Erik Mandaville
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Posts posted by Erik Mandaville
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I tried a 511B in a La Scala for a center channel and liked it. Never compared it or the original with any of the others mentioned.
I wonder what PWK's preference had been? Does anyone know about that?
I don't plan on changing the original squawker in our Klipschorns; it's responsible for a fairly significant portion of the overall voicing of the loudspeaker. However, I do agree with the idea of being open to different approaches, and the new tweeter Bob C. developed is IMO a worthwhile upgrade. Still, I know of some who find the older K-77s, particularly the alnico version, far more musical. Why try to fix somethin' that 'ain't broke?
Erik
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For the record: There is nothing wrong in the least with using horns and drivers from other companies than those originally designed and put into use by Paul Klipsch. I merely used that as an illustration and an example. I've had that opportunity, too, and agree that the 511 B is a nice sounding horn. I used it with a La Scala for center channel use for a time.
Erik
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This discussion of attenuation has been a curiosity for me for years. There have been those who made very significant alterations to Mr. Klipsch's original designs in the way of using completely different midrange horns and drivers (same for the tweeter) -- elements that arguably would alter PWK's original voicing of the speaker. However, replacing that single element of the crossover has been considered a sort of 'out-of-bounds' area in terms of another, in my opinion, less impacting and traumatic modification.
There are so many equally well-known loudspeaker makers and designers -- I've used Altec and JBL as examples in the past -- that use resistive L-pads in their designs, most often the variable type (which once set in the desired position are in fact 'fixed') that doubtless were aware of Klipsch's work on this subject. That gross alterations of horn and driver have been accepted as valid modifications to PWK's and the autoformer-to-fixed L-pad generally not is a mystery to me.
Others have said that Klipsch, due to its significantly higher cost, no longer uses the autoformer because they prefer to focus on maintaining a profit. What are the implications of such a statement? That they no longer care as much about performance? Perhaps it's because it was found that what the autoformer contributed in terms of what can actually be heard was not great enough, or in fact was found to be inferior to fixed resistor attenuation. There are loudspeaker designs costing exponentially more that rely on fixed resistive L-pads.
That it's okay on the one hand to toss out the drivers and horns that PWK worked so hard to develop yet oppose, often rather strongly, the simple change to a fixed L-pad is something I continue to try to understand.
Maybe there are other aspects of loudspeaker design more worthy of this sort of time and energy. With a little DIY ability and interested personal research, one can put oneself in the position of making a personal choice -- just as a personal choice can be made concerning the use of, for example, 511-B squawkers and JBL tweeters.
Thanks for the link!
Erik
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"Thanks Dean, spring-loaded it is. "
That is nevertheless a very good driver, and I would not give undue worry about it. There have been reports of a peak in the response on some of those drivers at around 9kHz, and even then some inconsistency was found. Series notch filters have been used for a long time, and one was developed for just this problem (if it is a problem). It's a frequency discriminating device referred to in Klipsch applications as the 'P-Trap'. Easy to make if needed, which I did with my K-55s, and found no difference whatsoever. I've compared some notes with others with the same driver, and they also had no problem.
The 4.5kHz modification is called a 'bandpass', which is needed since an acoustic roll-off of the squawker is not used because of the lower crossover point for the tweeter. The inductor in series after the autoformer (on Bob's design) operates at the higher frequencies to block highs to the driver, where the capacitor (in front of the autoformer) functions on the low end. Very simple modification. With the Bob's tweeter, you can go as low as 3.5kHz.
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That is pretty amazing. Thanks for the description of the 'Growler,' by the way. I was wondering what it consisted of.
...I'm just not used to that kind of horsepower. Even .5 of a good quality watt can be pretty impressive to me. Of course we seem to differ on what exactly it is that makes a watt a good one or a lousy one.
How did the Growler handle zero Hz? I'll bet even IT was down at least 3dB at that level!
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" Check out the frequncy response. Starts at "DC." What does that mean?"
''DC' is sometimes thought of as 0 (zero) Hertz, which is kind of an interesting thing to think about -- and subsequently most likely the only way we can experience it. Since an amplifier, just as any required component of the reproduction chain, is essentially meaningless without its associated signal source and loudspeakers, an amplifier with FR specifications that extend from bottom basement 'DC' all the way out to 100,000 Hz, for example, may be capable of measurement, but is rather broad in terms of its impact on human hearing. If that statement suggests that the response is hence very linear within the varying frequency limits of our ears and brain, maybe that's a good thing...........and maybe it doesn't say very much about the actual sound quality of the amplifier. I've heard kind of nasty sounding amps with otherwise very nice measurement characteristics.
What structural elements would be necessary for a loudspeaker to be capable of producing zero Hz?
Erik
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The modifications needed for a type A or AA at 4-kcycles or 4.5k-cycles are not difficult to do. Those networks, as originally designed, are very simple in the sense that they do not use impedance compensation circuits, and so forth. They are designed around the desired crossover slope, desired crossover frequency, and the reflected impedance of the drivers used. I just find the type A as originally designed kind of curious.
At either of those lower crossover frequencies (with the above networks), it's important to use a tweeter that can handle it.
