RSL iA255.1 Class D integrated amplifier discussion

[gafortiby]

I don't know anything about RSL, but this USA company is now designing/selling a budget-friendly class D integrated amplifier called RSL iA255.1. RSL says it is for "audiophiles." Price is $110 with free shipping as of this posting. From what I can tell, the company only makes speakers and this is their only in-house amp. So it looks like it was produced intentionally. I bought one because I need a spare amp, and will report my impressions once I receive it.

For now, here are some observations just based on product website. It'd be great if someone can do a proper review.

https://rslspeakers.com/ia255-1-integrated-amplifier/

Features:

• True 55W per channel (55Wx2) with 24V external power supply.
• Physical power toggle switch
• Inputs are Line-in, Bluetooth (chipset?), USB audio (chipset?)
• Physical toggle switch to pick between inputs--I hope this means bluetooth can be turned completely off.
• Physical toggle switch for 90Hz high-pass filter (12db reduction of freq below 90Hz)
• Stereo pre-out/ sub-out
• Tone controls at 100Hz and 5kHz.

Some interesting things specifically for this ASR community:

• I'm still new at ASR but it seems rare for a USA Company to design a Class D amp. (Unless we count Pyle Audio's many Class D offerings?) Unit is made in China.
• I wonder if the volume knob is taper A or not.
• I wonder if the tone controls have a center detent. I hope so.
• I wonder if the sub-out is volume controlled or not.
• Probably no option to push the RMS higher with power supply upgrade, since the manual suggests you can't change the power supply.
• SNR is a very respectable 105dB.
• Load dependence in the Freq Response looks nice and flat with 8ohm load? What is it at 4ohm? Anyway I can't really tell what I'm looking at because RSL is showing that chart with the HPF feature overlayed on it, making the vertical axis really large.
• They have a picture that shows SINAD but clearly it was not measured at 5W so I have no idea how to compare that number with the standard methodology here at ASR. But if SINAD is 50dB at 1%THD at 50W, it's obviously going to be better at 5W right?
• Chipset information not advertised. It's clearly an Infineon MA12070 based on pictures on RSL product page. (see below)
• Is it correct to call this a "2.1" amplifier? It powers 2.0 and then includes an unpowered sub-out.

Thoughts? Once I get my order, I'll try to comparing this with my recently acquired Fosi V3.

 

[ZINHAR]

I'm also new here, looking to get the Fosi V3 or RSL iA255.1 as they both seem to be great options. Waiting to hear your thoughts once you get your hands on the RSL, I'm particularly interested in the noise floor of these two models (when there's nothing playing).

 

[Matias]

Orchard Audio is also a class D designer and manufacturer in the US.

Orchard Audio - Home Audio & Stereo Equipment

Elevate the sound in your home theater, listening room, or recording studio with our range of highly reviewed, world-class amplifiers, streamers, and DACs.

orchardaudio.com

 

[Steven Holt]

Thank you for this thread. The topology looks quite nice. I would be interested to know how this one stacks up against the Topping PA3s.

 

[DVDdoug]

I wonder if the sub-out is volume controlled or not.

I assume so. It would be useless otherwise.

Load dependence in the Freq Response looks nice and flat with 8ohm load? What is it at 4ohm?

It's probably fine. Regular music is dynamic so you usually aren't "stressing" the amp. And frequency response is rarely a problem with solid state electronics.

They have a picture that shows SINAD but clearly it was not measured at 5W so I have no idea how to compare that number with the standard methodology here at ASR. But if SINAD is 50dB at 1%THD at 50W, it's obviously going to be better at 5W right?

Since SINAD is normally dominated by noise, you get a "better number" with a higher signal (higher output power). With noise, the important thing is if you can hear it during silence (or during quiet parts). The "ratio" by itself isn't actually that important. Once you drive the amp into clipping (distortion) SINAD gets worse as you increase power.

Is it correct to call this a "2.1" amplifier? It powers 2.0 and then includes an unpowered sub-out.

I'd say "no", but most preamps/integrated amps don't have that feature and they have to advertise/promote it somehow... And most "home theater" subwoofers are active so it's fine for most people.

Note that with movies, the "point one" LFE channel is thrown-away in the stereo downmix so you won't get the LFE from DVDs & Blu-Ray's. (But you'll still get the "regular bass" from all the other channels.)

 

[gafortiby]

Orchard Audio is also a class D designer and manufacturer in the US.

