Nick G modified Lentek Head Amp

[Wakefield Turntables]

Great post Alan. I could take mine apart and photograph it if you wish so you can see how mine's been modded. I agree with you that the Lentek won't be replacing the Paradise.

[337alant]

I finally got round to repairing Steves (Floydroids) Lentek as it had a rustling and occasional quac from the right channel
I tracked it down to a 15k resister that had no steady measurement is just kept climbing as you measured it ? also 2 x tantalum caps duff on the right channel so I replaced all resisters for metal film with the 100 ohm loading resisters for Dale RN60.
All tantalums changed for Elna Silmic 2 and all small value for polyprops all values were measured and matched.
The output transistors were also changed for matched pair of BD438.
Ouput cables Klotz MC5000 and Shark Phono plugs
It sounds great to me


20161127_190556 by Alan Towell, on Flickr

Alan

[Firebottle]

Good job Alan

[DarrenHW]

Good job Alan

+1, are the new transistors much quieter?

[Marco]

Excellent work as usual, Alan!

For me, the little Lentek head amp is a revelation and somewhat of a design classic. I've no idea why it sounds as good as it does [perhaps the sheer simplicity of the circuit and/or the design of the circuit itself, after all, some 'recipes' just work], in reality it has no right to sound so good, but I first used one of these devices in 1982, with my (then) Ariston RD11S/Linn LVV/Denon DL-103 combo, through a Sondex S230 integrated amp, which incidentally had a superb MM phono stage on board, and even then I couldn't believe how good the sound I was getting from vinyl replay.

Fast forward to 2016, at this year's MiBO show, and the little Lentek I brought with me, which incidentally was stock, apart from fitting some solid-copper Eichmann phono sockets, Cardas 21-AWG pure-copper litz shielded interconnect wire, complete with WBT 0102Ag RCAs, sounded just as impressive in a modern context, in conjunction with and also up against some very good equipment indeed, as I'm sure Alan (Firebottle) would attest to...

Even at home, it gives my £1500 Paul Hynes head amp/PSU a run for its money, which is just ridiculous, but the Lentek (especially in conjunction with a DL-103) imbues music with an infectious joie de vivre, PRaT [pace, rhythm and timing], which would give any Naimee a hard-on. It sounds 'punchy' and dynamic, simultaneously making other head amps and SUTs sound somewhat soft and limp, but once subtly fettled (with judicious replacement/upgrading of caps, resistors, etc) never strays into aggressiveness.

On that note, I would exercise caution, as the temptation is simply to rip out components that superficially seem 'wrong' or 'inferior', but are actually key to producing the effusive, fun-filled sound the Lentek is renowned for, and as such you can end up sucking the life out of it, filling it with so-called 'superior' audiophile components. Yes, those may be electrically superior, but sonically, not as well-suited to maintaining the optimal 'sonic recipe', and so you end up with a sound that's a bit too smooth and 'controlled'.

That's precisely why, with the current Lentek I've got, I've so far kept it simple and replaced the 'no-brainer' inferior items from the 70s/80s, such as the horrible (in comparison with what's available today) original phono sockets, signal output leads and RCA plugs. Honestly, the difference that made alone was rather surprising! And furthermore, it allowed me to hear what the circuit was doing 'as is', highlighting that there's not a lot wrong with it, but that it would benefit sonically from some light tweaking and the addition of a soupçon more subtlety and refinement.

However, the tricky bit now will be ascertaining which components are best changed/upgraded, in order to achieve that effect, but crucially without robbing the unit of its 'fun factor'! I think I'll start with the resistors and work forward from there to caps and transistors, so watch this space soon for various in-depth comparisons of such, before I end up with what I consider as optimal, and 'voice' the Lentek to my tastes accordingly!

Marco.

[Firebottle]

..... sounded just as impressive in a modern context, in conjunction with and also up against some very good equipment indeed, as I'm sure Alan (Firebottle) would attest to...

I'd not actually heard a Lentek before but have played with a transistorised head amp of similar vintage (the one I lent to Jimbo as a head amp starter).

I was impressed and as Marco suggests I think it is down to the simplicity of the unit. Replacing the capacitors for better lower loss versions is almost De Rigeur, but I would advise not to replace the transistors (unless your unit is particularly noisy) as the type was chosen for good reason.
They have a larger semiconductor 'chip' inside compared to the more traditional small signal transistor, being chosen for low noise performance.

[337alant]

Darren
No not much difference in the noise but at least these are matched as the ones I remove had a HFE of 50 and 105 so poor current gain matching
Generally though the Lentek does sound less noisy than the original
Alan

[RothwellAudio]

Sorry if I've missed it, but is there a circuit diagram for this headamp somewhere? That has to be the place to start if anyone is thinking of changing anything.

[Floyddroid]

I finally got round to connecting the Lentek to my Firebottle having reconfigured it back to MM. Straight away i noticed a much more lively and informative sound using my Denon 103. Transiants and attack where much tighter as if a spanner had been taken to the sound. Vocals didn't seem to have the depth as with the Firebottle on it's own but this was more than made up for by the overall musicality. Drum kit really did sound like a drum kit and guitars both acoustic and electris seemed to have more sparkle. Many thanks Alan, you are a gifted chap.

I finally got round to repairing Steves (Floydroids) Lentek as it had a rustling and occasional quac from the right channel
I tracked it down to a 15k resister that had no steady measurement is just kept climbing as you measured it ? also 2 x tantalum caps duff on the right channel so I replaced all resisters for metal film with the 100 ohm loading resisters for Dale RN60.
All tantalums changed for Elna Silmic 2 and all small value for polyprops all values were measured and matched.
The output transistors were also changed for matched pair of BD438.
Ouput cables Klotz MC5000 and Shark Phono plugs
It sounds great to me


20161127_190556 by Alan Towell, on Flickr

Alan

[RothwellAudio]

I looked online but couldn't find a circuit diagram. Anyone have one?