My Aragon 8008bb Amp is making thud sounds thru speakers

headrott

Schurkey wrote: »

1. The "classic" Aragon amps are common ground, HOWEVER, the resistance between the channels is higher than the SDAs like. I measured two of my BBs, and they each have ~20 ohms between the channels. A jumper connecting the negative posts eliminated a TRULY UGLY phasy/midrangey coloration from my 1Bs. Thousands and thousands of years ago, I had a jumper connecting the negative terminals of my 4004; I never did test the resistance between negative terminals--but after awhile I removed the jumper and I don't recall hearing any difference.

2. Even with ~20 ohms of "un-common-groundedness" of my 8008BBs, the amps DO NOT "thud thud thud".

3. The clicking you hear inside the amp is the protection relay. Don't piss it off. The fact that it's activating is telling you that it's unhappy for some reason.

4. The 8008s (and the 004 series before them) were unusually dependable. The first thing I'd be doing is looking for defects ahead of the amplifier; perhaps passing DC to the amp. Next, I'd be looking for a dead short downstream from the amp; perhaps starting with disconnecting the SDA cable. Any chance of a stray strand of speaker wire going from + to - ?

5. If nothing else, there's a fuse on the back panel; and four fuses under the "long" top cover. Might be worth a look, although the fact that you're getting sound "sometimes" probably means the fuses are good. I had an 8008BB delivered to me with one of four internal fuses dead; it took out that channel. Fuses required are (1) 12 amp SLOW-BLOW for the back panel such as a Bussman MDA-12; and (4) 10 amp FAST-BLOW for "under the hood" such as Bussman AGC-10. (yes, the Aragon will throw ~20 amps continuous per channel!) These fuses (especially the AGC series) are ordinary automotive-style glass units 1/4" X 1 1/4"; dirt cheap at any auto parts store or hardware store.
http://www.hbassociates.us/AragonFuses5May08.pdf

http://hbassociates.us/Aragon_FanPage.html

It's not anything before or after the Aragon, as when I hook up my tube amp everything works fine. As H9 ststed, when I removed the SDA cable the "normal stereo" worked fine. I will test the resistance between the 2 negative posts. If this amp is common ground, then as you said the resistance is so high it affects the SDAs from functioning properly. Did you use your Aragon 8008bb with SDAs and a standard SDA cable?

If this amp is common ground, but the resistance is too high for the SDAs would the AI-1 cable solve the thud, thud, thud problem?

The amp does have the jumper connectors in place, unless they are not fully seated correctly or they are in the wrong pins. I will check that too. Oh, also all the fuses are OK (visually) and both channels work OK and the power turns on. I'll do it and get back to you.

Greg

Schurkey

headrott wrote: »

I will test the resistance between the 2 negative posts.

Thanks. The two amps I tested were within one ohm of each other; one was 19.5 and the other was 20.3...I think.

headrott wrote: »

If this amp is common ground, then as you said the resistance is so high it affects the SDAs from functioning properly. Did you use your Aragon 8008bb with SDAs and a standard SDA cable?

SDA 1B--no AI-1 cable is possible with them. I ran the speakers without the cable, they sounded fine but of course no SDA effect. When I connect the cable (as supplied with the speakers in '86 or '87 or whenever it was that I bought them) the midrange turned to ****. 20 ohms makes ALL the difference!

headrott wrote: »

If this amp is common ground, but the resistance is too high for the SDAs would the AI-1 cable solve the thud, thud, thud problem?

No promises. Mine did NOT "thud thud thud" even with the 20 ohms between the channels. Just sounded terrible. Note that different speakers might produce different results; and YOUR crossovers are way different than what comes with the 1B.

The easy suggestion is to do what I did--jam a jumper into the negative posts so as to connect the channels. I used a foot of 12-gauge stranded wire; and when it worked and sounded good--I added banana plugs to the ends.

headrott wrote: »

The amp does have the jumper connectors in place, unless they are not fully seated correctly or they are in the wrong pins. I will check that too.

It's worth pulling them out and re-seating them. I was just SURE you were going to report that you were missing one or more of those jumpers. Darn. Lost a bet with myself.

headrott wrote: »

Oh, also all the fuses are OK (visually) and both channels work OK and the power turns on. I'll do it and get back to you.

Greg

Yeah, I kinda figured the fuses would be OK.

headrott

Thanks. The two amps I tested were within one ohm of each other; one was 19.5 and the other was 20.3...I think.

What were you testing the resistance of to get these values? Was it with a load or without?

