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

Pass Labs This forum is dedicated to Pass Labs discussion.

The BA-3 as preamp build guide
The BA-3 as preamp build guide
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 3rd December 2018, 01:23 AM   #1251
Itsmee is offline Itsmee  England
diyAudio Member
 
Itsmee's Avatar
 
Join Date: Feb 2009
The BA-3 as preamp build guide
Quote:
Originally Posted by jphabc54 View Post
...Both amplifiers have safety and signal grounds bolted directly to the chassis at different points. No NTCs or other components in the ground plain...
Try lifting 0V from the chassis of the F5 first then the BA3, if the hum stops, install ground loop breakers.

Never disconnect the mains safety earth.
  Reply With Quote
Old 3rd December 2018, 01:54 AM   #1252
nashbap is offline nashbap  United States
diyAudio Member
 
Join Date: Jul 2012
Location: New Jersey USA
Also with units on, turn the transformer until you find the position of minimum hum.


nash
__________________
F5TV3, AVC, BA3b pre, Salas DCG3b, OBL-15
  Reply With Quote
Old 3rd December 2018, 03:08 AM   #1253
jphabc54 is offline jphabc54
diyAudio Member
 
Join Date: Mar 2018
Thanks — tried different combinations of removing 0 v from chassis. With 0v removed just in the F5, the hum is gone in one channel and significantly lower in the other. Don’t want to pollute this thread since it’s clearly not strictly a BA-3 issue! I’ll double check the signal chain in the channel that’s still humming. Still dead silent with no inputs on the F5.

Appreciate the tips as always!
  Reply With Quote
Old 3rd December 2018, 03:15 AM   #1254
bkdog is offline bkdog
diyAudio Member
 
Join Date: May 2005
Location: in a house
The BA-3 as preamp build guide
As I recall, this is a relatively common problem - an earth loop when the preamp is connected. My memory is poor, but I think I recall AndrewT providing a fairly thorough analysis of working through this in the F5 thread, probably a couple of years ago. Good luck!
  Reply With Quote
Old 3rd December 2018, 11:50 PM   #1255
Eric is offline Eric  United States
diyAudio Member
 
Eric's Avatar
 
Join Date: Nov 2000
Location: Central PA, USA
The BA-3 as preamp build guide
A few thoughts:

Connecting ground in different places can potentially cause problems. Try connecting them at the very same place. Alternatively, try inserting a CL-60 between PSU/Signal ground and AC Mains Earth point. Sometimes, a little resistance removes a problem. Another thought is to use one of the diodes from a bridge rectifier between PSU ground and Mains Earth. I've had some amps that needed a direct connection in order to prevent hum. Some needed a diode, others needed a CL-60 to remove hum. Experiment with different configurations.
__________________
My DIY Basement Theater, Aleph-X Amps, Avro Open Baffle Speakers, LDR based BA-3 pre, Pearl II, highly modded Technics SL-1200, F4, M2, Aleph-J, MoFo, a40, several ACAs, FHXL, Tang Band 1772 bass-reflex
  Reply With Quote
Old 4th December 2018, 01:38 AM   #1256
jphabc54 is offline jphabc54
diyAudio Member
 
Join Date: Mar 2018
Thanks -- in preparing both my BA-3 and F5 builds, I had overlooked the role of the CL-60 in the grounding scheme. I had mostly focused on the role of the CL-60 as an inrush current limiter in these designs, which I didn't feel I needed for the BA-3 and am using the DIY Audio Store Soft Start Board for in the F5. I hadn't thought through the fact that the design I was implementing would introduce a massive ground loop, mainly because I've never built a pre/power amp combo (the F5 is my first power amp after a half dozen or so preamp/headphone/phono stage builds).

I ordered a bunch of CL-60s today so I will start there -- lifting the BA-3 and/or F-5 grounds. Really appreciate you sharing that it can be a trial and error situation. I'm most concerned that the hum is so much more prevalent in one channel, but we'll see what happens. I'll report back once I'm able to try some options.
  Reply With Quote
Old 7th December 2018, 07:47 AM   #1257
MEPER is offline MEPER  Denmark
diyAudio Member
 
Join Date: Nov 2017
Location: Copenhagen
Is there a schematic somewhere which includes an e.g. 50k pot/attenuator for vol. control? …...I want to see how it interacts with R1 and R2.....just to be sure. I can probably see it from the way 6L6 wire it in the start of the thread but just to be 100% sure I do it right when time comes…….
  Reply With Quote
Old 7th December 2018, 11:48 AM   #1258
iluminator is offline iluminator
diyAudio Member
 
Join Date: Jun 2010
Default pictures

Hallo


I am building BA3FE as an I / V Ad1865 converter with 2sk170V and 2sj74V jfets current 14.5mA input impedance to sources of approximately 10.4 R
mosfety to irf610 irf 9610 with 150mA . I would like to show the scheme but I can not load photos
how to do it , please help
  Reply With Quote
Old 7th December 2018, 06:49 PM   #1259
MEPER is offline MEPER  Denmark
diyAudio Member
 
Join Date: Nov 2017
Location: Copenhagen
Is the attached schematic the right way to connect an e.g. 50k volumen pot to the BA-3 pre?

The 1k R1 is just there to protect the JFETs?

A 50k pot/attenuator is a good value for this amp?
Attached Images
File Type: jpg DSC_3686_00001.jpg (199.6 KB, 143 views)
  Reply With Quote
Old 7th December 2018, 11:06 PM   #1260
Itsmee is offline Itsmee  England
diyAudio Member
 
Itsmee's Avatar
 
Join Date: Feb 2009
The BA-3 as preamp build guide
MEPER, all good, go for it.

Quote:
Originally Posted by iluminator View Post
...I would like to show the scheme but I can not load photos...
Click the 'Go Advanced' button, at the top you will see a paper clip to the right of the smily face, click it; a new box will open, click 'Choose File' select whatever you want, then click 'Upload'.
  Reply With Quote

Reply


The BA-3 as preamp build guideHide 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
BA-3 As Preamp vdi_nenna Pass Labs 1322 16th July 2018 01:23 AM
MyRefC build guide AndrewT Chip Amps 1119 29th July 2016 11:30 PM
Trapezoid build guide? mudchute Planet 10 hifi 22 10th November 2014 10:37 AM
MY FIRST BUILD BA-1 joesch1999 Pass Labs 15 15th May 2011 09:54 PM
FS: two burning amps (one each BA-1 and BA-2) without drivers Eric Weitzman Swap Meet 15 17th February 2010 03:35 AM


New To Site? Need Help?

All times are GMT. The time now is 08:38 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki