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StereoCoffee LDR Passive Preamp Upgrade Preview

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robmid   
Posted (edited)

TECHNICAL NOTES from Chris Daly

 

StereoCoffee LDR Passive Preamplifier Kit UPGRADE

 

My NEW 13A control board is the peak of over 8 years research into Audio coupling Light Dependent Resistors (LDR's).

 

Entirely different to other designs, including prior StereoCoffee boards, it considers the unique ability of the Light Dependent Resistors relationship with its anode and cathode to achieve a potential difference entirely separate from signal ground. It strictly has no relays or switching on its signal side leaving the signal side pure. 

 

As many inputs as are required can be catered for, not by switching the same L pad set with relays, but by having the LDR as both a switch when off, and when on resuming as an attenuator.  

 

Left Right balance is typically better than any commercial available attenuator, and remains so.

 

Built by listening intently and using new electronics techniques, the essence of music is heard perhaps for the first time.  

 

LDR's driven from voltage regulators, whilst a quick way and inexpensive way to power them, ignores their true definition as current driven devices. The stereo coffee precisely regulates and monitors current to bring a new approach to the way your music is heard.

 

All StereoCoffee designs are tested on Quad ESL57's to assess fine detail.

 

Chris Daly.

 

2017StereoCoffee.jpg.239560899ff96f285ae60b076d1e4ff5.jpg

Circuit boards have been built into a DIY perspex case


PREVIEW of UPGRADE 

I was obsessed with valve amps until I first heard a simple LDR Preamp, driving LS50’s with an 8” REL sub through my DIY $1000 Holton 150w kit amp.

 

To clear the air, I have no connection with Chris Daly (StereoCoffee) other than being a happy customer. I love the sound of LDR preamps having built the Chris Daly ‘StereoCoffee’ and the Uriah Dailey ‘CloneNote’ but I believe that LDR Passive Preamps are something that everyone should hear for themselves before dismissing them.

 

In photographic terms, a Passive LDR Preamp is like large format film compared to a basic digital camera/phone. An image from the phone looks sharp until you enlarge it. Then the image starts to get ‘jaggies’ particularly around the edges of the image.

 

A sharp image from a large format film camera requires no artificial sharpening to create perceived sharpness and an enlargement looks sharper and more realistic no matter how close you stand because the image has high resolution. 

 

The film image not only looks sharp but is smoother all over due to smooth gradation between hilights and shadows. The smooth gradation is there because of the large amount of ‘information’ in the image.

 

To my ears, the LDR preamp sound is like a large format image. There is no, harshness but resolution and gradation is very smooth but also crisp. No jaggies or artificial enhancement other than that of the original recording are noticeable, just bucket loads of fine detail.

I find the reproduction to have unexpected depth and separation, with a 3D presentation on many tracks which improves as the preamp warms up. Sustained harmonics on stringed instruments are a joy to behold. 

 

On one Jazz trio *track I heard at the weekend, a piano on the right occupied a very narrow band of sound stage and the lower notes were on the right of it, suggesting that the piano was angled towards the left side of the stage. * Stanton Moore - Driftin'  from Conversations Album.

 

To me, there is something magic about Passive LDR Preamp sound that can be heard but seems to be a mystery. You must hear one to understand.

Listening sessions quickly become addictive and the reproduction of all stringed instruments and brass plus all voices male and female have a degree of realism that is palpable in most cases. 

 

The StereoCoffee LDR Preamp kit costs around AU$175 with fully wired regulator board, control board and 3 input LDR board plus pot and rotary switch. The only soldering is for the rotary switch, pot and inputs/output. Connections are made with screw terminal blocks.

PROS

  • Low cost $175
  • Palpable reproduction of instruments and voices
  • Silent background
  • Fatigue free listening
  • No switches, moving contacts or interference with the signal side of LDR’s
  • Boards are pre-wired, tested and adjusted for instant use once installed
  • Simple DIY job that can be bench tested before putting in a case
  • Adjustable inputs and output for a balanced sound
  • Personal technical assistance from Chris

CONS

  • Low price. You can always tell your mates it cost thousands or just hide it in a cupboard
  • If your source material is bad, that’s how it will sound but it will still sound better than you have heard it before
  • An Elma rotary switch might be more tactile but it would cost more than the preamp
  • The circuit boards aren't pretty but they are well built

 

More info on LDR Passive Preamp Kits: http://robmid42.wixsite.com/diyaudiokits/stereo-coffee-preamplifier

Edited by robmid

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shaky   

I have and use one of Chris's LDR 3 input   Pre's, bought in kit form. It is a great piece of kit, an absolute bargain in my opinion, possibly one of, if not, my best bang for buck audio purchases. And I must say Chris himself has been an absolute pleasure to deal with in the 3 years I have had it. 

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robmid   

Yes, I have had mine for only about 12 months and found Chris to be very generous with his time. His new Control Board is a big improvement on an already excellent product.

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I spoke to him some time ago when investigating various passive pre's around.  Quite the gentleman....!

