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Recommendations for Power Amplifier

Wharfedale Evo 4.2

kratu

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I've a pair of Acoustic Portrait bookshelves with Scanspeak drivers. Sensitivity: 89dB at 8 Ohms. Currently, I've been driving these with Lyrita GM70 power amplifier. Being a 20W amp, this doesn't seem to drive the speakers that well. Especially, the lower frequencies are damp and imprecise. There is boom right now, which is primarily due to the room configuration (Earlier they were really great. I've changed the cables inside the speakers and that seems to have opened up the dynamic range).

I'm looking to pair this with a SS power amplifier to improve the microdynamics and speed. I like to retain the warmth of a tube sound. Therefore, my preamp (Lyrita Lync Pre) will remain.

I'd like to know these:

  1. What is the minimum power wattage should I look for in the power amp?
  2. Is it correct that adding a power amp helps in achieving the goal that I've mentioned?
  3. Any specific power amplifiers that I should look for? (under 50k).

Additional information: This is primarily for music. Source is a network audio player that can handle hires (DSD, FLAC) files. I prefer music that is slow, soothing, ambient, meditative, open soundscape; good vocals). I'm a low-volume listener. Occasionally, I can crank up the volume and listen to fast music that needs a lot of dynamics).

Please feel free to add any other things that I should consider. Thanks in advance.
 
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jai1611

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A starting point would be the Acoustic Portrait power amp - either the old 70w one or the current Swara

Given that you intend to use a tube pre, class D amps wont work due to impedance mismatch issues (mostly those are 10k)

Commercial offerings from mainstream brands are relatively few at that price point. You can look at some DIY options if willing to go down that route.

I'm on a similar hunt myself so will drop you a more detailed PM later today with additional notes
 

tuff

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Power amp under 50k would be difficult, unless you go the used route. Another way you can do is get a Crown XLS 1502 pro amp around 30k, and bi amp the speakers, if possible. Let the Lyrita power the tweeters and the woofers get powered by the Crown. I am using it to power the Magnepan 1.7's and they are brilliant. another fm @dheerajin is also using the Crown with PSB Synchrony floor standers with a tube buffer.
You may read upon the Crown drive core series, on different hi fi forums and see what they say. Mid-range is magical. Hope this helps.
 

dheerajin

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Crown would have an impedance mismatch issue with a tube preamp
Lot of users in US , using tube pre like IFI-ITUBE, which also acts as a buffer, so there is no impedance mismatch observed , For other tube preamps this could be an issue. But this crown XLS series is magical amplifier, Those who have heard it can vouch , Still it is in burning phase even after 10 months, everyday it gives surprises and FM @tuff has observed this too.
 

jai1611

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@dheerajin I was told an output impedance of 5k ohm for the Lyrita DHT preamp (after a redesign, used to 1250 ohm), which won't run anything below 50k ohm. Don't know where the Lync stands but even at 1250 won't work well with a 10k ohm

Don't know the ifi buffer specifically. one simple way to check impedance issues is by using different cable lengths. If there is a noticeable change in sound, you probably have an impedance mismatch. Using very short cable lengths can get around that
 

dheerajin

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My interconnect length was total 6 feet, 3 feet to buffer then 3 feet to power amp, Which was considerable high. So i reduced it half and there was perceivable change in sound, then I reduced it to 1/4 and no change in sound. So I dont think it was impedance mismatch issue, rather length was more compared to signal it carries. Ifi-Itube is known for solving the impedance mismatch issue.
But your observation for other tube pre amp is right.
 

Naturelover

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Have you checked with Siva and Viren Bakshi? Their opinion would probably point you to the best solution.
 

Kannan

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My interconnect length was total 6 feet, 3 feet to buffer then 3 feet to power amp, Which was considerable high. So i reduced it half and there was perceivable change in sound, then I reduced it to 1/4 and no change in sound. So I dont think it was impedance mismatch issue, rather length was more compared to signal it carries. Ifi-Itube is known for solving the impedance mismatch issue.
But your observation for other tube pre amp is right.

Sir, 6 feet does not deteriorate signal strength to any audible levels, in fact it will not be even measurable.
 

Indranil Sen

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kratu- Your speakers are sufficiently efficient at sensitivity level of 89db. Any well designed power amp will be able to drive it. No worries.
Since you have bookshelf speakers you would need a sub to effectively reproduce low frequency in the room. And when you add an active subwoofer it will immediately free up amplifier resources to improve the sound quality. So there is a couple of options that you have to improve your listening experience.
1. Add a good active subwoofer and place it carefully in the room such that it complements the bookshelf speakers when it comes to low frequency. You might find the existing amplifier under this configuration good enough to reproduce mid-high frequency band using your speakers.
2. If you still like to pursue the amplifier upgrade option with or without the subwoofer then there are several options available in the market. You need to shortlist a few of them based on your budget, audition them preferably in your room and select the one that blends well with rest of your system.
Regarding the power of the amplifier you don't have to worry much because your speakers appear to be an easy load and any well designed amplifier would be able to drive it. Anything more than 60W per channel would be good. The higher the amplifier power the better dynamic range it would have in handling transient peak current and sound smooth.
Thanks.
 

kratu

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@jai1611 Yes, I might need to check APs own amp. And thanks for your PM.

@tuff I’m new to biamping. I will check out more of this method.

@Naturelover I can check with Shiva and Viren Bakshi. My understanding is that Their amps pair well with their own speakers (and vice versa).

@Indranil Sen My bookshelves are quite large to be called that way. The lower frequencies are deep and wouldn’t need a subwoofer at all. I might first try optimising my room acoustics first. It is possible that there is lot of reverb due to sparseness of the room.

I know that most amps above 60w would work but I’m looking for something that pairs well with the preamp and could retain the warm sound signature.


You have mentioned the higher the power the better the dynamic range. Would this make the sound thin and bright?
 

Indranil Sen

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kratu- Any well designed higher powered amplifier would have enough buffer to handle musical peaks effortlessly yielding a very smooth response over the entire frequency band. This will not change the tonality of the music. Hence it would not make the music thin.

You have mentioned warm sound a couple of times above. This is mostly a characteristic demonstrated by your speakers and influenced by rest of your electronics. Given this choice brands like Accuphase, Parasound, Pass Labs, Plinius, etc which offer Class-A biassed amplifiers will fit your requirement better. They have neutral to warm sound signature which you might like. I am not the best person to comment on availability/price of these brands in India but other esteemed members in this group would surely help you on this.

Yes, you will be able to get a better controlled bass in your room with the existing speakers by optimizing the placement of room acoustics products in the room. However adding a sub-woofer or two in your existing stereo set up and integrating it properly with the existing speakers would further improve the low-end performance and the overall stereo performance in the room. You might consider it as a serious upgrade option in the future
Thanks.
 

kratu

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Yesterday I moved my system to another bedroom to test if this is about the room. This bedroom currently functions as a storage area of sorts, therefore has "better" acoustics. I started this as a small experiment but ended up spending close to midnight engrossed in the music. I wouldn't be able to write this in technical terms. I'd let you imagine what it means to be sitting for two hours.

This improved the low frequency performance, yes; but so did the mid-range and the highs. I realised that room acoustics make such a difference. Power amplifier can wait.
 

Naturelover

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Good for you! The room has often been said to be the most important part of an audio setup and, unfortunately, the most neglected.
 
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