IOTAVX PA40 Power Amp Specs

[WeekendWarrior]

I'm thinking of a getting a power amplifier with a bit more grunt than my LA90D (I know this is an integrated amp, but I'm using it as a power amp only). I'd like to stick with Class A/B because I use a high level connection to my subs, and I'm advised that either a Class D or a bridged amplifier topology (e.g. a second LA90D in bridged mode, or a pair of B200s) is not compatible with this connection method (something to do with "floating earth design").

So, I recently saw a positive subjective review of the IOTAVX P40, which is Class A/B, which got my attention, but I'd like a more objective opinion based on the specs, which are:

The trouble for me and my limited knowledge of how to interpret these, is that the specs for this amp use different criteria than I have seen in Amir's reviews (i.e. distortion @100W rather than 5W), and I'm not sure how to interpret them.

I guess what I am interested in is whether this amp, whilst perhaps not as pristine as the LA90D, will still provide audibly similar noise free output.

Thanks!

 

[Rit]

How much power do you want?
What speakers are you using?
Iota looks decent, but you can do better. if it were me I would look at Buckey amplifier (currently running the purifi setup), give Dillon a call.

 

[WeekendWarrior]

I've got Ascilab C6Bs. They aren't designed to play super loud, but the 70W output that Amir measured from the LA90D is probably bare minimum. And I've got some room correction EQ, which probably affects things too.

I'd be aiming for 200W+, and an amp that was capable at low impedance. The Purifi based amps are I think Class D so wouldn't work with the high level connection to my subs, unfortunately.

 

[EdW]

I've got Ascilab C6Bs. They aren't designed to play super loud, but the 70W output that Amir measured from the LA90D is probably bare minimum. And I've got some room correction EQ, which probably affects things too.

I'd be aiming for 200W+, and an amp that was capable at low impedance. The Purifi based amps are I think Class D so wouldn't work with the high level connection to my subs, unfortunately.

There are perhaps issues with using the balanced output of balanced amp into a sub (unless it has balanced xlr input). But a single ended output Class D is clearly no different from a Class AB. So just avoid Purifi 9040 based designs with the balanced output.

 

[WeekendWarrior]

There are perhaps issues with using the balanced output of balanced amp into a sub (unless it has balanced xlr input). But a single ended output Class D is clearly no different from a Class AB. So just avoid Purifi 9040 based designs with the balanced output.

Thanks for your reply. The issue my sub supplier (MJ Acoustics, a UK company) stated was "floating earth". If some Purifi designs don't have this then that's good to know.

Any views on the merits of the IOTAVX PA40s?

 

[EdW]

Thanks for your reply. The issue my sub supplier (MJ Acoustics, a UK company) stated was "floating earth". If some Purifi designs don't have this then that's good to know.

Any views on the merits of the IOTAVX PA40s?

I’m not sure what MJ means by floating earth. Does this mean that they are less susceptible to hum loops? Their website is unfortunately very light on technical detail. I can’t think that the IOTAVX PA 40 has a special characteristic which makes it better for driving subs than any other amp of any type. Clearly not in the same league as the Purifi based designs but much less expensive and almost certainly ok for your speakers. Check reviews with MEASUREMENTS not just subjective waffle, because any idiot can write that. Also check warranty and returns policies etc

 

[Sokel]

I’m not sure what MJ means by floating earth. Does this mean that they are less susceptible to hum loops? Their website is unfortunately very light on technical detail. I can’t think that the IOTAVX PA 40 has a special characteristic which makes it better for driving subs than any other amp of any type. Clearly not in the same league as the Purifi based designs but much less expensive and almost certainly ok for your speakers. Check reviews with MEASUREMENTS not just subjective waffle, because any idiot can write that. Also check warranty and returns policies etc

A lot of (usually) higher power class D amps have balanced OUTPUTS.
That means that they can't even smell ground from far away, and there should be huge disclaimers about it, as with the bridged class AB amps but more prominent.

That does not mean that all class D amps are like that though. Lower power ones or bridgeable (before bridging them of course) can be fine.

