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

The diyAudio Store A forum for discussing anything about the products available in The diyAudio Store.

Amp Camp Amp Kit V1.6
Amp Camp Amp Kit V1.6
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 25th May 2019, 05:15 PM   #521
wg45 is offline wg45  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Portland, OR
I recently purchased a second ACA 1.6 to run a monoblock pair. I built the second amp with a modified build to better match my low impedance speakers.

R11=20k
R12=90.9k
C1=4700uf
C2= 1000uf
C4= 100uf
R4=.50k

The second amp with the mods sounds great. When I used both amps as monoblocks (1st one original spec, 2nd one modded, parallel rca) the second was louder and seemed like it had more gain. I had to use the balance knob to even out the sound. I figured the second amp did have more gain due to the mods and I just needed to update the 1st original amp to match the 2nd.

I used the extra set of mod parts I ordered and updated the 1st amp. And it still has less gain than the 2nd amp. Iíve compared the two amps and canít see any differences in parts or wiring. ( attached is a pic of the modded 1st amp board).

Any thoughts where to start?
Attached Images
File Type: jpg 7FEBE938-B792-404D-BA98-958BEAC5E40B.jpg (651.2 KB, 194 views)
  Reply With Quote
Old 25th May 2019, 07:19 PM   #522
RafaPolit is offline RafaPolit  Ecuador
diyAudio Member
 
RafaPolit's Avatar
 
Join Date: Dec 2016
Location: Quito, Ecuador
If you feed a fixed input signal to both amps, do you measure the same output? Or does measurements follow what you are hearing?

Could this be just speaker placement / room reflections?
  Reply With Quote
Old 26th May 2019, 04:53 PM   #523
wg45 is offline wg45  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Portland, OR
Quote:
Originally Posted by RafaPolit View Post
If you feed a fixed input signal to both amps, do you measure the same output? Or does measurements follow what you are hearing?

Could this be just speaker placement / room reflections?
I donít think so.

When I noticed the difference in volume, I disconnected the amps and switched the amps to the opposite channel. I figured it was the easiest way to eliminate the room, cables, source and preamp. I found the same issue: my first amp wasnít playing as loud as the second amp, no matter what channel it was driving.

When I play the first amp only, that amp driving both channels, it sounds good. No odd sounds, no missing sounds, no hum.... When I play he second amp only, itís sound great. More dynamic, more interesting.

Some of that or most of it might just be the difference in gain. I donít have a golden ear, so itís hard to hear subtle differences.
  Reply With Quote
Old 27th May 2019, 11:56 AM   #524
Alan4411 is offline Alan4411  Wales
diyAudio Member
 
Alan4411's Avatar
 
Join Date: Oct 2011
Location: West Wales
A few questions,
Are both the PSUs 24 volt units? Have you swapped them round?
Are both the amplifier 'modules' in the quieter side working correctly? I.e. are they both as loud as each other if you do not use them in mono-block mode.
Have you used 'bridge' or parallel mode for the mono-blocks?
  Reply With Quote
Old 27th May 2019, 04:32 PM   #525
wg45 is offline wg45  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Portland, OR
Quote:
Originally Posted by Alan4411 View Post
A few questions,
Are both the PSUs 24 volt units? Have you swapped them round?
Are both the amplifier 'modules' in the quieter side working correctly? I.e. are they both as loud as each other if you do not use them in mono-block mode.
Have you used 'bridge' or parallel mode for the mono-blocks?
Thanks for the help.

Yes, both PSUs are 24 volt and I left each one with a channel as I swapped the amps. The lower volume signal followed the first amp.

If I compare the two amps when one amp is driving both channels, playing the same music with the same preamp settings, Iíd say he first amp is quieter than the second. Both channels on the first amp play and thereís no difference in volume between the two channels, though.

Iíve only played them as monoblocks using the bridged monoblock RCA input from the build guide. Iím not sure if that is parallel mode.

I do have a balanced preamp and I ordered XLR cables, due to arrive this week. Iíll try them with the bridged monoblock XLR input next.
  Reply With Quote
Old 11th June 2019, 07:59 PM   #526
wg45 is offline wg45  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Portland, OR
Update- I re-biased the amps and set up them up as bridged monoblocks using balanced connections to my preamp. Everything seems to be working well and each channel seems correct.

The overall system sounds great. It's a noticeable improvement over running a single ACA with single ended connections. It's worth the time and investment.

Thanks to Papa for the ACA and TungstenAudio for the ACA mods.
  Reply With Quote
Old 16th June 2019, 03:18 AM   #527
Azookey is offline Azookey  United States
diyAudio Member
 
Join Date: Jul 2018
Has anyone compared the single ended monoblocks vs the balanced monoblocks sound wise? Should they be identical?

Also I still can’t wrap my head around how the single ended monoblock works. With balanced inputs, one channel is inverted, but singleended you don’t have that inverted channel? How is it doing the same amplification? Is that one resistor flipping the signal?

Thanks
  Reply With Quote
Old 16th June 2019, 01:52 PM   #528
6L6 is online now 6L6  United States
diyAudio Moderator
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Amp Camp Amp Kit V1.6
The resistor isn't inverting the signal, the first side of the amplifier is. The resistor just connects one channel to the other.

Signal goes into the left side, is amplifier and inverted. Speaker output black is connected to this speaker post. Resistor takes that inverted signal, feeds it to the other amp board (right) and the signal is amplified and inverted again (making the phase positive) and the speaker output red is connected there. The speaker posts are 180deg out of phase with each other, which is precisely what balanced bridged is.

With XLR, the connection between the 2 boards never happens at the output (I.E., the resistor connecting the two) because the + and - leads of the XLR are already inverted when compared to each other.

As for sound, there is more 2nd harmonic overall when feeding the signal with the RCA, as the distortion spectra of the two sides of the amp end up being additive. It actually sounds quite nice overall. But it's absolutely different.
  Reply With Quote
Old 16th June 2019, 03:44 PM   #529
Azookey is offline Azookey  United States
diyAudio Member
 
Join Date: Jul 2018
Thanks that does help a lot. To be clear we should be connecting our speakers to both black output terminals correct? When you said the right channel output red you meant the wire to the speaker not the binding post itself, right?

The reason I’ve asked this is because, to my surprise, I’m finding that a single aca in stereo mode is sounding better to me than unbalanced bridged monoblocks. This is totally subjective and I have nothing to back it up but my gut, but there is something to me that I can’t put my finger on.

I was wondering if a balanced bridge connection would sound more similar to the stereo connection. I don’t have a balanced source at the moment so cannot test.
  Reply With Quote
Old 16th June 2019, 03:53 PM   #530
6L6 is online now 6L6  United States
diyAudio Moderator
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Amp Camp Amp Kit V1.6
You are absolutely welcome to like whatever you like!

Yes, I would agree that XLR balanced is more similar in sound to RCA stereo.


Connections -

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote

Reply


Amp Camp Amp Kit V1.6Hide 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
Amp Camp #1 PCB Rudi_Ratlos Swap Meet 43 30th September 2018 11:12 AM
Amp Camp amp tttubes The diyAudio Store 3 15th November 2016 01:57 PM
Amp Camp Amp GregBaker The diyAudio Store 0 11th January 2015 11:41 PM
Amp Camp! Jason Site Announcements 2 30th June 2012 02:57 PM


New To Site? Need Help?

All times are GMT. The time now is 02:44 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki