Holo Audio Serene Preamplifier

@GoldenOne unfortunately I do not have a second amp (with xlr inputs). I sent my Krell amp specs to Tim at KitsuneHiFi as he is looking into this as well. As @Buffdriver commented, my amp only has one set of xlr inputs so it’s hard to understand how the amp would be the issue (it could be of course, as I don’t know anything about hifi internals/technology 😊). As I want to keep xlr 1 for my headphones, I will stick with xlr 2 feeding the amp. I have to keep the serene volume/gain at around -5dB, however, for normal listening volume so this does not give much room to increase for lower volume recordings. 
 

On a side note, the sound quality of the May/Serene combo is heavenly! Thank you @GoldenOne for your review and introducing me to Holo Audio and thank you for the all the help!! 
 

Hi @GoldenOne

I love all of the work you have been doing and the help you have been giving everyone. Thank you 

Is the Serene in your review L1 or L2?

I see it has the Wildism badge, but I have not been able to determine if that means that it is a L2. 

Thank you

1 minute ago, drjimwillie said:

Hi @GoldenOne

I love all of the work you have been doing and the help you have been giving everyone. Thank you 

 

Is the Serene in your review L1 or L2?

I see it has the Wildism badge, but I have not been able to determine if that means that it is a L2. 

Thank you

I originally had level 1, but sold it and upgraded to l2/kte

On 7/25/2021 at 9:44 PM, Hish said:

I sent my Krell amp specs to Tim at KitsuneHiFi as he is looking into this as well.

Would appreciate it if you could post back what you hear?  I'd be interested to see the feedback (have a Serene ordered to go in front of a Krell 400 cxi).

@brightonjel For sure! I checked the specs of the 400xi and the input sensitivity is approx 0.6 V so I believe will work well (doesn’t need as much to reach max output from amp as the Evo 3250 with an input sensitivity of 2.4V).
 

Let me know how it works once the Serene arrives! 

@Hish Actually, I mistyped .. it's  Krell 400cx, not the integrated xi amplifier.  Sorry about that. Specs show input sensitivity around 2.7 v for that power amp.  Have it all up and running now, with Krell on XLR2.  Volume shows between -15db and -10db for listening at reasonable (i.e. loud, but not objectionably so) volume in a small room, depending upon the source material.  Can't comment on sound yet as it's only just unpacked and plugged-in. 

Beautiful setup! If you go off XLR 1, do you notice any significant volume increase?

For my setup (using XLR 2), when the Serene is set to approx -10dB gain, the volume is also a reasonable volume. Switching to XLR 1 and maintaining the same gain, the volume is definitely louder. 

@HishI'll try the other output once things have burned in and settled a bit.  Those volume settings are about what I was expecting, at least based on prior experience.  (Don't forget that max volume from the Serene comes at +6db, so even at -10db there is quite a bit of headroom left.)

Holo Audio gear is just beautiful stuff. Their industrial design is first-rate.

So off of xlr 2 I am listening at around -10 to -5dB. Volume is moderate. For some hi-res (192 kHz) classical tracks I have to get to 0 to max dB (at night I can lower this as ambient noise is much less). 
 

Another question I have is does running off xlr 1 (for the extra 16dB of volume) put less strain on the preamp and amp? I mean is the preamp/amp working more efficiently off xlr 1? Or is there a risk using xlr 1 as it doesn’t have Load resistors to protect the amp? 

@Hish .. I tried both XLR outputs from the Serene to the Krell.  I used the same track at a moderate volume and measured SPL via a phone app from one speaker, from a few feet away.  Got pretty much the same readings from both scenarios.  Didn't really hear any qualitative or quantitative differences, though it was just a quick test.

17 hours ago, Hish said:

So off of xlr 2 I am listening at around -10 to -5dB. Volume is moderate. For some hi-res (192 kHz) classical tracks I have to get to 0 to max dB (at night I can lower this as ambient noise is much less). 
 

Another question I have is does running off xlr 1 (for the extra 16dB of volume) put less strain on the preamp and amp? I mean is the preamp/amp working more efficiently off xlr 1? Or is there a risk using xlr 1 as it doesn’t have Load resistors to protect the amp? 

