Class D amp for my Marantz 2240B

[Darklude]

Hi everyone,

I'm looking to get a "Class D" power amp to help my vintage Marantz 2240B stereo amplifier drive my Nexus MTMWW tower speaker (from Matt Grant) I've build a few years ago. The is currently able to handle these speaker but I'm looking for something to help the amp drive these "bad boy". Would the Fosi Audio V3 Mono Amplifier or the AIYIMA A70 stereo amp be a good choice? Ideally I would like to keep the "warm sound" associated with my vintage Marantz amp.

Thanks for your help everyone!

 

[kyuu]

If you aren't having any issue with your current amplifier, why would you think you need a different one? A big speaker doesn't necessarily require a beefy amplifier. In fact it's often the opposite, as large speakers often have greater sensitivity (more SPL output for the same amount of power input) than small speakers.

In any case, if you really want to do this you should replace the amp entirely. Or you could hook up whatever you want to the Marantz's pre-outs if it is providing other useful functionality that you don't want to forgo. Amplifier don't have a "sound" unless they are defective or have a load dependency. The latter would be unusual for a class AB amp.

 

[Darklude]

Thanks

If you aren't having any issue with your current amplifier, why would you think you need a different one? A big speaker doesn't necessarily require a beefy amplifier. In fact it's often the opposite, as large speakers often have greater sensitivity (more SPL output for the same amount of power input) than small speakers.

In any case, if you really want to do this you should replace the amp entirely. Or you could hook up whatever you want to the Marantz's pre-outs if it is providing other useful functionality that you don't want to forgo. Amplifier don't have a "sound" unless they are defective or have a load dependency. The latter would be unusual for a class AB amp.

Thanks for the reply! Indeed the Marantz still doing a good job of "feeding" my speakers. I was curious to have opinion on adding class D amp to my Marantz preout to see if would help provide a better "sound quality" to my speakers and from other posts I see people really loving what Fosi or AIYIMA Class D amp bring to the table.

 

[JeremyFife]

Tend to agree with @kyuu - if there's nothing wrong with your venerable Marantz then why change it?

Of course, if you just feel like a change then it's your system and your hobby.

Class D amps are really good now: small, cheap, power efficient ... but changing Amp is unlikely to improve the sound.

 

[melomane13]

The speaker seems to have a very low impedance, EPDR 2 ohms.
I'm not sure the Marantz is suitable.
The specifications state 40 W 8 ohms, and at the time, in the 70s, the impedance of speakers was around 8 ohms.
With this difficult loudspeaker , I think an amplifier capable of driving 2-ohm loads would be much more appropriate, especially at high power.

 

[DVDdoug]

You want to use the new power amp with the Marantz? Does the Marantz have preamp outputs? If not, you'll need a speaker-level to line-level attenuator if you want to use it with a separate power amp, and that's not always ideal.

Ideally I would like to keep the "warm sound" associated with my vintage Marantz amp.

I also doubt your Marantz has a "warm" sound or any particular sound except for the effect of the tone controls and loudness control. The loudness control/switch boost bass at low volumes and it's rare on modern equipment so that might be a reason to keep it if you use that feature.

Plus, "warm" isn't well defined... Sometimes it means a mid-bass boost and sometimes it means slight "pleasing" distortion. You can't add 3dB of warmth since we don't know what it means.

Would the Fosi Audio V3 Mono Amplifier

Of course you'd need two for stereo.

 

[kyuu]

The speaker seems to have a very low impedance, EPDR 2 ohms.
I'm not sure the Marantz is suitable.
The specifications state 40 W 8 ohms, and at the time, in the 70s, the impedance of speakers was around 8 ohms.
With this difficult loudspeaker , I think an amplifier capable of driving 2-ohm loads would be much more appropriate, especially at high power.

View attachment 490951

That graph doesn't show the impedance dropping lower than 3 ohms.

 

[melomane13]

EPDR (Equivalent Peak Dissipation Resistance) takes the impedance and phase data and computes a new impedance that shows what equivalent load the amplifier will see.
The graph show the EPDR dropping lower than 2 ohms.
This is a very hungry current loudspeaker.
It's quite likely that the Marantz doesn't have the necessary "muscle" to drive these speakers.

 

[kyuu]

I'm aware of what EPDR is. It's not the actual impedance.

I wouldn't assume the Marantz can't handle it. We have no reason to assume that. I haven't seen a lot of good class AB amps that have an issue down to 2 ohms. And EPDR simply doesn't apply to class D amps.

If the amp is having an issue driving the speaker due to low impedance dips, I wouldn't expect it to be subtle. You should be noticing some serious power limiting, or, y'know, the amp shutting down.

 

[melomane13]

What is certain are the Marantz specs: 40 W into 8 ohms.
And the speaker’s impedance curve is demanding, with an equivalent resistance dropping below 2 ohms.
Under those conditions, it’s very likely that the amplifier won’t deliver much real power into that load.
I’ll stop here — I don’t wish to argue further.

 

[Chrispy]

I'd think an external amp could well provide more power and better impedance capability. If that's not an issue, probably not worth the expense.

 

[mhardy6647]

Yes, it's a tedious load for a vintage amplifier, and the Superscope-era marantz receivers weren't too adept at delivering the current required by a low impedance load...
but...
What is the sensitivity of the loudspeaker? It might not need more than a few watts.

 

[Luidspreker]

Though I am not very knowledgeable on the field of electronics, I want to add something here. I build, some 25 years ago, speakers Seas EX4. But the sound was not what I expected. Only after upgrading to Musical Fidelity A1 amp, I heard what I wanted. I streamed my music via Logitech .... and three years ago I bought the Yamaha WXC50, and this sounded pretty good.
About two years ago I was looking for a cheap amp for a friend, and I stumbled on the class D Behringer A800. Because my ears are not what they were some 25 or more years ago, I listen with two Phonak hearing aids, I asked my wife to listen. What I expected, she confirmed. This very cheap class D amp sounded better than the Musical Fidelity A1. Everything got better, the placing, the richness of the sound, etc. Buy one and try it, at the moment the price is less than €200.

 

[Hear Here]

Class D amps are really good now: small, cheap, power efficient ... but changing Amp is unlikely to improve the sound.

I agree and disagree!

Yes, good Class D amps (emphasising "good") now offer exceptional sound quality, but No, changing an amp is likely to improve the sound, provided the amp is chosen well - by home demo'ing a few likely contenders.

I was very surprised at the difference in sound quality when I home demo'd several high quality amps (£3-8K) when I decided to move from valve to sold state. I tried amps of Class A, AB and D and there were good and indiferent (none were bad) examples of all 3 groups. And their measurements gave no clue to their ability to deliver music in a life-like and exciting way. Indeed, one of the best measuring amp was drearly dull to the extent I was finding myself turning the volume down, rather than turning it up - kiss of death in an amp!

In the end I went for a Class D, but there was an exceptional Class AB and likewise an exceptional A in my test group. But results will depend on your speakers and your room - and probably your choice of music too, so please try at home first - it really will pay dividents, as otherwise you won't konw how much better your system can sound!.

 

[Luidspreker]

I agree and disagree!

Yes, good Class D amps (emphasising "good") now offer exceptional sound quality, but No, changing an amp is likely to improve the sound, provided the amp is chosen well - by home demo'ing a few likely contenders.

I was very surprised at the difference in sound quality when I home demo'd several high quality amps (£3-8K) when I decided to move from valve to sold state. I tried amps of Class A, AB and D and there were good and indiferent (none were bad) examples of all 3 groups. And their measurements gave no clue to their ability to deliver music in a life-like and exciting way. Indeed, one of the best measuring amp was drearly dull to the extent I was finding myself turning the volume down, rather than turning it up - kiss of death in an amp!

