Amps for Passive Monitors ideas?

[JohnRoberts]

I spent a lot time in a the amplifier trenches. A great deal of effort goes into making amps turn on and off gracefully. No not because of speaker damage, but because customers are worried about speaker damage.

In the sound reinforcement line level processing business a similar amount of design effort goes into providing benign turn on-off characteristics. I recall when DBX made their first effort in live sound reinforcement processing. They made a rack mount crossover (speaker management system). Since this was their first effort they neglected to make it behave nice during turn on/off. They learned from all the customer complaints and fixed it by their second generation roll-out.

JR

PS: To actually damage speakers the on/off transient would need to be significantly louder than the loudest program passages. In my years of paying attention to this I am not aware of much (any?) speaker damage caused by this, but I am aware of major customer preferences complaining about ticks, and pops, and thumps, and....

 

[Newmarket]

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

Indeed. Someone wrote up a funny/ serious tech report on it. As it happens came across it on the interns the other week. Will try to find it but not right now after too much time in the day job talking high voltage settling times and measurement methods

 

[Electrobumps]

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

They are not bad on NS10's.

 

[iomegaman]

So after spending a several weeks and a bunch of coin to get the Nikko Alpha 1 running...I sorta have it back on the bench...
BUT I was so impressed with the build quality and the design that I got another Nikko Alpha III off of evilbay...$80 and another $100 for a mule to carry it all the way from Juneau Alaska...took almost a month.

Got it today...took it apart it is in primo condition...looks brand new except for the power switch plastic knob missing...
Opened it up and the two 470uf Capacitors on the psu board were bad...$3.00 and a bag of fuses then about 2 hours trying to get the right channel to work...finally remembered seeing on AudioKarma a comment about these units having bad/cold solder joints so I heated up an iron and retouched the right side amp board...viola she lives!
This one runs on some really rare unobtanium Hitachi power mosfets...(Hitachi MOSFET 2SK134 - 2SJ49) sits at about 80 watts continuous...at this point i'm sorta done dorking around with amplifiers...it sounds pretty darn good and has that really cool LED "amp/power" display on the front of it...

I guess this was a popular thing to do back in the 70's I know my Carver TFM-15 CB has actual power/wattage meters (it also runs around 80 watts continuous)

Of course no one does meters like mcIntosh...but I'm not gonna spend $3000 for an amp to drive NS10's...

Here's a schemo if anyone is interested, they actually do a great job of explaining how to calibrate the entire amp/meters/balance/etc..

 

[Tubetec]

I remember the bog roll trick with the NS-10s alright ,
It did take a little glare from the upper mids , at least thats what my ears told me it did in comparative tests we ran .

Turning on and off big systems still needs to be done in a certain order or you get unpleasent noises , its not just the noise a single power amp makes at switch off , but if the line equipment that drives it is powered down before the resulting bang can do damage ,

Most decent poweramps start up in protect mode , only a couple of seconds later the speaker is connected when the voltages have stabilised , likewise at powerdown , the speaker protection relay should cut the signal before the noise occurs ,

Crossovers typically default to mute on powerup/down for a delay period ,
if a circuit breaker goes down and is reset you dont want the bass bins punching the bread basket out of the people in the front row either , these noises have no place in music .

We did a corporate gig once for the staff of call centre for a cruise line company , the DJ had around 15k of Dynacord which he allowed us to use , the moment he took the stage after the band he fused out the utillity panel by trying to play this huge synthesised bass transient as his intro , the entire venue went pitch black , luckily everything was well after they reset the fuse board .

 

[iomegaman]

Yea thats what impresses me about these Nikko amps they ALL seem to have delay protection circuits built into them...this Alpha III manual has a section on how to measure if the protection circuit is set within the proper time range...and how to set it.
Interesting thought about the Dynacord system fiasco...I've never really watched but I wonder how much heavy bass transients actually pull more wattage because the frequency wavelength is 50+ meters...I mean it makes sense on a certain level the inductance of a coil for a sub bass speaker is probably quite a bit different than the inductance for a tweeter by a factor of many...at some point the "reluctance of the inductance" is a come-up-ance...

 

[JohnRoberts]

Yes, customers value silent turn on/off characteristics.

Back when I first addressed this a few decades ago, I established a simple RC turn-on delay to release the turn-on mute. Turn off was not as simple since it also must be quiet if power gets randomly interrupted. I accomplished the quick turn-off (you want the output to mute before the power supply feeding the circuitry collapses) by using a modest sized reservoir cap charged by the transformer secondary through separate rectifier diodes that would discharge relatively quickly.

Most commercial designs pay attention to this.

JR

 

[lightningbefore]

I used a Hafler Transnova 9505 with my NS-10's and it worked great. Still an amazing amp at a decent price.

 

[13engrsapper]

We used a 200 watt Bryston to power the NS-10's here. Those and our old Mackie 824's were replaced with small Genelec's and a set of Barefoot monitors - I missed the Yamahas for about a day. They are good at what they do, I move around too much to lug an amp with me. The little Genelecs fill that void well, and I like them sonically over the Yamaha.

 

[Gavin Pursinger]

I have had much better results with capacitor Bank amps than high powered switchers...they are tighter...since you don't need to knock down walls..I love my sterile recapped Crown DC 300As on near fields and lows of the large 3 way tracking system.

 

[AtticMan]

I used a Hafler Transnova 9505 with my NS-10's and it worked great. Still an amazing amp at a decent price.

Never had NS-10s, but I've been pleased with my Hafler P3500 powering my Tannoy System 600 coaxials...