[drhiziracil]

Well I have bought four muses 8920 for output stage and burning in and using them for 2 weeks.

Sound became more alive and treble just got to the level my taste. They are very warm, detailed not airy but it seems like some rolling of at the treble is going on. V5i was much more alive, detailed airy and fun sound but I couldn't use them for long listening sessions.

Especially mids and vocals got much more better. Stocks was a little laid back. Bass is now goes a little more deeper now and more powerful than stocks. But to be honest stock outputs have more natural bass. With the muses01 at the input bass level is higher than its supposed to be. But its fun anyway.

Sound level is seems like a little lover compared to stocks. And with the treble is somehow rolled of and warmer I can go higher volumes without hurting my ears. That is what I liked most with these. I'm definitely gonna keep them. But you wont miss much just with the stock outputs.They are good and more natural they have less color. But that stock inputs definitely needed to be changed

 

[slackman]

Can someone tell me the output impedances for the High and Low outputs? Would be much appreciated!

 

[slackman]

Can someone tell me the output impedances for the High and Low outputs? Would be much appreciated!

I asked the question to SMSL support and they replied that the outputs are 10ohm and 150ohm.
They didn't say which is which, I asked this question in a reply, hope they will reply again with this info.
Though I'm guessing the "HIGH" output has an output impedance of 10ohm and the "LOW" output has an output impedance of 150ohm. (something similar was measured for the VA2 and some other headphone amps also have a higher output impedance for the "low" outputs for instance the Topping A30) They have probably lowered the volume after the output opamps with a resistor to get the lower volume including lower noise for more sensitive low impedance headphones.
This will of course work for lowering the volume but for some headphones the "LOW" output will then give less electrical damping and may give a stronger bass etc. The 150ohm output impedance isn't nessecarily crazy, I believe there's an old standard (the only one there is) that specifies 120ohm output impedance for headphone amplifiers, and the Beyerdynamic headphone amp has 100ohm output impedance etc. Though it is usually thought of as a generalized good idea to have an output impedance at least 8 times lower than the headphone impedance rating.
So perhaps this should be viewed as a great amp out of the "HIGH" output for headphones with an impedance of 80ohm or more. And with an added bonus of a "LOW" output to use without noise with sensitive headphones yet without optimal impedance matching possibly changing the sound of the headphone. (which could be a good thing for some headphones or personal preferences)

 

[ginetto61]

Hi two questions for all you guys who own and use a VA1.

1. Which headphone do you like the best with it ?
2. are you still using it or have found something clearly better ? what ?

thanks a lot, gino

 

[jeff7742]

Hi two questions for all you guys who own and use a VA1.

1. Which headphone do you like the best with it ?
2. are you still using it or have found something clearly better ? what ?

thanks a lot, gino

I haven't checked in a while. But yes, I'm still using the VA1 with (6) LME49990's op amps along with my T1 headphones. About a year ago I went to a meet and listened to several other very good amps. Can't remember all their names. Most were more powerful and some were very rich sounding, in a way similar to this amp with the LME49990's. But I don't think any of them were as detailed as the VA1 . This amp is unique and I don't think I'll replace it for a long time, although I might upgrade the op amps if better ones come along (which I doubt). The LME49990's do get hot, but they seem to work fine. No problems so far. And they're more than powerful enough to drive my 600 ohm T1's.

 

[ginetto61]

I haven't checked in a while. But yes, I'm still using the VA1 with (6) LME49990's op amps along with my T1 headphones.

Hi and thanks a lot for the kind and very helpful reply. The T1 must be an amazing HP indeed. Very revealing i understand (i do not have direct experience). I guess an excellent evaluating tool indeed.

About a year ago I went to a meet and listened to several other very good amps. Can't remember all their names.
Most were more powerful and some were very rich sounding, in a way similar to this amp with the LME49990's.
But I don't think any of them were as detailed as the VA1 .
This amp is unique and I don't think I'll replace it for a long time, although I might upgrade the op amps if better ones come along (which I doubt).
The LME49990's do get hot, but they seem to work fine.
No problems so far. And they're more than powerful enough to drive my 600 ohm T1's.

Thank you again for the very valuable input and advice. I would like to elaborate a little my thinking.
First of all i understand this little nice amp is an excellent platform for some modifications. The price is amazingly low and i really do not understand why ... you know what ? i am buying another one soon.
After peeping inside i can notice some issues:

1. the op-amps used are without marks ... as they are compatible with the LME 49990 i guess they are of the voltage feedback type
2. i see one OA for channel just after the inputs. So they are dual OAs. And i understand from your older posts that they are there to buffer the input signals. I guess it is a good thing ?
3. i see two OAs per channel after the volume pot and i understand they are in parallel and not in series. So i guess they are identical and share the task of driving the HP load.

I think that with the help of a friend and a little reverse engineering we could draw the schematics.

Still the brand and model of the OAs will remain unknown. A concern to me. I really do not think that SMSL is willing to disclose which OAs are used.

Another thing that i do not like in general is paralleling devices. I do not understand why they have not used just one more powerful OA per channel after the pot. That is what i would like to experiment. I was thinking to something like the AD811 a very powerful driver, even if this will imply taking out some caps (they are current feedback OA).
Then i would look at the passive parts used. Personally i have some weak spots for some resistors ... like Dale, Holco ... and i understand styrene caps for small capacitance are sublime.
So i am thinking to swap the original resistors and caps with something very high quality. I believe in quality parts adding something to the sound. Better they should be more transparent.
Moving a little out of the topic, i have found very interesting the thread on the amp THX AAA 789. For one time excellent measurements and sound "seem" to go together.
Unfortunately i have no chance to measure THD+noise on this little marvel ... but i think i have seen something around showing very little noise (i do not remember for distortion).
This nice amp seems to be excellent platform for testing different Op Amps.
But for me it will be a medium to long term project. 1st move would be to desolder the original OAs and put in place some sockets to make OAs swapping easier.

Thanks a lot again.
Kind regards, gino

P.S. if only i could know which OAs they have used ... that would make things so much easier that is unbelievable.

 

[jeff7742]

Hi... If you're looking for another VA1, you might want to wait for a sale. They're usually $239 but on occaison I've seen them go as low as $85. Of course, you have to add in the price of any new op amps.

As I understand it, all the original op amps were proprietary - made by SMSL. Some of them were supposed to be tuned to Sennheiser headphones, while others were tuned to Beyerdynamic - you could order the amp with two different configurations. But they do seem compatible with most other 8-pin op amps. I'm not an electronics guy, but this amp was said to employ a technique called "parallel amplification", so I guess they do things separately for each channel. It has balanced inputs, but I often wondered how far that balanced circuitry extends into the amp. I suspect it may extend up to the headphone jack, in which case it wouldn't be too hard to modify it into a balanced amp.

Doesn't the amp already have sockets for all six of its op amps(?). In any case, I had no trouble pulling them out and replacing them.