Monoprice 50w Hybrid Amp

Conradicles

zingo wrote: »

Well it looks nice!

Any initial impressions?

No loud buzzing noise like the hybrid I sent back. Gets pretty warm. Actually, really warm as expected.

Sound is a bit smoother than the hybrid. Still, the bass is a bit weak compared to the other amps I have rotated thru this little rig. Build quality is really good for a $230 tube amp. Great deal.

mhardy6647

the weak bass is partly endemic, but (probably) mostly represents the quality (or lack of same) of the output transformers. A single really good PP EL84 output transformer would cost [edit] about as much as the whole amplifier is sold for.

zingo

Congrats on a neat budget amp! Enjoy!

delkal

Just a heads up. The Monoprice 50 watt hybrid is on sale again for $160. It also appears you can get another 15% off with the coupon on the home page.

Its been a few months. Any updates from the people that bought one earlier?

Still running? Buzzing? Fires?

https://monoprice.com/product?p_id=16153

zingo

I’ll A/B it against my tube preamp and similar powered SS amp and report back.

mark090852

Mine is still working fine. For what I paid for it, and it's location in our vacation home, it was not money wasted. And, as I said before, my wife likes the looks of it a lot! I'm hoping that she will start to like the looks of this even more....so much so that she FORCES me to buy one!

https://www.mcintoshlabs.com/products/integrated-amplifiers/MA252

zingo

With upgraded tubes, it’s a darn fine amplifier. I am listening to the Monoprice integraded with two way monitors and it is well worth the money against a decent tube preamp and solid state amp; $500+ on the used market. The bluetooth input is decent and easy, but lower quality than lossless over WiFi. It’s a nice unit and better than anything I’ve heard at the price.

Clipdat

I'm glad that you are enjoying it. I didn't mind the sound it put out either. However, certain other things about it bothered me like the turn on transients, and the disgusting burned chemical/electronics smell that it exuded while powered on.

Edit: I'm referring to the 25w version. Maybe the 50w one has better build quality.

headrott

zingo wrote: »

The reviews on these amps have been mixed, but seem to be improving as Monoprice has tweaked them over the last few years. I had eyed them out of curiosity, but never felt like spending $200 for a maybe.

But today, Monoprice emailed that the unit is currently 20% off. I went to their website to check the reviews again, and the flash page offered a 20% code. I applied it assuming it wouldn’t work, but it did! I clicked checkout and it applied free one-day shipping; with tax and one-day shipping the unit cost me $136.

I’ll try the unit out and compare it to my Denon PMA-2000, but I see a great value in a Bluetooth integrated amp for under $150 with a warranty.

https://www.monoprice.com/product?p_id=16153

Just saw this. What about the VK-200 I bought from you? That is surely better than the Monoprice amp, right?

zingo

That was a great BAT amp and I loved the sound driven by a balanced PASS clone preamp.

zingo

Clipdat wrote: »

I'm glad that you are enjoying it. I didn't mind the sound it put out either. However, certain other things about it bothered me like the turn on transients, and the disgusting burned chemical/electronics smell that it exuded while powered on.

Edit: I'm referring to the 25w version. Maybe the 50w one has better build quality.

Yes it seems the 25w version under performs the 50w beyond the power rating from feedback on both, and mine doesn’t have any smell. Have you opened it up to look for something funky or melting?

mhardy6647

The 25 watter in question (it may be recalled) resides - or is at least being held hostage, much like @mrbiron's Reduction phono preamp - in New Hampsha now
It does not smell when in operation, and I don't find its power on/power off utterances particularly disquieting.

I was fiddlin' with some borrowed loudspeaker cables a little while ago, though -- and, after a fairly careful (and disappointing) audition of them with the aforementioned 'hybrid' amp, swapping to a good amplifier did reveal that the 25 watter (even with halfway decent Rooskie tubes swapped in) does leave much to be desired in terms of flesh-and-blood thereness compared to, say, the AmpCamp Amp

http://www.hifihaven.org/index.php?threads/unity-audio-cancer-fighter-speaker-cable-reviews.3476/page-4#post-75264

mark090852

zingo wrote: »

With upgraded tubes, it’s a darn fine amplifier. I am listening to the Monoprice integraded with two way monitors and it is well worth the money against a decent tube preamp and solid state amp; $500+ on the used market. The bluetooth input is decent and easy, but lower quality than lossless over WiFi. It’s a nice unit and better than anything I’ve heard at the price.

