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Little tech questions from your day

All your geeky questions about electronics, microphones, tape machines, etc.

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Re: Little tech questions from your day

Postby bishopdante on Tue Dec 26, 2017 10:43 am

Mason wrote:You know, though, the fact that there were no telltale glitches in the audio, like the choppy jittery kind, is kind of insanely admirable. Good job, Reaper.

I need to build more foundational knowledge on this kind of thing. I've been reading through the Yamaha Sound Reinforcement Manual and the López-Alt Food Lab book—I need to find the equivalent of those for digital recording (and am accepting recommendations).


Error codes require clever programming, it's "normal" for software to just screw up and carry on (like a car crashing).

Seems pretty shady that you didn't get an error code.

Reaper does have an error code to describe the issue:

Err=30 Buffer Size Mismatch


Might be that a large buffer setting covers up a failure-to-write issue, or that some feature in the 3rd party SATA controller is being Taiwanese and failing to report problems, could be the HD cache being weird... all sorts of possible explanations. Ideally you should see all of the performance being properly audited by the software and see an error code if things are behaving unexpectedly.

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Re: Little tech questions from your day

Postby Riff Magnum on Thu Dec 28, 2017 12:34 pm

How do in ear monitors actually work and what's a solid entry level model to try out?
By work, I mean how do they connect with the P.A. and do they require additional equipment or considerations?
New rehearsal space is tiny and loud and I'll be damned if I"m gonna tell the drummer to tone it down, so i've ordered some eargasm earplugs and if those suck, I might consider in ear monitors. Maybe monitor in one ear, plug in the other? We'll see
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Re: Little tech questions from your day

Postby Adam P on Thu Dec 28, 2017 6:12 pm

Feed a monitor mix to a headphone amp, just like you would with a wedge setup. Stereo or mono, depending on preference and system capability.
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Re: Little tech questions from your day

Postby Riff Magnum on Thu Dec 28, 2017 8:06 pm

Adam P wrote:Feed a monitor mix to a headphone amp, just like you would with a wedge setup. Stereo or mono, depending on preference and system capability.


Thanks. I have what I need then.
We'll see how earplugs work for now though. I've avoided them like the plague for 20 years, but our new situation seems dangerously loud.
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Re: Little tech questions from your day

Postby Raa on Fri Dec 29, 2017 7:56 am

Riff Magnum wrote: I've avoided them like the plague for 20 years, but our new situation seems dangerously loud.


Hi. I'm 42 years old this year and I imagine I've been at least as stupid or careless with my ears as the most stupid and careless of us, not limited to sticking my head in bass bins at full throttle, sticking my head in a kick drum for a few songs, some light industrial stuff (not the music genre.) In almost every conversation I have to ask someone to repeat something they've said and while listening to Triadic Memories for Piano a few days ago I wondered where the high notes had gone. They only appeared if I turned it up much louder.

Wear earplugs. Please don't mess around with this.
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Re: Little tech questions from your day

Postby ldopa_chicago on Fri Dec 29, 2017 11:16 am

Riff Magnum wrote:How do in ear monitors actually work and what's a solid entry level model to try out?
By work, I mean how do they connect with the P.A. and do they require additional equipment or considerations?
New rehearsal space is tiny and loud and I'll be damned if I"m gonna tell the drummer to tone it down, so i've ordered some eargasm earplugs and if those suck, I might consider in ear monitors. Maybe monitor in one ear, plug in the other? We'll see


IEMs are just high fidelity earbuds married to earplugs, basically. Unless you have a full band mix to send to your IEMs, they're not very useful.

I don't know if decent and cheap intersect when it comes to in-ear monitors, honestly. You're looking at at least $200 between a headphone amp and IEMs and that still assumes that you have a good full-band mix going to your mixer which I assume you don't have at the practice space.

Personally, I wear Etymotic ETY earplugs and strongly prefer them to no protection at this point. I wear them at every concert, practice and show. I don't know the Eargasm ones but they look pretty similar.
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Re: Little tech questions from your day

Postby Riff Magnum on Fri Dec 29, 2017 12:10 pm

yeah, it was between the etymotic and the eargasms. I recommended my bassist get the etymotics so we could compare.
I might just get a cheap monitor on craigslist and find a way to get it pointing right at my dumb face or find a way to get our current PA speakers pointing more toward me. Due to the nature of the room and our particular rigs I'm not really in the path of the p.a. speakers, so the guy who needs to hear the vocals the most isn't. Hard to explain. Damn room is so small, but everything sounds fucking great in there, so no-one wants to turn down and the drummer is playing like he's 16 again, so I'm not messing with that. Earplugs it is.......
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Re: Little tech questions from your day

Postby Riff Magnum on Fri Dec 29, 2017 12:18 pm

Raa wrote:
Riff Magnum wrote: I've avoided them like the plague for 20 years, but our new situation seems dangerously loud.


Hi. I'm 42 years old this year and I imagine I've been at least as stupid or careless with my ears as the most stupid and careless of us, not limited to sticking my head in bass bins at full throttle, sticking my head in a kick drum for a few songs, some light industrial stuff (not the music genre.) In almost every conversation I have to ask someone to repeat something they've said and while listening to Triadic Memories for Piano a few days ago I wondered where the high notes had gone. They only appeared if I turned it up much louder.

Wear earplugs. Please don't mess around with this.


Yeah, I'll be 43 in February and I've miraculously got great hearing at this point, despite having worked in factories, around heavy machinery, power tools, going to loud rock shows and playing loud rock music. But after just 2 practices in this room, I can feel it. I can hear the difference already, especially laying down to sleep at night or during meditation.
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Re: Little tech questions from your day

Postby JohnnySomersett on Sun Dec 31, 2017 5:45 am

So, what's the best thing to use as a dummy load for Amp servicing/maintainence? I seem to remember my last tech (before he moved away and I decided to start learning myself) had some kinda heatsink-looking contraption but I never asked what it was. Can I just build one out of power resistors?

Also, is it time to invest in a cheap Oscilloscope? I want to move on to the stage where I can pinpoint rogue noise in a circuit and measure actual output watts when biasing up/down. I think I need to go past the multimeter/bias meter stage and learn more.

I've been looking around and I can get an old analogue 'scope for not a lot of money and I think for my simple needs, and preference for actual dials and switches, I'm just gonna get one and start learning. I've done a little research and it looks like a signal/function generator is something that'll come in handy for measuring output wattage when tuning up.

Thanks.

*EDIT: I just snagged this cheap from eBay just a few miles from my house:

Image

Dunno if its any good but seems to have the basic functions I'm going to need. And it was £50
Last edited by JohnnySomersett on Sun Dec 31, 2017 12:17 pm, edited 2 times in total.
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Re: Little tech questions from your day

Postby Raa on Sun Dec 31, 2017 6:54 am

Riff Magnum wrote:Yeah, I'll be 43 in February and I've miraculously got great hearing at this point, despite having worked in factories, around heavy machinery, power tools, going to loud rock shows and playing loud rock music. But after just 2 practices in this room, I can feel it. I can hear the difference already, especially laying down to sleep at night or during meditation.


That dull hum is so scary. I've read on here arguments that tinnitus might be psychological as much as physiological but I dunno.

Also you've reminded me to get off the internet and meditate. Thanks!
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Re: Little tech questions from your day

Postby japmn on Wed Jan 03, 2018 8:48 pm

JohnnySomersett wrote:So, what's the best thing to use as a dummy load for Amp servicing/maintainence? I seem to remember my last tech (before he moved away and I decided to start learning myself) had some kinda heatsink-looking contraption but I never asked what it was. Can I just build one out of power resistors?

Also, is it time to invest in a cheap Oscilloscope? I want to move on to the stage where I can pinpoint rogue noise in a circuit and measure actual output watts when biasing up/down. I think I need to go past the multimeter/bias meter stage and learn more.

I've been looking around and I can get an old analogue 'scope for not a lot of money and I think for my simple needs, and preference for actual dials and switches, I'm just gonna get one and start learning. I've done a little research and it looks like a signal/function generator is something that'll come in handy for measuring output wattage when tuning up.

Thanks.

*EDIT: I just snagged this cheap from eBay just a few miles from my house:

Image

Dunno if its any good but seems to have the basic functions I'm going to need. And it was £50



I have this one:

https://www.amazon.com/dp/B00SXVUETU/ref=sspa_dk_detail_2?psc=1&pd_rd_i=B00SXVUETU&pd_rd_wg=xLfjG&pd_rd_r=DE7DR5W21KH57XDZKM1Q&pd_rd_w=y8Fyl

I bought it because it looks cool and I had a bunch of Amazon points to burn through. I haven't really ever used it but it is the size of an Ipod and is super cool looking.
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Re: Little tech questions from your day

Postby tarandfeathers on Thu Jan 04, 2018 2:59 am

japmn wrote:
JohnnySomersett wrote:So, what's the best thing to use as a dummy load for Amp servicing/maintainence? I seem to remember my last tech (before he moved away and I decided to start learning myself) had some kinda heatsink-looking contraption but I never asked what it was. Can I just build one out of power resistors?

