Household electrical problem

[TLS Guy]

Yeah, you are only out by 20%. Probably good to go in the schools you went to. Not mine.

(AC x 1.414 = DC) x supply/amplifier efficiency. There is no need to guess at the combined efficiency, you can get it from the values provided. It's not 65%.

Well I had a good look at the service manual yesterday.

The manual does admit to only partial protection. The protection is 7.5 amp fast bow fuses in the speaker outputs. Even partial I think is optimistic for that.

Anyhow 7.5 amps would deliver 225 watts into a resistive four ohm load. Probably less into most speaker loads. In addition I bet there is margin, so I doubt the amp produces more than 200 watts into a four ohm load.

The other thing I found interesting is that on the circuit diagram it specifies the load output impedance to be 5 to 8 ohms. This is at variance with the user manual. I have no explanation for this.

Now his W15 SEAS Excel drivers are actually only 6 ohm from the tuning peak to the impedance rise at 600 Hz, according to the published curve by SEAS.

So if you parallel two of those drivers it gives you three ohms in the peak power region.

However I did do a model in a tuned box, which is basically what a mass loaded TL is, although with some bass extension. I used SEAS T/S data. On the model the impedance was just a little below 4 ohms in that region.

However it would be good to actually have a measured curve, of his speakers. SEAS data is usually brutally honest.

It is certainly possible all this has something to do with that amp failure.

I have to say I was less than impressed with that amp. I do believe that speakers of the quality of SWERD's deserve better, and would almost certainly produce better sound with a better amp.

I would take this opportunity to put it out to pasture personally.

 

[Swerd]

Well I had a good look at the service manual yesterday … … … It is certainly possible all this has something to do with that amp failure.

Minor correction, the woofers in my speakers are SEAS Excel W16, not the smaller W15. Their impedance is slightly higher than in the W15, as seen below. I don't know if the higher impedance and greater output of the W16 drivers make a significant difference to your overall conclusion. Any idea?

I have to say I was less than impressed with that amp. I do believe that speakers of the quality of SWERD's deserve better, and would almost certainly produce better sound with a better amp.

I would take this opportunity to put it out to pasture personally.

I do follow your reasoning, and I have not rejected your conclusions. This includes your point that the amp's recent failure might be related to the switch from the SongTowers to the VST speakers. However, I am taking my time to find out if the B&K is repairable, and what it would cost. And yes, I agree there are tangible repair costs measured in $, and there are intangible costs in possibly improved performance and reduced risk to damage.

 

[Swerd]

Two other, unrelated thoughts:

It is clear that B&K inflated the power rating of their amp, but it's not clear by how much. Why speculate about amplifier power ratings and efficiency when it could be measured?

A big thank you goes out to my brother Dan, who came over to my house today and helped me straighten out some pesky home theater wiring issues. It involved running 6 RCA interconnects between my BR player and my non-HDMI AVR. We installed 10' long cables in place of 6' long cables to relieve length-related cable stress. It took two people, and four hands, to get the job done right.

 

[Irvrobinson]

Yeah, you are only out by 20%. Probably good to go in the schools you went to. Not mine.

(AC x 1.414 = DC) x supply/amplifier efficiency. There is no need to guess at the combined efficiency, you can get it from the values provided. It's not 65%.

Actually the 65% rule of thumb accounts for amplifier output watts being measured RMS and other inefficiencies in an amplifier. One differing factor is how the initial stages are implemented, like discrete versus IC, and the rule of thumb works better with high power amps than lower power ones, because the initial stages consume more power as a percentage of the total power consumption of the amplifier at lower power levels. And it is just a rule of thumb, so it is seldom perfectly accurate. I was using it correctly.

 

[Irvrobinson]

It is certainly possible all this has something to do with that amp failure.

I really doubt this is the case. I think the more likely reason is this amp is old and capacitors age, especially if the unit runs warm and Swerd keeps it in cabinet, and capacitors getting cranky can do all sorts of damage. And that's just one guess. Those speakers are an easy load for any quality solid state amp.

Mark, I think you're getting carried away here. Many of us know you don't like *any* amplifiers except for your beloved current dumpers.

 

[TLS Guy]

Minor correction, the woofers in my speakers are SEAS Excel W16, not the smaller W15. Their impedance is slightly higher than in the W15, as seen below. I don't know if the higher impedance and greater output of the W16 drivers make a significant difference to your overall conclusion. Any idea?

I do follow your reasoning, and I have not rejected your conclusions. This includes your point that the amp's recent failure might be related to the switch from the SongTowers to the VST speakers. However, I am taking my time to find out if the B&K is repairable, and what it would cost. And yes, I agree there are tangible repair costs measured in $, and there are intangible costs in possibly improved performance and reduced risk to damage.

Yes that would make a difference. Those 6" drivers have an impedance curve virtually identical to my 7" excel drivers.

So I have measured data on the 7" W18s. Your impedance curve will be pretty much identical except for having 2 tuning peaks. As you can see two of those make a 4 ohm speaker.

 

[Swerd]

Yes that would make a difference. Those 6" drivers have an impedance curve virtually identical to my 7" excel drivers.

So I have measured data on the 7" W18s. Your impedance curve will be pretty much identical except for having 2 tuning peaks. As you can see two of those make a 4 ohm speaker.

Thanks. Dennis Murphy likes the W16 drivers when combined with the OEM RAAL ribbon he uses in that MTM design. He says their break-up peak is at a higher frequency than with the W18.

I really doubt this is the case. I think the more likely reason is this amp is old and capacitors age, especially if the unit runs warm and Swerd keeps it in cabinet, and capacitors getting cranky can do all sorts of damage. And that's just one guess. Those speakers are an easy load for any quality solid state amp.

Yes, the amp is old, without doubt. But it runs cool; my AVR runs hotter.

Yes, I keep it in a cabinet, but there is a door which remains wide open whenever its in use. And I cut a large rectangular opening in the rear panel of the cabinet (¼" thick Masonite). With the open rear panel and the open door in front, there is always plenty of cross ventilation. I also run a large ceiling fan in that room which increases the ventilation.

Both Dennis Murphy and Jim Salk say those speakers are easy to drive, and wide variety of amps can drive them.

I know something in the power supply section failed. Other than that, there is no sense speculating about what failed, when I'll find out soon. It could be something terminal, or something as simple as a rocker switch or capacitor(s).

 

[TLS Guy]

Thanks. Dennis Murphy likes the W16 drivers when combined with the OEM RAAL ribbon he uses in that MTM design. He says their break-up peak is at a higher frequency than with the W18.
Yes, the amp is old, without doubt. But it runs cool; my AVR runs hotter.

Yes, I keep it in a cabinet, but there is a door which remains wide open whenever its in use. And I cut a large rectangular opening in the rear panel of the cabinet (¼" thick Masonite). With the open rear panel and the open door in front, there is always plenty of cross ventilation. I also run a large ceiling fan in that room which increases the ventilation.

Both Dennis Murphy and Jim Salk say those speakers are easy to drive, and wide variety of amps can drive them.

I know something in the power supply section failed. Other than that, there is no sense speculating about what failed, when I'll find out soon. It could be something terminal, or something as simple as a rocker switch or capacitor(s).

Yes, they are an easy 4 ohm drive with no extreme phase angles.

I don't think there is any difference in the frequency of the break up modes between the W16 and W18. They both max out at 4.75 KHz. They both start at 3 KHz. In fact the W18 has a smoother response before break up. In addition I get 200 watts of continuous power from a pair, and a lower F3. I needed a lower f3 to match the pipes half an octave apart.

I was able to notch the break up mode with low pass filter components without a discrete notch filter.

My biggest concern about that B & K amp is the lack of proper speaker protection. A fuse in the speaker output is not adequate protection. That is the reason I would not use it.

Running cool is just an indication it is biased more to B rather then A. I have long history with class A amps going back to the Sugden and Richard Allen amps. I'm convinced they sound better. The Quad gives you high power, cool running and class A performance.

 

[Johnny2Bad]

... (snip) ...
My biggest concern about that B & K amp is the lack of proper speaker protection. A fuse in the speaker output is not adequate protection. That is the reason I would not use it.
... (snip) ...

A fuse in that position will only protect the speakers from sustained clipping. A few seconds at least before it blows, or catastrophic failure of the output devices maybe a bit quicker but probably still not fast enough. It's something, but not much. I'm pretty sure running the amp into clipping isn't one of Swerd's likely problems.

 

[lovinthehd]

I'm pretty sure running the amp into clipping isn't one of Swerd's likely problems.

No teenagers have access to the system?

 

[Alex2507]

No teenagers have access to the system?

You mean like a squad of barely legal chicks with *****?
No, none o' that.