Since I am new to tubes (except for back in the day when my dad would send me down the street to the drugstore to pick up replacement tubes for our tv when it went on the fritz), what tubes would be a good upgrade for the 50w, and where would I get them? I'd appreciate any recommendations you could share with me.

verb

mhardy6647 wrote: »

The 25 watter in question (it may be recalled) resides - or is at least being held hostage, much like @mrbiron's Reduction phono preamp - in New Hampsha now
It does not smell when in operation, and I don't find its power on/power off utterances particularly disquieting.

I was fiddlin' with some borrowed loudspeaker cables a little while ago, though -- and, after a fairly careful (and disappointing) audition of them with the aforementioned 'hybrid' amp, swapping to a good amplifier did reveal that the 25 watter (even with halfway decent Rooskie tubes swapped in) does leave much to be desired in terms of flesh-and-blood thereness compared to, say, the AmpCamp Amp

http://www.hifihaven.org/index.php?threads/unity-audio-cancer-fighter-speaker-cable-reviews.3476/page-4#post-75264

I feel responsible for your disappointment

mhardy6647

No, no, no!

That amp need make no apologies at all for itself, on its own terms. It doesn't sound bad at all... think about the price, man!

mhardy6647

mark090852 wrote: »

zingo wrote: »

With upgraded tubes, it’s a darn fine amplifier. I am listening to the Monoprice integraded with two way monitors and it is well worth the money against a decent tube preamp and solid state amp; $500+ on the used market. The bluetooth input is decent and easy, but lower quality than lossless over WiFi. It’s a nice unit and better than anything I’ve heard at the price.

Since I am new to tubes (except for back in the day when my dad would send me down the street to the drugstore to pick up replacement tubes for our tv when it went on the fritz), what tubes would be a good upgrade for the 50w, and where would I get them? I'd appreciate any recommendations you could share with me.

I'm not @Zingo, and he should take the opportunity to reply himself but I will say that I got replacements from good ol' https://www.thetubestore.com/ (who list these Monoprice amps by name, which is helpful) and I was more than satisfied with the purchasing experience (first time I'd ever bought from them.

Just FWIW.

https://www.thetubestore.com/search?keywords=monoprice

N.B. I believe the "output" tubes in the 50W amp are different than those used in the 25W amp! The latter uses SV83 tubes; the former (I think) 6p1p tubes.

zingo

I swapped in a pair of Russian NOS 6P1P and 6N1P-EV that I purchased from Ebay. I have had good success on Ebay with good prices, but usually the same tubes could be purchased at a reputable vendor for a little more money. I have also used The Tube Store with good results, but I’m pretty comfortable with buying questionable tubes and testing them.

delkal

Well I had to do it. Just ordered one. They are still on sale for $160 and there is another 20% off from the promo code on their home page today. Add back $18 shipping and it should be here Mon or Tues for $147.

I hope I get a good one.............but considering I spent a lot more than that for a speaker cable (that I now just keep in a drawer) I figured I had to play with it. Even if it is not for me I can always give it to my daughter (once I determine it won't catch fire)

delkal

My amp came in and I had a couple nights listening to it. I have to say for the price I am extremely impressed. My amp is quiet (so far). If you put your ear right up to the tweeter you can hear a static grinding noise but you can't hear it when you are a foot away. I was listening with some Monitor 10A's and I don't think the bass was lacking at all. I would actually say there is a hump at 100 Hz. I wonder if they are quietly tweaking the electronics as they go? The volume pot at the lowest levels is a little squirrely. You can hear one speaker playing first but this is at a level lower than you would want ever want to listen at. At normal volume it is fine. Fire wise I might be OK too. The unit got warm in the back (not by the tubes) and I didn't notice any smell at all. One thing I don't like is the on/off LED is closer to a bright orange deathray laser. I bet it uses a watt by itself!

The upper midrange and treble are crisp, clear and detailed. I would say this amp is outstanding in that range. There is a little muddyness in the low mids / upper bass. It is hard to describe and others listening to it didn't notice but the amp seems to get a little confused on Rock songs where everyone starts playing at once. Listening to a jazz quartet sounded excellent though with good imaging and I was hearing some details during the quiet passages (like between tracks or the start of a song) I couldn't hear vs. the integrated amp I was comparing it to.

