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INTRODUCTION
Hi everyone, this is not a review as such – more an introduction to a product that should be going up on KickStarter in 2017.The creator for this project is an engineer in Auckland New Zealand, and big time audio enthusiast – Martin Young from IMS-NZ.com. I was fortunate to be able to meet Martin at a NZ Head-Fi Meet a couple of years ago. I was also able to help with a little testing and suggestions for his first KS – the IMS-HVA (portable hybrid valve amp)
To my knowledge, the portable amp (I have the DAC/amp version) has been pretty well received. When we were first talking about it, I said at the time to Martin that he should consider a desktop version. What I didn't realise was that he was way ahead of me – and it had been on his radar for a while.
So during 2016 I got a chance to play around with a few DAC prototypes, and one amp. And then 6 weeks ago Martin showed me what he's been working on (the working prototype) – so this thread is being started to convey some information about it, and hopefully answer any questions which might be posed along the way. With the pics below – this is a prototype – the finished version will have even better fit and finish.
Q & A
So what is it?It's basically a desktop version of the original HVA – but with a number of tweaks. It is wall-wart powered this time, and it is definitely intended for desktop use, or for lounge/ listening room use. It has settings for phonograph and also Bluetooth input (and both of these can be turned off to preserve clean signal path when not in use). It also has 50W output per channel – yes that's right 50W – and is ideal for powering full sized passive speakers!
OK – how big is it?
This is one of the best parts IMO. The main chassis is a mere 120 x 140mm, and stands just 35mm high. It's made of high-quality anodised aluminium alloy, has beautifully crafted and damped feet (to negate ringing with the tubes), and clear glass cover – so you can see both the tubes and the full internals. The glass for the finished version will be gorilla glass.
Surprisingly small but good looking chassis | Properly damped feet |
What about the internals?
The DAC is the SAVI SA9227 with resolution up to 32/384. For amplification, there are two separate headphone stages using Burr Brown OPA2134 – and each has its own volume control. The rear output (2 x 50W) is class D and uses a TI TPA3116. It is volume controllable via the center pot. The phono preamp uses an OPA2134 for low noise – with passive RIAA equalisation. The heart of the system is the two Raytheon 6418 valves.
Martin also tells me that the boards are 2oz copper tracks, caps are all low ESR, and resistors are all metal. There is also 4-point grounding of the PCB to standoffs milled into the case for better shielding and noise suppression. So basically he's aimed to keep noise at a minimum – especially having the ability to isolate amplification circuits.
Rear of the prototype chassis | Front of the prototype chassis |
Inputs/Outputs/Switches?
For the inputs – there is a USB connection, Bluetooth connection, and also input connector for the phono stage. For outputs, you have speaker taps at the back, and choice of two independently amplified headphone sockets on the front (so two can listen – each with their own volume control).
Front headphone outputs and controls for both H/Out and rear RCA | Rear inputs and outputs |
There is a side switch which allows you to move between standard input, Bluetooth input, and phono input.
Side switch for phono, Bluetooth or standard inoputs | Even though its just a prototype - it still has a certain style (I love it) |
MY IMPRESSIONS
Test equipmentSo far I've used my active monitors (JBL LSR 305s), my Celestion F10 passive bookshelf speakers, and my HD600, T1 and HD800S. I've performed a direct comparison with my iFi Micro iDSD. For input, I've used my desktop PC (running Linux – and using jRiver's Media Center 21), and also – for the Bluetooth – my iPhone SE.
Yep - Brookos listening and review area | HVA desktop is great with the HD800S & wonderful with the Celestion passives |
Impressions / use
First up – its a really pretty unit, and what I like about it is the size compared to the output. I'm one of those minimalist guys who likes a tidy desk. I've always used passive speakers – but when my iDSD arrived, it wouldn't power the Celestions well (no real volume – even on turbo), so I gave the Celestions and NFB-12 to my daughter, and stuck with the iDSD and LSR305's. But in the last 12 months, I've missed the Celestions. They have a wonderfully rich, full tonality which the 305's simply can't quite match.
So when it arrived in the courier, I plugged it in, fired up the 305's ….. and …… uggh, distortion and feedback/hum, and practically no play on the pot. So I rang Martin, told him the problems, and he promptly asked what setting I was using. Doh! – I had it set to phono. A quick flick, and the hum disappeared, but the distortion was still there. We figured that was simply the passive monitors reacting to the power output – and it was at this stage that Martin mentioned the 50W/channel output. The light dawned, I swapped the Celestions for the 305's, and since then it has been playing beautiful, gorgeous music. I have my Celestions back on the desk-top, and I couldn't be happier. Not only that, the amp will drive them to ear splitting levels – there is some serious power on tap here.
Switching to headphones, and I've tried my T1, HD800S, HD600, HD630VB and K553s. Like the original HVA prototype, I don't think Martin has the headphone outputs quite right yet. It is still possible to over-drive the valves to distortion – but turning down the output from the PC (to about 75%) immediately corrects this.
It really is tiny - but can definitely ............... | .......... power the Celestions, which sadly the iDSD struggled with |
The sound output is stunning though. Crystal clear, a slight bit of tube warmth (not syrupy – just that little bit of 2nd order harmonics). Having the independent volume controls for the headphones is incredibly useful too. I've sat down with Emma a few times and we've used different headphones to listen at the same time. She listens even quieter than I do – so separate volume control is a must in this situation.
Bluetooth is brilliant as well. Martin told me it is a bit noisy, and that he already knows how to lower the noise floor. All I can say to this is that we heard no noise (and my wife's ears are pretty sensitive). We used the amp along with my iPad mini and the Celestions when we had friends over New Years Eve. Absolutely brilliant. I can see myself setting a living room up with some decent speakers, this amp, and an iPad or tablet – great entertainment system right there. Simple to use and sounds fantastic.
Improvements?
The following is for Martin's benefit. It's easier to write these down and incorporate them in this introduction – it lends a high level of transparency, and I know Martin values that. At the end of the day – he wants a superior user experience.
- For the headphone output, the valves are being over-driven and just needs a tweak. There is still plenty of output power for headphones.
- Instead of the 2 sets of L/R speaker outputs, I've suggested switching to RCA connectors – that way there would be space for one set for passive and a second (lower output) for active monitors. This would just add to the flexibility
So is this a winner?
I can't talk for anyone else – but for me – yes. I haven't heard the cost yet, and I know Martin will want me to review the finished version (and probably tell me to keep it), but this is one of those times when I want to buy it. This will likely replace my current iDSD / LSR305 set-up, although I do love that set-up too. The beauty here is the ability to power the Celestions. And not only that, power them wonderfully
Great job Martin. I really will miss this when I send it back.
