The All Purpose Advice Thread - Part 2

I think I have 2-3 myself. One a rack mount, one a single outlet surge protector and another, I think maybe.

No filtering on those, just surge iirc.

 

Circling back to this. Had some heater maintenance done.

Brought the tech over to hear the sound I was hearing. He looked perplexed as it wasn't any of the above.

He pressed on the vent cover with his screwdriver and the noise stopped. The cover was vibrating as the air went through it! (easy to fix, at least.)

btw, did I mention this incessant, irritating, whining vibration from the vent cover was directly over my work desk...?

 

And if only folks who fret about changing cables,tubes, amps, etc. knew that everything vibrates and it can really affect what you hear.

Sounds like you had a happy ending, oh wait, did I say that!

 

Oof, that reminds me of a big fan unit at a studio we were working on. It kept making this squeaking noise that we were sure it was the motor or one of the bearings/bushings, but we couldn't just track it down. Finally through happenstance, we discovered that it was actually just the enclosure and two pieces of metal that were vibrating against each other and making the squeak. A quarter turn with a screwdriver fixed a problem that had taken us two hours and nearly a full disassembly of the entire damned thing.

 

Is there any reason why I should not use a powered monitor as a rear-surround with my Monolith HTP-1 pre-pro? I am trying to find ways to make this work and have looked at all sorts of options. Ideally, I would just run a 25-30ft balanced XLR around my room into a powered speaker and be good to go. I have a power outlet at each spot where I want the speaker.

Does anyone have a recommendation of a good self-powered monitor that could work in this scenario? I've looked at a few professional studio monitors and even considered the Buchardt Anniversary 10. If I could find something reasonably affordable (less than $1K) that would be my preference. Most of the crap I'm finding has Bluetooth yada yada and no real analog input.

Something like these IK Multimedia monitors or the smaller MTM monitors are what I’m envisioning. I cannot tell what has a direct analog in or not. These use DSP but I wonder if I could just not use that. Maybe these from Neumann?

 

I have a Turntables question - I have the opportunity to get either a Sansui P-D10 or Technics SL-23 locally here to me- was just looking for an entry level at a cheap price. Both these units work - very clean condition. Is there any compelling reason to choose one over the other or are they both about the same performance wise? Thanks!

 

Well, one of these 2 brands is know for turntables & one is not. Yet, lots of notes on Technics speed problems with this model.

I suppose it depends on your vinyl quality, phono pre quality, how much serious listening you might do, cartridge choice and how low your budget needs to be. If I were jumping back into the turntable game, I might try something new from Audio Technica or maybe even Fluance?

 

I haven't owned either model, but at the same price the Technics would seem to me a no-brainer. That Sansui looks like a very 80s, cheap, light thing with, from looking at the service manual, horrendous electronics you'd have to deal with at some point; whereas the Technics being a belt-drive is mechanically simpler.

Here's a service guy's perspective on each:

Technics:


Sansui (D20, but that's just the D10 with different switch gear):

 

I was also looking new at AT or Fluance, but I am not looking to do anything super serious, this is just getting my feet wet kind of deal. And the price of eitther of these used is under 100 and coming from an owner who took care of them.

Thanks - I think the Technics is the more serious of the two and seems to be the easier to repair. Thank you so much for the video links, it definitely puts things in a more clear perspective.

 

I have some of those cat toys that are shaped like fish, battery operated, and flap around when the cat plays with them. One day I was moving some stuff around in my office, and when I dropped something heavy on the floor this horrible clanging noise started coming from under the floor. I thought my furnace had catastrophically failed, but after 20 seconds or so the noise stopped. Fast forward a few weeks I had a friend over doing some painting and the same thing happened. While we were pondering the problem he noted one of the floor vents had no grate, and another cat toy was sitting nearby. Then a lightbulb went on. I could not see the fish, it was too far in, so I threaded the extension hose from my vacuum cleaner down the vent and as hoped it sucked onto the fish and I was able to pull it out. We had a good laugh about that.