I don't think the hyrbid amp section can keep up with the pre's potential. I didn't know this when I purchased it but it does have a pre out. When I am a little more confident that the amp is stable I will check it for DC and experiment with a SS amp.

Zingo-
How is your tube rolling working out? I am not sure if my amp needs 6N1 or 6N2 tubes and the ones that came with the amp are unmarked (the manual says 6N2 but the website says 6N1). Do you hear more of a difference replacing the P or the N tubes (or both).

zingo

Tube rolling is good, and I do suggest replacing both sets; they are pretty cheap and the NOS Russian tubes are easy to find on Ebay.

delkal

I do have some confusion whether to order the 6N1P or 6N2P version. My manual says 6N2 but I saw you used the Russian 6N1P version. I read the 6N2s have a higher gain. Do you notice a difference between them and the stock tubes when using the volume control?

I will definitely order some 6P1P-EVs and probably thru Ebay. Most of the listings are from Russia but you can get 8 NOS (supposedly) for $2-3 a piece. Are there any Ebay sellers you recommend?

mark090852

delkal wrote: »

One thing I don't like is the on/off LED is closer to a bright orange deathray laser. I bet it uses a watt by itself!

Thanks for the great write up. I've been very pleased with mine and felt the same way about the on/off LED. I used a couple of "Light Dims" and that brought its intensity down to the level of the other lights. Looks much better that way.

https://www.amazon.com/gp/product/B01BZBBITE/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

delkal

I thought i would resurrect this thread because i was playing with my Monoprice amp last night..........

I recently upgraded all of the tubes with NOS Russian 6P1P-EV and 6N2P tubes. To break them in I hooked up a source to the Monoprice amp then used the pre-out and connected it to an older Denon integrated. Not a conventional setup but this way I could turn the volume up on the Monoprice but turn the volume off on the Denon and not hear anything. Ran it 24/7 for the last 4 days.

Last night we wanted to listen to some music so we just started listening with it set up the same way. I could immediately hear a difference in my old and trusted system. It sounded TUBEY! My girlfriend didn't notice anything new and didn't know I was messing around with my system but after a while I took the Monoprice out of the chain and turned it back on. She instantly asked "what did you do, it sounds different". I asked her to describe the difference and she said it sounded "bold" and kind of in your face. Comparing the sounds I had to agree with her.

I didn't notice the tube bloom as much when just listening to the Monoprice amp separately. I don't think the solid state amp part is that good. But it sounds great thru a decent amplifier (even an integrated). Don't get me wrong......the sound doesn't come close to a modern (expensive) tube setup. I know I am adding a lot of distortion with the Monoprice. I would compare the sound to a vintage tube amp from the 50-60's. Warm, pleasant to listen to but with some weaknesses compared to modern systems.

It definitely adds an obvious tube sound!

pitdogg2

You could also search the russian and chinese tube numbers to find the U.S. equivalent and see what else you can roll in there.

delkal

pitdogg2 wrote: »

You could also search the Russian and Chinese tube numbers to find the U.S. equivalent and see what else you can roll in there.

Unfortunately there is no drop in replacement for these Commie block tubes. There are some American / European tubes that are close but you need a 7 to 9 pin adapter. There is another US tube that is close but it needs a 12 volt heater current and not 6. Supposedly you can mod an amp to use it but that is more than I can do.

I kind of like these Russian tubes anyway........they look cool. Original communist military manufacture, cool Cyrillic lettering and one even has a rocket logo. I will admit that is not the best way to pick a tube but it has to sound better than a recently made commercial Chinese tube. Doesn't it?

pitdogg2

The rocket logos ( Vishkods) are some of the best of Russian and are the only ones that come with the rocket logo I'm aware of.
So are yours 7 pin tubes or 9 pin?

When i searched the numbers you listed one came back as 6bq7 the other was 12ax7 . But yes i know some are not. I just did a search of said number. Like for instance 6n1p equivalent and you get a few.
Just a thought is all.

mhardy6647

6n1p is sort of a 6922 but not quite (different filament current requirement, if nothing else) -- the 50 watt amp doesn't use a 6n1p, though, does it? It uses (or, at least, it can use)= a 6n2p (doesn't it?).
https://www.thetubestore.com/product/1666 The 6n2p is said to be equivalent to the Western world's 6AX7 (a tube about which I don't know very much, FWIW). The 6AX7 seems to be (?) like a 12AX7 but without the center tapped filaments(?).

