Lentek Head Amp - Naked!

[DSJR]

Join the Open University and see if an Open degree can be constructed (it's modular and covers multi-subjects) to suit as I'm hoping to do.

I want to try the Lentek as-is with an external supply to start with. I have found a Maplin mutli-voltage regulated power supply with LM317T regulator inside (they're going for £9.95 at the mo) - http://www.maplin.co.uk/Module.aspx?ModuleNo=32754 - I'm getting a male DC socket and shall fit this to the Lentek trailing wires when it's delivered..

[Reid Malenfant]

Dave, i have 6 spare Os-con capacitors here which you are welcome to if you want them They are 22uf 20V, yes they may be different values to those tantalums but in reality it'll make virtually no difference to the way the circuit performs (except the sound ). The worst case scenario is that the LF rolloff might be a tad higher though i should imagine it'll already be very low anyway simply because the warp filtering will be taken care of in the phono pre-amp proper

[John]

Totally agree with Alex
Mark its great to have you on board

[Ali Tait]

Mark,have you got any further with trying the balanced trannies yet?

[Reid Malenfant]

Mark,have you got any further with trying the balanced trannies yet?

Hi Ali, sorry for going No you see i'm not going to get a listen until i build some kind of case, which in reality means a good one - the final one if you like. Now i have way more than enough MDF to make a suitable box & everything i need to make all the protection circuits

What i don't have is access to my table saw in the garage as there is rather too much stuff just chucked all over the place & i'll need room to move even a 4 x 2ft offcut of wood about, it's that bad This also explains the lack of input recently on the sub build thread

I'll get there in the end though, my apologies as it's not even as soon as i'd like myself. The mind is willing but the body is fu**ed so i have to take things miles easier & slower than that damn tortoise (that raced the rabbit)

When i do get some room both projects will progress in a very short time Hopefully pretty soon to as it's damn depressing tbh & not only for you!

[Ali Tait]

No worries,I just wondered! No pressure..

[DSJR]

Thanks for the offer mark. I'll be in touch shortly

I got the cheap Maplin supply hooked up and once I realised that the connections are inverted (two battery terminals have to be inverted to work together) I tried it.. There's a hum through the speakers from the supply which I think is lack of smoothing (I'll have to make my kit of parts up pronto).

As an aside, the Lentek works on 3V, the test light only just beginning to dim out compared to 6V+

[leo]

The Carbon resistors look like Allen Bradleys, if used in critical positions in the signal path they tend to add quite a heavy signature . Be warned if your planning on changing these to say 1% metal film types ,it will probably change the sound a fair bit . You may or may not like it.
Tants can sound thin and bright, hard to say if their decoupling or coupling, also if theres any ceramic caps used in the filter etc these can be bright/harsh

Its hard to work out the circuit from the pic, it may have poor PSRR, some circuits are very picky regarding PSU quality

[leo]

BTW if this thing was made for batteries I'd be careful going linear, it may make things sound worse unless the quality of regulation is better than average

[DSJR]

I was thinking that myself, but at least it's easy to put back to original.

This head amp was designed primarily for the Entre 1 cartridge, which Lentek originally imported. This latter had a velvet, almost smothered quality (by today's standards) and was great for smoothing out those nasty early dome tweeters. It wouldn't surprise me at all if Phil Swift didn't deliberately add a little "life" to the sonics to partially balance the Entre. A year or so later, the Entre itself changed and became more "spiky" in sound, althoigh it's irrelevant now ;: