Monoprice Monolith THX 887 Balance Headphone Amp: New Champ?

[JohnYang1997]

I recently acquired one of these 887 headphone amps and have been enjoying it immensely. I have noticed something peculiar, however, when my LCD-3’s are plugged into the balanced jack and my HD650’s are plugged into the single ended jack at the same time. Upon turning the amplifier on or off, there is an unpleasantly loud noise in both headphones that sounds like an electrical discharge of some sort. I wrote to Monoprice about this but have yet to receive a response, it being a weekend. Has anyone also encountered this issue?

I think I just remembered the answer to this. This only happens when you plug both in right? If you unplug any of the two it won't pop right?
The protection circuit iirc only opens the positive side of the amplifier output.
Let's first talk about two scenarios where only one headphone is plugged in.
Balanced: one v+ one v-. at startup v+ is open only negative side is connected to the v- hence the headphone is open so no pop.
Unbalanced: one v+ one gnd. at startup v+ is open so only gnd is connected so headphone is open so no pop.
These two scenarios, there should be no issues.

Now the issue comes in.
When both headphones plugged in, when start-up the pop will go from v- through both headphones in series and to gnd. Hence the pop.

 

[mackat]

Thank you very much for the responses and the detailed explanation! While I find it a somewhat strange design oversight, I really have no need to have 2 headphones plugged in at any given time. I just wanted to make sure nothing was out of the ordinary with my amp. I haven’t heard anything yet from Monoprice regarding this.

 

[Ntrax]

I cant find a D90 anywhere, lucky you.

Cant find?? are you able to purchase them from Aliexpress...but i would skip fow now surely will be delayed.

 

[Tks]

I recently acquired one of these 887 headphone amps and have been enjoying it immensely. I have noticed something peculiar, however, when my LCD-3’s are plugged into the balanced jack and my HD650’s are plugged into the single ended jack at the same time. Upon turning the amplifier on or off, there is an unpleasantly loud noise in both headphones that sounds like an electrical discharge of some sort. I wrote to Monoprice about this but have yet to receive a response, it being a weekend. Has anyone also encountered this issue?

Sorry for the late reply, but this also occurs with the Drop 789 as well. Anytime you have single-ended plugged in along with balanced. For whatever reason when turning devices off, there is a massive burst. Electrical discharge as you put it.

Seems to be inherently a hardware issue of some sort, who knows really. I'd wager it's present on all these amps tbh. Not really a concern now that I know to avoid it (simply unplug either the balanced or unbalanced device before shut-down.

 

[Celty]

Sorry for the late reply, but this also occurs with the Drop 789 as well. Anytime you have single-ended plugged in along with balanced. For whatever reason when turning devices off, there is a massive burst. Electrical discharge as you put it.

Seems to be inherently a hardware issue of some sort, who knows really. I'd wager it's present on all these amps tbh. Not really a concern now that I know to avoid it (simply unplug either the balanced or unbalanced device before shut-down.

Hmm never experienced any sort of burst or pop or whatever, but then I don't use the SE outlet, let alone at the same time as the XLR plug-in. Perhaps try the simple approach and just plug one set in at a time and see if that cures it.

 

[Tks]

Hmm never experienced any sort of burst or pop or whatever, but then I don't use the SE outlet, let alone at the same time as the XLR plug-in. Perhaps try the simple approach and just plug one set in at a time and see if that cures it.

I just expiramented, I don't actually do this myself (no sensible point in doing this really..)

 

[Celty]

A new video review:

 

[chlipong]

I was going to order it on monoprice.com but shipping was more than $100 to europe so I ordered the drop 789 instead.
Since, I found out that there is a monoprice.eu but they do not sell the 788, so I wrote to them to ask if they were intending to sell it in the future and the good news for european is that it will be avalaible at monoprice.eu around march.

 

[Masterxyr]

[QUOTE="the good news for european is that it will be avalaible at monoprice.eu around march.[/QUOTE]

this is very good news!
pity they couldn't squeeze more power out of the SE. Smsl's one is more than double at 600Ω than either the drop or the Monoprice.

