[Mr.Sneis]

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[cucera]

Hi folks,

I own a 303 with leather pads and an SRM 1 MK 2. Now I want to upgrade gradually. I am thinking about a 407 or 405. Would that be an enhancement, or do I have to upgrade the amp first?

 

[spritzer]

Quote:

XLR basically just gives the amp with lower gain more headroom and brings the benefit of higher slew rate. Other than these two... I don't think there is any more potential benefits worth mentioning.
 
I'm no expert, but yeah XLR do deliver twice the voltage (louder.) The distortion; however, shouldn't be effect. It hard to actually tell the volume by ear; hence, the need of equipments.  
 
Not fimiliar with 006t's schematic at all, but here is one possibility which is very remote.
the "-" channels of the amp has some problem that's causing the distortion. When using single ended, those "-" channel inputs are shorted to ground, so you most likely won't hear the problem.
 
Wait for Spritzer for more detailed diagnosis.
 
Quote:

 

 
win.

 
XLR output is usually double that of RCA but it's not a rule.  It's certainly in this case and as for the distortion,  more input voltage will not help with the natural limitations of the amplifier.  The 6CG7's will run in trouble with higher voltage (i.e. more volume) and the double input voltage only gets you there quicker.  It's a good circuit hampered by a tube that can't stand the 700V it's asked to work at. 

 

[e19650826]

Quote:

 
XLR output is usually double that of RCA but it's not a rule.  It's certainly in this case and as for the distortion,  more input voltage will not help with the natural limitations of the amplifier.  The 6CG7's will run in trouble with higher voltage (i.e. more volume) and the double input voltage only gets you there quicker.  It's a good circuit hampered by a tube that can't stand the 700V it's asked to work at. 

 
I know that higher input voltage will just push the amp to higher distortion faster.
but shouldn't the distortion of XLR be of the same maginitude of RCA, if the final output dB on the headphone are set to the same level?
(Not particularly familiar with how tubes work. I'm assuming that it works somewhat like a transistor.)

 

[arnaud]

Quote:

 
I know that higher input voltage will just push the amp to higher distortion faster.
but shouldn't the distortion of XLR be of the same maginitude of RCA, if the final output dB on the headphone are set to the same level?
(Not particularly familiar with how tubes work. I'm assuming that it works somewhat like a transistor.)

I though his response was clear enough. Distortion mainly comes from the output stage and it doesn't matter if the signal reaching was from xlr or unbalanced inputs, the output stage clips above a certain input signal level. Depending on the amp design (and hence gain settings) this may happen at same or different volume setting of the potentiometer, but it to occurs at the same loudness level since it relates to the output stage linearity.

 

[oogabooga]

Thanks spritzer and arnaud for your comments - I understand completely. All the more reason to try and convert the 006t to an SRM-600, if I ever get the cohones to start hacking up that amp!
 
 
Quote:

 
 
The D/AC1500 should be a fully balanced source so you should be technically better off via XLR; the clipping you are describing I can't really answer for but is interesting.  Speaking of the D/AC 1500 - how do you feel it fares sonically?  Maybe my ears are broken but I haven't found great synergy with any of my other amps and the Parasound yet.

 
Thanks for the links and the quotes - I've got some reading to do.
 
My sonic thoughts on the Parasound are that it's 'good', but I don't have a trained ear. I had a couple of weeks to compare it to an NAD M51, which I found had slightly better bass than the Parasound but it was something I could only pin down on one track (Phoenix by Daft Punk). Otherwise I could not discern a difference. 
 
 
Quote:

too bad so much of it is wrong

 
Could you elaborate (or perhaps reference another post that does)?  

 

[e19650826]

Quote:

I though his response was clear enough. Distortion mainly comes from the output stage and it doesn't matter if the signal reaching was from xlr or unbalanced inputs, the output stage clips above a certain input signal level. Depending on the amp design (and hence gain settings) this may happen at same or different volume setting of the potentiometer, but it to occurs at the same loudness level since it relates to the output stage linearity.

 
EDIT. Misread the entire original post. Stupidity on my side.
 
I thought he was saying that distortion happens at different volume level. :facepalm

 

[autoteleology]

Next step: a big battery pack to go fully mobile.

