Audio Research D250 - What have I just bought?

[Dazaa]

Anyone who has seen my NRG saga thread knows i'm a sucker for big amps, and an AR D250 just turned up untested so I decided to take a punt. All I know is that it powers on, looks like the seller got it from a recycling or house clearance source. Seems like it cost 6500 in the 90's and is one hell of a tube amp at 250wpc....anyone here got one or know anything about them?

 

[whoaru99]

Lots of tube... I know that much. And typically AR runs them fairly hot so usually need to be the good tubes, high rated, matched, and all that.

 

[a_retent]

@Dazaa
Here's some info for your D-250

 

[arts]

Unless you have an extremely skilled, experienced and very well equipped technician available, and you have very deep pockets,this amplifier is not a plan. It is one of the most complicated,powerful and tricky units ever designed.

All tube amps (especially older-model Audio Research units) run high voltages that are extremely dangerous. This unit exceeds those "usual" voltages by a wide margin,and can maintain them at current levels that would do an electric chair justice.

Take it from someone who has been working with ARC equipment for a very long time: You don't f**k around with one of these.Period.

 

[a_retent]

Unless you have an extremely skilled, experienced and very well equipped technician available, and you have very deep pockets,this amplifier is not a plan. It is one of the most complicated,powerful and tricky units ever designed.

All tube amps (especially older-model Audio Research units) run high voltages that are extremely dangerous. This unit exceeds those "usual" voltages by a wide margin,and can maintain them at current levels that would do an electric chair justice.

Take it from someone who has been working with ARC equipment for a very long time: You don't f**k around with one of these.Period.

Sage advice for sure.
Glad to see you're still around @arts, I hope you are doing okay.

 

[BillWojo]

Listen to Art, this one is a good one to flip, if you got it cheap you should walk away with a pocket full of money. Just sell it as is.
Post some pictures with the covers off, lets see what shape it's in.
BTW, DO NOT power it up without a load connected, if it goes into oscillation bad things can happen. A new set of tubes can cost as much as a decent used car for this unit.

BillWojo

 

[maxhifi]

Wow, now I know what to save up for.

 

[a_retent]

@Dazaa

Lots of tube... I know that much....

Yep, it's like a sea of 6550 tubes...8 matched pairs and 4 regulators (20 total), not to even mention the small tubes.

Listen to Art, this one is a good one to flip, if you got it cheap you should walk away with a pocket full of money. Just sell it as is.

A new set of tubes can cost as much as a decent used car for this unit.
BillWojo

I agree with both of Bill's statements, especially his last statement. I'm in the process of pricing out a set of (16) kt120 power tubes for my ARC monoblocks and looking at like $700+usd for a set that aren't even matched. This doesn't include the other necessary matched (8) 61np for an additional $100usd.

 

[Pio1980]

What luck! A greater white elephant than the NGGs. I'd definitely feel like a dog that had caught a needy luxury car if it were me. I'd be ecstatic but have no idea what to do with it, or the means.

 

[Dazaa]

Unless you have an extremely skilled, experienced and very well equipped technician available, and you have very deep pockets,this amplifier is not a plan. It is one of the most complicated,powerful and tricky units ever designed.

All tube amps (especially older-model Audio Research units) run high voltages that are extremely dangerous. This unit exceeds those "usual" voltages by a wide margin,and can maintain them at current levels that would do an electric chair justice.

Take it from someone who has been working with ARC equipment for a very long time: You don't f**k around with one of these.Period.

Interesting! Do you know if the D250 has any known weak points or service bulletins that need addressing? For all I know the previous owner died and it works fine... certainly appears to have most if not all the tubes present in the pics

 

[Dazaa]

Listen to Art, this one is a good one to flip, if you got it cheap you should walk away with a pocket full of money. Just sell it as is.
Post some pictures with the covers off, lets see what shape it's in.
BTW, DO NOT power it up without a load connected, if it goes into oscillation bad things can happen. A new set of tubes can cost as much as a decent used car for this unit.

BillWojo

not dirt cheap but certainly low enough to warrant taking a risk on. I know you shouldn’t power on a tube amp without a load but the seller has already confirmed it does turn on. I don’t have any massive resistors, can I just hook up some sacrificial speakers? Can tube amps blow speakers the way a shorted transistor amp can by sending dc to the speaker terminals? Even if it's faulty and I just flip as is i'd still like to learn the basics of tube amps whilst it's in my possession.

 

[maxhifi]

not dirt cheap but certainly low enough to warrant taking a risk on. I know you shouldn’t power on a tube amp without a load but the seller has already confirmed it does turn on. I don’t have any massive resistors, can I just hook up some sacrificial speakers? Can tube amps blow speakers the way a shorted transistor amp can by sending dc to the speaker terminals? Even if it's faulty and I just flip as is i'd still like to learn the basics of tube amps whilst it's in my possession.

