Monitor upgrade from Adam A7X

[James Perrett]

At that time I was using a Quad 405-2. It wasn't a treated room but it was reasonably quiet and, while there was a little hiss from the speakers, it wasn't really noticeable. However, the Hypex amp that I now use with them is even quieter - you have to have your ear right up to the speaker to hear anything and that's in a properly soundproof studio.

[RobinC]

i have to say that if I was buying now i'd probably be looking at the KH150/KH750 combo.

After more pondering that's the conclusion I've come to. I do use Sonarworks and having spent some time moving my speakers around, measuring then moving them again I think some level of DSP processing is needed in addition to the treatment that I have in the room.

As a follow up to my original post. The KH150s arrived earlier in the week. Very impressed with what the MA1 software does with them. There low end in these is also a step up from my Adams

[Nazard]

I'm glad the KH150s are going well. Phil Ward also wrote a bit about them on his website as well as the SoS review.

James, which Hypex modules did you use, please?

[James Perrett]

James, which Hypex modules did you use, please?

2 of the UcD180HG and an SMPS400 which I put into a Quad 405 case. Both of my 405's had issues so I took the good parts from each and made one good 405 and used the spare case for the Hypex modules.

[Arpangel]

I think I've found it

https://worldradiohistory.com/Archive-A ... 984-02.pdf

Interesting to hear about his converted Ampex machines - I think I may have used one of them back in my early days of recording.

That’s the one, there’s also another article by Tony in another issue, all about studio maintenance, I’ll dig it out.

At that time I was using a Quad 405-2. It wasn't a treated room but it was reasonably quiet and, while there was a little hiss from the speakers, it wasn't really noticeable. However, the Hypex amp that I now use with them is even quieter - you have to have your ear right up to the speaker to hear anything and that's in a properly soundproof studio.

I’ve been using a 405-2 for a few years now, I can’t say I really like it, it’s a dry, slightly hard clinical sound.
Hypex? I need to investigate something else, at the very least.

[Nazard]

Many thanks James for the info. Tony, the Hypex range of modules and DIY kits is a route I am planning on taking (I also have a 405). My only question is the possible longevity of SMPSUs......

Bruno Putzey, the designer of UcD, NCore and all round audio genius, was associated closely with Hypex but has set up Purifi Class C, with others and Purifi seems to be state of the art for Class C at present. Which is why I think Hypex have developed the Nilai range. In fact I was in touch with Hypex sales last summer to order the first Nilai kits, but they sold out instantly. Will be quicker off the mark this March....

[Nazard]

Correction: for Class C, I meant Class D

[ef37a]

Correction: for Class C, I meant Class D

AhAAA! You had me going for a moment there! I thought, "has some beardy tweak amp developer found a tiny design twist on established class D techniques and given it a fancy, silly bloody name?"

Now, I don't want to start a cow but a quick shufty at those class D amp's speccs shows me that they are about an order worse for THD than the very best class B* stuff that was designed over a decade ago. I am pleased to see that at least one monitor designer has moved on to 'linear' class G.

*Yes, I do mean "B".

Dave.

[Nazard]

I've made a couple of low power, 10-15 watts, Class C, RF power amps, using cheap, but fairly bulletproof IRF510 mosfets. But Class C is clearly unsuitable for audio.

Well, the Hypex Nilai 500DIY (400W into 4ohms), has a THD+N: 0.00015% @ 100W into 4 Ohm / 20 – 20.000 Hz. Fully driven, though, I don't know what the THD is.

The Benchmark AHB2, which I think is one of the lowest distortion amps around, is 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz. (190W into 4ohms).

To be honest, I can't say that the THD figures around nowadays give me any cause for concern. Of the two amps, if price and power output are taken out of the equation, I'd go for the Benchmark. (Even though it has an SMPSU).

[Arpangel]

That Benchmark looks good, expensive though, I think I’ll, stick with my free 405!
I’m mainly active, but if passive decent monitoring was my main thing, I’d be looking at something, like this.

[Hugh Robjohns]

The Benchmark AHB2, which I think is one of the lowest distortion amps around, is 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz.

I've been making some cables up for a forthcoming job, including some stereo 5-pin cables using Starquad cable. I normally use Van Damme two-pair individually jacketed multi for the job, but the budget wouldn't run to that.

Just because I've not done a direct comparison before, I hooked the cable up to the Audio Precision to take some measurements of crosstalk etc.

Your benchmark spec caught my eye because 25 metres of Starquad wired for stereo gave a THD+N figure of ... 0.0003%.

So the Benchmark distorts about as much as a long piece of wire! Very impressive.

[ef37a]

The Benchmark AHB2, which I think is one of the lowest distortion amps around, is 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz.

I've been making some cables up for a forthcoming job, including some stereo 5-pin cables using Starquad cable. I normally use Van Damme two-pair individually jacketed multi for the job, but the budget wouldn't run to that.

Just because I've not done a direct comparison before, I hooked the cable up to the Audio Precision to take some measurements of crosstalk etc.

