KEF R107 Kube OpAmp Upgrade

[dave101260]

Performed an opamp upgrade to my KEF R107 Kube.

Replaced the original TL072 with Burr-Brown OPA-2134. A very cost effective alternative!!

The work was easy, and went off without a hitch.

The change is a quite noticeable improvement in clarity and detail.

What I'm most pleased with is that the change has not altered the character of the 107's, but simply cleared them up. Improved bass and mid-range, without hardly any change (if any) to the high end.

Anyone considering an opamp upgrade, be forewarned: it will make these speakers even MORE revealing. Weaknesses will be heard.

 

[canuckaudiog]

Performed an opamp upgrade to my KEF R107 Kube.

Replaced the original TL072 with Burr-Brown OPA-2134. A very cost effective alternative!!

The work was easy, and went off without a hitch.

The change is a quite noticeable improvement in clarity and detail.

What I'm most pleased with is that the change has not altered the character of the 107's, but simply cleared them up. Improved bass and mid-range, without hardly any change (if any) to the high end.

Anyone considering an opamp upgrade, be forewarned: it will make these speakers even MORE revealing. Weaknesses will be heard.

I went with OPA2604s myself, and my findings are very similar, except I find it took away some of the laid-back presentation. But that was fine with me - I prefer it!

 

[dave101260]

I went with OPA2604s myself, and my findings are very similar, except I find it took away some of the laid-back presentation. But that was fine with me - I prefer it!

Hey Jeff,
Have you done the .47uF input cap yet?

I have 3 different brands on the way: Vishay MKP, EPCOS MKP, and some Panasonic PP ECWF.

I'm gonna socket the KUBE to make life easy.

THEN, I'm gonna do the ferro fluid.

 

[canuckaudiog]

Hey Jeff,
Have you done the .47uF input cap yet?

I have 3 different brands on the way: Vishay MKP, EPCOS MKP, and some Panasonic PP ECWF.

I'm gonna socket the KUBE to make life easy.

THEN, I'm gonna do the ferro fluid.

Not yet. I still have to replace the 4.7uF caps in the KUBE. I ordered 47uF caps last time and didn't want to replace it with the wrong part. So, finally the other week I ordered the right ones since I had to order filter capacitors for a power amp I am restoring as well.

I just need to find some time to take the KUBE apart again and to replace them. Hopefully soon! Let me know how the 0.47uF cap replacement goes, that's next after the 4.7uF caps.

 

[dave101260]

Not yet. I still have to replace the 4.7uF caps in the KUBE. I ordered 47uF caps last time and didn't want to replace it with the wrong part. So, finally the other week I ordered the right ones since I had to order filter capacitors for a power amp I am restoring as well.

I just need to find some time to take the KUBE apart again and to replace them. Hopefully soon! Let me know how the 0.47uF cap replacement goes, that's next after the 4.7uF caps.

Hi Jeff,

Just a quick fyi:

The .47 uF that CCheung speaks of is an INPUT coupling cap.

The only 4.7 uF caps are in the power supply section before and after the two voltage regulators.

Man Cave time for me

 

[canuckaudiog]

Hi Jeff,

Just a quick fyi:

The .47 uF that CCheung speaks of is an INPUT coupling cap.

The only 4.7 uF caps are in the power supply section before and after the two voltage regulators.

Man Cave time for me

Right. I've only replaced the 1000uF capacitors in the KUBE so far, so I've got the 4.7uF and also the 0.47uF to replace yet. I guess if the 0.47uF are in the input signal path they may make a bigger impact on the sound, so I should likely get on that. :yes:

 

[dave101260]

Right. I've only replaced the 1000uF capacitors in the KUBE so far, so I've got the 4.7uF and also the 0.47uF to replace yet. I guess if the 0.47uF are in the input signal path they may make a bigger impact on the sound, so I should likely get on that. :yes:

Is there some concern that the P/S caps are causing audible issues with the op-amps? Curious minds need to know lol
They're certainly cheap and easy to replace, but why mess with the KUBE any more than necessary?

 

[canuckaudiog]

Is there some concern that the P/S caps are causing audible issues with the op-amps? Curious minds need to know lol
They're certainly cheap and easy to replace, but why mess with the KUBE any more than necessary?

