Retro Review and Repair LFD NCSE Amplifier can I fix it's crackly volume control

One of my favourite amplifier manufacturers... should be a simple fix, how does it go???

[@michelcharest8346]

I just had one of those LFD NCSE on my repair bench. I have been doing repairs for over 40 years now and must say, I am totally unimpressed by this amplifier. There are so many things that are badly done that I don't know where to start. The one I have has a bottom and top cover made of 2 parts, "connected" together by duct tape. I thought I had seen it all... The threaded rod that connects the back panel to the front panel. If you tell me this is for a prototype I will understand but, use that in a production unit? Are you kidding me? The use of fancy speaker wires for the outputs is defeated by the fact that they are connected to thin PCB tracks running around under the PCB. Why use some fancy cables to connect the volume potentiometer to the amp card and the selectors if you use flat cables to bring the signal from the outside world? This configuration brings so much cross talk that I can't understand why no one is complaining about it. I read many times people complaining about the fact that the volume potentiometer is king of scratchy. I cleaned the one in the unit I had with minimal amelioration. I decided to look at it closer and discovered that there is around 13 mV at the potentiometer when you raise it to the max. Having some DC voltage on a volume potentiometer is a no no in any world I know. Don't bother replacing it as the problem is NOT the potentiometer. I'm pretty sure coupling capacitors are missing between the amp card and the potentiometer... Just for fun I took out one of the two capacitor banks to compare it with a normal 6800 µF capacitor. On the large capacitor I measured 2 mOhm at 1 kHz. On the capacitor bank I measured 5 mOhm. I decided to examine the PCB layout of the bank and found a better way to connect to it. Instead of using the two pins on the same side, it is better to use the external connections on both sides. I tried this with my LCR meter and could now measure 3 mOhm. The person that designed this PCB doesn't have much understanding of a proper PCB layout. I am pretty sure a better layout could equal or beat the large capacitor but not this time. One other thing I found is that even when the volume control is at zero, there is always some music going through. I turned the potentiometer to zero and measured 4 Ohm on both sections. Bizarre... Could this be caused by some cross talk? There are many more things I could talk about, maybe some other time... What is appealing about this unit is that there is much that can be done to make it better. The first thing I would do is install a relay card at the back of the unit to select the inputs. This way the signal won't have to go through the "crappy for analog" flat cable. Doing that will get you a better sound and will help get rid of most of the cross talk. The second thing I would do is put a relay delay when powering up the unit to get rid of the thump. The third thing would be a mute relay. The fourth would be a better potentiometer. When I think about all this, it would be simple to control all those upgrades with a remote control and motorized potentiometer. What is not appealing about this unit is that at that price point, you should not have to do all this to get a properly designed and built power amp. The creator of this amp may have golden ears but is an amateur when time comes to properly build amplifiers. It may be sounding great but its no excuse for the lack of professionalism when building it. Too many short cuts, too many beginners errors. Until next time!!

[@sean_heisler]

Wow, such a low quality pot in an expensive amplifier!

[@peteturnock3417]

The amp in the video is mine. The pot has been noisy for a while and hasn't bothered me too much until I recently decided on a re-vamp of some of my system. I owned a LFD Zero Mk 4 integrated probably 15 years ago - the brand being introduced to me by Phil, then the above NCSE integrated Mk 1. Having decided to replace the NCSE I looked for an alternative for over a year - listening to loads of amps up to about £4000. Nothing sounded anywhere near as good as my NCSE and I ended up with a two year-old NCSE Mk 3 (£6K new) - which has all the great NCSE qualities but spades more. When this Mk 1 is fixed it will probably be for sale - if I don't decide to keep it for a second system. I also use the LFD DAC 5 Mk 2 SE driven from a Bel Canto CD-2 transport which is as good a CD combo as I've heard south of £20k, and use LFD spiroflex speaker cable - also great value. I would advise anyone to try LFD equipment if they ever get the opportunity.

