# B+K Reference 200.5, Help!!!



## waculjr.903 (May 27, 2009)

I just bought a B+K Reference 200.5 amp. The unit powered up, done a sound check with my Onkyo test tones.All channels checked out good but the center channel. So I went to investigate, heard a faint buzz and smelled like something was roasting electrically. I immediately unplugged everything, pulled the center channel down, and took out one of the midbass drivers the voice coil was seized up and smelled charred and smoke was pouring out the rear port. And this was my newly purchased Paradigm Studio 590v.4, talk about some one getting irate and sweating bullets that it ruined my new center channel!!!!! I triple check all my wiring before I fired up.I called the original owner of the amp and he used the XLR"s inputs to his B+K Reference 50 preamp and never used the rca inputs. He had absolutely no issues with it, worked good when he pulled it from his rack, put it in the original box and there it sat in the closet. Ofcourse,running the Onkyo 806, I had to use the rca's. I tried another test, after pulling the fuses-all good- pulled cover off the top of amp, everything looked good, no blown fuses everything looked brand new, super clean!?!? So now I take a old speaker that I used for the rear channel hooked it up and no sound from it either! But at least it didn't get cooked like the Paradigm did. No issue with any direct short in that speaker at all, but no power from that channel from amp. Yes, there are fuses internally and also on each channel on the back, they all looked good, nothing smoked or broken element that I could see. I thought all these amps had protection from a direct short and so on? What can I do, or check, that I haven't thought of, what can I do? I live in Tyler, Tx. Where could I take it to have it looked at and fixed, if that is the case?:hissyfit::huh::hissyfit:


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## Gregr (Nov 2, 2010)

Hey Cool J 

Based on your description of your trial and error testing I am guessing you have a problem with the RCA connection circuits in the amp, at least now..., though I do not fully understand why, being 2,000 miles away. 

There is no way of knowing if there was a problem or if somehow you have created the problem. Fixing the issue or issues may provide some insight. 

Wish I could suggest where to go next but a search of the B&K web-sight for recommended repair tech's in your area is what I would do next.

Maybe somebody with a similar exp or professional exp will add to your post.

Best of luck


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## waculjr.903 (May 27, 2009)

I know B+K was bought by ATI technologies. They make ATI, B+K, Threshhold etc. I went to bk's website and went to support and found download of schematics, when I tried to access it it said file not found. So, I guess I will give them a call tomarow and see about getting that and about service. When I had the amp open I looked at the back of that RCA jack, there was a thin flat group of wires in clear plastic going to a circuit board. Couldn't see any thing wrong there either. Anyway I appreciate your input, thank you for helping me.


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## Glen B (Jun 11, 2013)

From the description of what happened, it sounds like the amplifier center channel suffered some type of internal failure which dumped DC from the power supply rail into your speaker. The B&K 200.5 does not have output relays and depends on fuses ("for limited protection") according to the owner's manual. IMO it is possible that enough DC could pass and burn up a woofer/midbass driver voice coil without blowing a fuse. 

I believe only the midbass driver was damaged because the HF cap in the crossover network would block the DC from the amp, preventing damage to the tweeter. Providing that the amp was in good working condition when it left the seller's hands, it is possible that it suffered some damage during shipment. 

The important lesson to be learned here is, ALWAYS check out a used amp with old/expendable speakers, never with your good speakers. I always measure the outputs of used amps for DC offset levels before first connecting speakers.


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## Gregr (Nov 2, 2010)

Yes..., after reading Glen's post (very insightful Glen) I was inspired/curious so I did a google search of the 200.5 looking for the schematics. I believe they have been moved into the archives. B&K may sell a copy or sell only to Lisc. Tech's.

What I did learn however is - B&K recomends a dedicated 20 amp circuit for the 200.5 amp. It seems the amp runs hot anyway but an extended peak demand of 17.5 amps and at 1800watts total there could be an negative effect on more than the amp. On less than a 20 amp circuit even with a much less demanding program playing a peak demand could cause problems.

You know if I had just plugged a B&K 200.5 or .7 into my system I would definitely want to hear/see what that show-horse will do. But now I don't have a dedicated 20 ampere breaker and circuit, nor do I have appropriately sized in-wall power cable and not even a 20 amp receptacle. 

