LDR3x.V2 DIY Passive Preamp Controller Board w/ Remote

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tortugaranger

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #20 on: 31 Aug 2013, 05:48 pm »
Just a quick reminder that if you've been hesitating about ordering a LDR3x Passive Preamp Controller Board w/ Remote, the current sale on the LDR3x ends at midnight next Sunday (9.1.13).
Right now the LDR3x goes for $195 including remote ($295 for the balanced Master/Slave board combo).
Visit our website/store to find out more: http://www.tortugaaudio.com/product/ldr3x-diy-preamp-controller-board/

In light of the extended Labor Day weekend here in the US, we're extending the sale price for the LDR3x up until midnight this Monday, Sept 2nd.

Enjoy the weekend!
Morten

tortugaranger

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #21 on: 31 Aug 2013, 06:50 pm »
I was asked recently about running dual outputs from the LDR3x since we do provide dual outputs with out LDR1. I thought I'd also post my response here since it may be of broader interest.

____________________________
The dual outputs on the LDR1 are simply 2 outputs in parallel. They're not isolated from each other. I have several customers running their second output into subs. No problems reported.

For quite some time I ran an early prototype of the LDR1/6 into an active stereo crossover that fed into twin 3-channel LM4780 chip-amps configured in parallel (so 6 ~100 watt chip-amps). These tri-amps drove each of the 3 way GR OB7's that I built from scratch from the basic OB7 plans. I bought the drivers and sound proofing from GR but didn't use/build a passive crossover. In addition to feeding the chip-amps, I also split off left/right signals that went to a pair of Rythmik Servo Sub Amps/Drivers. As far as I could tell, the OB7s were not impacted by the signals going to the Rythmiks. I ran this setup both with and without the subs - no problem.

Just FYI, I've since moved on in the total opposite direction of DAC into LDR6 into monoblock LM4780 amps into 8.5 inch Audio Nirvana full range drivers in a plain vanilla vented box. Stopped using the subs and will probably put the OB7's and Rythmiks up for sale one day. I'm totally in the tank with the Audio Nirvana full range drivers. Love em.

I have other customers who are starting to play with 12V batteries and/or cleaner linear supplies. My working theory is it won't provide discernable improvements but that's just a theory. Very interested in getting feedback on the results.


JohnR

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #22 on: 2 Sep 2013, 12:39 am »
While you could go with a Master/Slave dual board balanced approach on the input to the follower, I agree that putting a single passive on the downstream end is both simpler and cleaner all around.

Thanks Morten. Sweet and simple it is then!  :thumb:

tortugaranger

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Getting an unbalanced out for a subwoofer from a balanced LDR3x
« Reply #23 on: 10 Sep 2013, 03:30 pm »
An LDR3x customer asked about getting an unbalanced out for a subwoofer from a balanced LDR3x setup.

It may help to first get a basic picture of what's going on with balanced audio. Below is a succinct overview taken from: http://www.ians-net.co.uk/articles/balanced_lines.php  I also recommend anyone working with balanced audio to consult with this excellent article by Rane: http://www.rane.com/note110.html
Quote
To remove noise from a signal we need some way of working out what is our wanted signal and what can be thrown away. Balanced lines achieve this by transmitting two versions of the signal down their length. The source equipment sends the normal signal down one conductor and a polarity-inverted signal down the other. This is usually done using either transformer-based or electronic output stages.

The cable itself is designed with the conductors having very similar impedances and twisted along their length so that any noise is picked up equally by both conductors, no matter where in the cable it occurs.

The receiving equipment has a transformer or electronic differential amplifier, and takes the inverted signal and returns it to it's correct polarity. At this point, the wanted signals on each conductor are both the same polarity, whereas any noise is of opposite polarity. Summing the signals from the two conductors together reinforces the wanted signal and cancels anything unwanted, leaving a recovered signal which is very close to the original. (this is known as Common Mode Rejection - i.e. any signal which is the same on both conductors is removed.)