Orchard Audio - Home Audio & Stereo Equipment

Elevate the sound in your home theater, listening room, or recording studio with our range of highly reviewed, world-class amplifiers, streamers, and DACs.

orchardaudio.com

ah good point. I was really thinking more about the $100~$300 market. "Cheap" Class D.

 

[Chrispy]

RSL probably sells to no one except "audiophiles" fwiw. If not one, you probably haven't even run into the brand (unless old time LA area dwellers). The spec is pretty minimal but for some might suffice.

 

[gafortiby]

Quick first impressions. Everything works well and every feature is implemented as expected. Some notes and some comparison to my FOSI V3:

• The volume knob seems to be linear, not taper A. Still, it turns very smoothly and controls volume well.
  • Oddly, my volume knob's axis is bent and turning the knob makes it follow a wobble orbit.
• The two tone controls both have a center detent, so you can easily find the neutral position.
• The sub-out is a true sub-out and follows volume control. It is output only and it does not function as an input--which means this one is implemented correctly, unlike the FOSI V3.
• Comes with a branded power supply, just 24v but a healthy 7 amps.
• There is no speaker hiss at any volume level, at least from my speakers with my normal human hearing.
• Sound quality? Great for my ears. I can't tell the different between FOSI V3 and RSL.
• The max volume output would easily damage my bookshelf speakers. Strangely, I'd guess it's a whopping 30~40db(!! yes I know it's log scale) higher than my FOSI V3 even though this one has a lower RMS rating.
  • WHAT is going on??? On my FOSI V3 I could turn the volume to 100% and listen to music but this RSL already matched the max decibels of the FOSI V3 at about 60%, and I could not turn it past 80% before I thought I would completely blow out my speakers or damage my hearing. Assuming I didn't goof up the connections, either the RSL unit has a boosted input gain (almost like it has an internal preamp?) OR the FOSI V3 has a low input gain. I don't mean the FOSI has less output watts, just a lower input signal. I made sure I was using the same line input set to the same output volume.
• There is NO speaker pop. There is some kind of relay (that doesn't click?) or delay circuit that gives a delayed start.
  • On the FOSI I can hear a relay click. If the RSL is using a relay it's the silent type.
  • This delayed output happens when turning the system on, and also when switching between the 3 inputs.
  • The delay is annoying but probably protects my speakers.
  • I don't hear any pop on power off either.
• Internally, there is a tiny heat sink mounted to the UNDERside of the main chip that has thermal paste to make it conduct with the external chassis. Unfortunately the heat sink is slightly undersized so it doesn't make proper thermal contact with the chassis-- but I am guessing contact was the intent. see pictures below.
• The USB DAC is identified as ZhuHai-JieLi-Technology on MacOS. There's one chip next to the bluetooth and USB input. Maybe someone can identify it based on the writing on the chip. picture below
• Toggling the physical input switch works exactly the way I want.
  • Toggle to USB or LINE completely turns off the Bluetooth signal.
  • Toggle to Bluetooth or LINE completely disables the USB port. -- it disappears from the connected source.
  • Toggle to LINE completely turns off Bluetooth and USB.
  • Pairing with a different bluetooth does not always require a RESET. I think it depends on whether the unit can find the old device immediately.
  • All 3 inputs are closely level matched! Using my MacBook Air, all 3 produced similar volumes. Bluetooth with source set to 80%, and LINE set to 80%.
• Bluetooth works well even without the included antenna. I'm guessing he antenna will boost the range even more.

Below are some picture comparisons

 

[Opus_003]

Sound quality? Great for my ears. I can't tell the different between FOSI V3 and RSL.

I have the V3, wasn't crazy about the sound as set up in my system. That said, I'm really interested in the Ia255.1 because of the high pass filter. Does it sound exactly the same as the V3?

 

[TonyJZX]

thanks for this breakdown

its one of the few places that do this

I *think* these people are doing the same donkey thing as SMSL on the A300... they are bodging on a type-c for digital input and then routing it thru the bluetooth chipset, which is fine for many people

if it only supports 16/48 then there's further evidence

eg. https://www.zh-jieli.com/

i wonder who designed this, who makes it etc etc.

to my liking this thing is more towards the Fosi end because to get to the SMSL end where you have displays and switching thru remote and soft touch buttons is at another level

 

[ZINHAR]

this thing is more towards the Fosi end because to get to the SMSL end where you have displays and switching thru remote and soft touch buttons

I've noticed a lot of people on this forum refer to SMSL and Topping as being "higher-end" compared to Fosi or Aiyima. However, they seem to have more quality control issues due to added complexity in their designs.

