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

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

DIY four preamps in one chassis, switch between three.
DIY four preamps in one chassis, switch between three.
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 6th April 2020, 08:29 PM   #1
triode3 is offline triode3  United States
diyAudio Member
 
Join Date: Dec 2010
Default DIY four preamps in one chassis, switch between three.

I will admit I also posted this over in another forum that is not really read any longer. I thought someone here might appreciate it as I do use the PASS buffer in it. Not sure it if goes in the SS or TUBE, as it uses both kinds. Ah well.



So a long time ago I purchased an ARC SP 6 chassis (empty other than the front panel PCB) with the idea that I would put a tube preamp in it. After realizing that I had a few tube preamps, I decided I always wanted to check out tube buffers against other buffers...

So, in this one ARC SP 6 chassis, I have the following preamps:


Pass Labs Jfet buffer kit
Boozhound labs phono preamp
Boozhound labs Jfet buffer

John Broskie (Tube Cad Journal) low voltage Tube Buffer with 12AU7s.

I have hooked it up so the user can switch between the three buffers with a front panel switch. The mode selector on the ARC was busted, so it was not used. The input selector has an issue that cropped up after build, but I ordered another one and for now I am using the direct input, which I wired up like the original ARC to bypass the input selector and mode switch. The volume pot is a simple Noble Blue Velvet job, nothing great.

It is very eye-opening to be able to switch between preamps. I thought at first the Pass and Booz should sound very similar. I used the same resistors and same capacitors (Vishay Dale RN and Mundorf Mcaps) for the Pass and Booz. On the Tube Cad I used the "recommended" caps which are CDE. On the power supply caps, all of them are Nichicon Muse or greater. All wire is super great 9-9s Canare or better cable. Output jacks are the same that ARC purchases which I purchased from Michael Percy audio.

The power supply is of my own design, regulated, with just a bit more filtering than Pass calls for. Although I design preamps and amps, I decided I really wanted to check out someone else's work side by side.

So, what does this sound like?

It surely blows away the NAD preamp that I resorted to after my Mark Levinson computer controlled stuff blew up and would cost a fortune to replace. I went and grabbed some ancient NAD preamp I had (first gen preamp, I think a 1020) and I have been using that for a few years now... so it is hard for me to compare this ARC-THING to high-fi. However, I would note the following, at least.

It is certainly much more wide open, deep and spacious than the NAD. I mean, looking at the cost and parts count for any one of the three, including the phono, it would surpass anything you could get on the market near that kind of price range. Pick the Boozhound, AND get all of them from boozhoundlabs. What is that, like $340 for phono, buffer and power supply with parts? Lets add a pot and switch for $60 from TubeCad, add $100 for a chassis/feet/connectors. $500. I did not do that, as I had most resistors and caps, but the average audiohead could do it for that price. I do not think you could get a preamp to match it for that price.

Interesting notes, at least to me on my system:

The TubeCad is forward. The soundstage is in front of the speakers. Bass is deeper, or more pronounced for sure, than the other two. It seems sweeter, like someone was using a generic SS and then you plugged in your old Dynaco and went "huh, get a load of this... hrm, now that I think about it, I could listen to this all day" That is what it feels like when I switch to TubeCad from the others. The tubes are RCA cleartop 12AU7s.

The pass was the most surprising to me. I have heard one bagillion dollar pass and I was blown away. This pass seems to put the soundstage behind the speakers. It is just as wide, but the bass seems anaemic. For some reason, the TubeCad can drive the amp with authority... the Pass seems to not have enough current, or something. It is very strange.

I though the Booz would be super close to the pass. Honestly, they are nearly the same design and the same circuit. Heck, they used the same matched jfets. The pass seems more accurate. The booz seems more listenable. Both of them put the soundstage behind the speakers. The booz seems to articulate the high end more than the pass. For some reason, when I switch to the pass, I feel like it is subdued, compared to the Booz or TubeCad. Switching to the TubeCad is a big "whoa". I have owned plenty of tube amps and preamps, but to be able to go "click", oh, here is a tube pre vs a solid state. Wow.... even though it is more forward, it seems deeper, more lush, certainly more bass.