Even balanced lines aren't perfect, though - slight differences in impedance, twisting or input gain will allow some noise to slip through. This isn't generally a problem unless you're using very long runs or working in areas of high interference.


There are 3 basic options for getting an unbalanced signal from an balanced output to feed a subwoofer.

1) Quick and dirty - Just take the + (non-inverted) signal together with the signal ground and send it to the subwoofer. The downside is you lose half the original signal amplitude but that may not matter with a sub. The other downside is you've defeated the noise rejection capability of using balanced signals so any noise picked up along the way will still be there.

2) Transformer - This is the BEST way to convert a balanced signal to an unbalanced signal. The downside is it's probably the most expensive. Jensen makes top notch transformers for this that run somewhere around $75-100 each. Figure 2 of these for stereo unbalanced outs - $$$.  EdCor makes far less costly transformers for this ($~25 for a stereo pair) but some would argue at a loss of performance relative to Jensens; maybe...maybe not.

Info on Jensen: http://www.jensen-transformers.com/datashts/11bmcf.pdf
Inf on EdCor: http://www.edcorusa.com/c/47/ttpcseriesmatchers

2) Differential Opamps - This is the second best way. Cheaper than Jensens but then again you'll need a split power supply for the opamps. A company called ThatCorp (love that name!) specializes in differential opamps for audio signal line drivers and receivers.

Info on ThatCorp: http://www.thatcorp.com/Balanced_Line_Receivers.shtml

thingfish

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #24 on: 13 Sep 2013, 11:34 pm »
Hi Morten
I would expect for a 3 input design that there be 6 series LDR's and 2 shunts, otherwise we are back to compromises with switches, electronic or relays, which correct me if I am wrong why LDR's are used in the first place, ideally wired directly to the RCA socket.

It appears impossible to have anything less than 8 LDR devices if you want purity of signal path with 3 inputs 

Perhaps some discussion or answer on this could be enlightening.

Cheers thingfish



tortugaranger

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #25 on: 14 Sep 2013, 01:24 pm »
Hi Morten
I would expect for a 3 input design that there be 6 series LDR's and 2 shunts, otherwise we are back to compromises with switches, electronic or relays, which correct me if I am wrong why LDR's are used in the first place, ideally wired directly to the RCA socket.

It appears impossible to have anything less than 8 LDR devices if you want purity of signal path with 3 inputs 

Perhaps some discussion or answer on this could be enlightening.

Cheers thingfish

I will sidestep the topic of "purity" since wading into that territory all too often becomes indistinguishable from a discussion about religion or politics.

As to using LDRs as analog switches in lieu of mechanical switches, I'm a big fan!  :thumb: When LDRs are "off" they are well north of 1M of resistance - off enough! When they are full "on" they can be in the range of 40-60R which is de minimis relative to the downstream attenuator impedance. Again, on enough!

Thus, LDRs can indeed be used for selecting from multiple audio inputs. The argument for doing so is the avoidance of yet another mechanical interface point (the relay) in the signal path, gold plated contacts etc. notwithstanding. In fact, we use LDRs precisely for this purpose in our 6-input LDR6 Passive Preamp component. Including the LDR input "switch", we end up with 2 LDRs in series (1 fixed, 1 variable) and 1 in shunt (variable) per channel - or 6 total per stereo input.

Customers building their own preamps using our LDR3x DIY Passive Preamp Controller Board are left to their own devices as to how to implement input device selection. The LDR3x provides current sink switching  to ground for up to 3 relays.....or LDR circuits. While we don't currently offer an input switching board, we are considering offering one in the future and it would indeed use LDRs in lieu of mechanical relays.

I would offer one caution in using LDRs as signal switches. For purposes of longevity, I don't recommend running them hard up against their LED current limit (20-25 ma in the case of the Advanced Photonix units we use) even though this yields the lowest "on" resistance. Better to back them off somewhat despite the slight rise in resistance. Still, commercial LEDs have a nominal lifetime expectancy of 50,000 hours. If you listened to music 5 hours a day, that's 10,000 days or 27 years....long enough I'd say!

