Amps for Passive Monitors ideas?

[boji]

My reasons for resurrecting NS10's are because I went overboard replacing my old studio monitors (also HR8's!), and these boulder mkii's are more midfields than nearfields. I'm hoping to track and do a little mixing with the N10's and then switch over to check for LF/HF errors, and to get client impressions.

So far I'm not using any DSP. However being in a small, well-treated control room (*ahem*, bedroom), I find myself putting high pass filters on lots of modern pop music to 'correct' low end response. On that note, would anyone care to recommend DSP room correction hardware/software that sits on your Program output?

 

[iomegaman]

I grew up with a LOT of Peavey equipment, being a preachers kid in oklahoma playing in various rock bands Peavey was as common as Ford F150's...the elites had Marshalls and then Music Mans...the first band I was in the bass player used a Peavey PA stack for his bass...
Then I started playing Jazz and the Peavey stuff was not allowed...oh to be young and not stupid again...

 

[metalockpick]

It's not the amplifier power. If you're going by specs (and the specs are somewhat accurate) you want to see high slew rate (how fast the amp reacts; over 15 Volts per micro second), bandwidth (over 40kHz on the high end, at least 20 Hz on the low), and enough power that you won't clip. Really, though, just a/b amps in decent speakers and you'll hear the difference. The wet blanket sound happens @ every level.
Peavey earned their reputation for poor quality and low durability with their huge early mixers, and for poor quality sound with everything over the following 15 years. AMR stuff was great, but they'd already poisoned the well and left an opening for Mackie. Anyway, I bought a PV1.3k because it couldn't be destroyed in destructive testing @ another company, exceeded its good specs, and was $199, used.

 

[Electrobumps]

I absolutely loved a Bryston amp on NS10's. However it is a pretty expensive option. Hypex class D is very comparable at a fraction of the cost.

 

[cpsmusic]

This is the first time I've really paid much attention to how much a power amp affects the sound of NS10's but I gotta say it's night and day from how I had it set up...
Was using a Peavey PMA 200 and I just hooked them up to this Nikko in my work room so I could test it out and holy muffle batman it was like a wet sheet was removed from these speakers...really punchy and clear I can see why these speakers find use now...

Hi All,

Not wishing to derail this thread, however I'm wondering why there's such a big difference between these two amps? I'm currently running NS625s in my little home studio using an old Technics SU-7700 power amp. I was under the (possibly misguided) assumption that power amps were a "solved problem" a long time ago and that the SU-7700 would be fine.

Cheers,

Chris

 

[JohnRoberts]

It's not the amplifier power. If you're going by specs (and the specs are somewhat accurate) you want to see high slew rate (how fast the amp reacts; over 15 Volts per micro second), bandwidth (over 40kHz on the high end, at least 20 Hz on the low), and enough power that you won't clip. Really, though, just a/b amps in decent speakers and you'll hear the difference. The wet blanket sound happens @ every level.

Not for decades

Peavey earned their reputation for poor quality and low durability with their huge early mixers, and for poor quality sound with everything over the following 15 years.

Peavey's reputation came from the inexperienced entry level customers who owned Peavey systems because that was all they could afford.

AMR stuff was great, but they'd already poisoned the well and left an opening for Mackie.

Sadly I was in that scrum and Mackie spent more on advertising one mixer each month, than Peavey did for hundreds of SKUs over the entire year.

Anyway, I bought a PV1.3k because it couldn't be destroyed in destructive testing @ another company, exceeded its good specs, and was $199, used.

Oops the PV1.3k was a hand grenade that was borderline thermally unstable. When I was put in charge of product management for all power amps at Peavey, I inherited the 1.3k.... For a little inside information about the 1.3k, Jack Sondermeyer used a clever design trick to get away with using less output transistors. He used one power transistor to drive the other output devices, with a small resistance to the output so that combo power driver was also driving current into the speaker like an output. That worked more or less acceptably for 8 ohm loads and was marginal at 4 ohms, but didn't cut it for 2 ohm operation, that was becoming more popular.

I was not the typical product manager because besides managing cost/profit, I also had a clue about how amplifiers work... I decided to add one more pair of output transistors per side, and returned to using a conventional driver stage. Another problem with the PV1.3k is that they were not very stable thermally, so adding the extra 4 power transistors (2 per side) made the amp much better behaved and 2 ohm capable. I changed the name of the amp to PV2000 while it was pretty much the same amp as the 1.3k just with a few dollars worth of added power transistors. After that upgrade it was more robust.