When I get my new selector switch in, I will let it burn in more and listen again. Those are my preliminary notes, from a long time lurker.

The other parts of my system for this test was a Rotel amplifier and Snell Type E/III speakers. I also used some custom Focal driver bookshelf speakers to test. All cables are custom using Canare or Kimber cable and high end connectors from the usual sources. Input signals were from FLAC audio sources on my computer, through a custom DAC driving Kimber cable to the preamp.

Random notes:


On the pass I have off boarded the input selector and potentiometer.

On the entire preamp, grounds are isolated from power ground, and only connect together at one point.

It is dead silent, even when cranked, with no input applied.



I have attached two images, one is just the preamp boards on a plate. The other is of the boards stuffed into one chassis, the ARC SP6.
Attached Images
File Type: jpg preamp-mostlydone.jpg (1,010.2 KB, 155 views)
File Type: jpg three-pres.jpg (993.4 KB, 153 views)
  Reply With Quote
Old 6th April 2020, 08:57 PM   #2
rayma is online now rayma  United States
diyAudio Member
 
Join Date: Apr 2011
Do you switch the inputs also, or are they all permanently connected to the volume control?
  Reply With Quote
Old 6th April 2020, 10:31 PM   #3
triode3 is offline triode3  United States
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by rayma View Post
Do you switch the inputs also, or are they all permanently connected to the volume control?
The inputs are switched through the input selector. It grounds the unused inputs and only selects one at a time.


The three preamps are selected through another independent switch.


Signal flow is input jacks -> input selector -> vol pot -> preamp selector -> preamplifier (Papa, Booz or Brokskie) -> preamp selector -> output jack


Note, the input and output of the three preamps is switched. The phono preamp input is hardwired to the phono input jacks, but the phono preamp output is switched with the input selector like the rest of the intput jacks.

Last edited by triode3; 6th April 2020 at 10:33 PM.
  Reply With Quote
Old 6th April 2020, 10:32 PM   #4
UserAbuser is offline UserAbuser
diyAudio Member
 
Join Date: Sep 2019
Well since its a pre-amp...
Maybe the line level - pre-amp section would be more applicable.
Or maybe a shoe forum to discuss the shoe horn you used to cram all that in one case
  Reply With Quote
Old 6th April 2020, 10:43 PM   #5
triode3 is offline triode3  United States
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by rayma View Post
Do you switch the inputs also, or are they all permanently connected to the volume control?

The inputs are switched through the input selector. It grounds the unused inputs and only selects one at a time.



The three preamps are selected through another independent switch.



Signal flow is input jacks -> input selector -> vol pot -> preamp selector -> preamplifier (Papa, Booz or Brokskie) -> preamp selector -> output jack


Note, the input and output of the three preamps is switched. The phono preamp input is hardwired to the phono input jacks, but the phono preamp output is switched with the input selector like the rest of the intput jacks.
  Reply With Quote
Old 6th April 2020, 10:44 PM   #6
triode3 is offline triode3  United States
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by UserAbuser View Post
Well since its a pre-amp...
Maybe the line level - pre-amp section would be more applicable.
Or maybe a shoe forum to discuss the shoe horn you used to cram all that in one case
Ah shoot, that is a good suggestion.



I wonder if the mods would move it for me, or if I could move it. Delete and repost seems unnecessary.
  Reply to this post

Reply


DIY four preamps in one chassis, switch between three.Hide 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
FS: 2x Soekris DAM1021, Switch Board, LT3042 PSU, RPI, Chassis matt_garman Swap Meet 8 3rd September 2019 03:03 PM
Recommendations on front switch for 4U deluxe chassis javaught Parts 2 6th August 2018 04:18 PM
Tube Amp Chassis New with Power Switch, IEC, Fuseholder, Feet tomlang Swap Meet 0 3rd March 2016 02:18 PM
Rotary front panel power switch for 4U chassis bjorgens Pass Labs 5 8th April 2014 02:47 AM
Sanyo JCX2900KR - very special Main Switch - Solution without Switch wanted tiefbassuebertr Solid State 1 15th February 2012 03:38 AM


New To Site? Need Help?

All times are GMT. The time now is 02:25 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki