This isn't about cheap Asian-sourced amps/preamps -- but it IS about economics and value :)

J. Frum

Secret Society Member
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Mark, I think it'd make you feel good to buy the JBH Tube single-ended EL34 amp, available for $270 shipped with tubes, or $245 without.

Then you can report back to us about whether it was worthwhile!

I have no ulterior motive whatsoever, and would never use you as a guinea pig...

TB2LvxpbpHzQeBjSZFzXXa__FXa_!!2529159729.jpgEL34 SEP.jpg
 

paul_b

Active Member
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but this seems to be a sort of unsupported fear stoking that helps perpetuate common misconceptions. incendiary statements like that should be backed up by facts. has anyone documented a house fire started by audio gear? maybe so. if so, cite to it please.
I have several shorted power transformers from Chinese amps in my workshop, I'm happy to send you one if you'd like to pay for shipping. Depending on which winding shorts, you can do a whole lot of damage. For example, if we have an 845 amplifier and the 10V winding in the transformer shorts, it will burn up the transformer (the shorted 10V winding will cause no HV current to be drawn by the output tube, and the 10V winding can probably suck down 40A of current without popping a fuse). Luckily the unit that I have blew the HV winding instead. This particular pair is the "improved" design that wasn't supposed to blow up like version 1. (Version 1 had doubled up 500V caps in series for a power supply rail that would be about 1000V if you put 110V into the power transformer, but we have 120V in the US).

I have had a low voltage winding short, and though it didn't burn my house down, it did completely destroy the piece of furniture it was sitting on and the smell was atrocious. I knew my house wasn't burning down because all of the smoke was white.

As I pointed out above, a recent Nobsound kit I worked on contained counterfeit capacitors. While a blown capacitor isn't usually likely to cause a fire, these have the pressure relief vents covered by a piece of countertop laminate. I had planned to put these on my HV supply to see how long they took to blow, but I'm concerned that doing that would be more dangerous than normal due to that glaring assembly error.

In the early 2000s, Dell computer had an issue with a particular capacitor supplier using a stolen electrolyte formula. These failed caps would burp out a bunch of hydrogen gas, which is a serious fire hazard. This mistake really put these issues on the map.
 

fiddlefye

Senior Member
Site Supporter
I have several shorted power transformers from Chinese amps in my workshop, I'm happy to send you one if you'd like to pay for shipping. Depending on which winding shorts, you can do a whole lot of damage. For example, if we have an 845 amplifier and the 10V winding in the transformer shorts, it will burn up the transformer (the shorted 10V winding will cause no HV current to be drawn by the output tube, and the 10V winding can probably suck down 40A of current without popping a fuse). Luckily the unit that I have blew the HV winding instead. This particular pair is the "improved" design that wasn't supposed to blow up like version 1. (Version 1 had doubled up 500V caps in series for a power supply rail that would be about 1000V if you put 110V into the power transformer, but we have 120V in the US).

I have had a low voltage winding short, and though it didn't burn my house down, it did completely destroy the piece of furniture it was sitting on and the smell was atrocious. I knew my house wasn't burning down because all of the smoke was white.

As I pointed out above, a recent Nobsound kit I worked on contained counterfeit capacitors. While a blown capacitor isn't usually likely to cause a fire, these have the pressure relief vents covered by a piece of countertop laminate. I had planned to put these on my HV supply to see how long they took to blow, but I'm concerned that doing that would be more dangerous than normal due to that glaring assembly error.

In the early 2000s, Dell computer had an issue with a particular capacitor supplier using a stolen electrolyte formula. These failed caps would burp out a bunch of hydrogen gas, which is a serious fire hazard. This mistake really put these issues on the map.
Even companies such as Apple couldn't manage to keep bad counterfeit caps out of their production stream. My father had an early 2000s iMac that had the screen fail twice. The cause was a failed counterfeit cap and it was replaced under warranty. Even then the replacement cap turned out to be yet another counterfeit which failed. Third times turned out to be the charm.
 

paul_b

Active Member
Site Supporter
Mark, I think it'd make you feel good to buy the JBH Tube single-ended EL34 amp, available for $270 shipped with tubes, or $245 without.

Then you can report back to us about whether it was worthwhile!

View attachment 12384View attachment 12385
If the mods allow it, I can buy one and do an objective review of the measured performance, examine the legitimacy of the parts, and present any safety concerns.
 

mhardy6647

Señor Member
Site Supporter
If the mods allow it, I can buy one and do an objective review of the measured performance, examine the legitimacy of the parts, and present any safety concerns.
Why the heck wouldn't they*? Did you ever read the rules here? :)


* In (some) seriousness, I suppose there could be some concerns about slander, but, having poked considerable fun at the "Monoprice" 25 watt hybrid amplifier (given to me by its hand-me-down owner to evaluate) Elsewhere, I am in no position to talk!
 
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J. Frum

Secret Society Member
Site Supporter
If the mods allow it, I can buy one and do an objective review of the measured performance, examine the legitimacy of the parts, and present any safety concerns.

That sounds unabashedly awesome.

I dare say, though, that at that less than $300 delivered, a modest mod/rebuild and retubing are probably a given. I'd be more interested in whether the fundamentals of the chassis and iron are sound. The fit and finish look like a cut above the standard Nobsound fare. Even including a big choke at this price!

I don't think Nobsound is a manufacturer as much as a clearinghouse, btw.

Beware the knock-on effect, though: Anything less than a resounding denouncement will soon result in multipage threads somewhere loudly proclaiming "$250 Tube Amp is GIANT KILLLLR!" and "JBH Tube - Just Try This One Weird Trick".
 

mhardy6647

Señor Member
Site Supporter
Beware the knock-on effect, though: Anything less than a resounding denouncement will soon result in multipage threads somewhere loudly proclaiming "$250 Tube Amp is GIANT KILLLLR!" and "JBH Tube - Just Try This One Weird Trick".
Just beware -- that one weird trick might be hidin' a couple of ICEPower modules under the deck.

😎
 

mhardy6647

Señor Member
Site Supporter
Is the third rule that there are only two rules?
I mean, there is a Zeroeth* Law of Thermodynamics, because they realized that they forgot one when the first Three were promulgated. :)

Speaking of metaphysical conundrums -- here's a personal favorite.

This sentance has three erors in it.

🤪
________________
* or is that Zeroth?
 

prime minister

Site Owner
Staff member
Is the third rule that there are only two rules?
I mean, there is a Zeroeth* Law of Thermodynamics, because they realized that they forgot one when the first Three were promulgated. :)

Speaking of metaphysical conundrums -- here's a personal favorite.

This sentance has three erors in it.

🤪
________________
* or is that Zeroth?

The "enjoy" at the end of the rules feels more like a command then a statement.
 

paul_b

Active Member
Site Supporter
I'm just now noticing that it's 7 days for "order processing", not shipping time. This could take a while!
 

paul_b

Active Member
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This amp actually looks fantastic in my opinion. I really like the wrinkle paint, and I especially like that it didn't smell like the inside of a Harbor Freight store when I opened the box. Based on the packaging I can tell that this came out of the same factory as the Nobsound stuff, as they have a unique way of packing the tubes.
 

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paul_b

Active Member
Site Supporter
20190426_202151.jpg
Sadly the safety ground isn't connected to anything and that heatshrink isn't shrunk. To be fair, I don't use heatshrink for those connections on my own stuff.
20190426_202210_HDR.jpg
More NAPFCM CEBNVCON caps. There's only one this time at least, and it's not in the most heavily abused position, but it will be replaced. I have a real NCC 330uF/450V cap on order to replace this.
20190426_202245.jpg
I have absolutely no idea what brand that marking is, but it is at least marked!
20190426_202314.jpg
There are a few connections in the amp that aren't wrapped where they could be. This ridiculously oversized power switch is also a familiar Nobsound part.
20190426_202751.jpg
This pot is not made for the application. There are small/cheap volume pots like this with solder lugs, and these connections would be far more secure if the correct pot was used. Also note the grid stopper leaving the pot and heading to the grid, but there's also a grid leak resistor connected to the grid. This negates the effectiveness of the grid stopper, though a 6SL7 doesn't exactly need one.
20190426_204221.jpg
This amp has a big cap poking up through the chassis and it functions as the first capacitor in the power supply. I felt much more at ease when turning this amp on knowing that the counterfeit cap next to this one wasn't the first cap in the power supply, but when I look this cap up it is listed as both a motor run and a motor start capacitor. If it's a motor start capacitor, this will be a short lived amp! Just based on its construction, size, and that it's listed that it's filled with vegetable oil, I'm going to write that one off as a translation error. Again, I'm happy to see a name brand on this cap, even if it's one I'm not familiar with.
 

paul_b

Active Member
Site Supporter
I traced the circuit for this amplifier and the EL34 is run as a pentode with screen grid voltage dropped from the B+ with a resistor. The 6SL7 also draws current from this lower voltage supply. There isn't anything in the circuit that jumps out as being strange or poorly conceived. 20190426_211915.jpg
The problem with this design is that the book values for getting pretty hefty power from an EL34 call for lower voltage and about twice the current that's being run here.
 
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