As with everything, one must know its gear.

 

[EdW]

A lot of (usually) higher power class D amps have balanced OUTPUTS.
That means that they can't even smell ground from far away, and there should be huge disclaimers about it, as with the bridged class AB amps but more prominent.

That does not mean that all class D amps are like that though. Lower power ones or bridgeable (before bridging them of course) can be fine.

As with everything, one must know its gear.

Not too many medium power class D amps , such as the OP might reasonably consider for driving the ASCILAB speakers have bridged outputs. In the Purifi range it is only the 400/800/1400 watt 9040 amplifiers that are inherently bridged and they are well suited for driving high end power hungry speakers. The more modest amps are capable of 200W/400W into 8/4 ohms single ended

 

[Sokel]

Not too many medium power class D amps , such as the OP might reasonably consider for driving the ASCILAB speakers have bridged outputs. In the Purifi range it is only the 400/800/1400 watt 9040 amplifiers that are inherently bridged and they are well suited for driving high end power hungry speakers. The more modest amps are capable of 200W/400W into 8/4 ohms single ended

Correct (I haven't checked 7040 but you're probably right)

When I say "higher power" I always mean at least 400-500W/8 Ohm doubling down with halving impedance, so yes, just about there.

 

[EdW]

Correct (I haven't checked 7040 but you're probably right)

When I say "higher power" I always mean at least 400-500W/8 Ohm doubling down with halving impedance, so yes, just about there.

The 7040 designs with robust pos and neg 70 v rails is good for about 250/490/950 wats into 8/4/2 ohms. It is single ended as the power rails suggest. I have a pair of March audio P501 amps using the 7040 modules and with a 40A peak rating they are well suited to drive very low impedance speakers (most speakers these days?). Not as good as the more recent 9040 amps but certainly completely transparent.

 

[WeekendWarrior]

I’m not sure what MJ means by floating earth. Does this mean that they are less susceptible to hum loops? Their website is unfortunately very light on technical detail. I can’t think that the IOTAVX PA 40 has a special characteristic which makes it better for driving subs than any other amp of any type. Clearly not in the same league as the Purifi based designs but much less expensive and almost certainly ok for your speakers. Check reviews with MEASUREMENTS not just subjective waffle, because any idiot can write that. Also check warranty and returns policies etc

Specifically MJ told me that "if the negative terminal of the power amp output is not at the same ground potential as the normal audio ground used for the source connections" then not to connect the subs directly to the speakers via a high level connection lead (unless using a specific interface to make them compatible). Examples of this would be bridged amplifiers (e.g. Topping B200, LA90D in bridged mono configuration) and many Class D designs. I think this has been established in the discussions above anyway.

It's good to know however that not all Class D amps operate in this way, so should I change my amp I have some additional options to look at.

 

[DVDdoug]

They aren't designed to play super loud, but the 70W output that Amir measured from the LA90D is probably bare minimum.

Is your current setup loud enough for you? If you're not turning it up to the point where you're hearing distortion there's no need for more extra-unused power. You also may not want an amplifier with enough power to burn-out your speaker. (You can actually burn-out a speaker with and amplifier rated the same, or less, as the speaker if you push it into clipping because although the peaks are clipped/limited the average power continues to go-up as you continue to turn it up.)

There are myths about "headroom" but if you don't use the headroom you don't need it. And if you use it it's no longer headroom!

The trouble for me and my limited knowledge of how to interpret these, is that the specs for this amp use different criteria than I have seen in Amir's reviews (i.e. distortion @100W rather than 5W), and I'm not sure how to interpret them.

Amir combines noise and distortion as SINAD. Distortion is rarely a concern unless you over-drive the amplifier into Clipping. i.e. If you turn it up and "try" to get 110W out of a 100 Watt amplifier. Most manufacturer's power specs aren't entirely honest and sometimes VERY dishonest. Amir posted a review a couple of days ago of an amplifier rated at 1600W per channel and it was only capable of 450W!

