[jl123]

Very nice!

May I ask what camera you have?

You have great light in that room lol.

 

[MASantos]

Quote:

Originally Posted by Karlosak ...and the winner is: MASantos! Congratulations! The extra wafer/deck should control a light ring of 24 LEDs, indicating the volume for a given balanced channel. jarthel, if I wanted something "custom made" in your truest sense of word, I would have to take 100+ switches just to ensure ELMA would even speak with me and moreover be quite a wealthy man! For me it's satisfying that these switches aren't in the ELMA's catalog ilikepie, waffer was a typo, should be wafer. It's one of those green widgets .

That should look very nice. Will the leds be around the volume knob? How will you hook up that?

 

[Todd R]

Have fun soldering.
I built one of those last year and it took a couple days to complete.
Should keep you out of trouble for a while

 

[bperboy]

Nah, he'll probably be so excited to finish the shiny new attenuator that he'll pull an all-nighter!

Quote:

Originally Posted by Todd R Have fun soldering. I built one of those last year and it took a couple days to complete. Should keep you out of trouble for a while

 

[Karlosak]

Quote:

Originally Posted by bperboy Nah, he'll probably be so excited to finish the shiny new attenuator that he'll pull an all-nighter!

Hmm, temptation would be there...

But surely not, one must be really cautious and double-check everything, the inner resistors are very hard to desolder (fortunately there has been no need to yet).

Andrea, for a "sane human being" like you it may seem like a mess, for a true DIYer who loves soldering it's a pleasure! [size=xx-small]Though a change of mind during the soldering process is very probable...[/size]

Concerning the sonic differences between attenuators and standard pots: There is quite a clear difference between e.g. Alps Blue Velvet and stepped attenuators. And not just a better channel tracking at lower volumes - the sound is more transparent. Don't forget this is a balanced system and any imbalance between the symmetrical pairs translates into distortion and thus is more severe than plain L/R channel imbalance.
On the other hand, pots have a great advantage: infinitive number of steps. Especially low impedance headphones plugged into high-gain amplifier benefit from this. Nevertheless, this problem can be eliminated by using proper amplifier gain (or gain switch) and suitable attenuator taper. In the end, it depends whether you prefer ease of use or a slight sonic improvement at a higher cost. Since the DynaMight will be my definitive solid-state amplifier for the foreseeable future, I don't want to cut corners.

The camera used was Sony DSC-F828. The light in that room is actually quite bad

, a recipe for great photos is an external flash shot into the ceiling. Proper light conditions are IMHO much more important than the camera itself. So bad that my father is taking the camera for holiday and I won't be able to post new pictures for a week.

The LEDs will be laid out in a full circle around the knob. The hooking up is quite easy for a single color, but a bit trickier for bi-color LEDs (common cathode). I'll try to post a scheme or a pic. Does anybody know about a source for 2mm blue/red LEDs? So far I've only found 3mm ones here: http://www.lsdiodes.com/shop/index.p...products_id=57.

 

[jarthel]

Quote:

Originally Posted by Andrea All this mess because you don't want traditional volume pots? I've never had the slightest problem with them, nor they've ever seemed a bottleneck..

you can't compare a normal log potentiometer against a stepped attenuator. especially if the the builder decides to use matched resistors for all the channel.

 

[Karlosak]

The camera is back home, so after some time here comes the promised outcome of my "soldering marathon" in photos. It was fun, but sincerely I wouldn't like to earn my living with it. I don't know exactly how many hours went into the job, the soldering took 4 days altogether.
The switches haven't been tested yet. Hopefully I didn't make any mistake with any of the 192 resistors!

When I gather all the necessary parts, I'll start a new thread dealing with the progress of my DynaMight project.

 

[mb3k]

Wow, that's a spot on job! Looks like it has been soldered by a machine

 

[MASantos]

That is amazing! I love the color contrast of the red resistors against the PCB. I would place a plexiglass window over the attenuator in the final enclosure to make that excelent job visible. Now where's the schematic for the led volume display?

 

[Karlosak]

Quote:

Originally Posted by mb3k Wow, that's a spot on job! Looks like it has been soldered by a machine

After Xth resistor in place, I sort of felt like some machine doing its job...

Quote:

Originally Posted by MASantos where's the schematic for the led volume display?

Here is the promised schematic of the volume indicator made from bicolor LEDs:

and some real-life nightshot:

The schematic shows only 6 volume levels. It was the only wiring I was able to think out using bicolor LEDs with common cathode. The only downside is that the actual level shines in both colors which doesn't matter to me.
Should I use bicolor LEDs with only two legs (anti-parallel), the wiring would be easier, all the LEDs would be connected in series. If I wanted just one color, only one current source would be needed.

The LED indicator was already implemented in my Dynahi. 24 blue LEDs in series takes about 70V DC. This kind of voltage can be found between the main PSU capacitors. With DynaMight it will be trickier however. Since DynaMight is separated in two boxes, I would need to route 2+2 extra wires with adequate voltage between the PSU and AMP enclosure just to utilise this gadget. I've already bought 4-pin Speakon connectors, so it's settled - the LED rings will be only in red color (needs < 50 Volts). At least I can use LEDs with 2mm diameter (I never saw bicolor RED/BLUE LEDs this small).

 

[motherone]

Nice work! Are those IRC resistors or another brand?

 

[mb3k]

Wow, I'm very impressed by the volume indicator.

 

[phergus_25]

Any shots of it below full volume?

 

[Scimmia]

Quote:

Originally Posted by phergus_25 Any shots of it below full volume?

I think that is below full volume. If you check his schematic, the LEDs turn from blue to red (or vice versa, not sure how it's wired) as the volume goes up.

 

[phergus_25]

O wow, thats awsomer than I though it was. GOOD WORK!