4 minutes ago, brightonjel said:

@Hish .. I tried both XLR outputs from the Serene to the Krell.  I used the same track at a moderate volume and measured SPL via a phone app from one speaker, from a few feet away.  Got pretty much the same readings from both scenarios.  Didn't really hear any qualitative or quantitative differences, though it was just a quick test.

Sounds like something is odd. 

There shouldn't be any difference and if @brightonjelis seeing the same vol then it suggests an issue with @Hish's setup.

Just to check, Hish what cables are you using? Are they normal xlr? Not xlr to rca or something? 

@brightonjel @GoldenOne Problem Solved! (and I feel stupid I didn't realize the issue earlier). 

Because my 3 channel Krell Amp runs both my 2-channel music and my home theatre, I had two XLR Y-splitter cables feeding the Krell amp - one on the left channel and one on the right channel (the third channel was for my centre speaker so was fed directly by the AV processor).  One XLR end connected to my AV Processor and the other connected to the Serene. Once I removed the XLR Y Splitter cables from the left/right channels of the Krell amp and fed the Serene direct to the Krell amp, the volume off both Serene XLR outputs were the same (and both increased significantly - normal listening volume would now be -50dB on the serene!! Wow!!). Obviously the XLR splitter feeding the Krell amp was doing something weird to the signal (and that was magnified off of the XLR 2 output - I assume because of the higher impedance?).

So, next thing I have to figure out is if there is a way to connect the AV Processor and Serene to the Krell amp (XLR switcher?) or do I have to manually swap out the XLR cables feeding the amp each time I want to watch a movie (and back again when I want to listen to music). Any ideas you have would be greatly appreciated!

Thank you!!    

2 hours ago, Hish said:

@brightonjel @GoldenOne Problem Solved! (and I feel stupid I didn't realize the issue earlier). 

 

Because my 3 channel Krell Amp runs both my 2-channel music and my home theatre, I had two XLR Y-splitter cables feeding the Krell amp - one on the left channel and one on the right channel (the third channel was for my centre speaker so was fed directly by the AV processor).  One XLR end connected to my AV Processor and the other connected to the Serene. Once I removed the XLR Y Splitter cables from the left/right channels of the Krell amp and fed the Serene direct to the Krell amp, the volume off both Serene XLR outputs were the same (and both increased significantly - normal listening volume would now be -50dB on the serene!! Wow!!). Obviously the XLR splitter feeding the Krell amp was doing something weird to the signal (and that was magnified off of the XLR 2 output - I assume because of the higher impedance?).

 

So, next thing I have to figure out is if there is a way to connect the AV Processor and Serene to the Krell amp (XLR switcher?) or do I have to manually swap out the XLR cables feeding the amp each time I want to watch a movie (and back again when I want to listen to music). Any ideas you have would be greatly appreciated!

 

Thank you!!    

Probably best to manually switch. Less potential for all kinds of problems.

@Hish Ah - that's not good.  If I understood the connection setup correctly, the Serene was feeding both the high impedance Krell input and back feeding the low impedance output of the AV amp?  That could explain the volume difference with the XLR2 Serene output's additional series resistor and why overall the volume is low.  A decent switcher should work but no idea what impact (if any) it would have on sound quality.  I'd also only switch sources with all components turned off, just to be safe.

You want one of these:

https://www.amazon.com/gp/product/B07QVKPR2V/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

This way, the signal stops at the box and you are only driving a little bit more cable.

Spoke with Tim from KitsuneHiFi and as everyone suggested, a good xlr switcher would work. I’ll check a few options (including the Goldpoint). I’m hoping there won’t be any noticeable degradation in sound quality….

I am using the linked above switcher for this exact purpose, also feeding my Krell from either HTP-1 or Serene.  It is completely neutral.  

@GoldenOne Do you have recommendations for headphone cables off the Serene or does anything just sound great?

@GoldenOne

Thank you for your reviews on the Holo May and Serene.  I purchased the May KTE to replace my Marantz NA-11S1 and I love it.