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Funny. I was interested in one of these a number of months ago. I had quite a detailed email exchange with Chris in which we discussed the particular variation I wanted (and price). 

 

He was going to build it and let me know when done. He'd then pop it in his eBay store for me to buy. Didn't want any money upfront despite my offer. 

 

And then I never heard from him again. Odd 

 

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Darren69   
Posted (edited)

I love the look of the Townshend Allegri but I like a remote too much.

 

@Sir Sanders Zingmore common practice in the hi fi industry methinks.

Edited by Darren69

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A J   
Funny. I was interested in one of these a number of months ago. I had quite a detailed email exchange with Chris in which we discussed the particular variation I wanted (and price). 
 
He was going to build it and let me know when done. He'd then pop it in his eBay store for me to buy. Didn't want any money upfront despite my offer. 
 
And then I never heard from him again. Odd 
 



Where's the love ?


Sent from my iPhone using Tapatalk

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Ugly   

I've found Chris to be excellent to deal with. He is passionate about his work and he responds to emails very quickly.

I asked him a question about wiring and power supplies and he then offered to make life easier for me by sending me a new board with the power socket pre soldered onto the board. Brilliant support.

Sent from my SM-G900I using Tapatalk

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jrhill   

Unfortunately, I found his circuitry totally confusing - the sound, however, is very similar to George's original Lightspeed - that Java package is very attractive design and quite comprehensive

 

If transparency and low distortion is a desired characteristic, Uriah Daley's slightly 'clunky' 'CloneNote' is as good as it gets, IMHO - not everyone wants this, naturally enough

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robmid   

I have tested 3 upgrades to the StereoCoffee in the last 12 months and each has been an improvement but the latest Control Board has been totally redesigned over the last few months and there is NO COMPARISON in the sound quality and sheer realism compared to PREVIOUS versions.

 

If you are curious about LDR Preamps, I urge you to forget about technical arguments, forget any preconceptions you may have and just audition one. 

 

If anyone can get to the Sunshine Coast I can demo my CloneNote, which is superb and the latest StereoCoffee which has really surprised me with it's improvement in performance. Just send me a PM to work out a time.

 

 

 

 

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Bilbo   
On 02/06/2017 at 3:28 PM, Darren69 said:

I love the look of the Townshend Allegri but I like a remote too much.

 

@Sir Sanders Zingmore common practice in the hi fi industry methinks.

 

I used Uriah's "Lighter Note" for several years and thought it was great but the lack of a remote drove me nuts.  I now use a Tortuga LDR and I think it is a bit better plus it has a remote.  

@robmid

I might take you up on that offer when I venture up the north coast next time as I'd like to hear the difference between units though the lack of a remote volume control is a deal breaker for me.

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robmid   
Posted (edited)
The LDR kit as supplied is suitable for 3 stereo unbalanced line level inputs, selectable by turning the anode on , on the pair required, as there is No signal side switching. More inputs can be catered for by ordering a second LDR board, for instance 6 stereo inputs is achievable Or even 9 where the input switch is changed to have the requisite contacts.    
 
A stereo left right output is provided, however Chris says he has seen no problem from driving 2 stereo outputs,in this case just link to a second RCA pair to provide 2 stereo outputs. The audio quality is so high, in most cases you would very rarely use volume over 2 pm, even with power amps up to 1.5v sensitivity and 220k resistive loading. The source component should be capable of driving into a resistance of 600 ohms or less. Thankfully the vast majority of source equipment today easily exceeds this and is over specified with drive capability. DAC's for instance have typically 2v output and are capable of driving 100 ohms or less.   
 
Remote control can be done, a remote kit will be listed shortly.
 
Balanced Input through to Balanced Out can be done and requires two very well resistance matched kits. Chris can cater for True Balanced In and Out, but says it does take extra time to get the matching required. 
There are always custom combinations like 5 inputs, three outputs with ability to switch to mono. Yes, that one is being happily used today, and has been working well for 3 years. Chris says where he can find time he will do his best to assist. Most audio enthusiasts though  will find the 3 input kit with a stereo output the best addition they will ever make to their audio systems. 
 
As for cased versions - Yes these are coming.
Edited by robmid

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On 04/06/2017 at 5:31 PM, robmid said:
The LDR kit as supplied is suitable for 3 stereo unbalanced line level inputs, selectable by turning the anode on , on the pair required, as there is No signal side switching. More inputs can be catered for by ordering a second LDR board, for instance 6 stereo inputs is achievable Or even 9 where the input switch is changed to have the requisite contacts.    
 
A stereo left right output is provided, however Chris says he has seen no problem from driving 2 stereo outputs,in this case just link to a second RCA pair to provide 2 stereo outputs. The audio quality is so high, in most cases you would very rarely use volume over 2 pm, even with power amps up to 1.5v sensitivity and 220k resistive loading. The source component should be capable of driving into a resistance of 600 ohms or less. Thankfully the vast majority of source equipment today easily exceeds this and is over specified with drive capability. DAC's for instance have typically 2v output and are capable of driving 100 ohms or less.   
 
Remote control can be done, a remote kit will be listed shortly.
 
Balanced Input through to Balanced Out can be done and requires two very well resistance matched kits. Chris can cater for True Balanced In and Out, but says it does take extra time to get the matching required. 
There are always custom combinations like 5 inputs, three outputs with ability to switch to mono. Yes, that one is being happily used today, and has been working well for 3 years. Chris says where he can find time he will do his best to assist. Most audio enthusiasts though  will find the 3 input kit with a stereo output the best addition they will ever make to their audio systems. 
 
As for cased versions - Yes these are coming.

Hi Rob, 

I ordered LDR kit with 6 inputs and 2 outputs. Chris is just building it and with a new regulator. I am not a very technical guy. Hope this project is not that difficult for me. Are you based in Melbourne? Shall update this thread along the way. Chris is a wonderful and very helpful gentlemen. 

 

Cheers,

Tom

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robmid   

Hi Tom.

 

The the impossibly realistic sound from new regulator and power board is quite extraordinary.

 

The only soldering is to connect your RCA input/outputs if you aren't getting the installed version and you will need to solder the pot and selector switch unless Chris is doing it for you.

 

All the other connections use screw terminal blocks. I have found them to be a bit fiddly but as long as you tug the connection to make sure it is firmly in place you will be ok.

 

If you get stuck, Chris will always help. He is totally dedicated the the StereoCoffee.

 

I'm located in QLD on the Sunshine Coast.

 

Cheers,

Rob

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robmid   

Chris and I have been exchanging notes on the NEW preamp. This is his personal assessment, not advertising jargon.

 
"I have been listening mainly to ECM discs, source is my Yamaha CDR HD1500 through a 306 Quad and JR149's and is as realistic as I have ever heard, like piano is perfect no stridency. so a slight improvement on the board you are presently using I am fairly sure, erring toward utter realism. 
I am certain it would put $15k preamps or nearly anything regardless of price to shame - and given it is a DIY kit
represents a massive bargain. 
 
I recall hearing a mcIntosh valve balanced preamp with a 10k price tag and it was way too reserved compared to this 
as though they had backed off all the electronics deliberately, to make it polite as, but in the process losing everything that is important in music."

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robmid   

The StereoCoffee is purely an attenuator with virtually nothing in the signal path, hence the purity of sound. Adding an active preamp would defeat the purpose of minimal components.

I run my Auralic Mini music server into a 150watt Holton power amp and LS50's which aren't very high sensitivity and full room volume is 50% on the gain control. 

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3 hours ago, robmid said:

The StereoCoffee is purely an attenuator with virtually nothing in the signal path, hence the purity of sound. Adding an active preamp would defeat the purpose of minimal components.

I run my Auralic Mini music server into a 150watt Holton power amp and LS50's which aren't very high sensitivity and full room volume is 50% on the gain control. 

 

Thanks for taking the time to answer 

Its just - that in the past I have tried Passive preamps and found " in my system" the volume is very soft to 50% on the dial and then we get some loudness 

P.S. - If you are visiting Brisbane anytime soon you are welcome to bring the little COffeeLDR unit for a test on my system 

 

I forgot to ask about a remote control for volume adjustment 

 

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2 hours ago, Full Range said:

 

Thanks for taking the time to answer 

Its just - that in the past I have tried Passive preamps and found " in my system" the volume is very soft to 50% on the dial and then we get some loudness 

P.S. - If you are visiting Brisbane anytime soon you are welcome to bring the little COffeeLDR unit for a test on my system 

 

I forgot to ask about a remote control for volume adjustment 

 

Nothing wrong with only getting loud at 50% (assuming that beyond that level it gets loud enough)

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robmid   

The SC has a gentle slope up to 25% to 50% (knob position) fills my room. Above that is too loud for my tastes with my Auralic Mini. LP's need a bit more cranking up on my system.

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What is the phone stage you use for turntable? Do you use MM or MC cartridge? Chris just emailed me on the progress of my unit. He has commented the improvements of the new regulator board as well. I am looking forward to listen to this unit in my system. 

 

Do we have to use a step-up transformer with this unit to connect turntable? 

 

Cheers,

Tom

 

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robmid   
5 minutes ago, singleendedamp said:

What is the phone stage you use for turntable? Do you use MM or MC cartridge? Chris just emailed me on the progress of my unit. He has commented the improvements of the new regulator board as well. I am looking forward to listen to this unit in my system. 

 

Do we have to use a step-up transformer with this unit to connect turntable? 

 

Cheers,

Tom

 

I'm just using the budget MX Shure with a Project preamp. Wait till you hear it. The original SC was really good but the latest one will make you wonder how the performance it possible. 

I am sitting hear right now listening to Spotify Premium and perhaps it's fractionally less detailed then audio files or CD's I find my jaw dropping in disbelief every time I press play. Hence, I tend to stay up too late frequently now.

My perception of 'low cost' sound has been shattered and I now realise that less components in the signal chain can and does give more accurate reproduction with quality speakers.

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I think I will give a coffeeLDR a go 

But will need a unit with more inputs and output 

 

I assume that I need to make contact to ask for any changes ?

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