 

[TonyJZX]

i never said "higher end" per se

but topping are selling stuff at $350 and more... are the TPA guys there? i do not say this as a bad thing

my distinction is more than this RSL amp is using hard physical switches to move inputs

topping may use a remote and soft touch buttons

surely anyone should be able to see there's a different level of engineering involved? i make no comment on reliability as you should be able to make up your own mind there

 

[gafortiby]

RSL updated their website to include more specs. So my observed volume difference (vs FOSI) must be due to how the preamp is configured on this unit, compared to the swappable op-amps in the FOSI V3.

• Type: Proprietary audiophile pre-amp stage, Class D output using MA12070 IC by Infineon
• S/N Ratio: 106dB
• Channel Separation: 100dB
• THD+N: <0.006 % 1000 Hz ~10W

 

[lutefish]

I’ve had the SMSL A300 for about 6 months now, and have been very happy with it. I use an external DAC into the second set of analog RCA inputs to avoid the usb->Bluetooth kludge, though how much that matters is up in the air.

For comparison, SMSL report the following

• S/N Ratio: 103dB
• Channel Separation: 85dB
• THD+N: 0.004 %

 

[ampguy]

Interesting. I like the physical toggle switch, rather than the cryptic menu settings in say the SMSL A300.

 

[Don927]

Key items - 90 Hz bypass switch, toggle between 3 inputs, true sub / pre out, good tone controls & power and sound quality. A full review here would be great. From what I've read, most reviewers say this has more real world power than the Fosi amps, even though they may be rated at higher power outputs. A very interesting product from an American company.

 

[gafortiby]

I just found a nice video review here. This reviewer also mentions how the RSL has more "headroom" than the competition. No doubt he's hearing the same output decibel difference I heard. Going back to RSL's website it now says the iA255.1's input sensitivity is 185mV. I can't find the input sensitivity on my Fosi V3 but the BT20a is 280mV. Maybe that explains why my volume is much higher given same input signal.

 

[gafortiby]

I have the V3, wasn't crazy about the sound as set up in my system. That said, I'm really interested in the Ia255.1 because of the high pass filter. Does it sound exactly the same as the V3?

I did a side by side comparison of FOSI V3 and RSL iA255.1. Sample of things I tried:

• John Williams conducting Jurassic Park.
• Happy by Pharrell Williams
• Come Together by The Beatles

The only conclusion I reached was, my ears are not audiophile enough.

Seriously though, I have no idea how the ASR community judges sound quality in human subject terms. I could use the Cheapaudioman method and say things like "the soundstage and instrument separation is fantastic" but I don't have the prerequisite number of social media followers to make such claims myself. (I actually do like watching Cheapaudioman.) I can tell when an MP3 is overly compressed or if there is some interference hiss, but between these two amps I can't tell any difference in sound quality. My guess is that the RSL iA255.1 sounds as good as other good MA12070 amps, and the FOSI V3 sounds as good as other good TPA3255 amps.

One thing I did notice is that there is audible static (not high pitch just regular background noise) only the iA255.1 when a source is attached and the volume is turned to the max. However I think this is actually an amplification of my audio source's noise, because there is zero noise at max volume if the RCA input cables are disconnected.

 

[gafortiby]

One more note : the iA255.1's HPF is not a full cutoff. It only reduces it by "12dB/octave."
Flipping the HPF switch between "bypass" and "90Hz" makes an audible difference, but it does not fully cut 80Hz from reaching my bookshelf speakers.

ALSO! flipping the HPF switch produces a loud pop on the speakers

I think this is how low frequency cutoff systems normally work, but just clarifying expectations.
I have a Berringer miniFBQ and it also does "12dB/octave" on it s low frequency filter. https://mediadl.musictribe.com/media/sys_master/he4/hae/8849658773534.pdf

 

[TonyJZX]

here's the manual

https://rslspeakers.com/wp-content/uploads/2023/07/ia255-manual-rev4-6-25-2023.pdf

also:

• USB Audio DAC... for high-quality direct PC device connection with no software drivers needed. 16bit, 48kHz (pending device connection interoperability)

that video review also implies they want to add a remote

i assume these things do no have sleep or resume states?