Yamaha MX-600U + JBL L100 = No Love

gvl

Super Member
First time poster here.

Finally after many years in the dark with HT receivers and surround sound found the time and space for a proper 2-channel system again in my life. I did cast the net to the usual places where good stuff lives and pulled out a pair of JBL L100 Centurys in an acceptable condition, and 2 power amps Yamaha MX-600U and Adcom 2535, all for a whooping $200. Surprisingly everything works, but despite my high hopes for the Yamaha it just doesn't sound right with the L100s, the low-end is fine but the mids and treble are just too harsh and raspy. I'm familiar with the criticism that L100s get for their in the face character, but the Adcom produces a much better balanced sound I can live with, as does a Marantz 1060B I also have. It seems that the Yamaha has better resolution, but the coloring is just too tiring. So I'm scratching my head is this just because Yamaha doesn't match well with L100s or it needs work. Can bad caps contribute to this effect? I noticed at least one leaky cap on the PCB. I did replace my share of bad caps in my life in the past, but from my memory you typically get a weak or not-working channel, lack of low frequencies, or some odd noise with a bad cap, which is clearly not what is happening here. Any opinions?

As for my source, please don't laugh but at the moment I'm using a Sony Xperia z3+ phone with Spotify premium at 320 kbps. The phone actually has a decent DAC on it, and sounds better than one might expect. No preamp, I'm feeding from the phone to the amp directly.
 
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Could have something to do with input impedance and how each amp reacts to the input signal.

I owned the 4311b (studio version of the L100) and harsh and raspy was definitely the way they sounded. A lot of folks like them, but I couldn't wait to pass them on
 
I thought about the impedance mismatch, but the phone is designed to drive headphones so it should have fairly low output impedance relative to the amp input's, so at least in theory it should be ok. But yes, I should try a CD player for completeness, would be a better test, or with a preamp when I get one.

The L100 wasn't the type of speakers I thought I'd end up with, but the price was right so I thought what the heck. Now that I heard them I can definitely live with the kind sound they produce with the other amps I have just not the Yamaha. Perhaps it is the better amps that make them show their ugly side?
 
Your input from the phone sounds fine.

For some reason I missed the part about a leaky cap. That's important.

Which other speakers have you owned?
 
Which other speakers have you owned?

Nothing that's worth mentioning. I do have a pair of small Klipsch RB-15s that I use on my desk, they are bright, but I think L100s are even brighter. The midrange on the Klipsches is a bit disappointing, L100s do have some magic in the way they sound especially at lower volumes.

So a leaky cap can be a suspect for causing this kind of symptoms? I'm up for a recap unless it is a dead end. I guess the simplest is just to replace that leaky cap and see what happens, not sure yet how much disassembly effort there is, if significant perhaps it makes sense just to redo all of them at the same time.
 
, but the coloring is just too tiring.

I would beg to differ. Yamaha MX is generally one of the more transparent amps. Is the coloring of the other amps you prolly like. I have the same speakers. Can't say they are anything above average.
The Yammy should be as transparent as it gets. That said, it would not hurt to give it a refresh.
 
I tried some-new-to me L100s with a lowly Yamaha CR-400 and an iPod Classic. I was blown away with how good it all sounded. I was just glad the 400 could keep up.

I have an old Adcom 2535L in the closet; didn't even think to pair it with the 100s. Maybe next time...
 
I would beg to differ. Yamaha MX is generally one of the more transparent amps. Is the coloring of the other amps you prolly like. I have the same speakers. Can't say they are anything above average.
The Yammy should be as transparent as it gets. That said, it would not hurt to give it a refresh.

I suppose I should have said the coloring or the lack of it :) I have no illusions about L100s but to my, admittedly not too sophisticated, ear, they sound interesting when paired to seemingly warmer sounding amps, which is the kind of amps they probably had during the days when these speakers were designed.
 
I have an old Adcom 2535L in the closet; didn't even think to pair it with the 100s. Maybe next time...

I didn't even plan to use it but Yamaha sound left me unhappy, so I tried the Adcom and liked it better, but only as compared to the Yamaha. It did appear the Adcom sound wasn't as clean but the overall presensation was much more tolerable, that's what I wanted to say.
 
It's your imagination only. Have a friend plug in one of your amps and play it, while you're blindfolded. You will not be able to tell which one is which.
 
It's your imagination only. Have a friend plug in one of your amps and play it, while you're blindfolded. You will not be able to tell which one is which.

Oh no, this is one case when I can tell pleasure from pain :)
 
A quick update. Problem solved. Turned out it was the source after all, or whatever the mishmash between the phone and the Yamaha there was as the phone sounded alright with other amps and headphones. Picked a used Centrance DACMini CX from eBay, feeding Spotify@320kBps via optical to the DAC and then directly to the Yamaha, couldn't be more pleased with the results. Even the embedded motherboard audio from the PC sounded better than the phone, sans the noise. Obviously I don't have a good baseline to compare to, but the results are much better than I could have anticipated from 45 y/o speaker tech. Great soundstage. Mids were somewhat offending still but no longer harsh, so I tamed them a bit with the adjustment pots and will happily run the L100s with the Yammy for the time being. Now need to figure out how to add a Dual 604 TT to the mix I bought some 18 years ago and it was sitting in the closet since.
 
I didn't even plan to use it but Yamaha sound left me unhappy, so I tried the Adcom and liked it better, but only as compared to the Yamaha. It did appear the Adcom sound wasn't as clean but the overall presensation was much more tolerable, that's what I wanted to say.

Why not? Those Adcoms are excellent sounding amps. I have both Yamaha and Adcom and both do an excellent job given their price points. I would say that my 535L is i slightly warmer—I wouldn't characterize it as not clean— than the Yamaha MX630. Neither is as bright as the Brystons I've had or the Krells. The midrange and high end of L100s I've never really liked. If you want to find out why, then do a search on AK for Zilch and L100s.
 
also make shure all drivers have correct polarity, look at a l100 scematic.
i had some 4311 once that were making my ears bleed. turned out someone had fiddled in there hooking the midrange wrong way around.

L100.jpg
 
Why not? Those Adcoms are excellent sounding amps. I have both Yamaha and Adcom and both do an excellent job given their price points. I would say that my 535L is i slightly warmer—I wouldn't characterize it as not clean— than the Yamaha MX630. Neither is as bright as the Brystons I've had or the Krells. The midrange and high end of L100s I've never really liked. If you want to find out why, then do a search on AK for Zilch and L100s.

I have nothing against Adcoms except the fact they don't have speaker protection relays, it is just I got it on a buy one get one free kind of deal with the Yamaha which is what I really wanted, so the plan was to keep it as a spare or sell. The Adcom indeed was a bit warmer or softer if you will, with stronger but less defined bass. Now that I have a proper source I should do another A/B comparison. I did some reading on the L100s already, the main complaint as far as I understand is the primitive crossover and as a consequence excessive mids and highs. I like how they sound now, not quite neutral but engaging nevertheless.
 
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also make shure all drivers have correct polarity, look at a l100 scematic.
i had some 4311 once that were making my ears bleed. turned out someone had fiddled in there hooking the midrange wrong way around.

Interesting, I was reading a discussion about L100 crossover overhaul and someone stated he found the midrange wired out of phase as well. Mine were from the original owner, I don't think anyone messed with them. They sound much better now with a proper source.
 
Thing is them 4311wx i Had i never got to sound pleasing. Traded them later. Some years after i stumbled upon a pair of l100 witch sounded way way better. Must have been something wrong with the mids or tweeters in those 4311
 
Did the 4411s have adjustment pots? Mine are very finicky presumably from oxidation, could have something to do with them in your case.
 
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