In the end I went for a Class D, but there was an exceptional Class AB and likewise an exceptional A in my test group. But results will depend on your speakers and your room - and probably your choice of music too, so please try at home first - it really will pay dividents, as otherwise you won't konw how much better your system can sound!.

I am afraid I am Dutch.... The Musical Fidelity was not cheap, and it took me quite some (Dutch?) courage to buy it. That said. I cannot imagine, listening to the A800, that it is necessary to spend so much money on an amp, or whatever. I suspect that the high quality brands, the very high quality brands, i.e. McIntosh (MI502) don't want to get poorish. The audio world, I am afraid, has always been somewhat trying to trick the poor listeners into their awkward stories. Not always without reason, but we all know the cables, the stones and woods to placed just there on the cd-player, the marble upon the amp and the player should be placed to sound better, etc. That said, I am not going to deny the differences in quality of the stuff, but in my humble opinion, something like a good tuning of speakers and amp is essential. I think this is, maybe, easier with these class D amps.

 

[Darklude]

Thanks everyone for your input, very informative and sorry for the response delay... for a unknown reason wasn't getting the notification for new post. As mentioned, yes my Marantz 2240B still doing a good job of driving my Nexus MTMWW. From the creator of these speakers:

These are an 8 Ohm nominal design and their good sensitivity means you do not need a powerful amp to get decent levels out of them but an amp or receiver rated in the 100-200w range @ 8 ohms will truly make them come alive.

I was just curious to see if adding a class D power amp (Fosi or AIYIMA) connected to the Marantz could help driving these speakers.

Thanks everyone!

 

[mhardy6647]

You'd be more likely to hear a difference, I would think, with something like a Benchmark AHB2 power amplifier.

Benchmark AHB2 Power Amplifier

Benchmark's new AHB2 Power Amplifier - "The Quietest, Cleanest Audio Amplifier on the Planet"

benchmarkmedia.com

PS if the impedance curve of the loudspeakers actually resembles that shown in a previous post (and reproduced below), the designer's opinion that they're nominally 8 ohm loudspeakers is... amusing. One of the traditional ways to assess "nominal" impedance on a full range loudspeaker is to look at the impedance in the 100-200 Hz range. Lots of energy (signal) in that range, and there is (was!) usually a flat region in the impedance curve that far upstream of the resonance peak(s) of the woofer & enclosure, so it was a good 'rule of thumb' in the days of classical loudspeaker design. The impedance in that region for this loudspeaker looks like about 3 ohms to me.

 

[Chrispy]

Thanks everyone for your input, very informative and sorry for the response delay... for a unknown reason wasn't getting the notification for new post. As mentioned, yes my Marantz 2240B still doing a good job of driving my Nexus MTMWW. From the creator of these speakers:

These are an 8 Ohm nominal design and their good sensitivity means you do not need a powerful amp to get decent levels out of them but an amp or receiver rated in the 100-200w range @ 8 ohms will truly make them come alive.

I was just curious to see if adding a class D power amp (Fosi or AIYIMA) connected to the Marantz could help driving these speakers.

Thanks everyone!

What do you feel are the shortcomings of the current amp? More power could be nice, but if not using it...

 

[Darklude]

No real short coming ... more curiosity to see if it would help or not. To be honest I love my Marantz 2040B, it still doing a great job! I'm really not in expert in the "audio world", but was looking for advice from this great community. Thanks!

 

[Chrispy]

No real short coming ... more curiosity to see if it would help or not. To be honest I love my Marantz 2040B, it still doing a great job! I'm really not in expert in the "audio world", but was looking for advice from this great community. Thanks!

It would most likely just provide a bit more volume. Keep in mind it takes a doubling of amp power to raise spl by a mere 3dB (not a lot). Does one amp have a better feature set otherwise or connectivity you're wanting? If anything I'd consider more powerful amps altogether and just get that out of the way for any possible future use. Generally you'd change speakers (or work on your room) for general audible improvements, though.