KLH-1 Score

[Roger Gorke]

On another note, I have noticed a slight hiss with my ABC engaged. It is not volume dependent, IOWs the hiss stays at the same volume regardless of how high I turn the volume. I'm gonna switch out some of the caps and see if that helps.

 

[Roger Gorke]

I have begun to have an issue with my KLH1 speakers. The other day, I was listening to Pink Floyd Animals and had my Yamaha CA-1000 turned up to about 4.5 which is loud but not ridiculously loud. During the softer section when there are some low notes with dogs barking in the back ground, the top woofer started to rumble. It went a way when I flipped the low filter switch that cuts 12dB per octave starting at 70Hz. My first thought was that it might be a turntable rumble issue but that hypothesis was debunked when I used the aux input and a low frequency noise youtube video and had the same excursion of the top woofer.

My thinking is that this may be an issue with the ABC however with very little information on the ABC, I'm not sure how to proceed. I have replaced the two 1000uf caps and the two 50uf caps on the amp overload board (if that's what it is called) measure ok.

Any thoughts? Maybe I just leave the 70hz switch flipped but if something isn't correct in the circuit or the speakers, I'd like to figure it out.

 

[plenumpete]

I'm sure just a leaky cap for the pop. I'm planning on upgrading the 4136 quad op amp in the ABC to an OPA 1656 or OPA 1692 using one of these https://www.cimarrontechnology.com/product/browndog-060601-rc4136-upgrade-adapter . Question for you fans, what are the crossover frequencies and slopes on the Model 1? I thought of having this company that makes these slick crossovers make some https://www.humblehomemadehifi.com/crossover.html I have two pairs so I'd have 4 made, maybe we could get a few more of us in on it to bring the price down?
J

Another KLH-1 fan here, purchased them new in 1983! littlelabs I'm also looking at upgrading the crossovers and was wondering if you've had any joy with humble homemade?

I've replaced the acoustic absorbing foam that surrounds the tweeter and mid-range drivers with this: https://wilmslowaudio.co.uk/damping-materials/acoustic-foam-laminate-panel

 

[Louie_Bee]

Hi all another KLH1 owner Since mid 1990s. I've been lurking in the background here for a while & recapped both crossovers and ABC, replaced tweeters from klh4 and a mid... All based on info found here.

But I've also found my own fixes to ABC issues so thought I'd share them.

I had lots of hum from my Abc and also interface when turning on other electronic gear when running the abc. I think both LEDs about the in out switch were sometimes lighting together with odd fizz noise even when playing no music... The left led should only light when it thinks you are near the top of the amp ability as set by the rear pot (if you have the feedback wires connected to speakers (or amp as i do)., so an annoying fault.


I found a dead diode in my abc so the chips were only getting a positive voltage supply... No negative (don't remove them chips as 2 pins are not esd protected and you'll probably kill the chip.

I replaced the diodes and sounds awesome again. No rumble or fizz.

The interface from turning on other devices maybe down to a replacement power supply. Not sure if the original has built in noise suppression on the mains side (a rifa maybe). Without noise suppression any spikes on the mains will pass to the abc and likely into the audio circuit.

If the original psu had rifa noise suppression by now it won't be doing much as they deteriorate over time. My solution is to put a iec inline with the psu... Just one of these https://cpc.farnell.com/pro-elec/pe...2387&s_kwcid=AL!5616!3!605262956764!!!network}!310521767236!&gclid=CjwKCAiApaarBhB7EiwAYiMwqsaJekLBiVO7jDWl8nYX5YSaKjk7adkoI_3ZPXYPi8ajYyOHJSLtfxoCicgQAvD_BwE

I'd guess not many in the UK have KLH ABC. Don't know if you 120v mains folks have this kind of mains noise suppression but worth looking into to protect your ABC from mains spikes.

 

[Louie_Bee]

Here we go 1 dead diode... Actually it's a Zener Diode - & looking very suspect before even testing it:-



It was goosed!!





Part number is 1N4743 from my pictures and I replaced both with new or pence https://uk.farnell.com/multicomp-pr...-PMAX-US-DirectShip-Test1596&gross_price=true









There are 2 and it is 13V Zener so looks like the ABC runs plus and minus 13V on the UA741 Op amp (data sheet here https://pdf1.alldatasheet.com/datasheet-pdf/view/1424878/FAIRCHILD/UA741TC.html). From memory I had lost my -13V so it wasn't running right without that diode.







If your ABC won't power up, check the voltage across pins 4 and 7 on UA741 chips (make sure you know which pin is which) should see 26V... or put your volt meter black probe on pin 7 of the MC14007 for ground and check for UA741 pin 5 for -13V and pin 7 for +13V.





If you don't have a positive and negative voltage, the Zener Diodes are the first likely culprit... though looking again at my pictures I see 8 diodes so probably setup in 2 bridge rectifier configurations for full wave rectification - I can't remember as it was a couple of years ago I did this fix.





I'd suspect any other noise from the ABC would be smoothing issues from the 2 large caps.



MC14007UB chip... check out that chip date stamp week 23 of 1979 I believe 07923 would be... and above from 1978.



