A twisted tale about a logarithmic relay attenuator - Page 49

chalkandtalk · 1st March 2008, 06:04 PM

There is a buffer then the pot and then a gain stage.

As in the Naim 32.5 preamp.

chalkandtalk · 21st March 2008, 09:28 PM

I have built the JT and put it in my Naim style preamp. It sounds great. Many thanks Russ and Brian.

It's early days but it appears that quite a few aspects of the music are better: dynamics, bass for a start.

DFroehlich · 9th April 2008, 07:14 AM

Hi Russ,
will the Jshua Tree come back in stock in the next time ?

BrianDonegan · 9th April 2008, 12:18 PM

The Joshua Tree is being redesigned. We will post details when things firm up a bit.

Russ White · 9th April 2008, 01:26 PM

Quote:

Originally posted by DFroehlich
Hi Russ,
will the Jshua Tree come back in stock in the next time ?

It will not be long.

Joshua Tree has proven to be a solid design. So I will not change it much. Just adding some refinements and design changes necessitated by my new pluggable controller design.

I am actually working on it today, and should be ready to order the PCBs in the next week or so depending on how much time I can dedicate to it.

What I have in mind should allow for both the simple control mechanism of the current JT controller (just a pot) as well as more advanced configurations such as rotary encoder and/or IR control as well as display.

Also in the work is a simple I2C relay driver board that will allow you do you existing JT boards and even Darwin. So you will be able to create a full featured preamp with this controller scheme.

The nifty part is that the controller is designed to detach from the main application board (call it a motherboard if you will) and it will have a USB connector on it. So I can disconnect the controller from the application and simply plug it into the PC and reprogram it. This makes it possible to use the same little controller for lots of different projects.

It is not a trivial project. And it may be a bit complex for some users. I will do my best to document it. I will also have some example firmware for common applications.

Cheers!
Russ

robmil · 18th April 2008, 03:04 PM

Rob here

Can someone please explain what this attenuator 'looks like' electrically. I have attached a PDF of what my standard Alps in my preamp looks like 'electrically'... you all know it.

I know there are others here that would also like to know.

Thanks a billion.

R

Russ White · 18th April 2008, 03:07 PM

It looks like a series of LPADs. Each with the same output impedance so that the final output impedance is nearly constant.

Cheers!
Russ

robmil · 19th April 2008, 04:21 PM

What is an LPAD ?

cheers

Russ White · 19th April 2008, 04:27 PM

Simply put, it's a voltage divider.

MrMajestic · 23rd May 2008, 08:02 PM

Any updates on the new boards? I know you have a lot on your plates, but its not beginning of may anymore

9th April 2008, 07:14 AM	#483
DFroehlich diyAudio Member Join Date: Jan 2003 Location: Frankfurt / Germany	JT kit Hi Russ, will the Jshua Tree come back in stock in the next time ?

9th April 2008, 12:18 PM	#484
BrianDonegan diyAudio Member Join Date: Dec 2004 Location: Rock Ridge	The Joshua Tree is being redesigned. We will post details when things firm up a bit. __________________ Twisted Pear Audio

18th April 2008, 03:07 PM	#487
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	It looks like a series of LPADs. Each with the same output impedance so that the final output impedance is nearly constant. Cheers! Russ __________________ Less pulp more juice Twisted Pear Audio.

19th April 2008, 04:27 PM	#489
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	Simply put, it's a voltage divider. __________________ Less pulp more juice Twisted Pear Audio.

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1st March 2008, 06:04 PM	#481
chalkandtalk diyAudio Member Join Date: Jan 2006 Location: North west England	There is a buffer then the pot and then a gain stage. As in the Naim 32.5 preamp.

21st March 2008, 09:28 PM	#482
chalkandtalk diyAudio Member Join Date: Jan 2006 Location: North west England	I have built the JT and put it in my Naim style preamp. It sounds great. Many thanks Russ and Brian. It's early days but it appears that quite a few aspects of the music are better: dynamics, bass for a start.

19th April 2008, 04:21 PM	#488
robmil diyAudio Member Join Date: Jun 2004 Location: London	What is an LPAD ? cheers

23rd May 2008, 08:02 PM	#490
MrMajestic diyAudio Member Join Date: May 2007	Any updates on the new boards? I know you have a lot on your plates, but its not beginning of may anymore

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