If it has been on recently, you haven't got a lot to lose by connecting some "sacrificial" speakers and trying it with a signal. When you turn it on, observe the tubes through the top, and if anything starts "red plating" (look it up if you don't know what it means), then shut it down immediately. Once all the tubes warm up, if you're greeted with hum or oscillation, shut it down. If it is quiet, then apply a signal and try it out.

Learning about tube amps with these is about like learning to drive in an F1 car, but if you insist, it can be done

I know if I obtained this amplifier when I was on the sharp part of the learning curve, there's a good chance I'd have screwed it (or myself) up, but I was also young, careless, and impatient at that time.

 

[arts]

Glad to see you're still around @arts, I hope you are doing okay.

Thank you Sir,much appreciated! I'm still not up to my "usual self ",but I'm feeling great and I'm back to work. As I've mentioned before,it's nice to still be on the sunny side of the dirt

@Dazaa
I'm in the process of pricing out a set of (16) kt120 power tubes for my ARC monoblocks and looking at like $700+usd for a set that aren't even matched. This doesn't include the other necessary matched (8) 61np for an additional $100usd.

IIRC, aren't you running a pair of VM220s? Hee hee,that's another tube pig; and I thought my VS110 was bad

Do you know if the D250 has any known weak points or service bulletins that need addressing?

Other than the costs associated with maintaining or repairing one of these,I do not recall any design-related weak points other than the fans getting noisy (usually dry bushings,easily dealt with) and the internal filth that comes with a fan-cooled amplifier.

As for service bulletins,I will have to dig into my files and see if I have anything on that.

But by this time (big,expensive "but" here),it probably has a multitude of weak points.All electrolytics and any carbon composition resistors will be suspect. Also,verify that all of the semiconductors are the correct types as specified in the manual. You cannot just bung in whatever seems close,but many times this will have happened. Look for any evidence of previous repairs and if any are found, validate that correct parts and values were used.

And just to reiterate: PLEASE heed my electric chair warning. Also,if a blow-out resistor or semiconductor fails,it will generally do the electronic equivalent of a grenade,so if you run it without covers while working on it, wear safety glasses.
I don't usually do the "nanny" thing Dazaa,but trust me mate,this one is a seriously nasty piece of work.

Cheers,

Art

 

[vonclod]

One of my buds has one, the power rating is attractive, but from what I can tell, it's a problem child, and retube is gonna hurt, sending it to your tech will hurt your back as well.

 

[elcoholic]

 

[a_retent]

IIRC, aren't you running a pair of VM220s? Hee hee,that's another tube pig; and I thought my VS110 was bad

VM220s, correct a mundo and tube pigs they are. I guess it's the price one must pay for tube horsepower.
Very glad to hear your feeling better.

 

[930turbo]

Anyone who has seen my NRG saga thread knows i'm a sucker for big amps, and an AR D250 just turned up untested so I decided to take a punt. All I know is that it powers on, looks like the seller got it from a recycling or house clearance source. Seems like it cost 6500 in the 90's and is one hell of a tube amp at 250wpc....anyone here got one or know anything about them?

I used to have one . It was a D250 MK 2 Servo. It was a dream amp for me back in 2005 . I had it retubed , it was trouble free in my 10 years of owning it . But did not get much use because I also had the ARC Classic 150 monoblocks and a pair of ARC D79 B's w/c I use in biamp configuration . The D250 was a powerful amp but the Classic 150 was more dynamic , faster w/ a sweeter sounding midrange . The D250 was dry sounding compared to the Classic 150 & D79B's . I used it w/ my ARC SP10 MK 2 and SP11 MK 2 . The dryness was less when it was matched w/ the SP10. Make sure that what you have is the MK 2 or the MK 2 Servo. These are the reliable models . The plain D250 was troublesome . Hope this helps

 

[930turbo]

Cant update my signature , Classic 150 monoblocks ,D250 MK2 servo and SP11 Mk2 sold , these equipment were replaced w/ the ARC REF Phono 2 SE , ARC REF 610T monoblocks w/ KT 120 tube dealer upgrade and my new acquisition the REF 40 Anniversary linestage w/c replaced my REF 5SE.

 

[a_retent]

....ARC REF 610T monoblocks w/ KT 120 tubes....

Now there's some serious tubage requirements.
Isn't that like (32) kt120s for a stereo pair?

 

[930turbo]

Yes it is 32 KT120’s tubes when it’s time to retube . No need to get from the ARC factory , I can order them from Jim McShane.