$149 Monoprice Tube Hybrid Amp

+1 from me on Dat Chu's request for more information about this procedure for reducing/eliminating unwanted noise with these amps. The reports of noise in the amps has kept me from buying one, but if there's a way for non-techies (I'm capable of following instructions, but I don't have the foundational knowledge or experience to "figure it out" on my own) like myself to make some modifications to improve it, I would love to know what they are so I can reconsider buying a Monoprice tube hybrid amp.

(I'm currently using a Denon AVR-3801 receiver, driving up to 140 watts of power into Elac Debut B6 bookshelf speakers for stereo-only listening of CDs/SACDs. Sounds great, aside from the frequency drop-off of the bookshelf speakers around 44Hz, but I can't help but wonder if some "tubey-magic" could add an extra something that would be more musical and pleasing that what I'm getting with my current setup.)

Craig.

 

240v in Australia. Has anyone seen a problem with using a transformer ( to step down the power) when using this type of kit? Eg - will the transformer add noise that we know of?

 

Regarding HeadPhones and headphone jack and if the headphone jack is reduced etc - I wrote to Nobsound and this is the response.

Hi dear Mr Chris
Wish you have a nice day
we recommend you choose the 16-160ohm headphones
If you choose the 600 ohm headphones the sound will be very low
regards
Douk Audio -Vivian

 

My MP tube amp crapped out - no sound from either line input or Bluetooth, although the BT device does pair with the amp and line inputs do cause the meter to move.

I went ahead and ordered a full set of Soviet tubes from Ukraine. For a total investment of $10.28, we'll see if this fixes the problem.

I noticed that the glass on one of the 6N1 tubes is darker than the other, and the top is dark black (looks burnt) instead of mirrored like the other:

 

I haven't used one on this kit. However, I do use a stepdown transformer with my turntable, and it adds no noise to the signal that I can detect (the transformer itself emits a low but audible hum).

 

I figured out what the problem is, sort of. The headphone jack is dodgy, and it can cause the speaker terminals to mute if it gets even the slightest tap. I tapped them again, and it woke right up!

Meanwhile two of the four Soviet tubes have arrived from Eastern Europe and it sounds fine.

Just for fun I tried this amp with my LS50's... and it sounded like crap! It was clearly straining to drive them. It sounds shockingly good with Pioneer SP-BS21-LR's though!

 

Hi, I am going to be buying the 50w monoprice tube amp Amazon.com: Monoprice Tube Amp with Bluetooth 50-watt Stereo Hybrid and Line Output,Black - (116153): Electronics and am looking at rolling the tubes for them. I could not send you a PM, for some reason the site did not let me do that. I am interested in getting 6n2 and 6p1 replacements. Please send me a PM if you can and we can take this offline if you have them. Thank you. Gopal

 

Anyone figure out how to get rid of the whistling/ringing coming out of this thing? Causing me to get twitchy..

 

I switched to the BT connection - and it sounds better - I think the noise was coming from my PC through the simple RCA out.

 

BT = BlueTooth?

I didn't think it was possible for BlueTooth to sound better than RCA connection (all else being equal). In my experience with car stereos, for example, BlueTooth connection of my phone to the car stereo - to play the MP3s on my phone - always sounds way worse than connecting it via USB or some other connection.

Craig.

 

Something must be wrong with the RCA input or his PC.

 

Here's a video of a guy disassembling another brand of this type of amp, the gist is that the tubes don't do anything but light up. Has anyone disassembled a Monoprice version to see what's going on inside?

 

Here is a quick video of the amp before disassembly.

 

Take the tubes out. Hear anything? No.

If you read back, this thread discusses using Russian and other tubes to tweak the sound. The glass is definitely in the circuit.

 

in the video he shows that the tubes are simply completing a circuit and can be jumpered with 2 wires to produce sound, completely bypassing the tubes. Still I am curious about the Monoprice version specifically

 

I'm sure they run at or near the lower limits of their specs, voltage and so on. They are there for show but also for a tube sound. Rolling various tubes does have a nice effect in some cases. My MP is hooked up in a guest room, but I use it occasionally when I drag a project in there needing some room to spread out. I haven't had a problem with the MP other than some noise when I tried the headphone jack with lower impedance phones.

My unit will also not give full volume for at least 2-3 minutes after startup. Those tubes have to get glowing and then it plays plenty loud and clean with any speakers I own.

 

It's a 100 $ amp that supports BT and RCA inputs and has some glowing tubes and sounds pretty decent so who cares. Ignorance is bliss.


My issue was my monster PCs fan noise coming through the output I was using - I need to invest in a nice sound card until then I'll use the BT which can be a pain when it doesn't connect.

 

Hey Hey,

1st time posting here and signed up just some I could post about my MP 25watt Hybrid!

I am really liking this little guy and have had my eye on one for a while now. I recently was able to pick one up, shipped to my door, for a touch over $80 after shipping. Wow. I am not sure how I did it, it is NOT a refurb. I wish I had splurged a bit more for the 50 watter if only for the all black scheme.

Well with that said, I have had the amp for less than a month and I have already done a mod:

 

IMG_20170814_163910 by Mike Moore, on Flickr

IMG_20170903_100219 by Mike Moore, on Flickr

 

You may want to get a cable that connects your pin (on the bottom of your iPod) to the amp line in. Better signal. - I use an iStreamer (DAC) between my iPod and home stereo. Sounds awesome too!

 

I have been looking for something that would utilize the 30pin connection; thanks for the suggestion. Right now, if I am using the headphone jack, it is pretty easy to overload the input and get distortion on drum hits. The strangest thing is I hear this input distortion, through the speakers, even when the volume is turned down to a minimum. Anybody else experience this? Right now, I just back off the volume and that resolves the issue (impedance mismatch?)

 

Use the 30-pin line-out connector.

 

Thank you for sharing and welcome to the festivities.

Michael

 

What video do you mean? He didn't do that in the videos linked above. He said he wasn't exactly sure what the tubes did in the circuit but he would try to figure out whether he could bridge the main amp board to bypass the connector to the tube board and see if it would still work. He suspected it would but didn't say that for sure.