[Allanmarcus]

Thumbscrews, like on some computer cases, would work better.

Even better! Assume they fit. They would be a pretty a cheap "upgrade".

 

[Theabs]

Even better! Assume they fit. They would be a pretty a cheap "upgrade".

I still wonder about the lack of airflow/cooling.

 

[Allanmarcus]

I posted a few questions, and got some answers from MP:

Q: Is there a fan?
There isn't a fan. The unit does get warm, and we suggest keeping it in an a well ventilated area. I would not put this amp in any kind of enclosure.

Q: How hard is it to change the tubes? It looks like many screws to remove to access the tubes.
A: There is a top panel that can be unscrewed to access the tube. (Philips. 4 screws)

 

[Allanmarcus]

added to the first post

Note the 4 screws on the top plate. To change the tubes, one removes these 4 screws. I suppose you could just keep the top plate off for sustained tube rolling.

 

[phthora]

Much more manageable. Thanks for posting the pic.

I wonder if we can get a size for the screws, so that folks can work on finding a thumbscrew replacement for them.

 

[Allanmarcus]

I'm working on a tour, so if that happens, we'll know a lot!

 

[extraclassic]

Hi Everyone, this is my first post on the Head-Fi forum and I stumbled upon this thread and thought I would download my review of the new Monolith DAC/tube headphone amp. I just left a review on the Monoprice site, but it has not posted yet - probably Monday when the staff is back to review it. I have copied the review below.

First: This review is 100% genuine with no expectations on arrival.

OK, I will admit, I really wanted to like this headphone amp. It checks all of the checkboxes I want to see in an all in one unit. This is an ambitious project for the Monoprice folks, no doubt, and they were sooo close to pulling off the deal of the century. It has all of the right ingredients. The short review is that I think (total guess) that they rushed the design based on demand. The depth of sound, the power to the headphones and the quality of digital decoding - that is not an issue. In fact, if I ignored the issues with this unit, it would be a COMPLETE WIN. Issues listed in the Cons section, below. An important note: I returned the first unit and have similar issues with the second.

Pros: Depth of sound, power, decoding quality.

Cons: The cons are in two parts: Hum and Wiring

Con 1: Hum. Hum that never goes away. I rolled three other power tubes in this unit, a couple of which did reduce the hum, but not enough. Even a few hours in on the included Chinese power tube, the hum effect was reduced, but it did not go away. The hum is unaffected by volume. It sounds like an EMI issue - there are two transformers in the unit, a large toroidal a transformer and another large one for the high voltage supply. While the transformer department is well covered with oversized units, it may be placed too closely to sensitive signal paths. Alternatively, the grounding may be an issue. It doesn’t have that typical “ground loop” sound, but it still could be the issue. Either EMI or ground loop issue, the amp hums and it won't stop. Yes, it does get better with some powered tube time, but it's a sound you definitely don't want to hear in a unit of this price range.

Con 2: Wiring. The included Chinese power tube in the first unit worked OK for the first hour and then the sound died, like the sound of a tube quitting – the volume was super low after that hour, almost immeasurably low. I chalked this up to a bad tube, but did not want to take chances and told myself to return it the next day. The next morning, I tried it out before returning it. The volume went completely back to normal. I suppose the tube issue somehow fixed itself, but not sure, so I listened for a good while longer. I put in about 8 hours of listening. The volume cut from what I assume was the tube failing never became a problem again, but the hum I experienced with both units was always there. So I returned the first unit and received the second unit today. The second unit introduced a few voltage spikes into my high end headphones. Again, I thought that the Chinese tube was at fault, so I dropped in a GE tube. The GE tube started off OK (still had a hum), but after about 30 seconds, the tube sparked like mad and almost destroyed my headphones! OK, so I did a double check with a Philips/Mullard tube and while that one did not spark up a storm and sounded fine, the hum was still present.

Conclusion: This unit has all of the potential in the world, but there are too many bugs for me to recommend it. It’s not ready for primetime. It’s also a risky to use – the second unit I received could have turned into a fire hazard if I wasn’t watching it closely. That said, if you end up with a unit that does work, it isn’t because of the quality control process - it was probably pure luck. If you ordered one of these, I wish you luck. My second unit is going back, and this time for a refund. I wish that I could report differently, but it is what it is.

 

[Zachik]

Hi Everyone, this is my first post on the Head-Fi forum

Welcome to Head-Fi, and sorry for your wallet

 

[extraclassic]

Welcome to Head-Fi, and sorry for your wallet

Thank you, Zachik - since Monoprice is typically good about returns, I'll feel better once the $$$ is back in the bank.

 

[Zachik]

I have actually been (im)patiently waiting for their Spark amp (for $99)... Been delayed multiple times - originally I think was supposed to be out on April or May.
Now - Oct.14 (assuming no more delays)... This one should be a steal for $99.

