Arcam A25 Stereo Integrated Amplifier Bench Test Report

[gene]

The Arcam Radia A25 is a 100 watt/ch Class G slimline stereo integrated amplifier with digital input connectivity and MM phono preamp output. The A25 utilizes a very high quality ES9280A Pro DAC and the end result is excellent noise and distortion performance on our test bench. I thoroughly test the analog and digital circuits all the way through to the preamp and power amp sections. I discuss a couple of warts that I discovered in hopes that Arcam can improve upon in future models.

The A25 elegant sleek design packs a lot of performance and great aesthetics into a easy to use product that looks great on a credenza as it rewards you with clean audiophile sound for small to medium sized rooms.

Read: Arcam Radia A25 Bench Test Results!

 

[gene]

 

[Tankini]

@gene Before I even read your results, one look at the photo with the hood off, nice clean well design layout. I knew that product by Arcam, was going to punch above its weight class and have good measurements very nice article Gene, we'll be looking for the video to watch this afternoon thank you. Reasonably priced

 

[TLS Guy]

I don't disagree with rolling the bass off like that on the phono input, in fact I encourage it.

Very few records are cut with frequencies not rolled off below 30 Hz and actually usually quite steeply. The reasons are twofold.

The first is that cutting very low frequencies on an LP severely shortens playing time, as low frequencies increase the groove spacing.

The other important issue is that few LPs are perfectly flat, and so you have transmission to the speakers of the record warp frequency. This leads to large useless woofer cone excursions, which wastes amp power and harms LF accuracy. So starting a roll off on an RIAA input below 30 Hz is actually a very good idea. Peter Walker always started to roll his RIAA inputs off starting below 30 Hz. That is the correct approach.

I hope these amps are long lived. Class G power supplies have had somewhat of a checkered history and certainly have proved to be a point of failure in units employing that topography. If I were a potential purchaser that would be an issue of concern for me.

Otherwise this looks to be a very good unit, although I think in this day and age bass management should be part of the bundle. This is especially true for units like this, as they have a higher chance than usual of being mated with bookshelf speakers where a small sub can be tucked away.

 

[Danzilla31]

Great article Gene!!!!

 

[lovinthehd]

Seems to me something like this is okay, but still overpriced for what it is.

 

[gene]

 

[gene]

I don't disagree with rolling the bass off like that on the phono input, in fact I encourage it.

Very few records are cut with frequencies not rolled off below 30 Hz and actually usually quite steeply. The reasons are twofold.

The first is that cutting very low frequencies on an LP severely shortens playing time, as low frequencies increase the groove spacing.

The other important issue is that few LPs are perfectly flat, and so you have transmission to the speakers of the record warp frequency. This leads to large useless woofer cone excursions, which wastes amp power and harms LF accuracy. So starting a roll off on an RIAA input below 30 Hz is actually a very good idea. Peter Walker always started to roll his RIAA inputs off starting below 30 Hz. That is the correct approach.

I hope these amps are long lived. Class G power supplies have had somewhat of a checkered history and certainly have proved to be a point of failure in units employing that topography. If I were a potential purchaser that would be an issue of concern for me.

Otherwise this looks to be a very good unit, although I think in this day and age bass management should be part of the bundle. This is especially true for units like this, as they have a higher chance than usual of being mated with bookshelf speakers where a small sub can be tucked away.

Interesting about the roll off. Most phono preamps I've measured don't do this. I discuss in my YT video that drops today at 12pm.

This amp has a linear supply and it looks well built. So I think it will sustain.

 

[TLS Guy]

Interesting about the roll off. Most phono preamps I've measured don't do this. I discuss in my YT video that drops today at 12pm.

This amp has a linear supply and it looks well built. So I think it will sustain.

I have checked my notes, and Peter Walker always started to roll his RIAA inputs off at 6 db per octave below 32 Hz. That is identical to what is happening in that Arcam unit.

That is absolutely the right thing to do as it coincides pretty much with the usually adopted practice of rolling cutting lathes off at 28Hz, this is mainly for reasons of groove spacing.

The frequencies of what is known as warp wow, lie from 2 to 10Hz, usually peaking between 4 and 8 Hz. This is the cause of the large woofer excursions seen with many, if not most rigs playing LPs. If you use a Quad preamp from the Peter Walker era you will never see that happen. The filter gets it 12db down by 8 Hz and 18 db down by 4 Hz

All my LP rigs use Quad preamps from the Walker era. This is for many reasons, the HF roll off is one, but his unique HF cuts with 10K, 7K and 5K variable slopes deal really well with LPs that have issues in the HF area. My power amps are as well for that matter, and I own 10 Quad 909 power amps, seven of which are in the main theatre.

Arcam although now part of Harmon, are based in Cambridge as was Quad in nearby Huntingdon. I would bet some of those who designed that unit either knew, or even worked with Peter Walker at Quad. The curve has Peter's thumbprints all over it. And it is the right way to do it.

 

[luis1090]

					I have checked my notes, and Peter Walker always started to roll his RIAA inputs off at 6 db per octave below 32 Hz. That is identical to what is happening in that Arcam unit. That is absolutely the right thing to do as it coincides pretty much with the usually adopted practice of rolling cutting lathes off at 28Hz, this is mainly for reasons of groove spacing. The frequencies of what is known as warp wow, lie from 2 to 10Hz, usually peaking between 4 and 8 Hz. This is the cause of the large woofer excursions seen with many, if not most rigs playing LPs. If you use a Quad preamp from the Peter Walker era you will never see that happen. The filter gets it 12db down by 8 Hz and 24 db down by 4 Hz All my LP rigs use Quad preamps from the Walker era. This is for many reasons, the HF roll off is one, but his unique HF cuts with 10K, 7K and 5K variable slopes deal really well with LPs that have issues in the HF area. My power amps are as well for that matter, and I own 10 Quad 909 power amps, seven of which are in the main theatre. Arcam although now part of Harmon, are based in Cambridge as was Quad in nearby Huntingdon. I would bet some of those who designed that unit either knew, or even worked with Peter Walker at Quad. The curve has Peter's thumbprints all over it. And it is the right way to do it. I notby any means an expert on phono preamps. I'm curious mainly with the High frequency filters. You state that the low frequency filters cut 12 db at 8hz and 24 db at 4hz. but you mention High Frequency cuts a 10, 7, 5k hz with variable slopes. My question is: what are the specific slopes at every frequency? Won't you be able to basically use an equalizer to just adjust yourself those particular frequencies? My reasoning is that all that filtering sound like one size fits all solution and might be effective on some records but it might as well degrade the experience on some other records. I'm for one like to listen to the records the way it was intended by the recording engineer and I have records from the 80's and up and in some I enjoy the bass notes that seems to dig deeper and in some other the high frequency reverberations and little peaks. Peter Walker solution negates for the most part that and I believe it maybe make all the records sound the same. The equalizer option sounds better to me at least with high frequencies, if a record is to harsh let's say at 10k hz you just attenuate that frequency and that should fix the problem. In an opposite scenario if a record around 10hz is way to soft and you have a filter reducing output around that frequency even further your reproduction will be affected negatively. Keep in mind that my assumptions are base on your description of Quad preamps.

 

[TLS Guy]

					I notby any means an expert on phono preamps. I'm curious mainly with the High frequency filters. You state that the low frequency filters cut 12 db at 8hz and 24 db at 4hz. but you mention High Frequency cuts a 10, 7, 5k hz with variable slopes. My question is: what are the specific slopes at every frequency? Won't you be able to basically use an equalizer to just adjust yourself those particular frequencies? My reasoning is that all that filtering sound like one size fits all solution and might be effective on some records but it might as well degrade the experience on some other records. I'm for one like to listen to the records the way it was intended by the recording engineer and I have records from the 80's and up and in some I enjoy the bass notes that seems to dig deeper and in some other the high frequency reverberations and little peaks. Peter Walker solution negates for the most part that and I believe it maybe make all the records sound the same. The equalizer option sounds better to me at least with high frequencies, if a record is to harsh let's say at 10k hz you just attenuate that frequency and that should fix the problem. In an opposite scenario if a record around 10hz is way to soft and you have a filter reducing output around that frequency even further your reproduction will be affected negatively. Keep in mind that my assumptions are base on your description of Quad preamps.

You misunderstood. It is first order high pass at 32 Hz, so that is a 6db per octave cut at 32 Hz. So, 6 db at 16 Hz, 12 db at 8 Hz, and 18 db at 4 Hz.

Here is a picture of my Quad 22 I bought in 1966.

The knob far right sets the turnover frequency, and the knob to its left sets the rate of slope, from 1 to 25 db per octave.

Yes, you could do the same with an octave equalizer, but its a lot more bother and requires an extra unit. In practice that arrangement works very well for taming 'edgy' LPs.

This system was preserved right up to the Quad 44.

In the whole stereo era Peter Walker produced four preamps. The Quad 22, 33, 34 and 44. They are all really excellent for LP reproduction.

He got the high pass bass roll off dead right, as you can't really cut an LP without bass roll off at 28 Hz in the disc cutting process. And that warp wow is present on almost all LPs to some degree, and his filter slope stops it, so you don't have woofers doing useless wasteful excursions below 10 Hz. This also causes doppler distortion. His decision and Arcams are right on the money and should be standard practice and isn't.

The Quad 44 allows for precise setting of cartridge sensitivity and most importantly the loading capacitance from tip switches on the top.

I think the Quad 44 gives the finest LP reproduction possible, and in my book is number 1 for LP reproduction.

 

[head_unit]

Thanks for noting the "subwoofer" outputs have no filtering (which is OK as most subwoofers have it) and no time delay. BUT does the Arcam have any provision for highpass filtering? Without which, in my opinion, a subwoofer output is rather stupid (though I cynically understand why manufacturers do that).
- I would strongly request that 2-channel reviews specifically call out if it is possible to highpass the mains please please pretty please with cream and sugar

 

[lovinthehd]

Thanks for noting the "subwoofer" outputs have no filtering (which is OK as most subwoofers have it) and no time delay. BUT does the Arcam have any provision for highpass filtering? Without which, in my opinion, a subwoofer output is rather stupid (though I cynically understand why manufacturers do that).

They're just full range pre-outs, not particularly intended for a sub...no filters. Some subs can provide a high pass to the speakers, but this integrated amp doesn't have main in or processing loops either. My main complaint with most 2ch integrateds is that lack of bass management....or other features that would help in doing it externally....

 

[lovinthehd]

@head_unit forgot to mention as to the subwoofer having a "crossover" more likely the sub only has a low pass filter labeled crossover....altho some subs can help out.