I have a Balanced Audio Technology  VK-600SE amp, VK-52SE tube Pre-amp and Revel Salon2 loudspeakers, and I'm interested in the Serene to replace my tube amp.

One thing I'm looking to improve on is the sound staging in my system. I may have missed it in your review, but, would you mind commenting on the Serene's sound staging ability and, if possible, comment on what you suspect one might hear, as it relates to sound staging, between the Serene and my VK-52SE tube preamp?

Thank you.

Received my Serene L2 yesterday. What a nicely fleshed out sound. After less than 24 hours it's sounding pretty well settled. Have others noticed many changes after more hours like the May?

I haven't noticed any changes; it sounded superb on plugin and has been on continuously since then. But i didn't with the May either, so YMMV.

I've had my Serene for a couple of months now, sitting between May and a Krell power amp.  Given the patchy nature of my listening pattern then I put both the Holo devices into standby when I'm not going to be listening for a day or more.  I've never been able to decide if it's my ears that are adapting or the units warming up, but once I power-up and start playing music things usually take half an hour or so to settle down.  However, now I have enough listening hours under my belt (hat?), I do find there's a difference to the overall sound with Serene in the loop than with May running directly.  As always, this is hard to put into words so please bear with me.  

Firstly, I now listen at higher volumes than before.  I don't believe this is because May run solo is harsh in anyway.  Rather, it feels like Serene just adds a level of power and control to the picture; think swapping out a 4 cylinder motor and replacing it with a V6 in your favorite family car.  Crescendos no longer have me reaching for the volume control because I already had it cranked up to fully hear quieter passages.  Now, I should mention that the Krell is driving KEF LS50s plus subwoofer, so not a "standard" sort of set up by any means.  While they are very good speakers for the price, they are quite tricky to drive, I have found.

Secondly, this brings with it the effect of helping to present the ambience extant in recordings in a more realistic way.  In a good concert hall, you can almost feel the presence of the audience even when everyone is trying to be quiet.  Adding in the Serene helps to restore that aspect of the sound image.  And yes, I know it sounds like I am trying to explain the effect of adding compression to a  recording, but that's not what I'm hearing.  Let's try another example.  In some early Led Zeppelin recordings you can hear the amps buzzing in the background, just a fractional moment of sound before things kick-off.  With Serene?  Now you feel the amps pressurizing the studio space, not just buzzing.

Lastly, there's the question of transparency.  Has something been lost or is what I'm hearing actually a more realistic picture, a "more together" view of what's being performed?  I don't think I can answer that one, and I'm not even sure it matters.  Despite using a pre-amp again after 25 years of not doing so, a deletion I made in the 90s when switching to a Wadia CD player directly driving an amp, I've just decided that I prefer the sound with Serene in the loop.

(I should mention that all of the above relates to running NOS into the May.  I've tried quite a few HQP settings to see if I can find something that works, but haven't got there yet.  HQP PCM upsampling to 768k certainly changes things, and in some measures for the better.  However, it does so at the expense of soundstage depth.  What's in 3D in NOS mode ends up in 2D with upsampling, albeit with perhaps a bit more clarity and focus in exchange.  As always YMMV and I will continue to experiment, especially if I can find time to buy and configure a server and endpoint that can offer up another 2x of performance, but for me it's simply a more realistic picture that's painted in NOS mode.)

Thanks for the extended comments.  I just got my own May KTE last weekend and set it up.  Wow - what an improvement.  It made my old M&K speakers just stand up and play with joy.  The soundstage was bigger, cleaner and more "there". My quick listening also told me to just leave it in NOS.  Now, I am on the search for new electronics (mine is 24 yrs old and nothing special) and an update to my speakers. The Serene sounds interesting, but it may also be that just have separate preamp and amp now may be the biggest improvement.  For new speakers, I am leaning very much to the Spatial Audio X5.  Good luck with your system and enjoy!

HI, I am in dilemma

Pass Labs INT-60 or Pass Labs 30.8 amp with Serene as the pre-amp? Price will be the same.

Going for the best sound.