It was also my job to market those heavy, class A/B (obsolete?) technology power amps. Since I couldn't just ignore the heavy transformer and heat sinks, instead I advertised about how "heavy" they were as if that was a benefit.

JR

 

[iomegaman]

Hi All,

Not wishing to derail this thread, however I'm wondering why there's such a big difference between these two amps? I'm currently running NS625s in my little home studio using an old Technics SU-7700 power amp. I was under the (possibly misguided) assumption that power amps were a "solved problem" a long time ago and that the SU-7700 would be fine.

Cheers,

Chris

Depends on what you mean "solved problem"...I've sort of dragged this discussion into some fairly old tech (The Nikko Alpha was a 1970's audiophile device) so the question of slew rates is part of the table talk here...

I honestly think that if the SU-7700 is serving your needs and you know it's sound then there's no real reason to question it.

Some of this drifts into the same category as converter discussions...use what you like and enjoy it.

I was originally bouncing around ideas on powering the NS10's to a sweet spot and got distracted trying to repair an old amp...

 

[inkster]

Most of the studios I work in use 250w per side for the NS-10s, I've only heard 1 pair I liked and those had updated crossovers and were driven by a hefty Bryston.
GR research sells a crossover kit for NS-10s but I haven't heard it.
I have a pair of peavey HKS-8 powered monitors and I love them...had a pair of the AMR 3-ways and used them until a neighbor really wanted them and I moved on to powered monitors to replace them.
I also have the VCL tube limiter from peavey...and I live in the bay area...go figure.

 

[Electrobumps]

Most of the studios I work in use 250w per side for the NS-10s, I've only heard 1 pair I liked and those had updated crossovers and were driven by a hefty Bryston.
GR research sells a crossover kit for NS-10s but I haven't heard it.
I have a pair of peavey HKS-8 powered monitors and I love them...had a pair of the AMR 3-ways and used them until a neighbor really wanted them and I moved on to powered monitors to replace them.
I also have the VCL tube limiter from peavey...and I live in the bay area...go figure.

I'm driving mine with 180W per side. I know there is quite a bit of debate on this improving sound the next step up for Hypex was 400w which seems over kill. What was the crossover mod? My NS10's are sounding not right on the imaging. After sweewping the response I could see there is 1db down on one channel at the 2K-3K this is around the crossover. Not much chatter on the web about recapping NS10 crossovers.

 

[Electrobumps]

So far I'm not using any DSP. However being in a small, well-treated control room (*ahem*, bedroom), I find myself putting high pass filters on lots of modern pop music to 'correct' low end response. On that note, would anyone care to recommend DSP room correction hardware/software that sits on your Program output?

SoundID Reference really quick and easy to use.

 

[boji]

I could see there is 1db down on one channel at the 2K-3K this is around the crossover

Update: Amp arrived, went to do the A/B and... R speaker's tweeter is out. Pulled it, ran a 5k-20k sweep across it and...coil's intact. Waiting for a pair of AV10-MXO to arrive...

 

[JohnRoberts]

As I recall tweeter failures were common.. good luck.

Another perhaps urban legend was that hanging some toilet paper in front of the tweeters reduced harshness. IIRC measurements revealed that the TP did little to nothing to the frequency response.

JR

 

[Electrobumps]

Waiting for a pair of AV10-MXO to arrive...

I've just been looking at those. They use a metal film on the x-over for the tweeter. There is a gear space thread that talks about this.

https://gearspace.com/board/so-much-gear-so-little-time/1054744-yamaha-ns10m-cap-mod.html
Also there is a sound on sound review where he refers to the CLA's as brighter than the originals. Could this be the metal films on the x-over. If it is not that then it will be a brighter tweeter.

https://www.soundonsound.com/reviews/avantone-cla-10
The avatone crossover looks like a nice replacement, great speaker posts, easier to service drivers in future. I'm not looking forward to taking out and putting back in the originals

 

[iomegaman]

A couple of off the wall questions regarding wall voltage, old electronics, high heat, brittle aluminum wire and hard to find 40 year old high power transistors if anyone wants to wade it:

So I blew out the left channel of this Nikko Alpha 1...spent another few weeks sourcing parts and tracing problems...(old brittle "semi-fixed" resistors, 40 year old aluminum wire/etc...

At any rate because I am a curious sort of soul and just wanted to see what was happening in the world of physics I pulled out my infrared thermometer and shot the 2SD610 transistors because they are basically made of unobtanium...