Good to see the data sheet for this? https://www.alldatasheet.com/datasheet-pdf/pdf/11942/ONSEMI/MC14007.html
and some other pics





Yes the big blue caps are in the wrong way and I didn't spot it until it blew. looks like the replacement diodes are in as the grey ones are no longer there



Fortunately for me it didn't do any damage other dan blowing the cap so with the original grey caps back in it worked fine (no hum or fizz or exploding cap blast)

Think this is the before pic as the grey Zener Diodes are on the board:-

 

[Louie_Bee]

Couple of pics of the KLH4s I used just for the tweeters (same unit in all this rand 1 through 4 so I read)




Had replaced the tweeters with some Mapplin units I found while at uno - made them ultra bright as way different to the originales.


Just so wrong...


That will teach me to lend out my speakers - back to original tweaters & originals were blown late 90's (Grrr)

Now all original drivers & crossover recap was next



May have used the KLH4 foam too - better then no foam but not ideal

 

[Louie_Bee]

Ahh the crossover pics - just a before and after - think I did the resistors as some had been replaced with 10W resistors around the time the tweeters were blown





Not to mention the car sterio mids they'd been running... poor KLH1s I staarted out with..

 

[Louie_Bee]

But a happy ending my KLH1s live on my desk in my home office.





Perhaps not in keeping with the vintage theme im running my KLH1s from class D Behringer A800 power amp and also Behringer FBQ3102 31 band equaliser.. plenty of power at 250w into 8 ohm & able to drive way more power into 4ohm... No risk of amp distortion which is a big speaker killer?

I figure the inherent underdamping of class D amps would be ok with these overdamped speakers? I love the way they sound even if not pure . Rare i get to push them hard but sound awesome with that bottom end even at levels that don't get me in trouble.

Maybe one day I'll make some stands and have them not as deskstanders (yes my KLH1s are near field monitors on my desk at the moment.. really feeling them and working from home ).

 

[eiraved]

This thread is gonna make me get mine out of storage. I purchased them used about 10 years ago, along with the ABC and the original stands.

 

[Louie_Bee]

Another KLH-1 fan here, purchased them new in 1983! littlelabs I'm also looking at upgrading the crossovers and was wondering if you've had any joy with humble homemade?

I've replaced the acoustic absorbing foam that surrounds the tweeter and mid-range drivers with this: https://wilmslowaudio.co.uk/damping-materials/acoustic-foam-laminate-panel

Oh UK supplier... thanks I may be trying that too!! I don't think you need to upgrade the crossover in the KLH1. Replacing caps and resistors yes, but not sure what you have in mind - higher order crossover, different crossover freequenciesy?

I'd probabley go down the path of electronic crossover and multple amplifiers and remove the passive crossover altogether... but don't worry I'm not going to do that as I love them as they are... whatever the rolloff and crossover frequency is.

 

[Louie_Bee]

This thread is gonna make me get mine out of storage. I purchased them used about 10 years ago, along with the ABC and the original stands.

Hope yours are in better shape than mine were. Stored mine for a lot of years but they went into storage in a rather abused state and came out no better, but were a good project... sound better than ever now & so glad I hung on to them through the years

 

[eiraved]

Hope yours are in better shape than mine were. Stored mine for a lot of years but they went into storage in a rather abused state and came out no better, but were a good project... sound better than ever now & so glad I hung on to them through the years

It's been some time since I've laid eyes on them. If my memory serves me right, the speakers and stands were in good shape while the ABC had damaged wires.
They were relegated to storage duty after a fellow AK member made me an offer on a Cornwall III pair I couldn't refuse.

 

[eiraved]

Here we go 1 dead diode... Actually it's a Zener Diode - & looking very suspect before even testing it:-

View attachment 3050323

It was goosed!!

View attachment 3050241

View attachment 3050205

Part number is 1N4743 from my pictures and I replaced both with new or pence https://uk.farnell.com/multicomp-pr...-PMAX-US-DirectShip-Test1596&gross_price=true









There are 2 and it is 13V Zener so looks like the ABC runs plus and minus 13V on the UA741 Op amp (data sheet here https://pdf1.alldatasheet.com/datasheet-pdf/view/1424878/FAIRCHILD/UA741TC.html). From memory I had lost my -13V so it wasn't running right without that diode.







If your ABC won't power up, check the voltage across pins 4 and 7 on UA741 chips (make sure you know which pin is which) should see 26V... or put your volt meter black probe on pin 7 of the MC14007 for ground and check for UA741 pin 5 for -13V and pin 7 for +13V.





If you don't have a positive and negative voltage, the Zener Diodes are the first likely culprit... though looking again at my pictures I see 8 diodes so probably setup in 2 bridge rectifier configurations for full wave rectification - I can't remember as it was a couple of years ago I did this fix.





I'd suspect any other noise from the ABC would be smoothing issues from the 2 large caps.

View attachment 3050262

MC14007UB chip... check out that chip date stamp week 23 of 1979 I believe 07923 would be... and above from 1978.