Also, is it time to invest in a cheap Oscilloscope? I want to move on to the stage where I can pinpoint rogue noise in a circuit and measure actual output watts when biasing up/down. I think I need to go past the multimeter/bias meter stage and learn more.

I've been looking around and I can get an old analogue 'scope for not a lot of money and I think for my simple needs, and preference for actual dials and switches, I'm just gonna get one and start learning. I've done a little research and it looks like a signal/function generator is something that'll come in handy for measuring output wattage when tuning up.

Thanks.

*EDIT: I just snagged this cheap from eBay just a few miles from my house:

Image

Dunno if its any good but seems to have the basic functions I'm going to need. And it was £50



I have this one:

https://www.amazon.com/dp/B00SXVUETU/ref=sspa_dk_detail_2?psc=1&pd_rd_i=B00SXVUETU&pd_rd_wg=xLfjG&pd_rd_r=DE7DR5W21KH57XDZKM1Q&pd_rd_w=y8Fyl

I bought it because it looks cool and I had a bunch of Amazon points to burn through. I haven't really ever used it but it is the size of an Ipod and is super cool looking.


A DSO will never look as "cool" as a cathode ray scope but for doing actual productive work, a CRO just can't compete. I kept my old Hameg 203 and occasionally put stuff up on it if I think it will look pretty for my own amusement but I never use it for actual faultfinding, because it's not as accurate and can't do mask tests, pass/fail testing, single shot capture, doesn't have four channels, etc. I would highly recommend getting even a cheap DSO for these kind of features if you are interested in hunting down noise/pops/spurious signals in a circuit.

You can make a dummy load out of power resistors. Just remember that a 100W power resistor isn't 100W on it's own though, it must be attached to an appropriate heatsink, potentially have forced air cooling, and even then it will get hot if you dump 100W into it. Better to get a selection of resistors that you can parallel/series connect to make a few different "impedances" and spread the thermal load between them. The coolest (pun only semi intended) dummy load I have seen was made from a nominal 8 ohm heating element from some sort of toaster oven submerged in a large metal tube of mineral oil to take the heat away. Neat idea.
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Re: Little tech questions from your day

Postby Dudley on Thu Jan 04, 2018 7:09 am

I've got a Laney LC 30-ii, which I use with an aftermarket dual footswitch to switch channels and turn on/off reverb.

The channel switching works fine, but the reverb switch will only turn the reverb on, not off.

Sometimes when the amp is switched on, if there's no reverb present, hitting the switch will bring it in, but only sometimes. It never switches it off. If the reverb is on when I turn the amp on, the switch does nothing, until the amp is switched off again.

The connections on the switch are all fine, but the jack is a one-piece plastic body, so can't check that without cutting off and replacing.

Is the problem with the footswitch or in the wiring of the amp?
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Re: Little tech questions from your day

Postby Nate Dort on Thu Jan 04, 2018 7:58 am

Dudley wrote:I've got a Laney LC 30-ii, which I use with an aftermarket dual footswitch to switch channels and turn on/off reverb.

The channel switching works fine, but the reverb switch will only turn the reverb on, not off.

Sometimes when the amp is switched on, if there's no reverb present, hitting the switch will bring it in, but only sometimes. It never switches it off. If the reverb is on when I turn the amp on, the switch does nothing, until the amp is switched off again.

The connections on the switch are all fine, but the jack is a one-piece plastic body, so can't check that without cutting off and replacing.

Is the problem with the footswitch or in the wiring of the amp?


I take it this setup used to work, and suddenly stopped working?

It would be easy to confirm that the footswitch is functional with a multimeter across the ring and sleeve of the TRS plug. They should alternate between shorted and open as you hit the reverb switch.

Here's my hierarchy of where to look for general fault-finding / troubleshooting of electronic gear, in order of most-to-least likely root cause:

1. Connectors & Cabling (external first, then internal)
2. Switches
3. Tubes
4. Power Supply Circuits
5. Cold Solder Joints
5. Electrolytic capacitors
6. Active Components (ICs, transistors, diodes, etc.)
7. All other passives (ceramic caps, resistors, inductors, etc).
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Re: Little tech questions from your day

Postby JohnnySomersett on Thu Jan 04, 2018 2:45 pm

tarandfeathers wrote:
japmn wrote:
JohnnySomersett wrote:So, what's the best thing to use as a dummy load for Amp servicing/maintainence? I seem to remember my last tech (before he moved away and I decided to start learning myself) had some kinda heatsink-looking contraption but I never asked what it was. Can I just build one out of power resistors?

