Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Group Buys Members group buys

Versatile and comfortable passive pre-amp
Versatile and comfortable passive pre-amp
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th March 2014, 09:16 PM   #661
Gooniman is offline Gooniman  United States
diyAudio Member
 
Join Date: Jan 2012
Location: Dallas Texas
Really nice. I already have Subbu dac..This is made to order. I would like one, as well.
  Reply With Quote
Old 4th March 2014, 11:15 PM   #662
Howlindawg is offline Howlindawg  Ireland
diyAudio Member
 
Howlindawg's Avatar
 
Join Date: Apr 2009
Location: Dublin, Ireland
I'm watching this latest version develop with keen interest.
  Reply With Quote
Old 5th March 2014, 11:00 PM   #663
Kris0603 is offline Kris0603  Sweden
diyAudio Member
 
Join Date: Jul 2004
Location: Sthlm
Quote:
Originally Posted by Rudi_Ratlos View Post
TUO: my passive Pre-Amplifier is able to connect to (to choose between) five - music-sources (by means of the 5 relays on top of the PCB).
Was switching sources using LDR's ever considered? In this fashion the inputs each see their own LDR, and only one is activated at a time to let signal through(and attenuate at the same time).

I'm starting to put together a plan for a dac/pre combo and i'm leaning towards this solution, but i do need a way to switch digital sources into my JP/Subbu DAC, so i'm actively looking for solutions.
  Reply With Quote
Old 6th March 2014, 09:05 AM   #664
Rudi_Ratlos is offline Rudi_Ratlos  Germany
diyAudio Member
 
Rudi_Ratlos's Avatar
 
Join Date: Jun 2009
Location: Hamburg / Germany
yacuza: I have never considered LDRs to replace a relay.
It is already a hard job to find matched LDRs to do the attenuation of the selected signal, and I do not like to make it even more complicated.

I have some problems currently "marrying" the new version of the VCPre with the line buffer.
On the oscilloscope, with no amp connected, the output of the line buffer looks fine, but when I connect it to an amplifier, the music sounds "distorted".

I suspect my very cheap 7818/7918 line-buffer-PSU to be the reason for the distortion and have to wait for the delivery of a more "sophisticated" PSU.

Best regards - Rudi_Ratlos
  Reply With Quote
Old 6th March 2014, 12:04 PM   #665
Rudi_Ratlos is offline Rudi_Ratlos  Germany
diyAudio Member
 
Rudi_Ratlos's Avatar
 
Join Date: Jun 2009
Location: Hamburg / Germany
Gentlemen: please do not misunderstand my last post!
The VCPre itself does a very, very good job - provides the best attenuation that I have ever heard!

The implemented line-buffer is a gem as well, as I have been reported by many of my German DIY-friends!
So it must be due to the poor design of my line-buffer's PSU (+/-18VDC) that the marriage of the two of them does not sound as it shall!

Best regards - Rudi_Ratlos
  Reply With Quote
Old 7th March 2014, 12:58 AM   #666
wirewiggler is offline wirewiggler  United States
diyAudio Member
 
Join Date: Mar 2005
Location: Bakersfield Ca
Rudi,
My VCpre is sounding pretty good, I went with the modified JBIS for the gain. I used Owen's wire power supply board. It is a little overkill but is a nice design that is available, Granted some smt soldering but nothing as small as your regulator.

http://www.diyaudio.com/forums/vendo...-se-lpuhp.html

Many thanks for a great preamp.

Bill
  Reply With Quote
Old 7th March 2014, 11:27 AM   #667
atupi is offline atupi  Romania
diyAudio Member
 
Join Date: Oct 2010
Location: Bucharest
Rudi what buffer you will use, if is not confidential of course ?
  Reply With Quote
Old 8th March 2014, 11:35 PM   #668
wineds is offline wineds  Australia
diyAudio Member
 
Join Date: Apr 2006
Location: Melbourne
Quote:
Originally Posted by Rudi_Ratlos View Post
Gentlemen: please do not misunderstand my last post!
The VCPre itself does a very, very good job - provides the best attenuation that I have ever heard!