View attachment 3050251

Good to see the data sheet for this? https://www.alldatasheet.com/datasheet-pdf/pdf/11942/ONSEMI/MC14007.html
and some other pics

View attachment 3050242

View attachment 3050245

Yes the big blue caps are in the wrong way and I didn't spot it until it blew. looks like the replacement diodes are in as the grey ones are no longer there
View attachment 3050243
View attachment 3050286

Fortunately for me it didn't do any damage other dan blowing the cap so with the original grey caps back in it worked fine (no hum or fizz or exploding cap blast)

Think this is the before pic as the grey Zener Diodes are on the board:-

View attachment 3050268

This is some awesome information, thank you for sharing this!

 

[eiraved]

Had replaced the tweeters with some Mapplin units I found while at uno - made them ultra bright as way different to the originales.

I made the mistake of replacing the parallel 50mf caps in the crossover with a single 100mf. That change made the tweeter HF unbearable and probably caused my tinnitus, LOL!!

 

[Roger Gorke]

I made the mistake of replacing the parallel 50mf caps in the crossover with a single 100mf. That change made the tweeter HF unbearable and probably caused my tinnitus, LOL!!

Does the "LOL!!" mean you were joking? Did you replace it with a 100mF or 100uF? My KLH1s I am using a single 100uF cap for the mids.

Also, this would probably work for the foam:

Amazon.com

 

[eiraved]

Does the "LOL!!" mean you were joking? Did you replace it with a 100mF or 100uF? My KLH1s I am using a single 100uF cap for the mids.

No joke. I replaced the parallel 50μf caps in the crossover with a single 100μf, and I changed them back to the original state of parallel 50μf caps. In the cap world mf=μf=uf.

 

[Roger Gorke]

I came across this post on the Parts Express Forum today. The poster did an in depth review and upgrade of the KLH-2 speakers.

It's too big to post here but you can get it from the link I provided.

One thing he saw was a huge dip at ~3.5k Hz due to the inverted polarity of the tweeter. He changed the tweeter polarity and the dip went away.

As an experiment, I switched the polarity on my tweeters and it made a noticeable improvement in the sound.

 

[Louie_Bee]

I came across this post on the Parts Express Forum today. The poster did an in depth review and upgrade of the KLH-2 speakers.

It's too big to post here but you can get it from the link I provided.

One thing he saw was a huge dip at ~3.5k Hz due to the inverted polarity of the tweeter. He changed the tweeter polarity and the dip went away.

As an experiment, I switched the polarity on my tweeters and it made a noticeable improvement in the sound.

Wow, Just fantastic thanks for sharing. I've not read all the report just yet and swapped my tweeters round just out of interest on my KLH1s... How can this be? Well i don't think polarity is marked on the tweeters so 50 50 guess? Well they sure sound better after swapping!!

 

[Roger Gorke]

In my never ending quest (obsession) with maximizing these great speakers, I’ve been upgrading the crossover capacitors.

I started with a 4.7uf Jantzen Supreme in the tweeter circuit. This yielded great results in terms of clarity. Based on my liking of the Jantzen Supreme a month or so later I upgraded the 10uf in the mid circuit with a Supreme. Even though the 10uf is connected to ground, the improvement was significant.

My most recent upgrade is on account of realizing that I used a 4.7uf vs a 5uf…because a 5uf isn’t available with the Jantzen Supreme. In addition, I’ve been looking into the use of “bypass caps”, small values of really high quality caps placed in parallel with larger caps. The concept is that the bypass caps essentially improved the quality of the larger cap. I am probably butchering the concept but I think you can get the idea and/or already know all about it.

I ordered a 0.33uf Miflex KPCU-1 and installed that in parallel with the 4.7uf Jantzen. The imaging keeps getting better and better! I can now pick out flutes and piccolos left of center while listening to my Karajan Beethoven’s Pastoral!

Next idea will be upgrading the 100uf Erse cap I have in the mid circuit and also designing a point to point layout. The original board doesn’t have room for these huge caps!!!

 

[eiraved]

In my never ending quest (obsession) with maximizing these great speakers, I’ve been upgrading the crossover capacitors.

I started with a 4.7uf Jantzen Supreme in the tweeter circuit. This yielded great results in terms of clarity. Based on my liking of the Jantzen Supreme a month or so later I upgraded the 10uf in the mid circuit with a Supreme. Even though the 10uf is connected to ground, the improvement was significant.

My most recent upgrade is on account of realizing that I used a 4.7uf vs a 5uf…because a 5uf isn’t available with the Jantzen Supreme. In addition, I’ve been looking into the use of “bypass caps”, small values of really high quality caps placed in parallel with larger caps. The concept is that the bypass caps essentially improved the quality of the larger cap. I am probably butchering the concept but I think you can get the idea and/or already know all about it.

I ordered a 0.33uf Miflex KPCU-1 and installed that in parallel with the 4.7uf Jantzen. The imaging keeps getting better and better! I can now pick out flutes and piccolos left of center while listening to my Karajan Beethoven’s Pastoral!

Next idea will be upgrading the 100uf Erse cap I have in the mid circuit and also designing a point to point layout. The original board doesn’t have room for these huge caps!!!

Crossover pictures to be exact!