LDR.V25 (the "V25") Preamp Controller

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tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #100 on: 12 Jul 2017, 06:42 pm »
Hi Morten!

I'm still having problems with the impedance adjustment and my DAC and power amp are quite picky so I would really like to be able to switch between all 5 settings. Setting 1-3 is no problem but setting 4 seems to "erase" itself after finishing autocal so it goes back to 99.
Any ideas?      :scratch:

Also, how come you advised me not to buy the internal PSU for my balanced configuration and now you are using it in the new amps or is it a different new PSU? http://www.audiocircle.com/index.php?topic=151395.0
 
Many thanks!
/ Simon

Hi Simon,

The issue with the impedance not sticking on #4 is a reported bug that's on the "to fix" list. A firmware update will take care of that once we get it resolved.

I advised against our internal PSU because I don't like to waste my customer's money on something they don't need or that I don't think will improve the performance of the preamp. We still use that PS in our LDRx and LDRxB models because that's how they were originally designed. When we eventually update/replace those models we won't be using that PS anymore and will be using an external 12 VDC wallwart instead. The V25 board is way less sensitive to power supply quality than the V2. There's a very specific reason for that because the V2 used the incoming power directly to drive a pair of op amps in the control circuit. The V25 has a 2 stage DC-DC converter with the 1st stage being a switch mode converter followed by a second stage linear regulator. A good $10-25 12V wallwart is all you need. Anything way better isn't likely going to give you better results.

Best,
Morten

TheMonkey

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #101 on: 12 Jul 2017, 06:52 pm »
Thanks a lot for a fast and good reply! You are the best!!  :thumb:
Good to hear that about the PSU, reassuring and thanks for not wasting our money on stuff we don't need!  :D

WC

Re: LDR.V25 (the "V25") Preamp Controller
« Reply #102 on: 16 Jul 2017, 01:59 am »
Morten,

Does the current firmware support Uart control for the V2.5?

tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #103 on: 16 Jul 2017, 02:17 am »
Morten,

Does the current firmware support Uart control for the V2.5?


Yes it does although I've not yet published the commands and have not really thought through possible issues interfacing with devices that aren't also at same 3.3V level as the V25 processor. UART is how 2 V25s communicate in balanced audio scenario. It's a very simple system. Runs at 115k baud, 1 stop bit, no parity.

WC

Re: LDR.V25 (the "V25") Preamp Controller
« Reply #104 on: 16 Jul 2017, 04:16 am »
The Arduino Due I was planning to use is a 3.3V Uart controller. So that is good.  :thumb:

So any idea when you are going to publish the commands? On the website it mentions available upon request.


tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #105 on: 16 Jul 2017, 12:26 pm »
The Arduino Due I was planning to use is a 3.3V Uart controller. So that is good.  :thumb:

So any idea when you are going to publish the commands? On the website it mentions available upon request.


I'll move up the priority on the To Do list.  :thumb:

WC

Re: LDR.V25 (the "V25") Preamp Controller
« Reply #106 on: 25 Aug 2017, 08:02 pm »
Hi Simon,

The issue with the impedance not sticking on #4 is a reported bug that's on the "to fix" list. A firmware update will take care of that once we get it resolved.

I advised against our internal PSU because I don't like to waste my customer's money on something they don't need or that I don't think will improve the performance of the preamp. We still use that PS in our LDRx and LDRxB models because that's how they were originally designed. When we eventually update/replace those models we won't be using that PS anymore and will be using an external 12 VDC wallwart instead. The V25 board is way less sensitive to power supply quality than the V2. There's a very specific reason for that because the V2 used the incoming power directly to drive a pair of op amps in the control circuit. The V25 has a 2 stage DC-DC converter with the 1st stage being a switch mode converter followed by a second stage linear regulator. A good $10-25 12V wallwart is all you need. Anything way better isn't likely going to give you better results.

Best,
Morten

So would a meanwell Switchmode PS like the IRM 12V work just fine. I was looking at using it to power the arduino and the V25 board(s), since neither seems to need a linear PS.

tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #107 on: 25 Aug 2017, 08:44 pm »
So would a meanwell Switchmode PS like the IRM 12V work just fine. I was looking at using it to power the arduino and the V25 board(s), since neither seems to need a linear PS.


