Cheap 9V supply for Lentek Head Amp...

[DSJR]

The Lentek seems to work well with a PP3 style 9V battery, but the success of the simple home made 12V AC supply for the X10-D has got me wondering what the Lentek might do with a separate low noise DC supply..

12V AC supply here - http://www.rock-grotto.co.uk/easyxpsu.htm

As always, this will have to be done on a shoestring budget, any fancy bits costing many tens or hundreds of pounds are out I'm afraid.

Ready made, that Maplin CB supply looks good at around £20 as I'm sure the 13.8V can be reduced to around 10V as it can be increased for the Caiman. It's a bit fugly though and large.

Any ideas for an easy to assemble kit? The transformer suggested by Rock Grotto is silent, cool running and no hum fields I can see and should be fine once regulated and smoothed.

Any ideas?

[Techno Commander]

Is seven quid acceptable?

LINK (http://cgi.ebay.co.uk/Voltage-Regulator-Kit-AC-DC-in-DC-out-Based-LM317-/150446018070?cmd=ViewItem&pt=UK_ConsumerElectronics_SpecialistRadioEquipment _SM&hash=item2307480e16)

[DSJR]

Many thanks :)

Have you tried this yourself? I've ordered it in any case..

[Techno Commander]

I haven't. But there isnt much to a simple voltage regulator circuit.

[Reid Malenfant]

But there isnt much to a simple voltage regulator circuit.
I'll agree with that. With what you are likely to be powering that regulator will be bomb proof. The 317T is also one of the better adjustable regulators with less ripple & noise on the output & much better than a TO220 fixed voltage device ;)

[DSJR]

The PP3 is nominally rated at 9V, but would anyone know if increasing the supply voltage to 11 or 12V would make any improvement (or risk burning the thing out)? I'm sure that Duracell PP3's would be higher than 9V from new, wouldn't they, unless they sag under the loading?

[Reid Malenfant]

The PP3 is nominally rated at 9V, but would anyone know if increasing the supply voltage to 11 or 12V would make any improvement (or risk burning the thing out)? I'm sure that Duracell PP3's would be higher than 9V from new, wouldn't they, unless they sag under the loading?
It'd be helpful to know exactly what is being powered :) What i mean by this is not the device itself, but the circuit. If it contains electrolytic or tantalum capacitors they might be rated close to the present rail voltage - say 12V.

If it's an operational amplifier i feel sure that it'll accept a higher voltage, other components may not be so keen as i mentioned.

A new PP3 will probably read 10.5 - 11V on a high impedace digital multimeter, like you say though, under load this will sag somewhat due to the fairly high internal impedance of the battery. This depends on the load current & if the thing is op amp based it'll draw little current in reality.

Have you tried measuring the voltage of a new battery connected to the circuit?

[DSJR]

I shall do that when the time comes :)

The little circuit in the Lentek is potted in and I cannot see what is there. I haven't spoken to Phil Swift (latterly of Spendor) for many years and in any case it's over thirty years since he ran/co-ran Lentek and he may have forgotten what was inside this little device.

http://i132.photobucket.com/albums/q8/DSJR_photos/DSCF1358.jpg

In the event, I'll measure a new PP3 in situ and fine-tune the power supply for a similar reading once loaded..

Many thanks to all :peace:

[Nigel]

I have a similar type of moving coil head amp made by Rogers in the early eighties. It's also a box of semiconductors designed to be used with a 9v PP3 battery. I've often wondered if any benefit could be gained by running it off an SLA 12v battery made for security systems. Would this be safe to try or a foolish thing to contemplate?

Cheers.

[Arkless Electronics]

Lm317's etc are far too noisy for a head amp. I'd stick to the pp3 if I were you ;)

[Nigel]

Jez,

Would there be a worthwhile difference using a 12v battery instead of the 9v PP3?

I can't help wondering if these head amps were to be used with PP3 batteries for convenience. I can't remember 12v batteries for home use back in the early 1980's. Maybe that's why PP3's were chosen?

[Arkless Electronics]

Jez,

Would there be a worthwhile difference using a 12v battery instead of the 9v PP3?

I can't help wondering if these head amps were to be used with PP3 batteries for convenience. I can't remember 12v batteries for home use back in the early 1980's. Maybe that's why PP3's were chosen?

I would stick with the 9v and use an alkaline battery. There is a good chance that 12V would upset the internal biasing although it is unlikely to harm it. It only has to output a few tens of mV at most so it doesn't need the extra headroom.

[Nigel]

Cheers Jez. Many thanks for the advice.

[337alant]

The PP3 is nominally rated at 9V, but would anyone know if increasing the supply voltage to 11 or 12V would make any improvement (or risk burning the thing out)? I'm sure that Duracell PP3's would be higher than 9V from new, wouldn't they, unless they sag under the loading?

Dave
I use my Lentek with a 9.9V Lipo battery and its fine sounds a little brighter
The lentek is still a very good step up device
I don't recommend taking it out of its case BTW as it is very sensitive to mains and I couldn't get rid of the slight Hum in this set up

http://farm6.staticflickr.com/5458/9294345514_67d06f0104_z.jpg (http://www.flickr.com/photos/69508926@N05/9294345514/)
. (http://www.flickr.com/photos/69508926@N05/9294345514/) by 337alant (http://www.flickr.com/people/69508926@N05/), on Flickr

Alan

[nat8808]

Is the Lipo on a constant trickle charge there? Does that let any noise through from the charging process or can it be left connected with the battery a bit like a buffer tank?

[337alant]

Is the Lipo on a constant trickle charge there? Does that let any noise through from the charging process or can it be left connected with the battery a bit like a buffer tank?
No the battery has to be charged separately, in fact I have also removed the power supply and it all runs on battery's now, its definitely quieter but battery's are a pain in the a*se TBH

Alan

[shane]

There's a couple of relevant threads here:

http://theartofsound.net/forum/showthread.php?8431-Nick-G-modified-Lentek-Head-Amp&highlight=lentek (http://theartofsound.net/forum/showthread.php?8431-Nick-G-modified-Lentek-Head-Amp&highlight=lentek)

http://theartofsound.net/forum/showthread.php?7341-Lentek-Head-Amp-Naked!&highlight=lentek