 

[PENG]

Two other, unrelated thoughts:

It is clear that B&K inflated the power rating of their amp, but it's not clear by how much. Why speculate about amplifier power ratings and efficiency when it could be measured?

That's why AH, S&V, HCC, Miller Audio are my friends. but too bad there are still not that many amps get tested by reputable labs. Even with lab test results, we still have to refer to all available published specs and the test methodologies used, in order to compare apple to apple and collaborate all the information before we can say one is more powerful than the other, and in what way. One amp could be more powerful in terms of truly continuous average while the other may be the winner in terms of real world need such as much higher output at low distortion for short duration.

From the information I can gather, the EX4420 would probably be comparable to something like the Adcom GFA555. It should have no trouble making the mark of 200 WX2 (<0.1% THD) into 8 ohm and 300WX2 into 4 ohm (1% THD I would guess). It may actually do 350W or more into 4 ohms with one channel driven. My educated guess is based on the apparent size of the caps and the transformer. The transformer does look a little small, but the caps (2 per channel) seem to be of decent size, physically speaking anyway. I hate to guess, but I do trust B&K enough to venture such educated guess.

By the way, how about the going by ears part, did you find the amp lacking in power output for your needs?

 

[Swerd]

Yes, they are an easy 4 ohm drive with no extreme phase angles.

I don't think there is any difference in the frequency of the break up modes between the W16 and W18. They both max out at 4.75 KHz. They both start at 3 KHz. In fact the W18 has a smoother response before break up. In addition I get 200 watts of continuous power from a pair, and a lower F3. I needed a lower f3 to match the pipes half an octave apart.

I was able to notch the break up mode with low pass filter components without a discrete notch filter.

It's my understanding that Dennis was not referring to the performance of the W16 or W18 woofers near the crossover frequency, but that of the ribbon tweeter. He had to avoid crossing at a lower frequency because it couldn't go lower without unacceptable distortion. He indicated that it worked a bit better with the W16 than with the W18. The RAAL 70-20X ribbon tweet is made OEM for Salk (and others?) to allow a lower crossover frequency than any of it's other ribbon tweeters available for public sale. Instead of a ribbon tweeter, you used the SEAS T25 Millennium, with better behavior at low frequencies (Fs 500 Hz).

 

[Swerd]

That's why AH, S&V, HCC, Miller Audio are my friends. but too bad there are still not that many amps get tested by reputable labs. Even with lab test results, we still have to refer to all available published specs and the test methodologies used, in order to compare apple to apple and collaborate all the information before we can say one is more powerful than the other, and in what way. One amp could be more powerful in terms of truly continuous average while the other may be the winner in terms of real world need such as much higher output at low distortion for short duration.

From the information I can gather, the EX4420 would probably be comparable to something like the Adcom GFA555. It should have no trouble making the mark of 200 WX2 (<0.1% THD) into 8 ohm and 300WX2 into 4 ohm (1% THD I would guess). It may actually do 350W or more into 4 ohms with one channel driven. My educated guess is based on the apparent size of the caps and the transformer. The transformer does look a little small, but the caps (2 per channel) seem to be of decent size, physically speaking anyway. I hate to guess, but I do trust B&K enough to venture such educated guess.

That's what I had been told by others about B&K's larger amps in the past. In addition to that Adcom amp, it was considered similar in performance to the ATI 1802.

By the way, how about the going by ears part, did you find the amp lacking in power output for your needs?

Not while driving any speakers I used. With my old JBL L100s (with both original & new crossovers), as well as both Salk SongTowers and Veracity ST, the amp could produce clean sound without any audible sign of 'stress'. The bass was especially clean and abundant compared to that with smaller amps available to me.

 

[PENG]

That's what I had been told by others about B&K's larger amps in the past. In addition to that Adcom amp, it was considered similar in performance to the ATI 1802.
Not while driving any speakers I used. With my old JBL L100s (with both original & new crossovers), as well as both Salk SongTowers and Veracity ST, the amp could produce clean sound without any audible sign of 'stress'. The bass was especially clean and abundant compared to that with smaller amps available to me.

Sounds like a keeper, hope it just needs replacement fuses.

 

[Johnny2Bad]

No teenagers have access to the system?

Back in 1970, when the Crown DC-300 started being noticed by audio people (it was originally designed for "industrial use", Crown* were at the time not into the HiFi market at all, and like others such as Bryston (who previously marketed solely to sound reinforcement before the mid-70's) were surprised that people liked the Sound Quality on it's own merits) the power of the amp was so unusually high that there was talk of speakers exploding with an errant pop from a preamp.

