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Light Dependant Resistor 3 Input Preamp Kit

What is reasonable to pay for a LDR 3 input Kit

  • $150.00

    Votes: 33 80.5%

  • $180.00

    Votes: 5 12.2%

  • $300.00

    Votes: 3 7.3%
  • Total voters
    41
Jump to Latest
#102
Chris Daly said:
First tests of the H11F1M, show it must have approx 500k resistance in series with its input, appears to suit series connection, rather than L pad. the forward voltage is lower than for a LDR at 1.3v.
We obtained fairly useless volume range although it was reproducing audio quite well when at high volume, signal side resistance was at 3.5k Will see how it develops,
Click to expand...

Have found good use for the H11F1m, the first use was in the series LDR line, where despite adding resistance it appears to be much better sounding than without it. in this first configuration they were deployed to aid conventional switches for the series anodes, fed from our control board, our customer was very happy with the sound improvement.

In the second application we looked at the H11f1m replacing fixed resistance in our control board, and once again it has really improved audio presentation. So we are busy
getting these done.🙂

Cheers / Chris
 
#103
Chris Daly said:
Have found good use for the H11F1m, the first use was in the series LDR line, where despite adding resistance it appears to be much better sounding than without it. in this first configuration they were deployed to aid conventional switches for the series anodes, fed from our control board, our customer was very happy with the sound improvement.

In the second application we looked at the H11f1m replacing fixed resistance in our control board, and once again it has really improved audio presentation. So we are busy
getting these done.🙂

Cheers / Chris
Click to expand...

Chris, I'm watching with interest re. the H11f1m. I was considering a NSL32SR2 balanced kit for my (yet to be built) KGST headphone amp project, but, as I'm not in a mad rush, I'll see how things pan out. Do you think it likely that you'll use the new LDR's in future kits?
 
#104
h11f1m finds good purpose in regulator for LDR boards

Hi
The attached schematic shows how we have used a h11f1m in a forthcoming psu
regulator. Currently at prototype breadboard stage,it provides 12v and audio quality
partnered with control board and LDR board, that we are very impressed with
better than any we have heard to date.

Transformer used was 12vAC , rectifier bridge a DB104 and connection is shown for J40 J25 and J2 forming
a star earth, and J3 positive. Read Q1 as internal fet of the h11f1m pin 4 and 6
We are presently looking at R1 value shown as 1k2, as tailoring current
to the anode with h11f1m from prior experience ,usually leads to further refinement.

Expect to commit this to a pcb shortly.

Cheers / Chris
 

Attachments

Last edited:
#106
Updated Regulator schematic

Hi
Updated Regulator schematic, 10ma is the right amount of current to the h11f1m anode, however here done differently with a Vref/R 7805, 5/500R, and correcting reg ground after 22R

Detail and presentation is to say the least stunning... now destined for a pcb

Cheers / Chris
 

Attachments

Last edited:
#107
Chris Daly said:
Being a DIY kit the stereo coffee is very adaptable to more inputs, having two outputs switched or unswitched or other variations. Suiting every connfiguration of audio system so far we have done:

Balanced kit with three inputs
Single input with two outputs
Three inputs with two outputs
Six inputs and two outputs
Two inputs and a stereo output

Our standard products remain as Single Input kit with stereo output, and three Input with stereo output which are very popular.

Cheers / Chris
Click to expand...
Hello Chris,
How and where I can buy version "Three inputs with two output"?
Regards
Mirek
 
#108
Hi Mirek
Two outputs, do you need these contactless switched so you can have one stereo pair on at a time, or unswitched so they are on together. ?

A 3 input kit is needed,
If switched a pair of h11f1m is arranged to activate a second shunt pair on a separate LDR board by turning the anode on or off on that optocoupler that then turns the anode passing current to the LDR pair.

If unswitched a second control board is needed as current is being expended continuously
and a second LDR board.

Cheers / Chris
 
#110
Hi Mirek
For your biamp system, If resistive loading to ground on your power amps are more than 80k, then you
will be OK to run two outputs R+R and L+L from the a three input kit.

If under 80k resistive loading on each channel then it is advisable to use two three input kits, here
you would share each input with each board. Exceptions are amps that have sensitive front ends like the quad 306 that has 300mv sensitivity and has a 30k resistive loading, here the power amps sensitivity despite resistive loading is a asset.

My own system drives two power amps into two pairs of speakers, from the one LDR preamp, the same as bi amping, Advisable to have a source component with low impedance output,

Cheers / Chris
 
#112
I'm excited to build this as my first diy thing other than rca and xlr cables. I already have a bunch of parts leftover from when I was going to build a headphone amp cancelled the project. I just need a drill and stepped bit for casework and a DC input socket I can mount to the chassis.
Stuff I have:
Modushop case
4 rca sockets
volume knob
nylon pcb standoffs
hookup wire
a 12V DC high quality linear power supply

can you think of anything else I might need to complete the kit?
 
#114
Yes both are good choices. a toroidal transformer in my experience
may be slightly more reliable. A fuse is recommended, and very easy
if already in the IEC fitting. Rating of fuse should be 500ma fast blow
The circuitry in our kits consumes far less current approx 50ma.
Fuses though aside from downstream devices also are dealing
with transformer inrush hence 500ma is a wise choice,

The lily regulator has a on board rectifier and
capacitors, and there is a small blue trim for precisely setting to DC 12v,
although the regulator is usually exactly 12Dc when delivered.

I have emailed you instructions about earthing and getting the kit going
I am looking forward to how it sounds in your audio system.

a review here at post 567
Goldpoint SA4M-47 passive 'preamp' winging its way to Marco Towers... - Page 57

Cheers / Chris
 
Last edited:
#115
Just finished my KGST electrostatic headphone amp using one of Chris's balanced kits. Sounds fantastic! Thanks for your help along the way Chris.


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