Steg ST401 Review: 90 W x 4 and What Its Filters Can Do
The Steg ST401 is a four-channel amplifier from Steg's ST series, rated 90 W x 4 RMS into 4 Ω, 130 W x 4 into 2 Ω and 260 W x 2 bridged, in an all-aluminium chassis. Its Indian MRP is ₹49,990. Unlike the two Entry Level QM amplifiers we list, its listing gives filter ranges, a bass boost and a differential input, so it is easier to plan a system around. This review looks at what those filters can and can't do, how to read the power ratings, and how the ST401 compares with the ST402 and similar amps. See it on our Steg ST401 product page.
Quick summary
Rated 90 W x 4 at 4 Ω, 130 W x 4 at 2 Ω and 260 W x 2 bridged at 4 Ω. The listing gives no maximum-power figure and no supply voltage for these ratings.
Listed filters: high-pass 15 to 500 Hz, low-pass 50 to 4000 Hz, band-pass 15 to 4000 Hz and a bass boost of 0 to +12 dB. Slope and channel assignment are not listed.
A dual differential input is described as rejecting noise from the head unit. Speaker-level input is not mentioned.
We found no owner reviews, and the listing does not name the amplifier class.
Steg ST401 specifications
Specification | ST401 |
|---|---|
Type | 4-channel amplifier, ST series |
RMS power at 4 Ω | 90 W x 4 |
RMS power at 2 Ω | 130 W x 4 |
RMS power bridged at 4 Ω | 260 W x 2 |
Input sensitivity | 0.5 – 9 V RMS |
High-pass filter | 15 – 500 Hz |
Low-pass filter | 50 – 4000 Hz |
Band-pass filter | 15 – 4000 Hz |
Bass boost | 0 to +12 dB |
Chassis | All-aluminium |
Dimensions | 360 x 52 x 230 mm (axes not labelled) |
Weight | 3.41 kg |
India MRP | ₹49,990 |
All figures come from our store listing. We could not open Steg's own website from our research session, so none has been checked against a manufacturer page.
What the ST401's filters can and can't do
The three filters are the most useful thing the listing documents. A high-pass from 15 to 500 Hz suits door speakers: set it near 80 Hz, for example, and the woofers stop trying to reproduce deep bass. A low-pass from 50 to 4000 Hz can limit a channel to bass and midbass, and a band-pass confines it to a window. The listing doesn't give the slope, and it doesn't say whether the filters are set per channel pair or for all four channels together.
The limit is the top end. On the listed ranges the high-pass stops at 500 Hz, so it cannot protect a tweeter that needs a crossover at several kilohertz. Tweeters will need their own passive crossover, or the filtering done in a DSP. DSP tuning is a service we offer at VA3 Car Studio, and a processor is the usual place to set crossovers and time alignment for a front stage.
Power, bridging and subwoofers
The 90 W and 130 W ratings are per channel. The bridged rating, 260 W into 4 Ω, is quoted for each of two bridged outputs. That is close to the 300 W RMS of a JL Audio 10W0v3-4, a 4 Ω subwoofer, so one bridged output could drive it. The listing doesn't describe running one pair bridged while the other drives speakers, so check Steg's manual before planning a front-speakers-plus-sub layout on a single amplifier.
The listing also leaves out the supply voltage behind these ratings, the amplifier class and any fuse or current figures. It describes an audiophile transistor output stage but doesn't say which class that is. Take cable gauge and fuse size from the manual.
Inputs and head-unit noise
The input sensitivity is 0.5 to 9 V RMS, and the listing describes a dual differential input meant to reject noise from the head unit. That is a sensible design for a long cable run from the dash to the boot. It does not say the amplifier accepts speaker-level signals, though. If your factory stereo has no RCA outputs, a converter such as the two-channel JL Audio LoC22 is the usual route.