The 6p1p "output" tube (whatever the heck it may do in the amp circuit in the 50 watt amp) is -- an odd duck. Read about it here. It is kinda sorta related to a 6AQ5 in a 9 pin rather than 7 pin package, but, again, not quite.
https://www.thetubestore.com/product/20592

delkal

pitdogg2 wrote: »

The rocket logos ( Vishkods) are some of the best of Russian and are the only ones that come with the rocket logo I'm aware of.
So are yours 7 pin tubes or 9 pin?

When i searched the numbers you listed one came back as 6bq7 the other was 12ax7 . But yes i know some are not. I just did a search of said number. Like for instance 6n1p equivalent and you get a few.
Just a thought is all.

The tubes are 9 pin and the 6N2Ps are Voskods. The 6p1p-ev are Svetlana OTK military tubes. Seem like these are the ones people want. A lot of places market the 6P1P tubes as a replacement for 12ax7 but this is misleading. You need to modify the amp to rewire the heater coils. Not something I want to do but with the rising prices of 12ax7s I am sure people will start to do this. These tubes were $2 a piece (shipped) from Russia.

mhardy6647 wrote: »

6n1p is sort of a 6922 but not quite (different filament current requirement, if nothing else) -- the 50 watt amp doesn't use a 6n1p, though, does it? It uses (or, at least, it can use)= a 6n2p (doesn't it?).
https://www.thetubestore.com/product/1666 The 6n2p is said to be equivalent to the Western world's 6AX7 (a tube about which I don't know very much, FWIW). The 6AX7 seems to be (?) like a 12AX7 but without the center tapped filaments(?).

The 6p1p "output" tube (whatever the heck it may do in the amp circuit in the 50 watt amp) is -- an odd duck. Read about it here. It is kinda sorta related to a 6AQ5 in a 9 pin rather than 7 pin package, but, again, not quite.
https://www.thetubestore.com/product/20592

There is some confusion from monoprice. Their website says to use a 6N1P tube and the printed manual said 6N2P. To make matters worse the Chinese tubes that came with it were unmarked! I ended up comparing the tube to pictures and it is clearly a 6N2P.

As to what these do in the circuit is anyone's guess. There are reports of some Chinese amps where the tubes do nothing and are just for show. I will say the Monoprice tubes do something. The tubey sound is definitely there especially when used as a preamp.

mhardy6647

The tubes do do something in these amps -- it is not at all obvious what, at least in the case of the power tube!

I have been too lazy to trace out the circuit in the 25 watt amp, but I did do some armchairin' of one of the morphs thereof from internet photos of the PCB. Heck, maybe it was the Monoprice... I don't 'member no more.

SimTech

I just have to say something here that may or may not be relevant but I just bought a used 25w version of the his amp with no tubes (on purpose). I went through this thing with a fine tooth comb and repaired so many bad solder joints it was scary. This one uses two LM1875s for the output which should be OK. But then I started digging into the tube section and according to Monoprice it uses 2 6N1s and 2 6P15s. All my research shows a 6P15 to be an EL84. That's great because I have a couple but when I looked closer I noticed that this amp has pins 1, 6, 7, &9 connected together. That struck me as odd since on EL84s AND 6P15s pin 7 is the PLATE. That's where the high voltage (if any) should be. I'm not an expert on tubes but I'm 99% certain that there is no possible way a tube can operate with the same voltage on the plate that is on grids 2 and 3. In fact the only possible purpose for this tube is that the heater for it is connected in series with the smaller tube. That way they can run both of them off of 12v instead of the required 6v. If you don't have the big tube in there the smaller one doesn't work because it doesn't have any heater voltage. In the 25 watt version of these amps the larger tube is merely cosmetic and it's heater acts as a current sink so they don't have to spend 99 cents on a 7806 regulator. They serve no purpose in the signal path.
Currently I have begun gutting mine and will be replacing nearly everything inside with a completely different preamp section, a larger transformer, and 2 TDA7293 100w amplifiers.