I am not trying to insult you Cool J and I do not want to..., I do have to say when you get the 200.5 back up and running this is one amp that needs some breathing room. It cannot be plugged into the same power strip/surge protector as the other system components - not even for a minute. Be careful too and don't just replace the next receptacle in line with a 20 ampere receptacle and hope it will be alright. 

When your house was wired I am sure your electrician attached 2 maybe 3 receptacles in parallel on the same one line back to the breaker box/breaker. 

I am probably going on needlessly..., if you need more detail just ask...

FYI - You can buy wire molding that sticks to the wall and you can paint to match your wall paint. You can run a 12/3 (12/2 with a ground) solid wire line to almost anywhere very easily and most people will never even notice the wire molding. In addition you can buy a nice audio quality circuit breaker and receptacle and OFC copper 12awg wire. You can stick on the wire mold run the wire leaving a 6" loop at each end. Next, when your ready "hire a lisc. electrician (for .5 to 1 hour) to make the actual connections". 

I would buy high purity copper parts. I find the more I am able to replace brass, nickle and low grade copper with high copper content parts (I like OCC copper and cryo Treatment). The result is quieter noise floor and bits of added detail to music.


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## Glen B (Jun 11, 2013)

Gregr said:


> What I did learn however is - B&K recommends a dedicated 20 amp circuit for the 200.5 amp. It seems the amp runs hot anyway but an extended peak demand of 17.5 amps and at 1800watts total there could be an negative effect on more than the amp. On less than a 20 amp circuit even with a much less demanding program playing a peak demand could cause problems.


In my experience (with AC current draw measurements) an amp being run at moderate (read normal) listening levels will not draw anywhere near its maximum rated power. If it is driven hard, and into difficult loads, that may be a different story. On movie material, all channels are never called upon to deliver high power at the same time. Even then, 15A and 20A breakers will sustain many times their nominal rating without opening.



Gregr said:


> In addition you can buy a nice audio quality circuit breaker and receptacle and when your ready "hire a lisc. electrician (for .5 to 1 hour) to make the actual connections".


Audio quality receptacle yes, audio quality breaker no. I see these suggestions of using "audio quality breakers" from time to time on various forums. By code, you are permitted to use only the brand and type of breaker listed for use in your panelboard. Usually, this means the same brand of breaker as your panelboad. Exceptions are in cases where the manufacturer of the panelboard is no longer in business. Other manufacturers may make substitute/equivalent breakers, (e.g. Cutler-Hammer "BR" type breakers in Bryant panels) but those must be certified in writing as being eligible for use in the specific panel. 

A non-listed breaker may fit and work in a panel, but that does not mean it is safe to do so because that breaker has not undergone and passed testing in that specific panel. There is no telling what could happen in an overcurrent situation. Caution in substituting breakers is advised.



Gregr said:


> I would buy high purity copper parts. I find the more I am able to replace brass, nickle and low grade copper with high copper content parts (I like OCC copper and cryo Tx). The result is quieter noise floor and bits of added detail to music.


I agree on the use of high copper content receptacles and AC connectors. My favorites after trying many different brands are Furutech, and Oyaide beryllium copper parts.


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## Gregr (Nov 2, 2010)

Note: I mention a wire size that is to building code in my area for a typical length run. However you should contact your electrician or local Code Enforcement Officer for your specific or any special requirements. Also, your new dedicated power line should be the same length from the breaker to the receptacle as the remainder of your AV system power feed from breaker box to receptacle. That is, all of your Audio/Video equipment should be the same distance from the "Grounding rod" to the receptacle power feed and so on...


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## Gregr (Nov 2, 2010)

Hi Glen - nice work on your posts. very informative and as you well know "right on". Thanks for input. I appreciate the facts as well as Cool J will I am sure.

By the By "WELCOME to HTS!!!" I believe you are in the right place. This is a very nice Home Theater Forum. It is well organized, maintained and monitored. There is alot going on from day to day and many ongoing projects. After 5 posts you are automatically able to go anywhere (almost) and participate with any projects etc etc etc. 

If you have time - what I try to do is go to the "New Posts" tab and try to answer some of the questions, especially questions that are not getting much response. There are many elec professionals and engineers on this forum and everybody seems to enjoy giving a little but somehow some questions only get 1 or 2 responses. In any case I hope you have some fun at HTS.