 

I have some experience with the DC offset issue as it pertains to toroidal transformers, having worked with them a fair bit as an engineer at Panamax/Furman, developing solutions for home theater analog display applications (analog RGB was highly prone to hum bars when power/signal was co-located in conduit and other not-so-best-practice configurations).

Transformer DC tolerance has an inverse relationship to its leakage inductance. Toroids that are wound in a well-distributed manner have very low leakage inductance, and such configurations are highly prone to saturation on AC voltage peaks if there is sufficient DC bias. The field collapses 60 times a second in this case and the current spikes are fairly large, and the transformer itself will audibly hum from magnetostriction. Plitron used to (or maybe still does) make some toroidal transformers with intentional leakage inductance intended to provide some low-pass filtering and DC offset tolerance. This is accomplished by providing sectors of the toroid that have physical gaps between windings. Gapping the core (with a saw) is another method, but not at AC power scales.

This was especially an issue with loads on the line that were controlled using half-wave rectification (halogen lamp dimmers, space heaters with a 50% setting). Basically, those controls insert a single diode or SCR in series with the load current. The transformer doesn't need to be supplying the load; the DC offset on the line is what causes the issue.

 

If we're talking half-wave rectified supplies- yes, you can theoretically reduce DC voltage offset induced by loads on the line by running some of them with reverse L-N connections, drawing some of the current on the negative half of the voltage sine wave. Wire up a short reverse extension cord from parts at Home Depot.

 

I understood maybe every 3rd word of this (that's on me -- the writing here is clear as a bell). This is a fascinating post!

 

Here's an electrical audio thing I haven't had any luck googling about.

I have a Lab Gruppen C20:8X with GPIO on a phoenix connector.
I have an AVR with a 12v trigger via mono 3.5mm jack.

I cut up the 3.5mm cable and wired up the phoenix. When the AVR turns the trigger on, the Lab Gruppen turns on. When the AVR turns the trigger off, the Lab Gruppen does not. ;-( Seems like the pro amp wants a pulse while the 12v trigger is continuous?

googling reveals a lot of DIYers making their own circuits for this (555 timer?) I'm not a dIyer so just want something off the shelf.

Since the Lab Gruppen consumes a lot of power I don't want to rely on a 12v trigger power strip as most don't seem capable of passing all the energy the Lab Gruppen needs.

Is there something like a converter for this case of converting consumer 12v trigger into what the Lab Gruppen takes?

 

Several possible solutions.
Lab Gruppen wants a >200mS pulse to turn On and another >200mS pulse to turn Off again. This could be an arduino project as follows:

https://www.amazon.com/ELEGOO-Board-ATmega328P-ATMEGA16U2-Compliant/dp/B01EWOE0UU

pseudo code:
monitor a digital input for a state change
on state change issue a 500 mS pulse on a digital output
repeat forever

Brute force method with real 15 or 20 amp relays (much more expensive)

https://www.bhphotovideo.com/c/prod..._rlm_15_1ca_stand_alone_switchable_power.html
https://www.bhphotovideo.com/c/prod...atlantic_rlm_20a_switchable_power_module.html

 

You could also try emailing Lab Gruppen? Years ago I stumbled across one of their old amps which had been rebranded for a Bruel & Kjaer testing rig and had been modified inside. I emailed them asking if there was any way to unmod the amp and we had a few messages back and forth. Maybe I piqued their curiosity with such an old amp and really oddball question. Engineers can be a weird bunch sometimes.

 

I'm casually looking at the used ads for cables (interconnects). From time to time, I see some that are labeled specifically as "RCA Subwoofer" cables. Is there something to these that makes these inherently different than regular RCA cables?

 

Fat cables for fat bass.

But seriously, no. If a cable is somehow magically "tuned" for bass frequencies, wtf is it doing to the rest of the spectrum? if it's acting as some kind of low pass filter, then do the job right with a crossover not a magical cable.

 

Might just refer to a single/mono cable as well.

 

Nono, clearly the sub cable is that yellow plug on the red white yellow cable right?