As to why LDRs are used at all, my emphatic answer is because they are sonically superior in the signal path, i.e. they sound better! Better than pots, better than resistors, and by accounts from a growing number of our customers - better than transformer based volume controls.  :o

Cheers!
Morten


tortugaranger

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Mounting the IR Receiver to a front panel
« Reply #26 on: 18 Sep 2013, 12:51 pm »
Perhaps one of the bigger challenges to implementing your own passive preamp with the LDR3x is how to mount the IR receiver (assuming you don't mount it directly in the board but choose to mount it behind the front panel of your enclosure).

Mounting the IR receiver is inherently awkward. The good news is this Vishay receiver is very robust and doesn't need a perfect line of sight to the remote to work reasonably well. If you are able to cut a slot in your front panel roughly the width and height of the curved front of the receiver then you could simply glue it on to the back of the front panel. But cutting slots cleanly in metal isn't that that easy (doing a hack job of it is quite easy however!! ). The second approach is to drill out a round hole in your front panel -  try 50% the width of the receiver but no more than 100% the width. Then you'll need to glue a pair of standoffs (can be made from wood) on either side of the hole on the back side of the front panel. The depth of the standoffs need to be just a bit deeper than the depth of the receiver. Then, using either a pair of toothpicks or a piece of wood similar to the wooden stick/handle found in an ice cream bar, glue that on to the back of the receiver such that it overhangs enough to reach the standoffs. Then glue that assembly on to the standoffs.

The simple diagram below might help. It's a top view looking down on the edge of the front panel with the receiver mounted behind the drilled hole.





rklein

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #27 on: 18 Sep 2013, 02:14 pm »
I have read that the wooden stick from a Dove Ice Cream Bar has best damping qualities followed by Haagen-Dazs.  If you want Cheap & Cheerful I would recommend Good Humor or Popsicle Brands.  :wink:

Morten:

Thanks for posting this idea.  :thumb:

Regards,

Randy

tortugaranger

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #28 on: 18 Sep 2013, 02:29 pm »
I have read that the wooden stick from a Dove Ice Cream Bar has best damping qualities followed by Haagen-Dazs.  If you want Cheap & Cheerful I would recommend Good Humor or Popsicle Brands.  :wink:

I have it good authority that Dead Heads prefer Ben & Jerry's Peace Pop sticks for their IR Receiver backing plates. But personally, I go with the warmer smoother sound you get with Magnum's.  :icon_lol:




glynnw

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #29 on: 18 Sep 2013, 04:24 pm »
I mounted my board in a small metal case and drilled a hole in the face, gluing a red transparent piece of plastic behind the hole for cosmetic effect.  Using single strand stiff wire from the board to the leads of the infrared receiver, I am able to position the receiver wherever I wish and it stays there with no additional support, simply held in place by the stiff wire.  I'm not smart enough to have planned this, but I'll take lucky any day.

And I continue to be blown away by the sound quality.

WireNut

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #30 on: 18 Sep 2013, 05:22 pm »
I mounted my board in a small metal case and drilled a hole in the face, gluing a red transparent piece of plastic behind the hole for cosmetic effect.  Using single strand stiff wire from the board to the leads of the infrared receiver, I am able to position the receiver wherever I wish and it stays there with no additional support, simply held in place by the stiff wire.  I'm not smart enough to have planned this, but I'll take lucky any day.

And I continue to be blown away by the sound quality.

glynnw,

Send up some pics if you can.

 

glynnw

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #31 on: 18 Sep 2013, 07:20 pm »
I just posted some pictures under the Tortuga customer pictures thread.

gregfisk

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #32 on: 2 Oct 2013, 10:24 pm »
Morten, or anyone else that would like to chime in.

I purchased a kit and would like my preamp to have 3 inputs which I understand I need relays for. Could someone recommend a relay for this project? I'm in the alarm business and can get relays no problem, but not sure if they would be as good as something spec'd for audio.