No, it's not that. It's the fact that electrolytic capacitors dry out over time. 30 years is a long time for a cap, and most recommend to replace them every 20 years. It's not really messing, it's more maintenance than anything.


Sent from my iPhone using Tapatalk

 

[dave101260]

Hey Jeff,
Have you done the .47uF input cap yet?

I have 3 different brands on the way: Vishay MKP, EPCOS MKP, and some Panasonic PP ECWF.

I'm gonna socket the KUBE to make life easy.

THEN, I'm gonna do the ferro fluid.

TDK Corporation presents EPCOS MKP.

On the upside: Added detail to vinyl and CD sources. A subtle improvement.
On the Downside: Makes a revealing system, a tad bit more revealing.

 

[dave101260]

I have 3 different brands on the way: Vishay MKP, EPCOS MKP, and some Panasonic PP ECWF.

Vishay MKP: Slightly brighter than the EPCOS on some source material, ie digitally recorded & mastered CD's

Again, no huge difference in the overall presentation.

Somewhat disappointed

 

[Thundermud]

I upgraded my opamps in my Kube according to Cannucks recommendation a while back and it sounds great. The bummer is I really cant play older classic rock. Music becomes too thin and lacks bass. That is why I started using my Bozaks for older recordings to bring life back into the music.

 

[Raynald]

Thin, lack bass? Have you checked the surrounds and donuts?

 

[Thundermud]

I've redone it all. Old old deep down dirty rock does not cut it on these speakers.

 

[baco99]

I've redone it all. Old old deep down dirty rock does not cut it on these speakers.

my opinion: it's not that they *lack* bass, per se. the bass is so clean, you might not realize how good it is. it's not messy. it's something special with the bandpass woofer design. the 104/2 are the same. the bass doesn't rattle the house, but if you pay attention, it's all there. just more balanced. clean.

again, just my opinion.

 

[geoffwood]

Is there a schematic of the KUBE 107 available anywhere ?

Also, two pairs of internal presets are for L and R, MF and HF. The two unlabelled presets near the front panel are for what - LF level, or channel level ?

Grateful any tips ...

geoff

 

[dave101260]

KUBE Schematic

Hi Geoff,

if you send an email to Dave101260@gmail.com, I might have something.

-dave

 

[Hawkeye83]

Hoping a 107 expert or someone with a KEF KUBE sees this. I emailed @dave101260 just now about this. How do you get the KUBE apart? Here's the message I sent Dave.

Hi Dave,
I found your email in the KEF 107 op-amp replacement thread. I bought Thundermud's 107's, he was posting in that thread as well.

I have never taken the KUBE apart, but am looking to do so. It's very finicky as far as getting a hum...you have to wiggle the power supply cord, jump up and down, put your head, rub your tummy, etc...to get the hum to go away.

I'm wondering if there might be a loose connection somewhere.

Anyway, how do you get the KUBE apart? I see two screws on the bottom of mine. Those are out. The knob for the bass extension comes off, but the other two knobs are not wanting to come off.

If you recall what needs to happen to get the KUBE apart, please let me know.

Thanks,
Dan

 

[Hawkeye83]

I figured it out, I'm an idiot, or not awake yet, or both.

Two screws on the bottom.

Two screws in the back, by the connectors.

I think it may be the power supply. The one I have is an aftermarket power supply. I found if you push it in JUST RIGHT it stops humming. Maybe the barrel/connector is not quite the right size or length? I dunno. All I know is I can make it go away if I push in hard on the power supply connector.

 

[E-Stat]

When you're ready to take it to the next level, replace the OPA2134 or OPA2604 with Burson Audio FETs. My Music Hall DAC 25.3 used both and I replaced them with V5s.

Improved transparency and dynamics.

 

[SimplySound]

Hey Dave, JA pointed out in his measurement of the R107/2 that the Kube OpAmps were Signetics NE5532, You have established that the original R107 used TL072, correct? Is that in the schematic?

I'm thinking I might upgrade to the NE5532D (Latest iteration), but also considering the LM4562. I've read quite a bit of diverse opinions around "OpAmp Rolling" and the compatibility to the underlying circuit. I think I want to go with as close of a direct replacement as possible.

Thoughts?