2 Crown DC-300A's

[RoadrunnerOZ]

The reason we used 4 sets of spaced well apart speakers was to run the whole system at a much lower volume so that table conversation was not a shouting match at the front and a confused jumble of sound at the rear - one of the worst pair of venues for long distance slapback reflections and when we first tried with a front only PA the level to get enough sound at the back was causing massive feedback. With spaced speakers and timed delays the level through each pair was way down and the sound was crystal clear. Sunday arvo with African soul roots rock reggae was really laid back. The Thursday night Latin/dance gig by the river was in an old brick storehouse (3 linked together with the walls knocked out) - really long and massive reflection problems but the spaced system worked wonders again. The 4 1800’s were perfectly matched to the 802’s and ran nice and cool with lots of headroom so as the place filled up we could start to crank the level. I would just wander around the room and then go back to the stack and mixer to make EQ and level adjustments.

 

[RoadrunnerOZ]

PS; I don't want to start a heaviest amp contest but I recall some heavy iron from Crest back in the day.

Yeah - if I remember rightly those 4801’s were weighty - around 50lbs. QSC and Bryston had some heavies too.

 

[RoadrunnerOZ]

This system setup seemed to work out OK!!!

Would work great. But for local gigs and short touring, space always at a premium and is a luxury - large racks with not much gear in them is a problem in carriage for smaller vehicles as well as side stage or backstage placement, for smaller rigs at smaller venues - if nearly half the rack space is taken up with cooling you’re better off with bigger amps with no cooling requirements to keep space to a minimum.

 

[Brian Roth]

I also heard about a DC300 being used as an emergency desk PSU. One point of concern for me is the distinct possibility of accidentally sending a SERIOUS overvoltage to the desk if someone bumps the level pot(s) on the Crown.

Bri

 

[JohnRoberts]

Most large sound reinforcement amps use forced air cooling. Studio and hifi customers do not care for fan noise.
===
Forced air cooling makes a huge difference (a little air does a lot of cooling) but at Peavey I was also involved in many fixed install designs and that fixed install market really hated fans for reliability reasons.

I did one wall box amp design, a 150W fixed install amp mounted inside a wall box chassis for schools or institutional use (WMA-150). It needed fan cooling for heavy duration loads, but being a fixed install amp it could be sitting at idle 90% of the time or more. I ended up configuring a 3 speed fan controller... high speed for cooling during heavy power, low speed during only modest loads, and fan completely shut off for "idle" mode.

The fan and heatsink were all internal so that extra heatsink at the top of the rack in that picture is some other SKU.

JR

 

[RoadrunnerOZ]

Most large sound reinforcement amps use forced air cooling. Studio and hifi customers do not care for fan noise.
===
Forced air cooling makes a huge difference (a little air does a lot of cooling) but at Peavey I was also involved in many fixed install designs and that fixed install market really hated fans for reliability reasons.

I did one wall box amp design, a 150W fixed install amp mounted inside a wall box chassis for schools or institutional use (WMA-150). It needed fan cooling for heavy duration loads, but being a fixed install amp it could be sitting at idle 90% of the time or more. I ended up configuring a 3 speed fan controller... high speed for cooling during heavy power, low speed during only modest loads, and fan completely shut off for "idle" mode.

The fan and heatsink were all internal so that extra heatsink at the top of the rack in that picture is some other SKU.

JR

Stacked flight cases with inbuilt rear fans were the norm in a lot of rigs - 1 case per 1 amp with detents in the case top for the feet of the unit on top - all you did was take the front and rear cover panels off and plugged them in

 

[JohnRoberts]

When mixing brands inside a rack full of power amps with forced air cooling check that they all input cool and exhaust hot air in the same direction otherwise you can get loops where the hot exhaust air gets sucked into another amplifier's cool air input.

JR

 

[RoadrunnerOZ]

When mixing brands inside a rack full of power amps with forced air cooling check that they all input cool and exhaust hot air in the same direction otherwise you can get loops where the hot exhaust air gets sucked into another amplifier's cool air input.

JR

Same thing happens on the track at the Indy car races

 

[JohnRoberts]

Same thing happens on the track at the Indy car races

I'm not sure about open wheel cars, but full body race cars like nascar gain a benefit in reduced drag (wind resistance) from "drafting" closely behind another race car.

JR

 

[RoadrunnerOZ]

I'm not sure about open wheel cars, but full body race cars like nascar gain a benefit in reduced drag (wind resistance) from "drafting" closely behind another race car.

JR

Yeah and they suck in the hot air from the car in front and have to move out of the draft before they blow their engine, plus less oxygen is reducing performance, although more than offset by the draft, causing a power lag when they want to overtake. Tailgating has its drawbacks

 

[RoadrunnerOZ]

[if nearly half the rack space is taken up with cooling] -- You're right.....my bad!!! I should have thought of that beforehand. Silly me!!!