Also, could someone recommend wire that I should use in building my passive pre?

Thanks,

Greg

tortugaranger

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #33 on: 5 Oct 2013, 01:23 pm »
Morten, or anyone else that would like to chime in.

I purchased a kit and would like my preamp to have 3 inputs which I understand I need relays for. Could someone recommend a relay for this project? I'm in the alarm business and can get relays no problem, but not sure if they would be as good as something spec'd for audio.

Also, could someone recommend wire that I should use in building my passive pre?

Thanks,

Greg

There's a huge number of excellent electromechanical relays to choose from. I would focus on quality small signal DPDT relays that are sealed with gold clad contacts. One example would be: http://www.mouser.com/ds/2/316/ds-catalog-27518.pdf but the choices are mind boggling:  http://www.mouser.com/Electromechanical/Relays/Low-Signal-Relays-PCB/_/N-5g38?P=1z0x3ypZ1z0x3tdZ1z0x3ysZ1z0x3ubZ1z0x3yuZ1yzrzc0Z1yzsm3fZ1yzrygbZ1z0z2xk  I know this doesn't help narrow things down.

tortugaranger

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Revised LDR3x Pricing
« Reply #34 on: 6 Oct 2013, 07:08 pm »
Just a heads up note that we revised the pricing/structure on our LDR3x. We decided to pull at pricing info in one location which is why the details aren't located here.

You can find the details in our Product Pricing & Specials topic which can be found here: http://www.audiocircle.com/index.php?topic=119842.msg1265348#msg1265348

gregfisk

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #35 on: 7 Oct 2013, 05:48 pm »
Morten, thanks for all the good info. regarding relays.

What do people use for wire inside amps and preamps when building them.

Can someone point me to some info. or a source for what gauge or type of wire is typical?

Thanks,

Greg

tortugaranger

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #36 on: 7 Oct 2013, 06:02 pm »
Morten, thanks for all the good info. regarding relays.

What do people use for wire inside amps and preamps when building them.

Can someone point me to some info. or a source for what gauge or type of wire is typical?

Thanks,

Greg

Wire is one of those topics that some people follow into strange places that I prefer not to go.  :roll:
That said, I've had excellent results using MilSpec Teflon coated silvered wire from www.wesbellwireandcable.com up in New Hampshire.  :thumb:

tortugaranger

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New LDR3x Review on DIYAudio
« Reply #37 on: 8 Oct 2013, 12:09 pm »
Check out this latest review that was posted on DIYAudio. The reviewer manages a French/Canadian DIY forum called QuebecDIY (all in French) but also posted his impressions on DIYAudio.

http://www.diyaudio.com/forums/vendors-bazaar/230114-tortuga-audio-ldr3x-diy-preamp-controller-w-remote.html#post3658377

tortugaranger

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Encoder board/assembly
« Reply #38 on: 2 Dec 2013, 02:11 pm »
We are now offering an encoder board/assembly for those DIY'ers who want to control their LDR3x preamp controller manually. Our encoder provides effectively all the same functionality as the remote.

Using the encoder board avoids the awkward soldering of multiple wires to the 5 tiny encoder pins.   :thumb:

It's priced at $23 which includes shipping via USPS Priority in the US. There's an additional shipping charge for international orders (best to order at the same time as the LDR3x board to avoid add'l shipping costs).

Over the next 30 days or so we'll also be introducing a 2 digit (8 segment) display module and a 3 input switching board.

Here's a link to the encoder page at the webstore: http://www.tortugaaudio.com/product/encoder-board/


rklein

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Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #39 on: 2 Dec 2013, 02:34 pm »
Quote
Wire is one of those topics that some people follow into strange places that I prefer not to go.  :roll:
That said, I've had excellent results using MilSpec Teflon coated silvered wire from www.wesbellwireandcable.com up in New Hampshire.  :thumb:

Hi Morten:

Which part number for the above mentioned Milspec wire...   M22759, M16878 or M27500 ?

Thanks,

Randy