To me, the CT 125 sounds, as Dee indicated, even more open and clear when disconnected from the association with the autoformer and reconnected directly to the input of the crossover. That is in fact the way the majority of crossovers are wired, however some minor change in value of capacitance needs to be made.
Erik
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"The only purpose of this junk is to serve as a bad example of audio engineering."
I'm sure you're aware that there are those 'out there' that say something very similar in reference to horn speakers. I recall an experience at a 'high end' audio store where, when asked about what speakers I was considering -- to which I replied, "Klipsch La Scalas." The person who asked the question politely stifled an obvious laugh, but, not being able to similarly squelch a big grin, asked why I would even think of considering a speaker that, as far as he knew, was designed as a PA speaker for auditorium use. He went on further to explain how his one brief experience with the La Scala was enough because of its harshness and 'coloration.'
This fellow confirmed his correctness of the perception by revealing his many years of experience in audio, etc., etc.
"Okay," I replied, and wished him a good day.
Erik
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An in-rush current limiter may help with this, and it may not. I used a couple in series in the 6SN7 preamp I made several years ago, and in that case there was an improvement, but I still have to be conscious of turn-on sequence -- preamp first then amps -- to keep that little bump out of the speakers. It's an idea to try here, though. Those things were a source of some interesting discussion around here a few years ago.
I haven't ordered from Welborne Labs in a long time. I never, ever had a problem with them in the past, and can only speak about my own experience. Triode Electronics would be a great place to check for a new PT if one is needed. It seems the one in question is working okay.
As usual: Caution when working with any electronic component, even if it's unplugged. If there isn't a bleeder circuit in the modified power supply in this amp, the storage charge in those big filter caps can shock hard even days later.
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Hello, Kevin:
I'm just asking because that last long thread on the 901s you mentioned how they were kind of fun to listen to sometimes.
Ever get that new 45 amp going? I'm going to try to get a scratch-built one done by the end of the summer. The last I heard the 45 in a DRD I had here, it was really a wonderful sounding tube. I don't own one myself, though, but can make one. I have a couple of OPTs with the right primary impedance for it, and most of the other parts. Just no 45s. I'm going to have to save for those.
Erik
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Okay -- thanks for explaining that. Does your Fender amp exhibit anything similar? The amps of guitar players I've played with sometimes had a small 'bump' like that, but nothing that really rattled woofers.
How long is the standby on before you hit the other switch to play music (on the Dynaco)?
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Welborne Labs is out of stock on that transformer, anyway. Don't sit around worrying about your power trannie, though. It may be fine for years to come, and if something happens, than it can always be fixed.
So, when you first power up the amp, you should be operating it so only the filaments glow. Does doing just that cause the thud?
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Before anything else -- WELCOME HOME!!!
I've been preferring to build from scratch lately, but I admit those kits look really cool. Very tempting! Please do keep us updated!
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"The "pop" i refer to is a low thud, two actually."
A 'thud' is really much different than a snap or pop sound, and so is not the power switch but in-rush current thud. Do you happen to know which of the two switches is standby (tubes will glow, but no high voltage will be present) and which is the high voltage switch?
Your power transformer is actually being relieved of one of it's main current draws -- the filament supply that would normally be used for the vacuum tube rectifier. In fact, it may run a little cooler because of that. There can still be noises and stress associated with SS diodes working in conjunction with hefty filter capacitance -- often higher-pitched or sort of oscillation that can be filtered to ground on the AC side of the power transformer secondary (before rectification).
Do you know which switch is used for standby? It's important to know which is which and how to use each. The tubes may be getting slammed with high voltage before they even have a chance to warm. There are some robust replacement power transformers available for Dyna ST-70 if you even need one. Welborne Labs is one source. The photo is helpful, but just a little two distant to make out how the standby is wired -- whether it lifts the center tap of the power transformer or is in-line with B+ voltages (those are the high voltages of your amplifier).
Good luck
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Let Craig install a high voltage ceramic capacitor across the switch for you. That might help.
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" You also shouldn't have a pop when you turn it on as the output tubes haven't even had the heaters warmed up"
You shouldn't have a pop anytime. Dynaco included those snubber capacitors on brand new components.
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Bruce:
It's not the original switch, and there is also an additional switch. A higher pitched popping or snapping sound when using the switch is probably not related to in rush current, which is more more of a lower frequency 'thump.' Dynacos often used the small capacitor across the switch (PLEASE don't use fancy capacitors here). It absorbs the pop. Cathode stripping due to inadequate heating of cathodes is what the standby switch helps prevent, and sometimes there is a noise more like thumping when the center tap on the power transformer secondary, if that's where the standby switch is located, is grounded in order to apply B+.
That's why the extra switch is probably there -- as a standby that can be used to warm the cathodes before applying B+. Some people swear by the use of a standby switch, and others think they aren't necessary. There are also tube rectifiers, such as the 5Y3 that are directly heated, instant turn on types, and know a number of amps that still use them without a standby switch -- with no thumping or popping to speak of.
Filters for the kind of inrush current 'thump' that I have heard more often in solid state amps than tube can be more complex than just wiring a snubber cap across the switch.
Erik
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"Does anybody know how to stop the gate current "pop" when I first turn it on?"
What you're most likely hearing is an acrcing switch. I learned a trick from an old Dynaco schematic years ago that really helps, but you have to have a small amount of handiness and the ability to solder two connections. In rush current 'thump' is different from what you're hearing, and your problem can often be solved by adding a small value, high voltage (as in 1k volt) 'snubber' capacitor across the switch. It will absorb that little spark so you don't hear it. If you happen to have an inside shot of the amplifier, I should be able to tell you if that cap is there. If so, and it's the original, it or your power switch (if original) may need to be replaced.
Sounds like Dean is closeby (?), and maybe he could help you install that cap. Remember there can be very strong storage charges in those filter caps, so you need to be sure the amp is turned off, unplugged, and drained of all stored voltages before doing anything. Check with the voltmeter to make sure. I have been amazed a few times over the years about the kind of a shock an unplugged and seemingly totally unenergized component can give![:|]
a .01uf 1kV would probably do the trick.
Congrats on the Dyna!
Erik
edit: Okay, I noticed that the usual rectifier tube is not present, and that there is an extra switch on the front panel. If you have a couple of SS diodes in place of vacuum tube rectification, that extra switch may be a standby switch (?). It's use will allow the tube to warm before applying the high voltage plate supply. Is that what you have?
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Bob:
Thanks, I thought that might be the case, and was just wondering if you had considered any alternatives.
Fini: Keeping things simple when possible is of course always a good thing. There may be a couple of positive outcomes to the way I outlined the change above, and was wondering if Bob had ever thought of trying something like it. Since an inductor is also added to his design, that portion of the modification only has to do with where it's placed in the circuit -- after the autoformer; in what I proposed: before the autoformer. As in his approach, mine also requires an increase in capacitance, and the only extra step in this really has to do with the relocation of one connection -- the tweeter off the autoformer at tap 5 to the input.
I've learned that there are those who are not used to seeing the tweeter connected that way, but it's really the more common way to wire a crossover. I've wired them this way according to published schematics for almost twenty years; and the early Klipsch Heritage networks, including the use of an autoformer for driver attenuation, is an exception rather than the norm (which is an observation, only, not a value judgement). There may also be a small amount of additive series resistance associated with the 13uf capacitor in front of the tweeter filter, most likely not very significant unless the capacitor is quite old and out-of-spec, and to my way of thinking it's more straightforward (or in another word, 'simple') to treat each branch individually. Al K's ES networks certainly wouldn't be a lesson in KISS, however with the right ancillary equipment, may offer some real advantages for some people.
Thanks,
Erik
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Bob:
" This works well as a first order crossover crossing at about 4500 to the tweeter and rolling off the midrange to match."
Did you ever try:
1) remove tweeter from top of autoformer and reconnect to x-over input. Change capacitor from 2uf to approx 4.5uf (for an 8ohm driver)
2) calculate BOTH squawker bandpass elements (L & C) for 32ohms, and use about 1mH in series with 13uf but connect those IN FRONT of the autoformer rather than with the autoformer between them. The values of the capacitor and inductor in a first order bandpass are normally calculated for the same impedance, no? In other words, if the amplifier is looking at a 32 ohm load (reflected), what do you see happening if you use the inductance needed for that impedance? What you have done seems to work, and I liked the way it sounded, but I'm wondering if you considered this other approach.
Some small adjustment may need to be made to the 1mH as it relates to the autoformer, however I'm wondering if this was something you ever tried when developing the lower crossover point for the type 'A.'
Erik
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Okay.
My opinion is that ES networks would not be the best match for such a lower power amplifier, but only you can be the final judge of that. It would be possible to compare them with the more simple and efficient type 'A', and if you don't have one, I could make up a pair and send to you to try with the amp. One must start to compare some cost and performance issues.
I also probably wouldn't recommend this amp as a first time build project. You could actually build yourself a pair of type 'A's to use, which would give you a small amount of practice, as well as end up with something useful to use with the OTL amp if you decided to get one.
Erik
And Nailbender: Take good care out there!
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Sure.
"even though I'm short on t electronics experience, I did quite a lot of model building in my younger days and have spent the last 25 years as a chef and have won a number of awards for my show work...(talk about patience...I'll never do another show)"
If you built models, soldering won't be a problem once you get the feel for it. It's a rather basic manual skill which can be refined. Congrats on your cooking awards!
As far as the ES and SE OTL, I don't have experience with such high order slopes. I believe Shawn does, though, so maybe he can mention something about that. There is a fair amount of insertion loss because of the number of passive parts in those networks, which is NOT to say I think they aren't good crossovers. Al is a talented designer, and I'm mentioning this only because of the lower output ability of the Transcendent amp. The VRDs would fair better in that respect, IMO. There is always a compromise.
Erik
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"Don't get out much Eh? "
How are your 901s, Kevin? As I recall you finished them very nicely.
Erik
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I very much enjoyed the 901s, too.
Very nice, indeed!
La scala Build ( Done)
in Technical/Restorations
Posted
Great job!
Building your own networks and horn enclosures!