There are 2 sets per channel, offset by their cousins the 2SB630's which I found stateside...the 2SD610's have all left the country or never got visa's or something...haven't found anything like them stateside*

My SOP is to use a variac to gradually power up this older stuff...and there is a protector circuit that will not engage until we hit about 90v AC or so...

What I noticed that made me go "Hmmm" was that if I left the variac at a lower AC voltage...say just below 100v...(it uses a VU meter thats about as accurate as a weather forecast, always an approximation)...the SD610's crank up to about 125F (they are rated for 150 C so they seem to be operating well below the junction maximum)...

When I go ahead and push the variac to 110 (and actually measure it) they settle down to around 100F...

Thats a 20 degree temperature swing from a higher voltage...

This amp IS a push pull design...but I was wondering why such a temperature swing and down that road, since these are hard to come by...wold it make sense to trade out the "Z" channel anodized aluminum heat sink to something more modern with fins/etc...?

I have repasted everything but man those transistors run about 30 degrees hotter than all of the rest including the big power transistors...



* I have found some SD610's coming on a slow boat from China, literally, but who knows if its real or even going to get here, its been 19 days already)

 

[Disco Volante]

Hmm, higher voltage would give lower current for the same power (ohm's 2. law). Don't know how you're measuring exactly.
Also no schemo so just guessing here: check the low-ohm resistors near the output transistors? any other Rs out of spec from age? and are all the coupling caps ok? dc leakage can wreak havoc biaswise...

Happy tinkering;-)

 

[user 37518]

Really, though, just a/b amps in decent speakers and you'll hear the difference. The wet blanket sound happens @ every level.

Such a fallacy, unless you are a/b-ing a piece of crap from the 70s vs a good modern amp, this is not true. With modern amps the audible difference (if any) is extremely subtle, definitely not "at every level", and definitely not at the level of a wet blanket.

 

[JohnRoberts]

It is not productive to argue with people on the internet about what they say that they hear.

Life is short.

JR

 

[Tubetec]

We used an Amcron Macrotech 1200 to power the Ns-10's at a place I worked ,
thats 655W into 8 ohms , roughly three times the rated power of the speaker .
Studio B had much smaller amp on the Yamaha's and it was way easier to do damage .

Stability into 2 ohms was always handy to have in a mobile P.A. set up , it meant there was never an issue patching in an extra pair of 8 ohm speakers to get better audience coverage ,
Often we'd arrive at a gig only to find the other band brought their own PA as well , 2 ohm capable amps just made life easier for everyone .

 

[iomegaman]

Hmm, higher voltage would give lower current for the same power (ohm's 2. law). Don't know how you're measuring exactly.
Also no schemo so just guessing here: check the low-ohm resistors near the output transistors? any other Rs out of spec from age? and are all the coupling caps ok? dc leakage can wreak havoc biaswise...

Happy tinkering;-)

Yeah the schematic on on the first post...the transistors getting hot are Q707 (SD610"s) there's 2 of them , one on a heat sink and one without heat treatment...the one without is not getting as hot as the heat sink unit and its emitter feeds into the base of the heat sinked unit...
R719 sets the idle current and I think its gone wonky...its one of those old semi-fixed resistors (500 Ohm-B)...it feeds the base of Q1...

I've checked, double checked and triple checked resistors and its lot of those older low Ohm high Wattage cement resistors...

I have tried replacing a few of the ceramic caps but all but one that I've pulled out were within spec...
I think because of the design the hFE of the power transistors comes into effect here...anytime I end up with wonky DC voltage where it's not supposed to be one to those TO-3 power silicone transistors has shorted out...so far I've replaced all but 2 on the left channel.

Instead of turtles all the way down this thing is transistors all the way down...


The nice thing about it is I have a good channel operating that I can check voltages on...and by the way when I shot it with the infrared thermometer it was running a cool 10 degrees hotter on every transistor...
So I think I'm chasing a gnats fever here...

Gonna swap out the variable resistor with one that I can match to the right side, replace a diode and call it good.

 

[Whoops]

I need to set up some sort of soft-start "pop" preventer because the Nikko does not have a power switch, :

I’ve used this circuit for those duties, it’s pretty good and very good quality:

https://shop.dadaelectronics.eu/dada-electronics-loudspeaker-protection-108462936.html

For amps I’ve used the Quad 405 in the past for NS10, it worked well, although I don’t use NS10 for a long time