Your benchmark spec caught my eye because 25 metres of Starquad wired for stereo gave a THD+N figure of ... 0.0003%.

So the Benchmark distorts about as much as a long piece of wire! Very impressive.

Hugh, do I detect tongue slightly in cheek there? I was suspicious of some of the distortion figures bandied because 0.0003% is I would think very close to the residual in even the best analysers? the figure also equates to lower than -110dB and so is close to the limit of all but the best converters.

I would also be interested to know if the crosstalk of the stereo cables was acceptable?

Dave.

[Hugh Robjohns]

Hugh, do I detect tongue slightly in cheek there? I was suspicious of some of the distortion figures bandied because 0.0003% is I would think very close to the residual in even the best analysers?

Tongue not in cheek on that occasion. Benchmark design some incredible stuff and know how to test it properly. I'm not at all surprised their amp genuinely achieves Mr (Quad) Walker's famous 'straight wire with gain' goal.

I use an APx515 analyser which is the poor-man's Audio Precision model (intended for production compliance testing). With a short loop cable between analogue in/out my residual THD+N is 0.00027% or -111dB (and I get the same figure using the internal loop-back mode, proving my local wiring isn't degrading the measurement performance).

The best AP model (x555) claims a residual THD+N of -120dB or 0.0001% — twice as good!

So my 25m of mis-wired starquad cable adds a teeny-tiny bit of THD+N above the residual of my AP, which is what I'd expect.

I would also be interested to know if the crosstalk of the stereo cables was acceptable?

I measured -96dB at 10kHz, reducing to around -102dB at 1kHz on a 25 metre cable run. So definitely perfectly acceptable. (The x515 residual crosstalk is -136dB at 10kHz, so this is real measured cable crosstalk). I'd expect cat-5 carrying balanced audio to be about the same.

I've used starquad for stereo mics on 3 metre runs from a stereo dead cat on a stick into a shoulder recorder many times without any problems. But I was slightly nervous about a long 25m run — hence the AP tests. I need not have worried!

I have to go to my 'man cave' near town to retrieve my long two-pair multicore cables (with separately screened and insulated pairs) to see how they compare. I'd expect less crosstalk, but probably not that much lower. I'll report back once I've tested it.

[Hugh Robjohns]

As promised... a visit to the man cave to retrieve my two-channel multipair cables for a comparison:

There's a small difference, as expected, with the multipair cable (separately screened twisted pairs in separate jackets within the outer sheath) having no more than 2dB lower crosstalk across the range 1kHz to 20kHz compared with the Starquad cable (using opposite wires for the two pairs). Both were 25metres in length.

Not surprisingly, I found the destination impedance affects the measurement. The figures quoted in the previous post (-96dB at 10kHz) were with the AP test set presenting its default 200k Ohm load impedance. In this graph I used the 600 Ohm option which is a closer approximation of a typical mic preamp and gives about a 3dB better crosstalk figure overall. So we're looking at roughly -99dB at 10kHz for the Starquad, and -101dB at 10kHz for the multipair.

Starquad costs half as much as the multi-pair cable for a given length! So it's a no-brainer to use starquad for balanced stereo audio cable, at least for lengths up to 25m... unless you need to break out into separate tails in which case the multipair wins hands down for ease of construction.

Hope that's of interest.

[Nazard]

Benchmark design some incredible stuff and know how to test it properly. I'm not at all surprised their amp genuinely achieves Mr (Quad) Walker's famous 'straight wire with gain' goal.

I'm looking for a new power amp, around 100W into 8ohms and the Benchmark is a contender. It's quite expensive, but I don't buy much gear and what I do lasts pretty much indefinitely. And it's a very interesting design.

I'm lucky in that my 'man-cave' is a barn at the bottom of the garden, a plus for the house we bought last year. Currently I have an old Leak 3200 receiver, (a rebadged Made in Japan Rotel), feeding 1969 KEF Crestas, (my late parents had them in their old kitchen) listening to R3. They sound great, though I think the barn accoustics help a lot too!

[sonics]

Currently I have an old Leak 3200 receiver, (a rebadged Made in Japan Rotel), feeding 1969 KEF Crestas, (my late parents had them in their old kitchen) listening to R3. They sound great, though I think the barn accoustics help a lot too!

Wow, memories! I have an old Rotel and a couple of pairs of old KEFs here. I do hope that's FM R3 you're listening to so they all "match"!

[Nazard]

Yes, it's R3 on FM, but all radio transmissions have had digital feeds in the UK, for many years. Of course, I could put one of the old reel-to-reel recorders, or turntables, playing pre 'DDD' recordings, to good use.

But, because the natural accoustics are so good, I am thinking of doing building mods and setting up a very beefy sound reproduction system.

And the Leak, 35W per channel, cost £28, via Ebay, ten years ago, half of which was postage. Absolutely immaculate, unmarked and very nice electronics, which needed nothing doing. I rigged up an FM dipole and there we go!

[Hugh Robjohns]

Yes, it's R3 on FM, but all radio transmissions have had digital feeds in the UK, for many years.

.

Since 1972, in fact, thanks to NICAM 3.