For the V25 I think it would work fine. The output hits another switching DC-DC regulator on the board and then a linear regulator.  :thumb:

WC

Re: LDR.V25 (the "V25") Preamp Controller
« Reply #108 on: 3 Oct 2017, 02:12 pm »
Yes, with dual boards you can mix balanced and single-ended inputs.

It gets a bit messy to explain/show but with balanced signals the master board handles the + phase for both the right/left channels and similarly the slave board handles the - phase for both channels. This arrangement is necessary in order for the channel balance adjustment feature to work properly.

To add single-ended inputs you would would only connect inputs to the master board's right/left channels.

The output wiring follows the same approach as the inputs. When a balanced input is selected that attenuated signal would also be present on the RCA output jacks but only from a single phase so the volume would be reduced. When a single-ended input is selected the balanced output would have a signal present on only one phase.

V25 Balanced Wiring


V25 Single-Ended Wiring


I was thinking of this. Could I use the second slave board as a balanced board for 2-channel use and as a single ended for multichannel use? I would have a DAC and phono inputs for 2 channel input. Both could be balanced. I would have two multi-channel inputs which are only single ended for total of 6 channels. I would switch the outputs so that the right outputs get the correct signal to the amp and speaker.

tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #109 on: 3 Oct 2017, 09:07 pm »
I was thinking of this. Could I use the second slave board as a balanced board for 2-channel use and as a single ended for multichannel use? I would have a DAC and phono inputs for 2 channel input. Both could be balanced. I would have two multi-channel inputs which are only single ended for total of 6 channels. I would switch the outputs so that the right outputs get the correct signal to the amp and speaker.

I'm probably not clear on the specific arrangement you described but will try to answer your question this way:

1) With dual boards you essentially have 4 independent channels that in theory you can use any way your want in terms of mixed balanced and single ended but with the constraints/limitations discussed in 2) below.

2) When you adjust channel balance towards the right or left you are raising the volume of one channel on a board with respect to the other channel on that same board. Withe dual boards this happens to both boards the same way at the same time. With balanced signals if we wired both phases to just a single board and then adjusted the channel balance all you'd accomplish was raising one phase with respect to the other on both left and right stereo channels - resulting in no channel balacne shift. The reason the balanced wiring is the way it is is in order for the channel balance adjustment feature to work properly. If you didn't care about channel balanced adjustment you could wire both balanced phases to either board rather than splitting the phases between both boards  (as shown in the diagram).

WC

Re: LDR.V25 (the "V25") Preamp Controller
« Reply #110 on: 4 Oct 2017, 01:15 am »
I would run the positive phases to the master board and the negative phases to the slave board as a normal configuration for 2-channel. For multichannel, I would run single ended channels 1 and 2 on the master board, single ended channels 3 and 4 on the slave board. That seems possible based on what you said. Now I just have to switch the output signals so they go to right location.

tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #111 on: 4 Oct 2017, 01:34 am »
I would run the positive phases to the master board and the negative phases to the slave board as a normal configuration for 2-channel. For multichannel, I would run single ended channels 1 and 2 on the master board, single ended channels 3 and 4 on the slave board. That seems possible based on what you said. Now I just have to switch the output signals so they go to right location.


Yep, that should work!

WC

Re: LDR.V25 (the "V25") Preamp Controller
« Reply #112 on: 6 Oct 2017, 10:50 pm »
Can you stack the boards, if you are using multiple boards? If so, how much space is needed between boards?

tortugaranger

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Re: LDR.V25 (the "V25") Preamp Controller
« Reply #113 on: 8 Oct 2017, 11:39 am »
Can you stack the boards, if you are using multiple boards? If so, how much space is needed between boards?

I'm sure you can but having considered doing this myself I decided not to in order to ensure ease of access. I'd allow for 0.5 inch space below and 0.8 inch space above each board as a rough guide. The limiting item on the topside is the 5 V regulator with is about 0.75 inch tall. The bottom side has a 2x5 pin header used only for initial programming of the processor and also a pair of low profile relays active only during calibration. The version B of the V25 board in development will likely do away with both the relays and the pin header on the underside but that's not been verified yet.

P.S. Your board ships this week.