[@edwardgonczy3170]

First, I love your channel. Now I say the nasty part. What a piece of crap amplifier. Why? The lack of any attention paid to the volume pot. If he was really obsessed with quality, he would at least use an ALPs pot. No excuse. Wouldn't give him $1,800 for that kit. And for an amplifier of that simplicity and the renewed interest in analog playback, a modest MM phono stage? Naim Audio any day of the week.

[@jdekong3945]

Horrendous little pot considering the effort put into the rest of the unit, should have bought an ALPs to replace it

[@matthewtaylor7355]

Looks like a 1.59 GBP pot from old Maplins. Classy British generosity😂 Can't they use switch cleaner

[@redleather100]

It’s got more than a crackle , more of a buzz😅

[@hoobsgroove]

Definitely a lot of buzzing but he didn't comment on it I'm assuming it must be the microphone

[@stevesmyth4982]

It's good to see a large number of smaller supply rail smoothing capacitors rather than the usual two large ones. Bigger capacitors are more inductive and can cause a poor PSU transient delivery - the small amount of inductance in parallel in each capacitor reduces the overall milli Henery value.

[@charlybeagrie1119]

Low F**king Distortion.

[@jimsregaturntableshifijukebox]

Another good tip for those not in the know.

[@hoobsgroove]

It sounds like a breakdown of a component a resistor or transistor more likely, but could be galvanic corrosion, worth checking the connectors and using some of that cleaner on the connectors pulling them in and out. and I don't like the mains block next to the transformer these can get loose so check it for tightness could be some arcing going on. Might be interested in getting one how much can you pick one of them up for couple hundred, the originals you like what was the model?

[@rosshardy6223]

Cut out that criminally cheap $5 pot and treat it to a TKD 2CP-2511 20k pot. Thats what I did.

[@zumanju1356]

Do you think this TKD 2CP-2511 20k pot would work with LFD LE IV Signature also? I need to replace mine and all I see is A20K on the OEM pot.

[@CraftyZA]

I can hear mains hum a lot more than the crackle. With my home made SRPP+ pre-amp (6922 tubes) and gecko audio vanguard power amp I can set the volume to max and not hear a whisper. Notice at 7:55 when you touch the metallic knob the humming gets louder, and a bit of crackling as well. You are dealing with a ground loop. You can try to float mains earth. Also if there are multiple routes to ground, install a ground bus bar, and reroute them.I can see mains earth connects to the chassis, and your 0v rail connects somewhere else.

[@bernardchesneau3091]

I agree , loads of hum, ground loop and or supply caps in bad shape.

[@stephenfurley1025]

Interesting... I think Howard Popeck was a fan. Not sure if he had a tri-amped system using LFD. An alternative is to switch amp off and simply rotate the volume control back and forth about 20 times without using any switch cleaner. The input you used, was it shorted? Probably not, I think. If it was, I don't think you would have had the buzz. Thanks for something different.

[@terrynicklin417]

Odd there was no mention of the deafening hum! I guess if you're splashing out on such kit you have to believe it's wonderful. I can't say I'm impressed with the internal layout or choc. block power connector.

[@davidthom7127]

Am I right in thinking that even amplifiers that are unplugged and are off, things like caps still retain charge ?

[@walriley48]

Could be the volume pot isnt securely fixed to the amp frame. That would cause noise issues with the body of the pot only intermittently earthed. Also, before delving in, give it about an hour with no power connected in order for those main reservoir caps to discharge. Them buggers can cause injury.

[@bradmilne863]

Like seeing under the hood ...do see some familiar caps that I use on my amps, do all three pots

[@robh9079]

Looks a budget pot - I'd replace that with an alps....

[@dingskydongsky]

of course !

[@jasonme3557]

volume potentiometer

[@paulpaulzadeh6172]

filter cap

[@bernardchesneau3091]

I would look into that also.

[@vmaletailic5237]

Look like toy!

[@rosshardy6223]

yea that is very musical, pure and valve like, go figure.