 
If I knew how to do this, I would. My portable setup at the moment is rubbish and I have a lot of empty room in my bag.

 

[Michgelsen]

Quote:

 
(...) I have a lot of empty room in my bag.

 
If the SRM-Xh takes the same input as a 252, namely 12V, that would put it in car battery territory. 

So much for mobility though...
 
Seriously, you would have to hook up some batteries in series to get 12V, for example 8×1.5V or 10×1.2V, find and buy the same connector as on the adapter, connect it via a wire to the batteries, while observing polarity, and you should be set.

 

[bearFNF]

Quote:

 
If the SRM-Xh takes the same input as a 252, namely 12V, that would put it in car battery territory. 

So much for mobility though...
 
Seriously, you would have to hook up some batteries in series to get 12V, for example 8×1.5V, find and buy the same connector as on the adapter, connect it via a wire to the batteries, while observing polarity, and you should be set.

Or this maybe? dont know much 'bout 'lectricity i 'r mechanical engineer:
Anker® Astro3 10000mAh Multi-voltage (USB output: 5V, 2A; DC output: 9V / 12V, 2A) External Battery Pack ( Dual USB Output plus DC Output ) for Samsung Tablets, Netbook, Digital Cameras, DV Recorders, PS Vita, Nexus 7, NDS, NDSL, GoPro; iPhone 5 (Lightning Cable not Provided), iPad, iPod; HTC Sensation, EVO, One X; Samsung Galaxy S3 [12 connectors for mobile phones, 6 connectors for tablets, US AC adapter included]

 

[e19650826]

you need clean and regulated PSU for the amp, otherwise it will most likely sound like crap.
those multi purpose battery pack meant for charging batteries have quite a bit of noise making them not of best choice for audio.
best way to go is find yourself a 120V battery pack and plug the existing wallwart PSU into it... drawback is you will have to carry a suitcase around with you

 

[Michgelsen]

Most Stax amps do not use regulated PSUs. Battery power is most likely much cleaner than what a typical (internal) Stax power supply delivers. Voltage drop could be a problem when the batteries are running out, though this should be harmless.
It should be really easy to use typical household batteries of 1.5V, or rechargeable ones of 1.2V for this purpose. Just connect them in series and you have a stable 12V power supply until the batteries run out.
A 120V battery would need to be a massive array of cells in series and then you still need to carry the transformer around to transform it back down to 12V: this is very unpractical and unnecessary.

 

[e19650826]

Quote:

Most Stax amps do not use regulated PSUs.

This is new to me. Thanks for the info. I assumed that they all would have some form of regulated PSU like most comercial/DIY ones, since they are charging quite a bit for them.
 
still, something like 001 is much more suitable for portable use.

 

[autoteleology]

The battery that bearFNF seems like an extremely useful electronic gadget, regardless of even whether it works with the amp or not (though it appears that it would).

 

[milosz]

Quote:

I have a question about the difference between the XLR and RCA inputs on my SRM-006t. The 006t has two inputs, one is RCA only, the other is selectable between RCA and XLR.  I currently have my Parasound 1500, which I can hookup using either connection (using Monoprice cables, and SR-007s FWIW).
 
When I listen via XLR I find the sound to be considerably louder. Am I correct in assuming this is because XLR delivers twice the voltage of RCA?  I cannot, however, discern a sonic difference between RCA/XLR.
 
More importantly, if I listen at high volumes, I find that that the amp begins to distorts at the same overall sound level using either XLR or RCA (i.e. not the same setting on the volume dial, but the same sound level at my ears).  Put another way, using XLR does not seem to give me any more 'headroom'.
 
Are my experiences consistent with the engineering of these amps, or have I missed an important step somewhere?  I am trying to better understand the benefits of using the XLR inputs, so I can decide how to proceed with future purchases. Thanks!

 
 
Balanced lines ( XLR ) have several inherent advantages over single-ended ( RCA )  but in home audio these advantages are not always important or even audible.
 