The implemented line-buffer is a gem as well, as I have been reported by many of my German DIY-friends!
So it must be due to the poor design of my line-buffer's PSU (+/-18VDC) that the marriage of the two of them does not sound as it shall!

Best regards - Rudi_Ratlos
Rudi, I recommend you try this power supply :

Scalable PSU/regulator GB

Many years ago when I built an active pre I tried numerous power supplies. This one was by far the standout. Compared to 3 terminal regulators the difference was night and day. Maybe Jens or Bob will give you permission to use it.

Last edited by wineds; 9th March 2014 at 12:04 AM.
  Reply With Quote
Old 13th March 2014, 04:20 PM   #669
Rudi_Ratlos is offline Rudi_Ratlos  Germany
diyAudio Member
 
Rudi_Ratlos's Avatar
 
Join Date: Jun 2009
Location: Hamburg / Germany
Gentlemen, I have connected a Version -1 VCPre to the Calvin-Buffer prototype and measured and listened to it!

Click the image to open in full size.
http://abload.de/img/ldr005k6qri.jpg

It worked as designed and sounded delicious (even using a 7818 / 7918 PSU)!

Then I ordered one piece of the "All-in-One" (VCPre and Buffer on the same PCB as shown in post #637)) prototype PCB.
I soldered the PCB, it did not work, I managed to find the error (in the interface between VCPre and buffer - I have mixed input and output tracks), but was unable to fix the issue.

I will therefore not offer the "All-in-One" PCB.

On the one hand: it is very (too) complex to troubleshoot, in case you made an error, on the other hand: if you are going to build an integrated amplifier that has a suffienctly high input impedance (>20K, f.e. the SYMASYM),
you do not need a buffer at all.

I will instead offer two distinct PCBs (see the attached images):

- Buffer (the PCB-size is 50x60mm)
This is a Stereo-Buffer based on Calvin's buffer and has a 3 - connector - interface: Power, 2-channel Input and 2-channel Output

- Passive Pre-Amplifier (the PCB size is 100 x 80mm)
It is equipped with LDR-attenuation, LCD-interface, 5 source input selection, mute, SoftPowerOn interface, ..., everything can be remotely controlled

I will order 10 pcs of each of the PCBs this weekend - and restart again.
I am quite sure that everything will work this time.

As PowerSupply I will use LM317 / LM337 circuits (already ordered), but I do have an eye on building a PowerSupply based on TI's TPS7A - regulators as well (even on WINEDS's recommendation).

I will keep you informed.
This is DIY.

Best regards - Rudi_Ratlos
Attached Images
File Type: png Buffer.PNG (146.4 KB, 315 views)
File Type: png R-Pre.PNG (167.4 KB, 307 views)
  Reply With Quote
Old 15th March 2014, 01:09 PM   #670
Rudi_Ratlos is offline Rudi_Ratlos  Germany
diyAudio Member
 
Rudi_Ratlos's Avatar
 
Join Date: Jun 2009
Location: Hamburg / Germany
Gentlemen, I will give my R-Pre- and Buffer - PowerSupply the best available transformer and received it today.

Best regards - Rudi
Attached Images
File Type: jpg R-SYM_Transformer 001.jpg (217.3 KB, 226 views)
  Reply With Quote

Reply


Versatile and comfortable passive pre-ampHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Designing a versatile pre with balanced and unbalanced in/out Nikon1975 Analog Line Level 56 28th December 2012 11:56 PM
Passive pre-amp Davy Solid State 20 25th August 2008 10:11 PM
Is this possible from a passive pre-amp? mr.duck Everything Else 7 3rd December 2006 12:57 PM
passive pre amp mschwilson Solid State 10 27th July 2005 02:43 PM
Passive pre amp vs powered pre amp fatmarley Solid State 21 21st November 2003 03:01 PM


New To Site? Need Help?

All times are GMT. The time now is 02:10 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki