Good deal BUT

[Ken Pachkowsky]

Unfortunately the great deal I got on the Boulder 250 was dashed somewhat when I powered it down for the first time after hooking it up. Ouch!

Nasty thump causing minimal cone excursion on the Gauss 10", then about 3 seconds after that a low pitch squeal graduating to a higher pitch as the capacitors drained (is my guess?). Any time I have read about a problem like this it usually has something to do with DC on the inputs during shutdown?

This is one reason I have always prefered amps with gain pots. I hated that when I owned a pair of Crown 150's without channel gain controls. They thumped and popped from day one.

Off to Colorado for repair. $%$#

Ken

[Titanium Dome]

Sorry to hear that, man. That sucks.

No damage, though?

[Ken Pachkowsky]

Sorry to hear that, man. That sucks.

No damage, though?

I don't think so. I disconnected the amp at pulled the top off just to see if I could see anything obvious like a loose/burnt/broken wire. None to be seen. But here is something interesting.

When I turn the amp off the wire connected to one of the storage caps sparks.

I don't beleive this is normal?

And yes, I will be very carefull not to touch the storage caps until they are drained.

["Duke" Spinner]

Nooooooo


it's not normal ..!!....:(

[Ken Pachkowsky]

Gonna post a couple of photos.

[Ken Pachkowsky]

This is the one that sparked. I don't beleive it was arching to the positive but it may have?

I am waiting till I get a 0 reading off the storage caps and will try to see if the scews are loose. Maybe my scews are loose?

Pretty sure this is going back to Colorado for a physical however.

Ken

[Ken Pachkowsky]

The screws are so loose I can take them off by hand. Anyone think this is the culprit? I will tighten them up and see if it solves the problem.

Ken

[Ken Pachkowsky]

Ok, I tightened them up and now when I turn it on there is no noise at alll on my test speaker. There is a smaller thump when I turn it off and it only thumps once.

I will still send it in.

Ken

[Chas]

Maybe my scews are loose?

Ken

I thought this state of mind was mandatory here? :p

Ken, obviously you had a physical connection issue with the Bouder BUT before you further judge the amp to be at fault, consider your upstream equipment. You may find that the Boulder simply powers down slower than the stuff ahead of it. Particularly if the equipment is op-amp based and has soft power supplies, i.e. minimal energy storage vs. load current. This can be a source of turn on and turn off transients.

Disconnect the inputs to the Boulder and see what happens when you remove power.

[johnaec]

There is a smaller thump when I turn it off and it only thumps once.

I will still send it in.I'd give them a call first. This may be normal and we all know how well amps often go through shipping... :(

John

[Ken Pachkowsky]

I thought this state of mind was mandatory here? :p

Ken, obviously you had a physical connection issue with the Bouder BUT before you further judge the amp to be at fault, consider your upstream equipment. You may find that the Boulder simply powers down slower than the stuff ahead of it. Particularly if the equipment is op-amp based and has soft power supplies, i.e. minimal energy storage vs. load current. This can be a source of turn on and turn off transients.

Disconnect the inputs to the Boulder and see what happens when you remove power.

Chas

I already tried disconnecting the inputs to make sure there was no outside source. The outcome was the same so the amp is the problem. Its not as bad but not normal. I will send it for repair. I contacted the seller and she runs estate sales. She knows nothing about electronics but was quick to offer a 200.00 credit on my purchase. I thought that was most generous and fair. That will cover all shipping costs and a couple of hours of bench time. Hopefully I should come out even or close to it with an amp right up to factory specs.

Ken

[Tom Loizeaux]

Ken,
As you know, turn-on and turn-off thump is very common. Most quality amps have delayed turn-on using timed relays. Many amps do show some turn-off transiants. I'd talk with a tech at the company to see if they feel the "thump" you're experiencing is not normal.
I bought a Crown PT 2.1 power amp a while back and experienced some turn-off thump. I spoke with Crown and they said a little of that is normal with that amp.
In my view, very high quality amps shouldn't have any of that .

Please keep us informed.

Tom

[Ken Pachkowsky]

Ken,
As you know, turn-on and turn-off thump is very common. In my view, very high quality amps shouldn't have any of that .

Please keep us informed.