I got .01 ohms between the 2 negative posts with no load on them, haven't tried with a load yet. I will also try to reseat(completely pull the out and put them back) the connector jumpers to make sure they are seated correctly. They are in the correct pins though.

hoosier21

amp off, and speaker wires disconnected for the resistance test

heiney9

While you're doing that also check the DC offset. Simply measuring at the (+) and (-) while powered with a load. Hopefully it measures in mV.

headrott

Yep, the resistance is 20.5 ohms. That does seem high for the SDAs to work correctly. So, strapping the 2 negative binding posts together is OK for this amp? I could try that and hook the SDA cable up to see if that solves the thud problem. I still need to do the DC offset, but have to wait a bit to do it. (Can't get to the amp right now).

Schurkey

headrott wrote: »

Yep, the resistance is 20.5 ohms.

That seems to be a normal reading for these amps.

headrott wrote: »

That does seem high for the SDAs to work correctly.

OHHHhhhhh Yeahhhhh.

headrott wrote: »

So, strapping the 2 negative binding posts together is OK for this amp?

Not a problem at all. I've done that to two of mine.

headrott wrote: »

I could try that and hook the SDA cable up to see if that solves the thud problem.

I absolutely would try that.

headrott wrote: »

I still need to do the DC offset, but have to wait a bit to do it. (Can't get to the amp right now).

I may have the specs for DC offset; I know I have the adjustment procedure for the 004 amps; I'm not sure I have the procedure for the 8000-series.

heiney9

The 8000 series could be servo controlled so there may be no adjustments. I only suggested it since he was already probing around with the VOM. I always check DC offset on a new to me amp before I hook it up.

I think strapping the negative terminals will solve his problem which is most likely because the 8008 isn't exactly a common ground amp since there is a reading between the neg. terminals.

H9

headrott

OK, here is what Rick at Indy Audio Labs sent to me regarding strapping the negative posts together:

"Hi Greg,



The 8008 is a common ground (not bridge-tied-load) topology, however, when powered down, the speaker minus terminals are floating or disconnected from ground via the output relay. Even when powered up, there is a finite resistance between the channel minus terminals and ground. This is actually a safety-related feature. Therefore, strapping the negative terminals together at the amp is not recommended. I don’t have direct experience with the Polk SDA’s, however, if the AI-1 interconnect cable is transformer isolated, you should be OK.



Let me know if that helps answer your question.



Thanks,

Rick"

I think that he wouldn't suggest "strapping" the negative posts regardless of anything, for safety and possibly legal reasons. He did say the AI-1 cable should work OK though. He said that the is "a finite resistance even when the amp is powered up" so as H9 said, this amp is not exactly a common ground amp (a non-common ground, common ground amp.....Or something like that.)

If you have strapped the negative posts together though Schurkey, and didn't have a problem then I don't see why mine would. By the way, did you have the "original 8008bb amp (made by Mondial)? Or the newer one made by Klipsch?

Schurkey

headrott wrote: »

If you have strapped the negative posts together though Schurkey, and didn't have a problem then I don't see why mine would.

Agreed. Worth a try. I have tried to contact the amp's designer, but so far I've gotten no reply.

headrott wrote: »

By the way, did you have the "original 8008bb amp (made by Mondial)? Or the newer one made by Klipsch?

To my knowledge, there is no difference in the functionality of the Mondial 8008BB vs. the Klipsch 8008 Mk II other than the styling and a blue light. The circuitry is virtually identical.

For the record, all my Aragon amps have been the Mondial version; and all bought at a discount--either as "store demo" or outright "used" through Audiogon or eBay. The Klipsch versions were WAY too expensive for me. I did get a Klipsch-era Stage One; but again I bought it during "close-out" at drastically reduced price.

Yup, I'm tight.

headrott

Ok, I got another 2 e-mails back from Rick about the amp. They are(with my questions asked):

Hello Rick,

I get a reading of 20.5 ohms between the 2 negative terminals on my VOM. So, even though this is a common ground, the resistance is too high for the Polk SDAs to work correctly. The way the people at Polk Audio Forum have found a way around this is to (1) Strap the negative binding posts together (assuming it's a non-common ground amp) or (2) use the AI-1 cable.

Could it be that since the resistance is so high (between the negative binding posts) that the SDAs think it's a non-common ground amp? I ask this because when I tried hooking up my speakers to the Aragon with the SDA cable in place I got a consistant thud sound and the circuit protection initiated. When I tried the amp with the SDA cable disconnected, it seemed to work fine. But, my speakers only worked in "normal stereo" without the SDA effect. I am ordering parts to make an AI-1 cable and that should be the safest way to hopefully solve the problem. I just thought I would try strapping the negative posts with the SDA cable in place to see if the amp and speakers work correctly. I have been talking to another Polk audio forum member who strapped his Aragon 8008bb and Aragon 4004 together and he said his amps didn't have a problem. I just thought I would ask the source just to make sure before trying it. Thanks again Rick.