What owners and reviewers say about the Steg ST401
When we checked in October 2026, we found no owner reviews, forum threads or magazine tests of the ST401. The nearest page is an eBay catalogue entry for the larger ST402. It is not a review, it lists the ST402 as sold out, and its title says Class A/B. That wording is eBay's, concerns a different model and is not confirmed by Steg, so treat it as a hint, not a specification. If you run an ST401, tell us how it behaves in your car.
ST401 vs ST402 and similar amps in our store
The Steg ST402 (₹54,990 MRP) lists the same filters, boost and input range. It is rated 120 W x 4 at 4 Ω, 190 W x 4 at 2 Ω and 380 W x 2 bridged, measures 440 x 52 x 230 mm and weighs 4.21 kg, against 360 mm on the longest side and 3.41 kg for the ST401. Below it, the Steg QM75.4 (₹34,990) gives 75 W x 4 and no filter ranges.
Outside Steg, three four-channel amps in our store are a fair yardstick:
Zapco HB 104D II (₹22,990 MRP): Class D, 100, 150 and 250 W (4 Ω, 2 Ω, bridged), RCA and speaker-level inputs, and a 30 to 250 Hz filter in its quick guide.
Alpine R2-A60F (₹55,999 MRP): Class D, 100 W x 4 at 4 Ω, 150 W at 2 Ω and 300 W x 2 bridged, with 50 to 400 Hz filters plus a range reaching 6 kHz.
Deaf Bonce MLA-4120 (₹28,990 MRP): Class AB, 120, 150 and 300 W, RCA and high-level inputs, and filters from 10 Hz to 12 kHz.
All three list more power per channel at 4 Ω than the ST401, and the Zapco and Deaf Bonce do so for a lower MRP. Where the ST401 goes further is its low-pass, which reaches 4000 Hz while the Zapco and Alpine stop at a few hundred hertz. The Deaf Bonce filters go higher still, and its high-pass reaches 12 kHz where the Steg's stops at 500 Hz. The Alpine's high-pass range also reaches 6 kHz on channels 1 and 2.
Who should buy it, and who shouldn't
Consider the ST401 if you want a four-channel amplifier whose filters are documented, for door speakers or a bridged subwoofer, and you will confirm the points the listing leaves open.
Look elsewhere if you need to high-pass tweeters from the amplifier, want a speaker-level input confirmed, or want more power per channel than 90 W.
Installation notes for Indian cars
At 360 mm on its longest side and 3.41 kg, the ST401 needs a flat, rigid mounting area. The listing gives no thermal figures, so leave air around the chassis, because a closed boot in an Indian summer gets hot. Route the signal cables away from the power cable, even with a differential input.
VA3 Car Studio in Ghaziabad offers professional installation. If the amplifier is feeding a bridged subwoofer, we also build custom enclosures to the maker's published volume. For the 10W0v3-4, JL publishes 0.65 cubic feet (18.41 litres) sealed.
Price and where to buy
The Steg ST401 has an MRP of ₹49,990. VA3 Car Studio often sells below MRP, so check today's offer on the ST401 product page.
The bottom line
The Steg ST401 documents more than the two QM amps we list do: three filters with ranges, a bass boost and a differential input. Its limits are a high-pass that stops at 500 Hz, no stated class or supply voltage, and no reviews. If you want a Steg four-channel amp for door speakers or a sub, it is worth a look. If you want more power per channel or wider filters, compare the alternatives above.
Steg ST401 FAQ
What filters does the Steg ST401 have?
The listing gives a 15 to 500 Hz high-pass, a 50 to 4000 Hz low-pass, a 15 to 4000 Hz band-pass and a bass boost of 0 to +12 dB. It doesn't give the slope or say whether the filters work per channel pair.
What is the difference between the ST401 and the ST402?
The ST402 is rated 120 W x 4 at 4 ohm against 90 W for the ST401, and its longest side is 440 mm against 360 mm. Both listings show the same filters, bass boost and input sensitivity.
Can the ST401 high-pass a tweeter?
Not on the listed ranges. Its high-pass stops at 500 Hz, which is far below a typical tweeter crossover. Use a passive crossover or a DSP for the tweeter channels.
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