Tom

Tom it's great to hear from you. I agree, but this goes a little beyond that. Its the secondary squeal that bothers me. I am calling Boulder today.

Ken

[boputnam]

In my view, very high quality amps shouldn't have any of that.:no:

Active Inrush Limiting eliminates AC inrush current, removing the need for expensive power sequencers
On/Off muting,
DC-fault power supply shutdown

[Robh3606]

Ken hope it works out for you.

It depends on the amps I guess. I have Crown 150 Series 2's and the original and all have some gentle turn off bumps with a very low level whurrr?? as the caps go. My Crown PS-200's are completely silent on or off.

Rob:)

[Zilch]

My JBL 6260's thump, but only occasionally, when the relay doesn't drop out fast enough on turnoff, I figure....

[Regis]

Good luck on the problem, Ken. I don't know anything about this amp, but depending on it's time-era, the thump can be normal or totally out of context. My mid 70's ESS Eclipse has a pretty good thump on the start and the cap draining noise on the power-off. By the late 70's, early 80's, just about everybody had a built-in circuit to soft-start the whole shebang.

[Ken Pachkowsky]

Thanks Guys

I am sure it will all work out. I have been damned tempted on going all QSC Bo. They do have a stellar reputation. I know of one major studio that has gone from Brystons and Crown Reference Series to all QSC's and are extremely happy with them. They have a whole new series coming out in the first quarter next year. Very high end. Unfortunately the SRA series was a flop and they dropped it within a couple of months of introduction. They have since gone back to the drawing board and redesigned it.

Ken

[boputnam]

Hey, Ken...

I winced at your story - that is one characteristic I never face with these.

But, you're more current than am I on QSC's lineup, it seems.

I've had them in my studio and roadracks for over 5-years. They just friggen' work, and stand-up to all manner of abuse - physical and current related. They sound great - er, make that fantastic. But, I got lucky - they were recommended by my engineer, who uses them in all his installs 'cause they themselves don't ever result in a service or unsatisfied client call to him.

[Ian Mackenzie]

But Bo,

Joe said to me (and may have commented to you ) he though your system sounded a bit sterile.

Perhaps you ain't been playin enough sexy music man!

Ian

[Ian Mackenzie]

Ken,

Internally, are the compression drivers protected via a series capacitor?

Ian

[transducergeek]

This thump is pretty normal on many amps without relays, or other delay circuits. The squeal is another issue, but I will guess is in the "range" of normal for this amp circuit. It obviously has no "thump-delay" circuit functioning. Not in the design, or malfunctioning. If it were me...(IIWM)? I would first call and talk to an ENGINEER, not a sales helper, or some other service flunky...I would ask specifically,
One... "does this model amp have a protection for TURN ON/OFF THUMPS?"
And two.. "does this model amp normally squeal on power-down?"


If the first answer is "yes" .... send it in... ask them if they will make it perfect and quiet..

If the second answer is "No" ... send it in...

If the answer is "No...."
and "Yes" save all the shipping hassle/cost.. nothing will change with the amp.... just your wallet... and put in a cutoff switch for the speaker lines, you flip the switch after amp is on for a few seconds (10?)... and a few seconds after it is turned off (30?) ... problem solved...

[Ken Pachkowsky]

I spoke with the head tech at Boulder today. Apparently the Roderstein Electrolytic Caps used on the main board have a history of leakage over time. He was sure that is the problem. They want me to send it back and do a 500.00 fix. At the end of the conversation he said no charge.

Gotta like that.

Ken

[transducergeek]

N/C is the correct answer..... Ship it!

[soundmotor]

N/C is the correct answer..... Ship it!

Abso-freakin-lutely!

Especially when they acknowledge the component going bad. I've worked for 3 different speaker manufacturers over nearly 20 years & still find my employ at the last. If you have a known failure that occurs after the warranty period, you take care of it at N/C or at the least, at your cost. It is just what you do.

[duaneage]

I bought a plate amp from Madisound in 1997 while visiting their warehouse in Madison. 6 years later it lost a cap and rectifier bridge. I returned it to them and they repaired it , shipped it back in a week, and did not charge me a cent. I even offered to send them money for the shipping but they would not take it.

Long out of warranty and not an expensive, high margin item either.
Made me a long term customer for sure.