Balanced lines are pretty much the "standard" for transmitting analog audio signals in recording studios, music venues, broadcast studios, movie production studios and the like.  This is largely because using a balanced line makes signal transmission more immune to picking up electrical noise from the surroundings, and also using balanced lines one can transmit audio without connecting the chassis-grounds of various mixers, patch panels, processors, recorders etc together, reducing the likelihood of noise from ground loops. 
 
GROUND LOOPS
A single-ended "RCA" type cable usually (not always) connects the two chassis of the source and the preamp / amp / recorder together. This is not really a problem, but these two pieces of gear may also have 3-prong power cords, connecting both chassis to powerline earth ground.   If the resistance between one chassis and earth ground is even slightly greater than the resistance seen by the other chassis- well do your Ohm's Law calculation and you'll see that there now exists a potential ( i.e., voltage) difference between the two chassis, that stray capacitance / inductance leakage from the unit's power transformer is going to create a slightly higher 60 Hz AC voltage on the chassis with the higher resistance to earth ground than on the other chassis. The RCA cable between them electrically connects their chassis, and so a 60 Hz AC current starts to flow between the two chassis along the RCA cable's shield. This is a tiny current, to be sure,  but nonetheless it IS a current.  And, because the preamp or amplifier is using this shield/ground as 'reference' to the audio signal on the center conductor, this AC current shows up on the input... it gets amplified and you hear it on the output as a buzzing HUM.  A buzzing hum, and not a dull hum,  because the leakage from the power transformer that sets up this current in the first place is mostly capacitively coupled, the reactance of which is allowing mostly the higher harmonics of the 60 Hz power line to pass. (The windings of a transformer have a certain amount of capacitance inherent between those windings and the metal frame of the transformer....which in turn is bolted to the chassis. A leakage current consisting of high harmonics of the AC power frequency can therefore be coupled to the chassis through this capacitance.  60 Hz in the US, Canada and others; 50 Hz in the U.K., Europe etc.)
 
So, if you connect two chassis together by the RCA shield AND the power line 'third pin' ground, you might well get  a ground loop.
 
With a balanced cable,  in common practice the shield is connected to ground only at the source end of the cable. The audio signal propagates along the + wire inside the cable, referenced to the - wire, not referenced to the shield as in an RCA cable.  So the two chassis are NOT connected together through the shield of a balanced audio cable as they would be when using an RCA unbalanced type cable.
 
Also, in a balanced line, both the +  and - wires inside the cable will absorb electrical noise from the environment in equal amounts. But since one wire carries a - audio signal and the other wire carries a + signal, the two audio two signals are 180 degrees out pf phase with each other yet the induced noise will be in phase on both lines. The audio stage that receives them can REJECT any noise signal that is NOT out of phase between the + and -  inputs.  Thus any noise from EMI, power line hum, even noise induced by some MECHANICAL means, is fully rejected by a well designed balanced audio receiver stage. 
 
Unbalanced RCA cables in consumer setups are usually fairly short, 2 meters or less, and being short they don't usually pick up too much of this kind of noise.  But recording studios and radio stations typically have audio lines that can be hundreds of feet long, so this kind of noise pickup could become an issue if balanced lines are not used.  Almost all studio type audio gear uses balanced lines for audio either on an XLR or on a TRS phone plug.
 
Some elaborate home-theater setups benefit from the use of balanced lines also, because their complexity requires long audio cables, and because so many devices (TV set, pre/processor, power amps, cable and satellite boxes, BluRay players, audio sources, computers, game consoles, etc)  are connected together that avoiding ground loops without resorting to balanced lines becomes difficult.
 
ALL THAT BEING SAID the main benefit of balanced lines in home audio tends to be that they help avoid ground loops. But if you connect your gear with RCA cables and have no atrocious hum issues, then you have avoided ground loops without using balanced lines.
 
There are also some advantages possible in using balanced signal transmission and amplification all the way from source to transducer in terms of lower distortion- that is, IF all the stages are implemented properly to take advantage of the cancellation of distortion which can occur at the speaker / headphone driver when the +  and  - phases of the balanced signal "meet" in the speaker / driver. This is a less common situation, because quite often there are transitions from single ended to balanced somewhere in the reproduction chain that have outputs that are actually NOT highly symmetrical, truly "balanced" signals.