Stax Amplifiers SRM-D50 and SRM-500T – Full Review

Hi Guys,

Today we are talking about a couple of amplifiers, well, one is a DAC/Amp combo, from Stax Headphones. These are both electrostatic amps, and are nearer the entry level in terms of new pricing for desktop electrostatic amplification. The D50 is a solid state DAC/Amp combo unit, and the SRM-500T is Stax’s current entry level tube amp. The D50 retails for $1260USD, and the 500T retails for $1499USD, so they are fairly similar in their pricing. One of the main barriers for people who are interested in electrostatic headphones is the amplification needs, so I was curious how a couple of Stax’s more affordable amp models would fair in a comparison. 

The D50 also includes a ESS Sabre 9018 based dac, so can be used as an all in one unit. The 500T is purely an amplifier, so does also need a DAC of some form to be used. 

I tested the D50 as an all in one, and also with a couple other DACs to get an idea of its separate sections performance. With the 500T I used a Topping D10S, and a Schiit Audio Yggdrasil A2. 

Now, the Stax own amplifiers get a fairly rough reputation from the DIY crowd which surrounds the electrostatic end of the headphone hobby. I’ve owned a few of those designs (BHSE, DIYT2, KGSSHV Carbon) so I was curious how I would feel about the more entry level Stax amps, and how they would perform in comparison to the more expensive DIY designs. 

D50 Front

First, lets talk about the D50 as an all in one unit. It is pretty much a plug and play solution for electrostatic headphones. I just used my laptop, direct into its USB input, and tried it with a few various headphones. As an all in one, its slightly bright, and somewhat lean sounding, but has a decent amount of power whilst also being a very manageable size. If you are looking for a decent all in one performer, and don’t have a lot of space, the D50 makes a good argument for its use in that situation. The DAC section struck me as being slightly bright and sharp sounding, and the sonics did improve using a slightly warmer and thicker sounding DAC to balance out the response between the two. With that being said, I think that if you already have a DAC on hand, the SRM-400S might be the better buy, as its amp section is supposedly slightly better than the D50’s, and costs about the same (1200USD.) I think that the D50 is best used as an all in one, and certainly has enough power for the Lambda series, and the 009S. For the 007mk2 I think I would recommend something with a bit more power on tap, as they are a very power hungry headphone. The X9000 is likely to be used with higher end amplification, but if the D50 is all you have, it would work in a pinch. As an all in one, easy to use, and compact solution, the D50 works very well with the Lambda series headphones. Their slightly warmer and less bright signature pairs well with the D50’s leaner brighter nature, and I never really had any problems with the sonic performance I was getting. 

SRM-500T Front

The SRM-500T is a tube based amp. As mentioned previously, it is also an amp only solution, and it’s a few hundred dollars more expensive at MSRP than the D50. There is a slight warmth and “tube” sound to its overall sonic signature, but its not overly gooey and thick sounding as some tube amps can be. It manages 100v less overall in terms of output power than the D50, but for the Lambda series, it worked especially well. I just found it to be a more preferable sonic signature and easy to listen to. I tried my Topping D10s which is an ESS Sabre based unit, similar to the 9018 in the D50, and that did work quite well. I’d say the performance between the two DAC units was quite similar. Stepping up to my Schiit Yggdrasil A2, the sound did absolutely improve, but spending $2599 on a DAC for a $1500 amp maybe doesn’t make a ton of sense. There was slightly more detail from the Amp section of the D50, but the overall tonal balance, timbre, and sense of ease from the 500T, to my ears, was preferable. 

D50 Rear

I think that if you need a DAC, or want an all in one, smaller unit, the D50 is the way to go between the two. If you happen to already have a DAC of some form, and are going to be driving a pair of Lambdas, the 500T is the right choice. Or, if you have a DAC of some form, but want a slightly less warm and more detail oriented sound, I would guess the SRM-400S would be the right choice. With that being said, I think the 500T makes an argument for its use particularly with the Lambda series, as they just seemed to be a really synergistic pairing. 

500T Rear

In comparison to the (sometimes much) more expensive DIY options, these two Stax models aren’t awful. I think that the difference between the two categories of amps has been overblown over the years. Are the good DIY builds of the BHSE, and KGSSHV Carbon better? Yes, they are. They are more powerful, supply better, more detailed and seemingly faster performance, BUT, if you are using a pair of Lambdas or easier to drive electrostatic headphones, and just want to enjoy them without breaking the bank (as much…,) some of Stax’s own amp designs do the job perfectly well. 

The D50 is a nice, all in one combo unit. It isn’t very large, it looks nice, and would fit in on any modern computer desktop. The SRM-500T fits the more traditional look of Stax amplifiers, being long and narrow. It has the preferable sonic performance to my ears, but does have slightly less power and detail than the D50. Really, I think it depends on your needs, sonic preferences, and the headphones you will be using with it, as to which is the better choice for your uses. 

Size Comparison

I think the main take away I have from my time with these two amplifiers is this – Don’t let amplification needs, and the supposed drop in performance in Stax’s own amps vs the popular DIY designs stop you from trying out electrostatic headphones. If you are simply curious, and buy a pair of L300, and pair them with the D50 or SRM-500T, it would let you try out electrostatic headphones, and see if you like them. You can always buy more expensive things later on should you end up really getting into the hobby, but the Stax amps are more affordable, and still let you drive your headphones to let you hear what they are all about. With the Lambda series in particular, I’ve found they don’t scale as high as the Omega series with more expensive amplification, so maybe a 500T would be all you would ever need. 

I’d certainly recommend trying out the Stax amps if you are a beginner, and I really enjoyed my time getting to know a couple of them. “Theres always a bigger fish” as Qui-Gon Jin would say. 

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s