 

[Allanmarcus]

Hi Everyone, this is my first post on the Head-Fi forum and I stumbled upon this thread and thought I would download my review of the new Monolith DAC/tube headphone amp. I just left a review on the Monoprice site, but it has not posted yet - probably Monday when the staff is back to review it. I have copied the review below.

First: This review is 100% genuine with no expectations on arrival.

OK, I will admit, I really wanted to like this headphone amp. It checks all of the checkboxes I want to see in an all in one unit. This is an ambitious project for the Monoprice folks, no doubt, and they were sooo close to pulling off the deal of the century. It has all of the right ingredients. The short review is that I think (total guess) that they rushed the design based on demand. The depth of sound, the power to the headphones and the quality of digital decoding - that is not an issue. In fact, if I ignored the issues with this unit, it would be a COMPLETE WIN. Issues listed in the Cons section, below. An important note: I returned the first unit and have similar issues with the second.

Pros: Depth of sound, power, decoding quality.

Cons: The cons are in two parts: Hum and Wiring

Con 1: Hum. Hum that never goes away. I rolled three other power tubes in this unit, a couple of which did reduce the hum, but not enough. Even a few hours in on the included Chinese power tube, the hum effect was reduced, but it did not go away. The hum is unaffected by volume. It sounds like an EMI issue - there are two transformers in the unit, a large toroidal a transformer and another large one for the high voltage supply. While the transformer department is well covered with oversized units, it may be placed too closely to sensitive signal paths. Alternatively, the grounding may be an issue. It doesn’t have that typical “ground loop” sound, but it still could be the issue. Either EMI or ground loop issue, the amp hums and it won't stop. Yes, it does get better with some powered tube time, but it's a sound you definitely don't want to hear in a unit of this price range.

Con 2: Wiring. The included Chinese power tube in the first unit worked OK for the first hour and then the sound died, like the sound of a tube quitting – the volume was super low after that hour, almost immeasurably low. I chalked this up to a bad tube, but did not want to take chances and told myself to return it the next day. The next morning, I tried it out before returning it. The volume went completely back to normal. I suppose the tube issue somehow fixed itself, but not sure, so I listened for a good while longer. I put in about 8 hours of listening. The volume cut from what I assume was the tube failing never became a problem again, but the hum I experienced with both units was always there. So I returned the first unit and received the second unit today. The second unit introduced a few voltage spikes into my high end headphones. Again, I thought that the Chinese tube was at fault, so I dropped in a GE tube. The GE tube started off OK (still had a hum), but after about 30 seconds, the tube sparked like mad and almost destroyed my headphones! OK, so I did a double check with a Philips/Mullard tube and while that one did not spark up a storm and sounded fine, the hum was still present.

Conclusion: This unit has all of the potential in the world, but there are too many bugs for me to recommend it. It’s not ready for primetime. It’s also a risky to use – the second unit I received could have turned into a fire hazard if I wasn’t watching it closely. That said, if you end up with a unit that does work, it isn’t because of the quality control process - it was probably pure luck. If you ordered one of these, I wish you luck. My second unit is going back, and this time for a refund. I wish that I could report differently, but it is what it is.

Wow, nice review. Seems like they will need to take the amp off the market and fix those issues. Sounds like they didn’t test the amp design. Bummer.

 

[Rick_B]

Right!? And, enclosing that rectifier and pre-amp tubes in a metal box seems like it's going to make the entire case uncomfortably hot to the touch.

The 6N5P/6080/6AS7 tube is not a rectifier tube, it is the output tube, like used in in the Darkvoice 336SE...it is a dual triode that kind of approximates 2-2A3 tubes in one tube, but are not directly heated...it has cathodes for electron emission.

6080 tubes are sometimes used in voltage regulator circuits, though...so rectifier, regulator, it's all vacuum tubes...

 

[kphooligann]

I still wonder about the lack of airflow/cooling.

I was born in 1963. I remember the TVs of the pre-solid-state days. Lots of tubes, ran hot, and had less ventilation than this amp. From that, I doubt airflow/cooling will be a problem.

 

[extraclassic]

I was born in 1963. I remember the TVs of the pre-solid-state days. Lots of tubes, ran hot, and had less ventilation than this amp. From that, I doubt airflow/cooling will be a problem.

No problem with cooling - the sides and top are definitely open enough.

 

[extraclassic]

Well, I had submitted the same review on Monoprice as I did in this thread, but I guess Monoprice did not want to post it. A couple of other posts were allowed by Monoprice that had positive outcomes - who knows, maybe I just ended up with two lemons, but my assumption is that the hum is an issue that is part of the design, so I passed on receiving a third unit. I did end up returning the second unit and received a refund. On to better options!