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On Impulse I ordered a Boyuu Reisong A10 EL34, class A. Any experience? Add your opinion on it.
- Thread starter Old Guy8
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BMC
Active Member
Rotated ADS L880s (89db spl) in to replace L470/2 (92db spl). Oversized for 11'x12' room, maybe. These 10" three ways have the sweet ADS midrange. They play plenty loud for my jazz listening. That 6 watts goes a long way. At 7 feet with volume at 12 o'clock gives 70-75 dbs readings. Higher than I need.Sounds better than it has a right to!
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Valko67
New Member
Thanks BMC , yes i bought the adapter too but first will give a try with The 6N2P-EV , and will upgrade them later on , i read about the 6CA7-Z X 2 people chosen for upgrade , i presume this is with the 12AX7 adapter , this would be a little cios in compare to the 123 € for my order amount payed now , yes , i am sure they will be 123 times worthed to spend , so Many many thanks you guy's and specialy you BMC for your experience and to share them , very nice and highly appreciated , i wanted to mention this , and i would doing the same with pleasure for one other audiophil friend here on AudioKarma.org Forum , .....Thank YOU ,....my best greetings to all Peoples here , Have sweet Sunday Folks ;-)
Valko67
New Member
they look very sweet
Got my A10 today! Wow! Thank you everyone for helping me this choice!! Currently breaking it up with forte iis, Spotify via bluesound node 2i. Comparing Herb Alpert music on Spotify with my Cambridge cxa81. So happy. Not as much bass compared to ss. But will let it break in. Ordered the tungsol el34b and the voshkods for tube rolling in the future!
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Would like some advise, I came across a gentleman who is selling vintage US tubes near me. He is selling them in match pairs and quads and have the following:
5AR4/GZ34, 6CA7/EL34, 6L6 , 6SN7, 6V6, 5751, 5881, 6550/KT88 and my question is: would be just drop in replacements for the default preamp and amp tubes? Ie, no adapter. I appreciate any advise. Many thanks!
5AR4/GZ34, 6CA7/EL34, 6L6 , 6SN7, 6V6, 5751, 5881, 6550/KT88 and my question is: would be just drop in replacements for the default preamp and amp tubes? Ie, no adapter. I appreciate any advise. Many thanks!
Jeff banker
Active Member
I’m thinking about ordering a Reisong amp. Before the world goes crazy again and can’t be shipped. If you know what I mean. It may be somewhere in the thread and I missed it. What preamp would you recommend using with this?I would like to keep
Somewhat to a budget like this amp.
Somewhat to a budget like this amp.
I'm no tube expert, BTY.
Since you have a set of pre and power tubes already in order. I would just get a spare rectifier tube for now. Try out the stock Chinese and the Russian tubes you ordered. It will take some time to break in the tubes, and judge them. You'll have plenty of time to decide if you want to try a third set of tubes. I'd allow 50 hours plus for break in tube set.
My 2 cents
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This is an accessory that I saw recommended in AK for tube gear. A plug-in ground fault device (GFCI). If there's a power dropout and power comes back on, it stays off until manually reset button pressed. It would save tubes from coming back on. Allowing you to wait a safe time to turn back on. Maybe save tube life. I use with my tube amps.
Not all brands have manual reset. I mistakenly bought a Husky brand that automatically turned back on in error. This one in pic, is Carol brand. Was $43 checked price today. Maybe cheaper elsewhere. I don't have any affiliation with sellers.
My 2 cents.
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FlaCharlie
Super Member
Welcome to AK.
So, is he selling tubes or amps? Maybe both?
With all due respect, people who are new to tubes don't usually have enough knowledge to determine whether a vintage tube or tube amp is "worth the price". I know you're excited about getting a tube amp but if you take some time to learn you will avoid a lot of costly mistakes.
Also, before you ask about specifics, discussions of value are not allowed on this forum. There's another forum called Dollars and Sense for that.
I would agree with Old Guy8. Listen to the stock tubes and whatever you already ordered before you buy more.
Tube sellers use the term "matched" very loosely. Depending on the seller it can mean pretty much anything. For many, it's just a marketing term and has no technological basis. Just because they might be the same brand, the boxes look the same, same date code, etc that does not mean they are matched electrically at the real world voltages they will see in your amp.
But, to answer your question . . . the only ones that are really suitable are the 6CA7/EL34. Some of the others will drop in but will change the voltages in the amp because it was not designed for them.
