New "Kit" on the Block - BrianGT /LM3886 Upgrade - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 23rd April 2012, 03:26 PM   #31
bcmbob is offline bcmbob  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Bay City, Michigan
Hi Carlos - good question. No I did not for a couple reasons. The MyRef is a much more sophisticated/complex design and I don't have the expertise to know where it might integrate along the path.

Also, the sonic payload/characteristics the RR delivers to the BrianGT amp is similar to the result provided by extensive (multi-year) tests and tweaks done with the MyRef centering around C9,C13 and linuxguru's LFO-1.

Uriah was heavily involved the the MR development path and maybe he will/can give us some ideas if and where the RR can be applied.
__________________
Bob M.
"Arrange Whatever Pieces Come Your Way."
  Reply With Quote
Old 23rd April 2012, 04:11 PM   #32
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Hi Bob,

Sorry, my confusion. I was talking to Dario about that mod, and he told me the LDR replaced one resistor. I thought you were using the whole LDR volume pot.

Dario had recommended me the SMD precision pot sold in eBay and that's the one I installed on my MyRefC. And the only reason to go for an LDR type to replace it is to remote the volume control.

Remoting an LDR pot should be much easier than with resistor switching pot, which I think is the best type there is compared to traditional pots.
  Reply With Quote
Old 23rd April 2012, 04:49 PM   #33
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Interesting idea. I was reading about these Siliconix LDRs from their website, they use a semiconductor as the conductive material (CdSe & CdS). They have low distortion when there is very little voltage across them, but distortion rises with signal. I suspect it's mostly 2nd harmonic, which is favourable.

I wonder how the LDR compares with a Tantalum resistor for sound ? - Tantalum is often reported as the gold standard for audio resistors, but they are darn expensive.

I used a Tantaum cap in an amplifier once (in the feedback path), it was very favourable to the sound. Tantalum caps generate 2nd harmonic distortion.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 23rd April 2012, 08:15 PM   #34
bcmbob is offline bcmbob  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Bay City, Michigan
O.K. Now I understand. We are doing a little apples and oranges thing here. The Resistor Re-placer is a very good amp upgrade, while the LDR attenuator kits are a volume control approach.

For the MyRef builds I have, the Lighter Note is my favorite piece of equipment. I also have Uriah's Lightspeed that I use mostly for testing and setup situations. Both attenuators pass extremely clean signals.

As I have posted in several places, While my "Sunflower" DIY speakers are the best I have owned, they are on the inefficient side. The very top end of the LDR units don't allow the SPL I like with some types of music in this combination. There is also a slight left/right drift at the last 5 - 10% approaching full max rotation.

My solution was to add a JC-2 preamp to the V1.3 system. It is as clean and colorless as anything I have heard. This allows "loud" at near 12:00 on the LN pot and the image is stable throughout. With more efficient speakers a listener may never need to rotate the pot that far.

The new Fremen Edition that Dario is developing, in combination with the Mini2496 DAC and a WASPI feed from a computer, so far has satisfied my volume requirements. The pot that Dario recommended is what I am using till I get a chance to remove the LN from is't current home in an integrated build to compare it on the FE.

IMHO, the bare pot or a discrete LDR unit are both excellent choices for volume control and that choice is just a matter of builder preference.

I'm interested in more applications for the RR but that's an orange,

P.S. I've been poking around the DCB-1 threads but haven't yet decided if I want to build and compare one.
__________________
Bob M.
"Arrange Whatever Pieces Come Your Way."

Last edited by bcmbob; 23rd April 2012 at 08:20 PM.
  Reply With Quote
Old 23rd April 2012, 08:31 PM   #35
diyAudio Member
 
Join Date: Mar 2001
Location: Brazil
Bob,

What I seem to understand, correct me if I'm wrong, is that your MyRefC needs more signal level to move your Sunflower speakers, right?

Then you're using the JC2 to increase the level.

So the pots just work as passive attenuators if you don't that. Is that so?

Usually the "right" level setting comes when your amp clipping level, as seen on a scope with a load similar to your speaker's lowest, is with the level pot completely open.

Have you seen where your MyRef clips?
  Reply With Quote
Old 23rd April 2012, 08:55 PM   #36
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Tantalum resistor for base stopper at the input(s)? Interesting! But, much like the carbon resistors in series trick, the Tantalum resistor isn't variable, so we wouldn't get all of the features (fine tuning) that an LDR could do.

But there are two inputs. . .
Inverting input resistor (on a non-inverting amp):
So, if a Tantalum resistor (or series carbon resistors instead of only one resistor) were in-between the inverting input and NFB cap, the gain setting would be more stable than using an LDR in the feedback settings. The audio effect is similar.

Last edited by danielwritesbac; 23rd April 2012 at 09:21 PM.
  Reply With Quote
Old 23rd April 2012, 09:05 PM   #37
bcmbob is offline bcmbob  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Bay City, Michigan
I don't own any scopes so I can't give you a scientific answer. Early in the FE development I asked Dario to describe it's advantages and one was more driving power.

One of the things I like about the MyRefs is the thermal protection has always triggered before I hear any clipping. Insuring good heat transfer to the heat sink has always solved that problem. With the JC-2 I'm sure I could/would blow something on the speakers before I turned it up high enough to make the amp clip. There appears to be enough headroom designed into the MyRefs to avoid clipping in the builds I have done. Hope that answers your questions.
__________________
Bob M.
"Arrange Whatever Pieces Come Your Way."
  Reply With Quote
Old 27th May 2012, 08:29 AM   #38
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
Has anyone heard from Uriah lately? I've emailed and sent pm's but haven't had any replies.
  Reply With Quote
Old 29th May 2012, 09:18 PM   #39
SoIL4x4 is offline SoIL4x4  United States
diyAudio Member
 
Join Date: Nov 2011
Location: Carterville, IL
Quote:
Originally Posted by Marra View Post
Has anyone heard from Uriah lately? I've emailed and sent pm's but haven't had any replies.
X2
  Reply With Quote
Old 30th May 2012, 08:15 AM   #40
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
I hope the guy is OK
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Building an LM3886 BrianGT Kit -- Questions wes-ninja250 Chip Amps 10 29th September 2005 12:35 PM
BrianGT snubber power supply upgrade PMeade Chip Amps 3 7th May 2005 01:45 AM
BrianGT's LM3886 board, and hiss Russ White Chip Amps 9 20th March 2005 08:10 PM
BrianGT's LM3886 Kit scott_jcp Chip Amps 11 4th March 2005 07:07 PM
FS: BrianGT gainclone kit. LM3875 Dual Mono Kit mattjk Swap Meet 3 16th November 2004 12:24 AM


New To Site? Need Help?

All times are GMT. The time now is 06:44 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2