New "Kit" on the Bolck - BrianGT /LM3886 Upgrade

[bcmbob]

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.

[carlmart]

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.

[Bigun]

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.

[bcmbob]

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.

[carlmart]

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?

[danielwritesbac]

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.

[bcmbob]

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.

[Marra]

Has anyone heard from Uriah lately? I've emailed and sent pm's but haven't had any replies.

[SoIL4x4]

Originally Posted by Marra

Has anyone heard from Uriah lately? I've emailed and sent pm's but haven't had any replies.

X2

[Marra]

I hope the guy is OK