Regards


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## waculjr.903 (May 27, 2009)

Next weekend, I will run the conduit from the breaker panel, to the wall behind my system and push multi stranded 12-3. I bought red, black, and green to run my 20 amp circuit. The length of this run is fifty- six feet. I talked with my electrical inspector to make sure it is up to code and plenty to do what I want. He suggested the multi strand instead of solid, he said that there is more surface area on multi. for the electrons to flow for max juice. This run is connected directly to b. box located under meter box , on pole. So juice should not be a problem . I just checked all my fuses in the amp with continuity, all good except for two 2 amp slo-blow fuses that are on top of circuit board on top of capacitors. I checked them for continuity, and nothing. Also there are relays right next to each of the two fuses in question. Did I check the two fuses right, checking for continuity? Shall I try replacing the two amp slo blow fuses, hook up cheap speakers and give it another whirl?


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## Owen Bartley (Oct 18, 2006)

waycool, that's a bummer about your Paradigm, I hope the repair isn't too much trouble. It seems like you're going about things the right way, and if you can get the amp issue resolved, I would definitely test with some less valuable speakers. 

Just a thought, if the previous owner used XLRs, could you use an RCA to XLR for the CC connection to skip the possibly faulty RCA circuit? It might make sense to do that for all channels, just to be consistent if it works.


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## waculjr.903 (May 27, 2009)

The only thing with that is level matching. I had to use an ART Clean box to convert and level match to run a pro audio amp. Would that be the case with this situation as well?


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## Glen B (Jun 11, 2013)

waculjr.903 said:


> Next weekend, I will run the conduit from the breaker panel, to the wall behind my system and push multi stranded 12-3. I bought red, black, and green to run my 20 amp circuit. The length of this run is fifty- six feet. I talked with my electrical inspector to make sure it is up to code and plenty to do what I want. He suggested the multi strand instead of solid, he said that there is more surface area on multi. for the electrons to flow for max juice.


Stranded wire is also easier to pull, especially at 56 feet. Cable pulling lube would help the job go smoother, and help prevent damage to the wire insulation. You can find lube in squeeze bottles at Home Depot, Lowes or any place that sells electrical supplies.


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## waculjr.903 (May 27, 2009)

Have the conduit lube in my shed as we speak.


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## waculjr.903 (May 27, 2009)

Can someone tell me if the levels will work as is with RCA's coming out of Onlyo 806, to the XLR's inputs of the B+K 200.5S2?


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## Glen B (Jun 11, 2013)

waculjr.903 said:


> Have the conduit lube in my shed as we speak.


You ARE prepared.


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## waculjr.903 (May 27, 2009)

I try to be very thorough when I plan to execute a task at hand. Years ago, I worked for a wireline outfit under TXU Electrical Utilities and we used a gallon of the **** to help push quad 500 wire, talk about getting a workout! Sure we used the Case 660 trencher and pulley to help pull the wire, but I was the one pulling wire off a 1200# spool and stabbing it down the conduit.


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## Owen Bartley (Oct 18, 2006)

waculjr.903 said:


> Can someone tell me if the levels will work as is with RCA's coming out of Onlyo 806, to the XLR's inputs of the B+K 200.5S2?


I think it depends on how strong the pre-out signal from the Onkyo is. You might be right thinking about an ART Clean Box, especially if the signal isn't strong enough. Which will add to the cost of the project of course, as always!


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## waculjr.903 (May 27, 2009)

If I remember correctly , Apex makes a seven or eight channel converter with all good specs. They run around$575 new, occasionally you can find a used one on eBay. I guess I might as well get myself an Integra or a Marantz 8003 used of coarse. Onkyo is millavolts not 1.4volts required for pro audio which should be the same as theater consumer gear. They both use XLR's when you are using pre-pro setup.


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## waculjr.903 (May 27, 2009)

I rechecked the fuses inside the amp. I missed two ceramic looking fuses that are on top of capacitors on the circuit board. They are labeled 250v/2a . I checked continuity and nothing, I guess they are not good. I replaced them with the exact equivalent. Do you think I should give it another try? Can I fire it up, not connecting any speaker wires and do some sort of check with a multimeter to see if it is safe and functional to hook up to my speakers? Or do I just need to send it somewhere for pro service?


