anyone actually tried them with any luck? How'd they sound compared to the 6P14 variants?
Thanks!
First of all, I have some soldering experience but have never tackled a full kit like this, I've built a couple guitar fuzz pedals. Is this too much for my first build? Or is this a good place to start?
Second, I'd really love to be using EL84s as I have a couple nicer quads that are just sitting around here. Has anyone actually tried them with any luck? How'd they sound compared to the 6P14 variants?
Thanks!
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Have you seen the XraytonyB YouTube build series? The link is on page 1 of this thread. 6P14s and EL84s are for most purposes, including use this amp, identical.
Cheers, Steve
Cheers, Steve
- This also was my first time building a full kit. Previously I had done small projects and upgrades, but never a full kit. Thus, this thread was born.
- I would practice on a small, inexpensive test project to make sure you are comfortable with soldering properly and consistently. There are lots of small, fun projects on AliExpress. Something like this: https://www.aliexpress.us/item/3256805926540684.html
- Use a good soldering iron and good rosin-core electronics solder. My iron is old and desperately in need of replacement. A good iron makes the work much easier. Keep the tip clean.
- I hate lead-free solder. Ordinary 60/40 is fine. I use Kester 2% silver solder, but a little extra care is required.
- The components on the PCBs are soldered onto it outside the amplifier so you can work on it easily, inspect it thoroughly, and clean off all of the soldering flux before mounting it inside the chassis. You do need to make sure that the solder has flowed through the hole and you have a solid solder joint on both sides, especially the tube sockets. I used a scrap of cardboard to ensure that the required gap between the components and the PCBs was proper.
- You must have and be comfortable with using a voltmeter to test your voltages, and you MUST respect the 340 volts inside the chassis! Always keep one hand behind your back is the rule. One nice thing about the power supply is that it has LEDs on it to help indicate that high voltage is present.
- Fitting everything into the chassis during final assembly and routing all of the wires neatly is the most tedious part of the build I think. It's a small chassis with a lot of wires inside. Be patient and pay attention to details.
- Attaching the heater wires to the PCB I would say was the part of the build that tried my patience the most. It requires patience. Don't rush it.
- I highly recommend watching the video series by XrayTonyB for this amplifier on YouTube. He does an excellent job. You do not need to re-orient the output transformers as he did in the video.
- Please download and thoroughly read the directions that I translated. There is a link to them earlier in this thread. If you can't access that link, I can figure out a way to get them to you.
Notes:
- If you are in the USA and have 120V at your wall outlet like most people do now, you need to change the resistor in the power supply to 200 Ohms 10 watts as I noted. I also had to use a small resistor on the driver tube heaters to lower that voltage.
- Also, if you are in the USA and have 120V at your wall outlet, you need to use the included "spare" 91V Zener diode in the power supply to drop the regulated voltage as noted in this thread. I broke the one that came in the kit and had to order one. It was fragile and I broke it in half. Oops.
- There is a little wire jumper on the PCB that is not noted in the directions. The board will work without it I think, but I recommend installing that jumper.
- Two 100 Ohm 2 watt resistors are used on the output tube heaters as shown in the instruction manual and they are not included in the kit.
- I opted to replace one very old Philips power supply capacitor that comes in the kit. The others seem fine. It only cost a few dollars. Better safe than sorry.
- I used Nichicon UKA series 220uF cathode bypass capacitors instead of the weird ones that come in the kit. It now appears that 470uF might be a more appropriate value, and I have changed them to Nichicon UKA 470uF in my amplifier. Some people prefer Elna. I checked and Elna Tonerex 470uF are available.
- I really didn't like the hookup wire that came in the kit, and I replaced all of it.
- I lowered the bias a little bit by using 160 ohm resistors instead of the included 150 ohms.
The latest version of the kit comes with PSvane EL84 tubes instead of Beijing 6P14, but I am not sure if they are authentic PSvane tubes. Good quality EL84 tubes should be fine. What do you have?
I'm here every day and I will be for a good while as I am building a second one of these amplifiers and likely will be trying a little single-ended kit after that. I'm happy to answer questions about the kit as I already built one and I have a second one sitting here in progress. 👍
Sounds great! I spent some time listening to it last night. Maybe I'll play some Christmas music tonight.
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