4 Channel Downstream Analog Preamp

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OCD

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4 Channel Downstream Analog Preamp
« on: 23 Oct 2017, 05:28 am »
Hi,

Not sure where this post should go but here goes....

Is there any news on a 4 Channel Downstream Analog Preamp as mentioned in the below article?

I have a miniDSP 2x4HD that would slip in front of a 4 channel pre very nicely...:)......(like the 2nd last diagram in the article)

https://www.tortugaaudio.com/articles/case-active-dsp-crossovers/

Thanks in advance

WC

Re: 4 Channel Downstream Analog Preamp
« Reply #1 on: 23 Oct 2017, 03:50 pm »
If you are into DIY, you could make one. Tortuga makes building your own easy, but they don't have a 4 channel one to sell.

OCD

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Re: 4 Channel Downstream Analog Preamp
« Reply #2 on: 25 Oct 2017, 03:12 am »
If you are into DIY, you could make one. Tortuga makes building your own easy, but they don't have a 4 channel one to sell.

Which is why I asked the question....sell a 4 channel that can be slaved to each other or even better/easier an 8 channel for multi-channel systems.

EG: miniDSP nanoAVR HDA / LDR3.V25 Passive Preamplifier / Amplifiers.......job done.

Cheers

Mr Peabody

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Re: 4 Channel Downstream Analog Preamp
« Reply #3 on: 27 Oct 2017, 03:58 am »
If you are just asking for this brand ignore this post.

Both McCormack & Conrad Johnson made 5-channel analog preamps, both no longer produced, so I'm assuming not widely accepted although a good idea for those who put sound quality first.  I'm not sure what they go for used if you could find one.  I believe the CJ model was MET.

The older A/V preamps with multichannel analog inputs could be another option, using the analog in would bypass all the difital & video stuff.  Older Krell, Primare etc. without HDMi and later features are going cheap and a good deal for someone wanting a quality preamp.  Maybe not as good as a current $5k preamp but a lot better than most you'll find for $500 or so, what you can find these used for.

jk@home

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Re: 4 Channel Downstream Analog Preamp
« Reply #4 on: 27 Oct 2017, 12:37 pm »
I use a (now discontinued) Nuforce MCP-18 for the same type setup. The higher quality L/R channels to my main speakers, the other channels to subs. MiniDSP NanoDIGI as the crossover.

artur9

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Re: 4 Channel Downstream Analog Preamp
« Reply #5 on: 27 Oct 2017, 01:05 pm »
An older Cary Audio Cinema 11 might also fit the bill.  Loved the sound of mine.

tortugaranger

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Re: 4 Channel Downstream Analog Preamp
« Reply #6 on: 29 Oct 2017, 07:30 pm »
Hi,

Not sure where this post should go but here goes....

Is there any news on a 4 Channel Downstream Analog Preamp as mentioned in the below article?

I have a miniDSP 2x4HD that would slip in front of a 4 channel pre very nicely... :) ......(like the 2nd last diagram in the article)

https://www.tortugaaudio.com/articles/case-active-dsp-crossovers/

Thanks in advance

Apologies for the late reply on this but have been off on a little vacay/travel.

I've not made a decision on whether to offer this option yet for the simple reason I've no idea of the demand. I also have a 2x4HD that I use in my main personal rig and I do want to test this out. I'm sure it will work just fine but have yet to do it.

This 4 channel arrangement would essentially be the same internally as our LDR1B.V25 which is a 4 channel balanced attenuator.  The rear panel would have to accommodate 4 RCA inputs and 4 RCA outputs which is doable with current enclosure form factor and available panel real estate but would need a new rear panel design. Could not handle a balanced version within current enclosure becasue it would require 8 internal channels (twice the boards/hardware etc.) which simply would not fit.

As someone pointed out, if you're willing to go DIY your could adapt our LDR1B.V25K balanced preamp kit with a different custom rear panel that you'd have to source yourself plus RCA jacks. If you're willing to accept a bare aluminum 4 channel RCA rear panel (no brushing, anodizing or labels) I could fabricate one for a $100 adder.

Cheers,
Morten

OCD

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Re: 4 Channel Downstream Analog Preamp
« Reply #7 on: 1 Nov 2017, 02:07 am »
Apologies for the late reply on this but have been off on a little vacay/travel.