Specifically, using some of the other output tubes will cause the heater voltages to rise because their heaters draw less current. Given that most Chinese amps have power transformers that are designed for 110v rather than the 120v+ that most homes have, your heater voltages may be on the high side already. Doing anything that raises them even higher would not be wise.
The 5AR4 rectifier will also drop in but it will raise the B+ voltage because it drops less voltage than the stock tube.
Valko67
New Member
FlaCharlie
Super Member
This is a prime example of what I just posted about the possible pitfalls of using different tubes.
The 7581A will "work" in place of an EL34, no adaptor is required. BUT, it's heater only draws .9A while the EL34's heater draws 1.5A (67% more current). So two 7581A output tubes are draw a total of 1.8A vs 3A for the EL34s. If you draw less current the voltage rises.
According to the schematic, the power transformer used in the A10 has a 110v primary. The 6.3v secondary is rated at 3.5A and the stock output tubes only draw 3A. So, even if it's fed 110v from the wall, the heater voltage will be slightly high.
What's your actual wall voltage? In almost all cases it will be over 120v. In some places you might see 124v, 125v, depending on the time of day. So, even with the EL34s, drawing 3A, the heater voltage will be quite a bit higher.
Now, if you drop in the 7581A, which draws less current, your heater voltages will be even higher. Running heaters with excessive voltage will drastically reduce the life of the tube. It could even burn out the heater.
How high is too high? Here's the data sheet for the 7581A. The heater voltage is specified at 6.3v +/- .6v. It's a pretty safe bet that you are exceeding that maximum voltage. You may even be exceeding it, or cutting it really close, with the EL34s.
https://tubedata.altanatubes.com.br/sheets/127/7/7581A.pdf
I would definitely recommend that you get a meter and measure the heater voltages.
Tube rectifiers create a voltage drop in the high voltage supply (known as B+). The amount of drop will vary depending on the circuit but, basically, the 5AR4 drops very little (17v).
Unfortunately, it's difficult to find full information on some of the Chinese rectifiers. The Chinese 5Z4P is not the same tube as the American 5Z4, for instance. It seems to share some characteristics with a couple of American types. Except for the fact that it's indirectly heated and has a different base, it looks essentially the same as the American 5AZ4 electrically.
So, again, you really need to measure the voltages. If it has a low voltage drop, like the 5AR4, no problem. If it's like the 5AZ4, which drops 60v, then you're raising the B+ substantially by installing a 5AR4.
This would change the operating points throughout the amp. In addition, some of the lower cost Chinese amps are known to use parts that are run right at the ragged edge. If those parts are run at higher voltages, they may fail. There have been posts in some threads showing such failures, even when the amps are running in stock form.
So, while some other tubes will plug in and "work", there could be serious consequences unless you measure and make adjustments to the circuit to compensate. Most buyers of these amps seem to be new to tubes and are unlikely to have the expertise to go poking around inside an amp that has a few hundred volts inside (which could be deadly).
So, my suggestion is to use only the tube types that came with the amp.
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BMC
Active Member
Thanks for the comments, FlaCharlie. I was going by the DIY thread that was linked in this thread. They were recommending KT66, 6L6GC and equivalents with no bias adjustment necessary.
I’ll look at the voltages now that you mentioned the heater issue. I also use 12AX7 with adapters which draws 12v vs the 6.3 for the 6N2. So testing is in order.
I’ll look at the voltages now that you mentioned the heater issue. I also use 12AX7 with adapters which draws 12v vs the 6.3 for the 6N2. So testing is in order.
FlaCharlie
Super Member
Well, this amp doesn't have adjustable bias. It has what's known as cathode bias, or sometimes it's called self-bias. So it's not that different tubes don't need to be biased differently, it's that it's not possible to bias them differently.
Anytime someone claims that a variety of output tubes can be used without any bias changes what they aren't telling you is that, for most of the choices, the operating points are not optimal, they are a compromise.
Different tubes operate best under different specific conditions - certain plate voltages, screen voltages, bias currents and output transformer loads. It's not one size fits all.
Also, using a 12AX7 with an adaptor doesn't change the heater voltage. The 6N2 can only be run at 6.3v. The 12AX7 can be run at either 6.3v or 12.6v, depending on how it's wired. And the pins of the two tubes are arranged differently. The adaptor just allows you to use either one without having to rewire the socket. The specs of the 6N2 are actually closer to the 5751. Both have an amplification factor of 70 vs 100 for the 12AX7.