 

[escalibur]

https://www.audiophonics.fr/en/sede...-headphone-amplifier-symmetrical-p-14387.html is another European distributor.

 

[Madhatter]

I wonder if I can drive my active 111db/w 16ohm compression drivers from this. Any possible quality/safety considerations?

 

[JohnYang1997]

I wonder if I can drive my active 111db/w 16ohm compression drivers from this. Any possible quality/safety considerations?

So it's a loudspeaker? No.

 

[Madhatter]

As far as I understand, I wont ever need more than 1watt at 16ohm. In fact most of my listening would be at some hundred mW, so could you expand a bit more?

 

[JohnYang1997]

As far as I understand, I wont ever need more than 1watt at 16ohm. In fact most of my listening would be at some hundred mW, so could you expand a bit more?

It's a headphone amplifier. The SOA (safe operating area) of the output stage as well as the heatsinking capability are not up to the same standard for a speaker amplifier. For testing at short period of time it's safe. But for every day use, people is probably only using 10mW for the most time. 1W is probably gonna put much stress on the amplifier shorting the lifespan.

 

[Madhatter]

I understand your principles in general. But specifically for my application 15mW/16ohm actually put out 94db/m, which is hardly in comparison to 99% of commercial loudspeakers. In addition, it will handle only a limited bandwidth above 500hz.

So according to Amir's measurements it seems to me the 887 is capable of delivering the power needed, well within its distortion sweet spot.

Is there another technical aspect I should be aware of?

 

[Daimiel]

There are much diference between the SMSL SP200?

 

[Veri]

There are much diference between the SMSL SP200?

3 gain switches. And XLR output here = double power over single ended output.
SP200 = only normal and high gain, no low gain. And XLR=SE, same output.

 

[Daimiel]

3 gain switches. And XLR output here = double power over single ended output.
SP200 = only normal and high gain, no low gain. And XLR=SE, same output.

And in sound quality?

 

[Jimmy]

Most solid state amps (unless the design is broken or they are underpowered) sound alike. I've bought a THX 887 (still waiting for it), and to be true I chose it mainly for looks, but I've noticed the following (it may justify the price difference) :

1. The 887 uses 4 x OPA564 per channel vs 2 x OPA564 in the 888. In a quick visual inspection the 888 seems to use less components (not a good or a bad thing per se).
2. The 887 has headphone protection circuitry, the 888 may have ir or not (unsure).
3. 3 gain choices (887) vs 2 (important in high power hp amps like these).
4. External (887) vs internal (888) power supply.

Anyway as I said, I doubt that they sound any different when level matched.

And in sound quality?

 

[JohnYang1997]

Most solid state amps (unless the design is broken or they are underpowered) sound alike. I've bought a THX 887 (still waiting for it), and to be true I chose it mainly for looks, but I've noticed the following (it may justify the price difference) :

1. The 887 uses 4 x OPA564 per channel vs 2 x OPA564 in the 888. In a quick visual inspection the 888 seems to use less components (not a good or a bad thing per se).
2. The 887 has headphone protection circuitry, the 888 may have ir or not (unsure).
3. 3 gain choices (important in high power hp amps like these).
4. External (887) vs internal (887) power supply.

Anyway as I said, I doubt that they sound any different when level matched.

789 and 887 are balanced with true differential outputs. The sp200 and hpa4 don't have balanced output. But this doesn't mean thx 888 can't be used with balanced implementation. The complexity of 888 is higher where it has flying power supply (one opa1612 matching with one opa564 instead of half of a opa1612 with one opa564 in 887 or 789). Both the opa1612 and opa564 's supplies are modulated by input signal also the thx888 is a differential amplifier instead of just non-inverting amplifier. The flying supply reduces the common mode distortion of the input stage of the opamps which is something to worry about in this level of performance. So 888 is a more complex implementation where 887and 789 are only half way there.
However the 887 circuit can have a lower noise because there is some restrictions in resistors due to the topology of 888. Without the restrictions the 887 was able to achieve better output noise. For the most part and real world use, better noise will be much more likely to have better results as the distortion components will be lower than noise in normal listening levels.