Greg
Response:
It may be OK to try, assuming the amp is working normally, but I would not recommend this on a long-term basis from a safety perspective. The 20 ohms you measure is about right for the internal ground clamping circuitry. The relay cutting out is an indication of some sort of ground fault with the speakers connected. I don't know enough about the SDA circuitry, but it sounds like the SDAs need less resistance than that between channels - i.e. as close to a short as possible. The AI-1 cable sounds like the way to go, particularly if it transformer isolates the two speakers. Keep me posted.


Thanks,
-Rick
My response to Rick:
Can you tell me what a normal reading for the DC offset is for this amp? I am trying to make sure the amp is funtioning correctly before I strap the terminals. Thanks again.

Response:
Hi Gregory,



Should be near zero at the speaker terminals (i.e. a couple mV or less). It is a DC servo design that self-corrects for any DC offset. If not, the amp may have a problem.



-R

I still need to measure the DC offset (I will have to hook up the amp again to do it).

heiney9

I figured it was a DC servo design. Just measure to be sure there isn't another issue with amp. The DC servo can only correct so much, so if you are measuring unsafe levels of DC at the output's it certainly is an indicator of amp issues.

H9

headrott

OK, so I measured the DC offset of the Aragon and it was 00.0 mV between on (+) and (-) set of posts and 00.1 mV between the (+) and (-) of the other. Seems well within specs to me. The only problem has to be that the resistance of 20.5 ohms is just too damn high. Next I will jumper the negative posts and try the amp with the SDA cable hooked up. We'll see how that works.

Greg

hearingimpared

Greg
Response:
It may be OK to try, assuming the amp is working normally, but I would not recommend this on a long-term basis from a safety perspective. The 20 ohms you measure is about right for the internal ground clamping circuitry.

Greg it doesn't sound like Rick gave his full blessing on that. I would be very careful and get that AI-1 going as soon as possible.

headrott

I was hoping someone would reply. I just hooked the jumper up, but came back upstairs to see if someone replied to this. You did. I have almost all the parts ordered for the AI-1. (Just need the aluminum case for the transformer to be ordered). Should I just wait for the AI-1? Or should I test it with the jumper and standard SDA cable?

hearingimpared

headrott wrote: »

I was hoping someone would reply. I just hooked the jumper up, but came back upstairs to see if someone replied to this. You did. I have almost all the parts ordered for the AI-1. (Just need the aluminum case for the transformer to be ordered). Should I just wait for the AI-1? Or should I test it with the jumper and standard SDA cable?

Well if a technician from the company that made the amp states you can but and I paraphrase, "not make it a permanent work around," says okay I can't see any problem trying it for a short period of time. Just be very careful . . . the first sign of distortion or thud, I would shut her down and get the AI-1 in the mix ASAP.

headrott

Yup, that's what I was thinking. OK, I'm gonna try it with great hesitancy though.:(

headrott

OK, so here are the results. First off, it worked (if you want to say "worked" as an appropriate word) I need a better jumper between the 2 negative posts. I say this because when I first turned on the Aragon amp there was so much noise added to the output signal that it made me sick. It was like having bad tube put into the mix. Second, when I tried the into to Electric ladyland, I there were many things wrong with the output signal. I could hear all kinds of high frequency stuff going on (as a matter of fact my ears still hurt) that it silly. Also, the SDA effect was crippled so much, that it was cut down about 1/3 of what it should be.

That was just the trying this first CD. I will try to get a better jumper and adding it between the negative posts and we'll see what happen. SOrry if this was not a coherent post as my bloodsugar feels like it's about 35 right now. Gotta test and see. Then eat something I'll get back to you.

Greg

Schurkey

I don't know what to say. MY 8008BBs drive my SDA 1B JUST FINE with a jumper between the negative terminals. Two amps tested--two amps "passed".

Your speakers have a very different crossover; I suppose that can make for entirely different results--but--that is NOT what I expect.

The jumper-between-the-negative-posts in my system--using two different 8008BB amps--does NOT create any problems I'm aware of; and in fact makes my 1B speakers LISTENABLE and PLEASURABLE; removing the jumper IMMEDIATELY and POSITIVELY creates a HATEFUL midrange "effect" that I cannot properly describe but is repulsive to listen to.

This midrange effect does not provoke the protection relay as has happened with you. Again, the 1B speaker has a very different crossover arrangement than your speakers.

Short story: I'm GENUINELY surprised that installing a jumper between the negative terminals does not TOTALLY ELIMINATE the problems you have.

Beyond that--I can only say that I'm much too inebriated to discuss this properly at the moment.

Your blood sugar...my blood alcohol...Tomorrow may be a better day for communication.

God bless spell-checkers.

dacoupedeville

Headrott,

Didn`t you just finish rebuilding your 3.1tl`s? Maybe the lack of burn in on the caps and crossovers is what you are hearing. It took quite some time before mine started sounding good, and improved dramatically with more time.

