Problem With Klipschorns and SET Amp Could Use Some Help

[Old-Tube-Sound]

Hi All,

I have a SET amp I recently built using Eimac 75TL's for output tubes, its a wonderful sounding amp and runs about 6 watts. My Khorns were built in 1982 and I recently changed out my AA crossovers and I'm now using ALK crossovers. My problem is this, the amp is having a real hard time dealing with the 4 Ohm K-33 drivers, by design the amp would be happier and do much better with higher impedance drivers like 16 Ohm drivers but that creates another problem finding the right crossover point and making a change on my ALK crossovers if in fact it can be done, with the original K-33 drivers the sound distorts at higher volumes depending on what CD or vinyl I'm listening to at the time, if I disconnect the K-33's I can turn up the volume as loud as I can stand it and the sound is crystal clear, hook the drivers back up and the sound is muddy again at higher volumes, at low and mid volume everything is fine. I'm kind of curious as to why Klipsch chose to used a 4 Ohm woofer, a 16 Ohm mid-horn and a 8 Ohm tweeter in their design. I'm looking for suggestions as to how I can make the 4 Ohm drivers less taxing on my amp and get rid of the distortion at higher volume levels, I could purchase JBL D130 16 Ohm drivers, but then there is the crossover point issue and sensitivity issue. I have even toyed with the idea of running a SS amp on the bottom, I'm not real excited with that idea but it is an option. If anyone has any suggestions as to how I can resolve this driver problem it would be greatly appreciated. I love my Khorns and my new SET amp I just need to get them to shake hands better than they are right now.

Dave

[Guest " "]

 

You can use an autoformer to increase the apparent impedance.  I have a pair that will increase by a factor of 3.51.  So a 4 ohm woofer would be just a little over 14 ohms.  Using autoformers will reduce distortion and increase dampening factor.  Shoot me an email if you want more info.

 

 

[cjgeraci]

Dave, the problem does not lie with the K33 drivers, it lies with your SET amp. First of all, I have no desire to turn this comment into a SET v. PP (or other topology) debate.

Please remember that Al's networks provide a constant 8 ohm load to the amp, regardless of the ohm of the drivers being used. Therefore, the amp does not see the individual drivers but only sees a 8 ohm load from the network as a whole. Switching out to JBL D130 woofers is a bad idea. Not only would that move the crossover point but the JBL parameters are all screwed up for maximum performance out of the Khorn bass bin. Plus, I am not aware of any easy fix to Al's networks that would make it work with those JBL woofers. Additionally, short of going to ultra-expensive TAD woofers, almost every other woofer that replaces the K33 would be a step backwards, from a performance perspective.

Since your SET amp is seeing a constant 8 ohm from the network, it could be the strain of trying to power the woofers that is causing the problem as opposed to their impedance. Unfortunately, you could either replace the amp or preferably go with a solid state amp on the bass bin. I used to passively biamp (called fool's biamping) with my ALK universal networks but they were set up for it, and I also used in line crossover/filters between the source and amps to protect the tube amp being used on the uppers. Now, while I still use Al's networks in the rear (Belles), I've gone to an active crossover for my front modded Khorns, with either a push-pull tube amp or digital chip amp on the top (depending on my whim) and a solid state amp on the woofs.

Good luck.

Carl.

[Daddy Dee]

I may be all wet on this one, but I was thinking the K33 is a 16 ohm speaker.

[Cut-Throat]

I would go with a simple type Klipsch "A" crossover long before I replaced drivers and I would never think about replacing the amp to solve a simple problem like this.

If the ALK crossover cannot handle this, get rid of it!

[G.Kennedy]

I agree with Cut-Throat.  Put your AA's back in and see how it sounds.  Maybe just recapping your originals is a better option.  My '81 La Scalas absolutly rip on 8 watts of Bottlehead SET with stock crossovers that have been recapped with Sonicaps

[seti]

I'd like to see a picture of your amps : ) What other amplifiers have you run with your khorns?

 

I ran Canary Audio 300B SET amps George Wright WLA12A preamp with Belles A crossovers without issues. They did not have trouble driving them in my room. After living with several other amplifiers I miss the 300Bs more than anything else I have owned.

 

 

[LousyTourist]

yeah, I would dump the ALK networks first.

What seems odd to me is that the woofer has nothing more than a 2.5mh coil as a lowpass filter with both ALK and most other networks.

[Deang]

When you horn load the K-33, it's not a four ohm woofer anymore.

http://www.peavey.com/support/technotes/concepts/impedance_3.cfm

The original ALK is said to present a "constant" 8 ohms to the amplifier, but it actually varies between 6.5 and 11 ohms. Keep in mind that the low pass section in that network used the same single 2.5mH coil as the early Klipsch networks. With the recent design change by Al, the impedance of the low pass section is probably not the same as it was, but I doubt it dips any lower than the original. At any rate, I agree with Carl, and I think you're driving the amp into clipping -- six watts clearly isn't enough for you.

[Coytee]

At any rate, I agree with Carl, and I think you're driving the amp into clipping -- six watts clearly isn't enough for you.

Ohhhhhhhhh baby... another canidate for a Crown!!

Slap a K1, K2, or XTi on your bottom (of your SPEAKERS of course [:$]) and put your 6 watts on your mids/uppers & let er rip!

Ahh...somehow I feel refreshened by saying that.

[]

[kaiser SET say]

I'd like to see a picture of your amps : ) What other amplifiers have you run with your khorns?

I ran Canary Audio 300B SET amps George Wright WLA12A preamp with Belles A crossovers without issues. They did not have trouble driving them in my room. After living with several other amplifiers I miss the 300Bs more than anything else I have owned.

The infamous 20/20 hindsight[] I miss them too[:'(]

[cjgeraci]

yeah, I would dump the ALK networks first.

What seems odd to me is that the woofer has nothing more than a 2.5mh coil as a lowpass filter with both ALK and most other networks.

If the ALK Universal's lowpass filter is the same as most other networks, then, of course, dump the ALK networks first because it must be those $%#* networks.

Heh, heh, heh...........not the SET.

Carl.

[NOSValves]

Keep in mind folks this is a home brew amplifier and could simply be poorly designed. All it takes is an impedance mismatch reflected back the output tube or a poor driver selection for the output stage and your screwed.... especially when talking an amplifier with very little headroom to start with. I'd point my finger at the amplifier long before I would the ALK crossover although the simpler type A may help its never going to solve a problem this servere.

Craig

[mikebse2a3]

When it comes to using small wattage amplifiers with the Khorn and the ALK the issue isn't the woofer section(all the networks use a 2.5mh coil in series with the woofer) but actually in the midrange area where the ALK Network will demand more power.

Your Amplifier will run out of power sooner with the ALK than either the A or AA Networks. Contrary to what some people might think the ALK network will demand more power from the amplifier due to the fact it is Impedance compensated to present an 8 ohm load to the amplifier. The AA and A networks have a much higher impedance especially through the midrange area so what will happen with the ALK network is the amplifier will have to deliver more current into the compensated(ie: with the swamping resistor on the autoformer) 8 ohms ALK versus the higher impedance A and AA Klipsch networks and this is were the ALK network can be difficult for people who want to use small wattage amplifiers and still listen at a pretty high SPL Level.

Also keep in mind that the A and AA network were used in Klipschorns at a time when Tube amplifiers were probably the most common amplifiers to use with them and so I'm sure the A and I would assume the AA equiped KHorns were voiced with that combination in mind. to use an ALK network should definitly give you a different sound whether someone considers it better or not is subject to many variables and ultimitely depends on the individuals taste which he might prefer.

Bottom line IMHO just because the ALK has impedance compensation doesn't necessarily make it the best choice in every situation.

mike tn[]

[mike stehr]

http://www.mif.pg.gda.pl/homepages/frank/sheets/090/7/75TL.pdf

[Erik Mandaville]

"Keep in mind folks this is a home brew amplifier and could simply be poorly designed."

Keep in mind as well that the fact that the amplifier is home built may have nothing whatever to do with the fact that there (MAY) be some matching concerns going on. Lots of amps that appear on these electronic pages are 'home built' and work very well. Some amps built at home, regardless of poor or excellent design have parts that fail, causing worse problems.

Nor would I jump so quickly to the conclusion that the amplifier is clipping. Many use amplifiers of even more modest output with Klipschorns -- like 1.5 watts. I think I've heard our K-horns clip with the Moth amp, and that was playing at very, very loud levels with SACDs.

Good luck, you'll get to the bottom of it!

I agree with Mike and Kevin on the type of crossover you have with this particular amp. Al K. is an extremely good builder, and despite the fact that I have learned to prefer not to use autoformers in my networks, he makes a good product that would work well in the right circumstance; and that is something that applies to any component.

Here's a part that failed in an amp (actually a pair) that was a factory built unit. IMO, the cathode resistor on the output stage was also way too close to the filter choke, which in this case was a negative filter design.

Erik

edit: Can't find the picture. It was a very severely scorched filter choke.

[Old-Tube-Sound]

Thanks to all who have replied, looks like I have alot options here to try out...First off let me start out by saying this home brew amp is not a poor design it was well thought out and sounds better than anything I have ever heard bar none. Eimac 75TL's are real sleepers that very few know about. The design of the amp is a pair of very rare Telefunken EC8020 triode drivers, Eimac 75TL outputs and WE 354A Thyratron half wave rectifiers ( those are the pretty blue ones ) instead of coupling caps I used 1:1 interstage trannies and the output trannies also very rare are Nature Sound NS-70SE's...The problem is not the amp, its the drain the speakers put on the amp or a impedance mismatch, The mids and highs sound spectacular its the bottom thats in the mud. I'll try some of the suggestions I have received here and let you all know if any one of them worked.

[Guest " "]

nice amps....

 

 

[Erik Mandaville]

Nice work!

If you're using 8 ohm taps on your output transformers, you really should not have a problem with the Klipschorn low end, which due to its horn loading is a bit higher than the rated 4ohm impedance. I've used MANY single ended amps of even less power and without experiencing quite the problem you are having.

You mentioned transformer coupling. This is between the input/driver and output stage, correct? Depending on the design of your amplifier, which looks fascinating to me, I wonder if there is the possibility of a phase reversal taking place. Just out of curiosity (not that it will necessarily bring about an improvement), but have you tried reversing the polarity between the amplifier outputs and input to the crossovers?

Erik

[seti]

WOW Those amps look like they stepped out of Frankensteins Castle...... They look like tubes Josh would use at ElectronLuv.com .