Discrete That 1510

[Monte McGuire]

So does anyone here have opinion about removing output mute transistors, and their effect on sound? I guess it's the same circuit BLA calls current limiting circuit. Not sure if it's the same thing though.

Are we sure that those are actually transistors and not dual diodes arranged as clamps to the + and - supplies? Parts like the BAV99 and BAV199 come in an SOT23 package like that and would be pinned exactly as shown, as far as I can tell.

 

[kingkorg]

This is the best shot i could take.

 

[Monte McGuire]

I noticed the reference designators say "Qnnn" so I guess they are transistors... sorry not to notice that earlier!

In general, clamp diodes and other semiconductors hanging across a signal line can contaminate it, but the likelihood of damage depends upon the impedance of the node that the semiconductor is attached to. If the impedance is low, then the nonlinear conduction of the clamp or mute switch will be swamped by the low impedance of the line, and if the impedance is higher, then the nonlinear conduction of the device can cause measurable and possibly audible problems. Determining the expected degradation depends on the specific circuit.

 

[iampoor1]

Not to get too off topic....but has anyone independently heard a BLA mod and actually thought "wow this is a noticeable improvement?". I haven't. 

 

[abbey road d enfer]

There is a claim by BLA

Who (what?) is BLA?

that if current limiting circuit is removet from the outputs, the sound opens up significantly. Which ii did remove, and that did exactly nothing!

As Monte explained, in a well-designed circuit, the contribution to THD of the clamping circuit should be negligible.
The issue there is that people tend to hear what they wish to hear. Most of the times, after working at modding a circuit, one expects to hear a difference. Apparently, you are an exception to the rule. 

 

[kingkorg]

It's Black Lion Audio. They do mods on these units. Recap the whole thing, install additional caps, change opamps, the clock, remove clamping circuit, etc. While the price of their mod is justified by the amount of work required to pull it of i struggle to hear any improvement in modded units.

I want to be able to measure the "improvements" i make, or at least confirm something is really different by doing null test.

I have occasionally made changes and i could swear i heard the difference, but the signal cancelled out 100% after the mod. So i am aware of psychological issues that can occur, and do my best to avoid them.

Adding transformers made the only real difference.