As it turned out, the fears were unfounded, but the Crown manual was revised to include recommended fuse values based on how much power you want to limit your speakers to. You can get the manual on hiFi engine dotcom if interested.

*Crown was kind of an unusual company. Run by devout Christians, they had corporate rules such as working on Sundays being strictly prohibited, and they vetted dealers based on their devotion, or lack thereof. They felt their work building amplifiers was divinely inspired and the designs evolved via the unseen hand of God.

By the time I got into the business in the late 70's the amps sounded dated and ragged on the top end versus the competition, but people still liked them for ruggedness and to power subs. As it turns out, the problem was high order harmonics, due to massive global feedback, an area then being explored by designers like Nelson Pass (Threshold), Tim de Paravinci (Luxman) and Mark Levinson (MLAC) amongst others.

Like so many companies, the modern incarnation has no relation to the original. Interesting tidbit: outside of the US, Crown was branded Amcron, do to a trade mark issue with a Japanese company also named Crown.

 

[lovinthehd]

Back in 1970, when the Crown DC-300 started being noticed by audio people (it was originally designed for "industrial use", Crown* were at the time not into the HiFi market at all, and like others such as Bryston (who previously marketed solely to sound reinforcement before the mid-70's) were surprised that people liked the Sound Quality on it's own merits) the power of the amp was so unusually high that there was talk of speakers exploding with an errant pop from a preamp.

As it turned out, the fears were unfounded, but the Crown manual was revised to include recommended fuse values based on how much power you want to limit your speakers to. You can get the manual on hiFi engine dotcom if interested.

*Crown was kind of an unusual company. Run by devout Christians, they had corporate rules such as working on Sundays being strictly prohibited, and they vetted dealers based on their devotion, or lack thereof. They felt their work building amplifiers was divinely inspired and the designs evolved via the unseen hand of God.

By the time I got into the business in the late 70's the amps sounded dated and ragged on the top end versus the competition, but people still liked them for ruggedness and to power subs. As it turns out, the problem was high order harmonics, due to massive global feedback, an area then being explored by designers like Nelson Pass (Threshold), Tim de Paravinci (Luxman) and Mark Levinson (MLAC) amongst others.

Like so many companies, the modern incarnation has no relation to the original. Interesting tidbit: outside of the US, Crown was branded Amcron, do to a trade mark issue with a Japanese company also named Crown.

Didn't know that about the religious angle with Crown, very interesting. My Crown XLS Drivecore manuals do advise that some models may be exported under the Amcron name (altho wonder if they indeed first import them from China then export them these days rather than direct distribution).

 

[Johnny2Bad]

Didn't know that about the religious angle with Crown, very interesting. My Crown XLS Drivecore manuals do advise that some models may be exported under the Amcron name (altho wonder if they indeed first import them from China then export them these days rather than direct distribution).

We could get Crown gear, their only authorized dealer in the province, even though our staff looked more like a rock band than the suits some HiEnd resellers sported at the time, and maybe I was the worst offender ;-).

The Canadian distributor were sort of dour people to deal with, though.

I suspect that unless assembly is done in the US, they would distribute directly from the factory. Shipping from China to the ports here is expensive, and with all the China carriers, including just mail, there are abrupt jumps in cost based on size limits, not just weight.

I remember Andrew Jones when he was with Pioneer saying in an interview that if the carton was only one inch larger on just one dimension, it killed the container yield enough that it would add something like $40 to the retail price, and with containers and typical audio contents, the weight is usually a non-issue. Plus there is the time factor, most of these ships only make maybe six or fewer trips a year, and that's going full out, only staying in port as long as absolutely necessary.

 

[Irvrobinson]

Didn't know that about the religious angle with Crown, very interesting. My Crown XLS Drivecore manuals do advise that some models may be exported under the Amcron name (altho wonder if they indeed first import them from China then export them these days rather than direct distribution).

Oh yeah. Crown's roots were in tape recorders, which were originally designed for use by missionaries. I had a mint CX822 I used for years for live recording. An awesome machine. I sold it when Ampex 456 went out of production.

 

[PENG]

Good morning Swerd, any update? Again, I would check the ac main fuse first before paying the repair shop, assuming there was never any smoke, flame, pops high heat etc., observed.