I've not made a decision on whether to offer this option yet for the simple reason I've no idea of the demand. I also have a 2x4HD that I use in my main personal rig and I do want to test this out. I'm sure it will work just fine but have yet to do it.

This 4 channel arrangement would essentially be the same internally as our LDR1B.V25 which is a 4 channel balanced attenuator.  The rear panel would have to accommodate 4 RCA inputs and 4 RCA outputs which is doable with current enclosure form factor and available panel real estate but would need a new rear panel design. Could not handle a balanced version within current enclosure becasue it would require 8 internal channels (twice the boards/hardware etc.) which simply would not fit.

As someone pointed out, if you're willing to go DIY your could adapt our LDR1B.V25K balanced preamp kit with a different custom rear panel that you'd have to source yourself plus RCA jacks. If you're willing to accept a bare aluminum 4 channel RCA rear panel (no brushing, anodizing or labels) I could fabricate one for a $100 adder.

Cheers,
Morten

Thanks for the reply Morten,

No apology needed, hope you got some rest.

Re enclosure: would purchase preamp in kit form and supply my own enclosure and assemble myself, more than likely a rack enclosure as its going in a rack, doesn't have to look pretty, but neat and tidy would be nice and most importantly it has to work.

What you propose could work. However it would be going into a 5.2 channel system, so I would still need an extra input(L+R) from the surround processor, so potentially a 2nd V25 board.

However correct me if I'm wrong, from what I can see the V25 board has 4 outputs(2 pairs)? If you could have minimum 3 inputs(or as many inputs as you care to offer), input 1(lets say used for sub channels from 2x4HD) is 'assigned' to output 1 and is always 'on'. Then input 2 and 3(or other inputs) are switchable to output 2. For level volume control everytime you switch between inputs 2 and 3(or others) the volume automatically goes to 35(or 50% as talked about in this thread....http://www.audiocircle.com/index.php?topic=120337.0 ) on ALL inputs, which is what I think already happens? and then to get the 'HT bypass' affect you have to(using the remote) put the volume upto full?

Is that possible? If you need a little diagram let me know.

Regards,

Mitch








WC

Re: 4 Channel Downstream Analog Preamp
« Reply #8 on: 1 Nov 2017, 03:40 am »
Each Board has from 1 to 6 inputs per channel which can be switched. So 2 channels single ended per board. It also has 2 outputs per channel on each board, but they are not switchable and have the same signal. If you want to use it with a miniDSP 2x4HD use 2 boards to with 2 channels each for a total of 4 channels to vary the volume. So it would be Source>MiniDSP>Tortuga>Amps. So the miniDSP would be input 1 on both boards. If you have another source, such as your HT surround processor you can use another input on the Tortuga, but It would be directed to the same outputs as the miniDSP. Not sure if that would work it your situation.

OCD

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Re: 4 Channel Downstream Analog Preamp
« Reply #9 on: 1 Nov 2017, 04:32 am »
Each Board has from 1 to 6 inputs per channel which can be switched. So 2 channels single ended per board. It also has 2 outputs per channel on each board, but they are not switchable and have the same signal. If you want to use it with a miniDSP 2x4HD use 2 boards to with 2 channels each for a total of 4 channels to vary the volume. So it would be Source>MiniDSP>Tortuga>Amps. So the miniDSP would be input 1 on both boards. If you have another source, such as your HT surround processor you can use another input on the Tortuga, but It would be directed to the same outputs as the miniDSP. Not sure if that would work it your situation.

Yes understood, but using 2 boards(unless going balanced, which I'm not) is overkill and more $$ when one board could do it, it seems. Just needs to be implemented.

 

tortugaranger

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Re: 4 Channel Downstream Analog Preamp
« Reply #10 on: 1 Nov 2017, 02:31 pm »
Yes understood, but using 2 boards(unless going balanced, which I'm not) is overkill and more $$ when one board could do it, it seems. Just needs to be implemented.