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## Glen B (Jun 11, 2013)

The risk you run in powering up an amp that has caused speaker damage and blown fuses is that you can make any internal damage worse. The call is yours. You can check the amp for DC at the output by connecting a digital multimeter (DMM) set to the VDC (volts DC) scale, to the center channel output binding posts. Power up the amp and see what reading you get on the meter. Anything greater than ± 500mVDC, do not connect speakers but turn the amp off and report back with the DMM reading you get. DC offset greater than about ± 500mV will usually cause the protection system in amps that have that feature (which your amp does not) to kick in.


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## waculjr.903 (May 27, 2009)

Can I do this not hooked to any source,? Or does it have to to get output?


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## Glen B (Jun 11, 2013)

Its a good thing you asked. I forgot to mention, check DC offset with nothing connected to inputs or outputs.


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## waculjr.903 (May 27, 2009)

Ok, thanks!


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## waculjr.903 (May 27, 2009)

I am not trying to beat the dead horse so to speak, but I came across some relevant info. On the specification page on my manual, it gives the fuse info as follows; A/C line-15 amp, slow blow, Rails-6 amp/250v time lag, Speakers-6amp/250volt slow blow, IN RUSH/2AMP, 250 VOLT SLOW BLOW. So it doesn't seem that there is a problem with the power rails, just inrush current, which is probably my fault for trying it out before setting up my dedicated power circuit for this amp prior to trying it out for the first time. I couldn't help it about being impatient, I was like a kid in the audio candy store! Ya, I am guilty ha ha! Now am I making the right assumption , with the correct fuse labels?


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## Glen B (Jun 11, 2013)

I've never heard an amp manufacturer specify "inrush" fusing, but that could probably have something to do with a soft start circuit. I can't picture not being on a dedicated circuit having anything to do with a speaker burning up. If that were the case, the many people running high powered amps on shared branch circuits would all have their speakers popping right and left. If the amp does have a soft start circuit, that by itself makes whether the amp is on a 15A or 20A line even more irrelevant. Inrush current would be pretty low. The amp would not "know" its on a 15A circuit unless/until driven to very high levels. I am still of the opinion that some incident occurred which dumped a high amount of DC into the center channel speaker. The only source of such direct current in an amp is the high voltage supply rails.


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## Stereojeff (Apr 23, 2012)

In my very professional opinion, your impatience did not cause the DC fault in your amplifier.

Jeff


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## waculjr.903 (May 27, 2009)

I checked it with my meter channel1 read 5.9 mv ch 2 read 5.7 mv channel 3 read 47.5 ch4 read 5.0 ch5 read 8.6, checking DC.


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## Glen B (Jun 11, 2013)

The figures for channels 1, 2, 4 and 5 are good at under 10mV. The 47.5mV reading for channel 3, while not enough to cause speaker damage is still of some concern. With that level of DC offset, 2nd harmonic distortion in that channel will be substantially out of manufacturer's spec. You need to have a technician look at the amp, and get that offset figure as close to 0mV as possible. Some amps have DC offset trimpots and some don't. If your B&K has such trimpots for each channel, adjusting offset will simply be a matter of adjusting those pots. Amps that have no offset trimpots rely on very close gain matching of the differential stage transistors to keep DC in balance.


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## waculjr.903 (May 27, 2009)

I have been on the net and phone chasing down a service tech. I called ATI that I thought took over and continued the bk line. They just absorbed their assets during bankruptcy . So I asked the tech who could check it out. He said that in Houston, Tx is a place called Bammel Tv. That they do an excellent job and highly recommended. Tomarow I'll ship it to them to get it done. Thanks Glen, for your help. I'll post the remedy here when finished , so if someone else has a similar problem, maybe it will help them out.


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## waculjr.903 (May 27, 2009)

I looked up Bammel's reviews and they weren't good 18 out of 20 said fair to poor rating. I got a line on Atlas Electronics, they are good and authorized service for Onkyo and other major brands. They called me and said nothing wrong with the amp, but the pre- amp section had to be replaced-$270. So as soon as parts show up, I'll have it back. I'm chomping at the bit to get it and try it out! I ran two dedicated 20 amp circuits for my HT. I went to the main box under the meter box , and snapped in two 20amp breakers, on stranded 10gauge wire, good thing I used a fish tape! I get a solid minimum120v, with everything running and Qsc amp cranked, and power is good and strong. So I am all set and ready with my two dedicated outlets on separate breakers, on the same bar of the box. I ran it all myself and terminated it also. At least I know enough about electrical to not need a electrician to hook it up for me and save some cha-ching.