Noise can be a concern. Amir measures SINAD at 5W which allows you to fairly-compare different amplifiers. If you measure relative to maximum power a higher-power amp with more noise (hum hiss or whine in the background) might get a better signal-to-noise rating than the lower power amp, even though there is more noise coming out of the speakers. Since there is more than one way to measure noise the manufacturer's specs are mostly useless. You need comparable measurements like you find in the reviews here. Beyond that, it's still tricky because the audibility of the noise depends on character of the noise (our ears are most sensitive at mid-frequencies*), the sensitivity of your speakers, how close you are to the speakers, other ambient noise in the room, etc.
.


* A-Weighted measurements take this into account so they better represent the audibility of the noise. And they allow the manufacturer to publish a "better number".

 

[Rit]

Personally I believe you are putting yourself in a corner. Drive the speakers and the subwoofers with independent amplifiers.

 

[WeekendWarrior]

Personally I believe you are putting yourself in a corner. Drive the speakers and the subwoofers with independent amplifiers.

They are driven by independent amplifiers. My speakers are driven by my LA90D. The subs both have their own amps; the high level connection to the speakers is just providing a signal for them to amplify.

 

[Matias]

I'd like to stick with Class A/B because I use a high level connection to my subs

This is the problem right here. Drive your subs with line level outputs and open your choices for any amp you like.

For example:

'Apollon NCx500ST Stereo Amplifier Review'

Sep 7, 2023

This is a review and detailed measurements of the Apollon NCx500ST stereo class D amplifier based on Hypex NCOREx NCx500 modules. It was kindly drop shipped from the member and costs 1,090.00€ (US $1,168) with standard opamp.

While the case is stamped aluminum, it is a heavily customized one with attractive side vents. You get to select your color of choice. The back panel is where you notice the high value add:

You have no less than four gain settings and even an LED brightness switch! FYI, I will have to confirm which op-amp is included with this...

• amirm
• Replies: 961
• Forum: Stereo and Multichannel Amplifier Reviews

• 

 

[KL....]

I'm thinking of a getting a power amplifier with a bit more grunt than my LA90D (I know this is an integrated amp, but I'm using it as a power amp only). I'd like to stick with Class A/B because I use a high level connection to my subs, and I'm advised that either a Class D or a bridged amplifier topology (e.g. a second LA90D in bridged mode, or a pair of B200s) is not compatible with this connection method (something to do with "floating earth design").

So, I recently saw a positive subjective review of the IOTAVX P40, which is Class A/B, which got my attention, but I'd like a more objective opinion based on the specs, which are:

View attachment 477373

The trouble for me and my limited knowledge of how to interpret these, is that the specs for this amp use different criteria than I have seen in Amir's reviews (i.e. distortion @100W rather than 5W), and I'm not sure how to interpret them.

I guess what I am interested in is whether this amp, whilst perhaps not as pristine as the LA90D, will still provide audibly similar noise free output.

Thanks!

@WeekendWarrior
Power Doubles, 150W/RMS (8Ω, 2 Channels) to 300W/RMS (4Ω, 2 Channels).... note RMS (continuous power level) not Max/Peak (temporary short-burst power level)
You should be able to use a high level (Speaker/Stereo (not Bridged)) connection (A or B) to your subs (powered or passive/unpowered, depends on the subs) but check with iOTAVX.

Rec OUT.... it appears that these are Line Outs which you could/can feed to your (Powered) Subs (note, re Volume Level, that the Line/Rec Out signal/s needs to match the Line/Input signal/s and Amps/Speaker Output Level gain, wouldn't it?) but check with iOTAVX.
THD+N <0.003% (100W, 1 kHz).... this suggests THD+N @ 100W (2/3rds of Rated RMS Power)

• SINAD ~ 20*log10(THD+N%/100) = 20*log10(0.003%/100) = 130.5 db @ 100W (which is exceptional, isn't it?. If the RMS Rateing doubles for 2Ω Load (not indicated) then this Amp could be regarded as (definitely) Transparent, couldn't it?)