But.....what you see in my above images is what I came up with in order to keep cool over 250 - "10,000-Watt Transportable Audio Amplifier Racks" that were used by a major concert sound-reinforcement company for use by some of the biggest names and tours in the entertainment industry. There were 5 of the 1U 9-fan chassis that were placed at the front of these racks and in-between each of the high-powered amplifiers. The "Air-Intake" assembly was placed at the rear of the rack towards the bottom, but above the AC-power and signal-input panels and the "Air-Exhaust" rack-panel was also placed at the rear of the rack, but mounted up at the top.

As far as smaller racks go that also need some cooling consideration, just let me know what you are dealing with and I can design something on a smaller scale. That's one of the neat things about using 3D CAD-design software.....it can be so, so flexible in "real-time".

/

I constructed new power supply arrays for a Neve console last year as the old supplies were noisy, failing and hot - I mounted them in lockable rack drawers on their sides to facilitate easy adjustment and place them in an airflow path. I removed each supply’s noisy little fan and used a superquiet fan in each drawer - 6.8dB(A) so you can’t even hear them - the Noctua
NF-S12B Redux 700. The supplies run at under 35degC at full load. The 36Ch console has a supply set for each side. Photo below before fan fitting:

 

[RoadrunnerOZ]

1) What are the two different models of the power-supplies that you had used? Are they "Meanwell's"?

2) What is the model number for the cable glands?

3) Is that a 5U or 6U chassis-drawer?

4) It -- kind of -- looks like the AC-power inlet also has an EMI-filter as a part of the assembly. Does it?

1: They are Meanwell medical grade low noise adjustable. For this we needed three supply types 2 heavy 20A for the + 16 then 3 x 10A for the + 25 and the -15 and the baby one in the back right corner for the +48. All this if I remember correctly. I’ll get the model numbers for you when I next go to the studio - can’t drive at the moment as I just had shoulder surgery. Star ground in the box and the rack it’s in has its own safety earth run back to the mains distribution box which is 2 metres away with 2 dedicated 6 way power strips strapped to the rack.
2: EPAGN25 for the DC power multicores
3: 6RU the front panel is higher than the rear chassis top which is 1RU lower so this provides open air intake which the fan pulls in, over and around the supplies.
4: Yes and it’s actually also built into the distribution board these and the amps and monitors are supplied from - they all have the same filtering. Star ground back to the dedicated audio 240V distribution box on the wall behind them. Metal ducting all around the walls and through the vocal booth for the audio multicores, separate duct channel for all power to AC outlets - all grounded back to here as well. Stake to the earth from the distribution ground bus also.

 

[NoisyIndividual]

HEY! Whilst we're Willy Waving, a studio I am closely associated with had the SSL 4000G+ power supply monstrosities with the obligatory AC cooled room, replaced with a single PSU of 3U that requires no cooling whatsoever other than the fans within.

Go talk to Malcolm Toft if you want one of those.

 

[RoadrunnerOZ]

HEY! Whilst we're Willy Waving, a studio I am closely associated with had the SSL 4000G+ power supply monstrosities with the obligatory AC cooled room, replaced with a single PSU of 3U that requires no cooling whatsoever other than the fans within.

Go talk to Malcolm Toft if you want one of those.

I found the built-in fans of the power supplies too noisy which is why I ripped them out and used a single big fan. Must have a quiet fan in the one you mention.

 

[NoisyIndividual]

It's an SMPS . Doesn't need much of a fan at all.

 

[NoisyIndividual]

I talked to Malcom, the biggest problem was getting rid of the noise of a SMPS IIRC.

Probably more of an art than a science from what I gather.

 

[JohnRoberts]

I talked to Malcom, the biggest problem was getting rid of the noise of a SMPS IIRC.

Probably more of an art than a science from what I gather.

filters are mostly science....

JR

 

[NoisyIndividual]

Maybe you want argue that with Malcolm then.

I think when you consider that the power supplies tend to be connected to the desk retrospectively with many metres of cables, then there are other things that need to be taken into consideration other than the local science.

But HEY!!!! I don't know.
I just fix broken stuff.

 

[RoadrunnerOZ]

I talked to Malcom, the biggest problem was getting rid of the noise of a SMPS IIRC.

Probably more of an art than a science from what I gather.

I left the banks of filter caps already in place on power distribution rails inside the Neve and there are a lot - no noise, no ripple - these supplies were the lowest noise versions they supply at those current ratings. Because they’re slim supplies the inbuilt fans are tiny high speed things and make too much noise for supplies housed in the control room.

 

[NoisyIndividual]

OK, so Neves being Class A and all that, SSL being not that, I currently see a SSL 4000G+ at 48 channels drawing around 19A per 18v rail.

That seems to be easily achievable with a SMPS in a 3 U rack mount.

Neve mileage may vary.
Maybe 6U.