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## Gregr (Nov 2, 2010)

Yeah Man..., well done!!! You've done nothing in a "this will do" half step, mode. You now have the foundation for a "cost is no obstacle" Home Theatre system. Now, as long as Nature and the power company don't cut you short your K&K should really sound off on demand. 

Do not forget if you ever need a home appraisal for selling purposes you need to point out the 2 independent 20amp circuits with top quality wire etc. The appraiser will give you full value of the circuits but not labor except in final evaluation of overall impression and saleability of the home. However if your evaluation is for taxes don't say a thing about nothing.

Too bad about replacing the pre section but now I believe you won't have any issues..., hopefully the speaker x-over suffered no injury.

Nicely done, I am impressed..., I hope you end up liking the amp ha ha ha - funny how things go sometimes, ya just gotta be able to laugh


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## waculjr.903 (May 27, 2009)

I called Atlas Electronics and part is back ordered . While I was waiting this week, I found a good deal on an Integra 9.8 . I received it yesterday and it is just like new- excellent condition. I wanted to take advantage of the best/cleanest route to my amp the XLR I/O. I was contemplating the Marantz 8003, but one I had my eye on sold before I had a chance to get it. I have had three generations of Onkyo, and have been more than satisfied. I still have my first one working perfect at my computer station after15 years since I purchased that one. The question I have now is........ DO I STILL HAVE TO USE A COOLING FAN in my cabinet for this Integra, this 9.8 doesn't have any amplification in it, so it should keep nice and cool by itself RIGHT? I got a real good deal on this Integra that if for some reason I wanted to upgrade again in the future, I won't be loosing any money on selling it, so either way I can't complain! Question #2; is there any setting in the menu of it that you have to change to go from using the RCA's to using the XLR jacks? Also, can I use both at the same time? I have a powered sub on the RCA sub out that I run the majority of the time for my wife to use. But when I am using it, I want to use the XLR out for my QSC RMX2450 amp for the 18" sub! I have been using the Onkyo806. I am familiar with all the menus on it but have not found out about these items yet on the Integra. Also, if anyone has had this pre-pro before, if you could shed some light on anything else that I should know, I'd appreciate it a lot. Thanks to you all for all the help you have given me!!!! I am an individual that really appreciates any help that I do get from anyone! I just thought I should let everyone know that your efforts in helping are NOT in vain!!!


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## Glen B (Jun 11, 2013)

waculjr.903 said:


> DO I STILL HAVE TO USE A COOLING FAN in my cabinet for this Integra, this 9.8 doesn't have any amplification in it, so it should keep nice and cool by itself RIGHT?


Nice score on the 9.8. It depends on how much heat it puts out. I have two cable converter boxes in my HT system cabinet that run as hot as amps, even when off. I have a cooling fan on the rear panel of the rack running 24/7 to draw the heat out and minimize heat buildup.



waculjr.903 said:


> Question #2; is there any setting in the menu of it that you have to change to go from using the RCA's to using the XLR jacks? Also, can I use both at the same time? I have a powered sub on the RCA sub out that I run the majority of the time for my wife to use. But when I am using it, I want to use the XLR out for my QSC RMX2450 amp for the 18" sub!


I see no mode switching menu item in the owner's manual. The 9.8 is not a true differential design, so the balanced outputs are likely opamp based. Both the XLR and RCA outputs should be simultaneously active, especially in the absence of caveats about the connections. Just make sure your amp's XLR inputs follow the same XLR configuration as the 9.8 (pin 1 ground/pin 2 hot/pin 3 cold) or signal polarity will be reversed. Since the pre/pro is not truly balanced, I don't see any benefit to using the XLR connections, unless your cable runs are long.


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## waculjr.903 (May 27, 2009)

One more question, as far as the B+K's preamp section, what exactly is that? Is that the RCA/XLR signal input section to one of the circuit boards? Also as far as that part, is that a very item specific part? Or is it one that fits quite a few different amps? I am curious for my own knowledge.


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## Glen B (Jun 11, 2013)

What the tech is calling a "preamp" section could be either the input buffer/balanced converter stage or the input differential stage of the output section, but I think he means the former. The buffer stage is likely op-amp based. The input differential stage employs very closely matched transistors, either a pair of individual devices, or two in a single package. The following block schematic (showing one of two channels) will give you some idea of what I mean. There is the switch to select between RCA and XLR input, followed by input buffers, then the output section.


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