BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)

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H

Hans Polak

Member
Joined 2005
tvicol said:
Hans,

In fact Maya employs a very genuine logarithmic R-2R ladder network with constant output impedance. :)
Schematic is attached.

Regards,
Tibi
Click to expand...
This might be a bit of definition, but all resistors in a R-2R laddernetwork are having the ratio R : 2R per ladder.
See https://en.wikipedia.org/wiki/Resistor_ladder.

A logarithmic ladder has a slightly different setup, also referred to in the same WIKI page.
What you enable is a perfect logarithmic ladder, just as we need.

Hans
 
H

Hans Polak

Member
Joined 2005
With only 3 positive reactions so far, it is very unlikely that the quotation for 100 PCB´s will be met.
For that reason, Tibi suggest for those who are interested in using this remote control, to use subscribe to the group buy for the complete MAYA set.

http://www.diyaudio.com/forums/group-buys/289544-maya-r2r-advanced-volume-controller.html

There are no quantity limitations, so every order will be accepted.
The consequence of this solution is that you will receive the whole MAYA set, including the R-2R PCB and the softstart PCB which you won't need.
Tibi gave the following info on pricing:

Price is 189euro + 20%VAT if you live in EU, if you are outside EU there is no VAT for you, also if you have a business in EU and provide me EU VAT code than I can deduct VAT as well.
This include bluetooth module.
Display is OLED, blue 2 x 16 characters. The information is presented in Android application, front panel drawings, pcb dimensions, latest firmware, menu algorithm and other informations are available for download at http://vicol-audio.ro/maya.php
Shipping prices:
Europe EU €22.00 EUR
Europe Non EU €32.00 EUR
North America €38.00 EUR
Latin America €38.00 EUR
Asia €38.00 EUR
Africa €40.00 EUR
Oceania €44.00 EUR

Here are some pictures that Tibi sent me on how the dispay represents the information
View attachment 20160412_023.zip

Before I start designing the relay board with the 64dB logarithmic pot replacement for the BPPBP, I will wait and see whether there is any interest in this elegant solution .

Hans
 
H

Hans Polak

Member
Joined 2005
This is the concept circuit diagram to replace the analogue pot for a digital one.
Steering is performed from a MAYA CPU based remote controller with OLED display.

Realay Board.jpg

I have included one relay RE7, to replace switch S1 on the BPPBP, to enable switching between the two input channels through the remote control.

Is there anybody who would need a balance control, because this might be possible to be added in three steps as follows: L/R, +1dB/0dB, 0dB/0dB, 0dB/+1dB.
On the other hand, it will make the PCB bigger because of 2 extra relays. I have personally never felt the need for a balance control.

Hans
 
H

Hans Polak

Member
Joined 2005
I have finalised the PCB design.

3D.jpg

Dimension is 68 x 28 mm.
Flat cable from MAYA can be directly connected. This includes the 5V Power Supply.

On the back side of the PCB the connector should be positioned to replace the analoque pot.
The extra 2 pins on this connector called GND1 and GND2 are to be connected to the + inputs of the resp. output Op-Amp.
Connector J2 should be used to replace S1 on the BPPBP to enable switching between the two input channels with the remote.

The Gerbers are available for free.
I won't go into PCB production, but will support whoever needs it.

I skipped the balance option, because it will need a software update.

Hans
 
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P

prasanthgnath

Member
Joined 2015
Hi,

I was trying to use an e-bay remote volume control kit like the one below to use with the Bruno Preamp. It has a log pot with 50K Ohms. I was hoping to replace it with a linear 5K pot.

I am unable to find Alps motorized linear pots of 5k. Tried mouser.


Q1. If I use the log potentiometer itself (of 10K resistance), will that be OK.
Q2. I have already participated in the BP group buy project. If the above does not work, what is the simplest that I can do to have a remote volume control?


I couldn't find a motorized linear pot on Mouser.




Hot!! Digital led + 2 channel Remote Motor ALPS Volume Potentiometer Control 50KA Free shipping / tracking number-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
 
A

AndrewT

R.I.P.
Joined 2004
If I understood the Members who responded to my qustions, then the linear vol pot works because the current density through the vol pot track does not change.

It's this constant current density that allows the inverting amplifier to not create added distortion.

You will lose this if the vol pot is not linear.
 
H

Hans Polak

Member
Joined 2005
prasanthgnath said:
Hi,

I was trying to use an e-bay remote volume control kit like the one below to use with the Bruno Preamp. It has a log pot with 50K Ohms. I was hoping to replace it with a linear 5K pot.

I am unable to find Alps motorized linear pots of 5k. Tried mouser.


Q1. If I use the log potentiometer itself (of 10K resistance), will that be OK.
Q2. I have already participated in the BP group buy project. If the above does not work, what is the simplest that I can do to have a remote volume control?


I couldn't find a motorized linear pot on Mouser.
Click to expand...

I wouldn´t use the logarithmic part, but my advise would be to go for a 10K Linear pot.
You will have a tiny bit more noise, but this will be below hearing limit, since all the stages before the output stage are producing more noise ( 11nV/Sqrt.Hz versus 7.5nV/Sqrt.Hz with 10K in the worst position)

Looking on the internet I can find several linear motorized 10K pots on Ebay.

Succes
Hans
 
N

NATDBERG

Member
Joined 2006
I've a question..

I want to have a second variable output ("Tape out") for sending signal to an A/D converter with the perfect level set for maximum dynamic range utilised.

With two Bruno boards, what do people think would be the best way to do this keeping best sound quality?

My obvious answer would be to split the input after the input relay selector and simply send to both boards - would there be any problems with this splitting of the signal so simply like that; level problems, interference problems, impedence problems etc?

I'm sure most of the time I will be listening to the same thing as I'd be digitising so for now that is fine...
 
H

Hans Polak

Member
Joined 2005
There are several ways to achieve a second variable output with two BPPBP boards.
The most optimal seems to leave U1 and U6 from the second board, and to make 2 twisted pair connections from the 4 outputs of U1/U6 on the first board to the 4 nodes of R2/30 _ R7/34 and R13/40_R16/43 on the second board.
In that way you keep everything perfectly differential, without ground problems.

Alternative, if you have complete populated boards, instead of leaving U1 and U6 on the second board, you could take the same buffered outputs as above from the first board, and lead them to the input J1/J7 of the second board, in that case the two boards will remain completely intact.

Hans
 
N

NATDBERG

Member
Joined 2006
jan.didden said:
I assume you want the output of one board to go to your listening system and the other to the ADC, is that the plan?

In that case the only thing to check is that you now have half the input impedance to the boards (two boards instead of one).

If your source can handle that, no sweat.

Jan
Click to expand...

Yes that's the plan, thanks.

Because I will be using Enrico's 6-input switch, that's why I was thinking I'd steal the signal from after the input relay. So it will be a permanent halving of impedence over all inputs won't it.. I'm sure most things I use will be fine, only the Paradise phono stage and whatever cassette deck I'd be using to check out.

A quick think about it now, I guess I can make use of the twin inputs of the second board (for the A/D) and have input 1 as the split input from the main listening preamp and input 2 as an independent input (with it's own socket on the rear) but which is itself split, appearing as Input 6 on Enrico's input board.
 
N

NATDBERG

Member
Joined 2006
Hans Polak said:
There are several ways to achieve a second variable output with two BPPBP boards.
The most optimal seems to leave U1 and U6 from the second board, and to make 2 twisted pair connections from the 4 outputs of U1/U6 on the first board to the 4 nodes of R2/30 _ R7/34 and R13/40_R16/43 on the second board.
In that way you keep everything perfectly differential, without ground problems.

Alternative, if you have complete populated boards, instead of leaving U1 and U6 on the second board, you could take the same buffered outputs as above from the first board, and lead them to the input J1/J7 of the second board, in that case the two boards will remain completely intact.

Hans
Click to expand...

Thanks Hans. I'll have smd populated boards coming my way and a few completely unpopulated boards also from the recent GB. I shall check out the components you're refering to as I can't recall what they are off the top of my head.

EDIT - just checked which U1 and U6 were. OK, I get your gist. The first plan would be optimal but require me to keep the functionality of the whole simpler (nothing more than a dual variable output). And the second option would then allow me to switch inputs for the A/D preamp too should I want that independence (one of those things that may be a nice idea but is rarely used in practice).

Are U1 and U6 fine with (I presume) seeing half the impedence at their outputs?
 
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