I use an Aragon 8008x3. It has only one transformer in it though (like the 8008st) not two stacked for dual mono like yours. It seems like strapping the grounds should work.

headrott

OK, I threw together another (better) jumper cable. The difference in the SDA effect is rediculous!! The SDA effect is back in a BIG way! The nest I've heard from any amp I have heard! I listened to Madonna's Ray of light album (great for SDA) and you could hear sounds from everywhere! So a big improvement there. Also, all the little high end artifacts a (basically) gone.

Unfortunately, the hum I heard before is still there just as loud (I think). This is noise that is intoduced from the amp I think. The only way to get rid of that is to use the AI-1 cable with no strapping.

dacoupedeville, I did just replace the caps in the speakers but that is definately not what is causing the hum or artifacts. I believe that was coming from strapping the negative posts. The artifacts a much better, but as I said the hum is still there. This is why as Raife stated a while back, it is better to use the AI-1 than jumper the negative posts because strapping the posts feeds back the amplifier noise to the output signal.

I have all the AI-1 parts on order and should get them in about a week. that should make this a great amp to use with these speakers. I can't wait to hear the SDA effect using the AI-1!!

headrott

OK, I found out where and why the buzz is happening from. This articale explains it pretty well. http://www.hometheaterhifi.com/volume_6_2/aragon8008x3.html

Particularly this portion of the article: Also, a weird feature of the amplifier makes it incompatible with directly connected passive attenuators. Because the input stages are balanced, fed by an unbalanced jack, if a substantial impedance is placed between the hot side of the input and ground, and the hot input and the hot output simultaneously, the situation causes an irritating buzz, much like a ground loop. I've noticed the same thing with Bryston 7-B monoblocks when configured for a balanced input. When the input directly connects to an active output, or a shorting plug, the electronic background falls into a dead quiet. Go figure. That’s not a real issue in a home theater situation, or even most two-channel applications. But, if you turn the amplifier on with speakers connected but no source, it’s going to buzz. It’s not broken, it just does that, so be aware of it.

The question is, is there a way to prevent this without getting a balanced outpu for my AMC 1030as pre-amp? Anyone got some ideas? Thanks again.

Greg

ben62670

Tie the XLRs ground, and v- together. No more buzz. I use an XLR plug to make the jumper.
Ben

headrott

ben62670 wrote: »

Tie the XLRs ground, and v- together. No more buzz. I use an XLR plug to make the jumper.
Ben

Well Ben, it didn't work.:( I tried a couple different cables in there but neither solved the problem. Have to try other means. i wish I had some kind of pre-amp output with XLRs. I would be interested to find out if that solved the problem. Thanks again Ben.

If anyone has ideas please let me know. Thanks.

Greg

It lies somehwere in these statements I think (from the review of the 8008X3): Also, a weird feature of the amplifier makes it incompatible with directly connected passive attenuators. Because the input stages are balanced, fed by an unbalanced jack, if a substantial impedance is placed between the hot side of the input and ground, and the hot input and the hot output simultaneously, the situation causes an irritating buzz, much like a ground loop. When the input directly connects to an active output, or a shorting plug, the electronic background falls into a dead quiet.

One other thing I thought of is that I am using XLR connectors going from the CD player to the pre-amp and then RCA connectors from the pre-amp to the amp. Taking the above statements into account, wouldn't this cause the buzzing, especially if the output impedance of the pre-amp is <200ohms?

ben62670

Sorry it didn't work. I'm stumped.

RuSsMaN

So, is the AI-1 happening?

headrott

Yes, but I still need to get the parts for it (about a week). Unfortunately, I don't think that will fix the buzzing problem though. (see above post)

Schurkey

Put a shorting cover on each RCA jack and use a pair of these instead?????
http://www.fullcompass.com/product/297984.html

I'm sorry, I think you're now officially way past what I can help with.

heiney9

Schurkey wrote: »

Put a shorting cover on each RCA jack and use a pair of these instead?????
http://www.fullcompass.com/product/297984.html

I'm sorry, I think you're now officially way past what I can help with.

These work EXACTLY the same way the shorting pins work. If I'm understanding what the issue is. The adv to the above is you can use RCA's instead of XLR connections or these will short the proper pins so you can use the RCA terminals provided on the amp. Either way same solution.

H9

headrott

That's the strange thing is that there are umpers in the XLR 1 and 3 pins already. So, theorhetically it should not be buzzing unless the impedence from the pre-amp is too high for the Aragon (Or the aragon is too low for the pre-amp??). I am going to try a few things to see what affect it has on the Buzz. Can a power cord cause a buzz sound? Like if there is too much RF getting through tthe cord and entering the amp? Thanks for your time and help.

Greg