Perhaps there's a basic misunderstanding of channels vs. inputs. Each V25 board can handle only 2 channels of audio input with corresponding 2 channels of output. Those 2 channels can be whatever you want them to be. The left/right channels of single-ended stereo or the plus/minus phases of one side (left or right) of a balanced system are the two most common examples. If your goal is a 5.2 system that's 7 total channels (7 attenuators) which would require 4 V25 boards (7 channels plus 1 unused). In such a multi-channel setup you would also have the possibility of switching between up to 6 different input sources per channel.

True, it's possible to design a variation on the V25 with more than 2 channels. A 4 channel version would be the most likely - more ideal for balanced audio. There may be some economies of scale in doing so but I question whether the market demand would justify the development time/focus.

What's is more likely to happen first is a Rev B of the V25 board that substantially shrinks both its size and parts count....and thus its cost.

OCD

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Re: 4 Channel Downstream Analog Preamp
« Reply #11 on: 2 Nov 2017, 12:14 am »
Perhaps there's a basic misunderstanding of channels vs. inputs. Each V25 board can handle only 2 channels of audio input with corresponding 2 channels of output. Those 2 channels can be whatever you want them to be. The left/right channels of single-ended stereo or the plus/minus phases of one side (left or right) of a balanced system are the two most common examples. If your goal is a 5.2 system that's 7 total channels (7 attenuators) which would require 4 V25 boards (7 channels plus 1 unused). In such a multi-channel setup you would also have the possibility of switching between up to 6 different input sources per channel.

True, it's possible to design a variation on the V25 with more than 2 channels. A 4 channel version would be the most likely - more ideal for balanced audio. There may be some economies of scale in doing so but I question whether the market demand would justify the development time/focus.

What's is more likely to happen first is a Rev B of the V25 board that substantially shrinks both its size and parts count....and thus its cost.

Thanks for the clarification.

Below is what I'm trying to achieve, 2 boards would be required if Im following you right.

What I would need is for input/output 1 to remain 'on' and switch between input 2 & 3, but I'm thinking if I switch between input 2 & 3, input 1 will go 'off' in a master/slave setup, is that correct?

How would I stop that from happening if correct?

Please excuse my crappy drawing :lol:





WC

Re: 4 Channel Downstream Analog Preamp
« Reply #12 on: 2 Nov 2017, 01:52 am »
Looks like you need two boards to do what you want. 2 boards with two inputs each. Input 1 on both boards is your L and R mains. Input 2 is your Subs (split the signal in the preamp to go to both boards). Input 2 is run full scale and the AV processor controls volume. Input is Volume controlled by the V25 board.

OCD

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Re: 4 Channel Downstream Analog Preamp
« Reply #13 on: 2 Nov 2017, 04:28 am »
Looks like you need two boards to do what you want. 2 boards with two inputs each. Input 1 on both boards is your L and R mains. Input 2 is your Subs (split the signal in the preamp to go to both boards). Input 2 is run full scale and the AV processor controls volume. Input is Volume controlled by the V25 board.

can you sketch that out for me? I'm not getting it :oops:

I think I would need 3 boards if run as master/slave, as Morten said it's 2 channels in 2 channels out, and I have 6 channels coming in, and 4 out, so I could combine the L & R of 2 of the boards at the RCA output of the enclosure to get down to 4 outputs.. Thats the only way I can see it happening, or I combine the L & R of the DAC and the surround processor before input 1 of board 2. I dont think thats ideal.
 

OCD

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Re: 4 Channel Downstream Analog Preamp
« Reply #14 on: 2 Nov 2017, 06:22 am »



Would this work?

board 1 = L & R from DAC to Input 1
               L & R from Processor to Input 2

board 2 = From RCA in on enclosure, split L & R sub channels 4 ways, L & R into input 1 and L & R into input 2

Thoughts?
« Last Edit: 2 Nov 2017, 07:41 am by OCD »

WC

Re: 4 Channel Downstream Analog Preamp
« Reply #15 on: 2 Nov 2017, 11:38 am »
That should work.

tortugaranger

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Re: 4 Channel Downstream Analog Preamp
« Reply #16 on: 2 Nov 2017, 02:08 pm »
That should work.

I agree.

This would allow you to switch between L&R coming from either the processor directly or through the miniDSP. As you switch between those the same sub-L&R signal would be selected. You'd use 2 inputs on both boards. On the sub-board the same signals would be connected to both inputs.