Also, is it time to invest in a cheap Oscilloscope? I want to move on to the stage where I can pinpoint rogue noise in a circuit and measure actual output watts when biasing up/down. I think I need to go past the multimeter/bias meter stage and learn more.

I've been looking around and I can get an old analogue 'scope for not a lot of money and I think for my simple needs, and preference for actual dials and switches, I'm just gonna get one and start learning. I've done a little research and it looks like a signal/function generator is something that'll come in handy for measuring output wattage when tuning up.

Thanks.

*EDIT: I just snagged this cheap from eBay just a few miles from my house:

Image

Dunno if its any good but seems to have the basic functions I'm going to need. And it was £50



I have this one:

https://www.amazon.com/dp/B00SXVUETU/ref=sspa_dk_detail_2?psc=1&pd_rd_i=B00SXVUETU&pd_rd_wg=xLfjG&pd_rd_r=DE7DR5W21KH57XDZKM1Q&pd_rd_w=y8Fyl

I bought it because it looks cool and I had a bunch of Amazon points to burn through. I haven't really ever used it but it is the size of an Ipod and is super cool looking.


A DSO will never look as "cool" as a cathode ray scope but for doing actual productive work, a CRO just can't compete. I kept my old Hameg 203 and occasionally put stuff up on it if I think it will look pretty for my own amusement but I never use it for actual faultfinding, because it's not as accurate and can't do mask tests, pass/fail testing, single shot capture, doesn't have four channels, etc. I would highly recommend getting even a cheap DSO for these kind of features if you are interested in hunting down noise/pops/spurious signals in a circuit.

You can make a dummy load out of power resistors. Just remember that a 100W power resistor isn't 100W on it's own though, it must be attached to an appropriate heatsink, potentially have forced air cooling, and even then it will get hot if you dump 100W into it. Better to get a selection of resistors that you can parallel/series connect to make a few different "impedances" and spread the thermal load between them. The coolest (pun only semi intended) dummy load I have seen was made from a nominal 8 ohm heating element from some sort of toaster oven submerged in a large metal tube of mineral oil to take the heat away. Neat idea.


Yeah, I understand they're a little archaic but (especially for the small amount of money) I think having such a basic one to start with will help me, and the way my brain learns, figure out the basics on a more fundamental level.

I have bought a couple of this type of resistor:

Image

...after watching a couple of youtube videos. I think I can construct something easily enough that will work and I can keep cool long enough to test power output.

I also grabbed one of these:

Image

Although I need to figure out what the 'normal' output voltage from a guitar would be to test correctly (approx 200-400mV?)
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Re: Little tech questions from your day

Postby Nate Dort on Thu Jan 04, 2018 5:43 pm

JohnnySomersett wrote:Although I need to figure out what the 'normal' output voltage from a guitar would be to test correctly (approx 200-400mV?)


If only you had a scope, you could measure it yourself.
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Re: Little tech questions from your day

Postby JohnnySomersett on Fri Jan 05, 2018 1:18 am

Nate Dort wrote:
JohnnySomersett wrote:Although I need to figure out what the 'normal' output voltage from a guitar would be to test correctly (approx 200-400mV?)


If only you had a scope, you could measure it yourself.


*facepalm*

touché
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Re: Little tech questions from your day

Postby TomWanderer on Thu Jan 11, 2018 9:53 am

Ok, this is very minor, but I'll ask anyway. Yesterday evening I was putting our practice space back together since our last show and I ran into something puzzling...specially since I was in a state of mind to spin out on a small issue. I got some dc power supplies mixed up and found that my Signal Flex phantom power supply, which requires 15 volts, came from the manufacturer with a 12v supply. Additionally, my Rolls headphone mixer, which requires 12v, came with a 15v supply. One is positive tip, one is negative, and the tips are different sizes to boot, so I can't just swap them. As long as polarity is correct, is plus or minus 3vdc going to have any affect on this equipment? It seems like this stuff works fine, but then again I have only used it with the original (slightly) mismatched power supplies. I was very confused.

..And now I see that the current version of the Signal Flex SF-8060 requires only 12v, not 15...
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Re: Little tech questions from your day

Postby JohnnySomersett on Sun Jan 14, 2018 11:15 am

If I buy an old amp that runs on 117v can I just take a measurement of the voltages the other side and replace the power transformer with one that takes 240v and spits out the same?

It's a 50w tube amp...any idea of power consumption?

I have a step-down transformer already in the house somewhere but I don't like those things really.
Last edited by JohnnySomersett on Sun Jan 14, 2018 11:46 am, edited 1 time in total.
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Re: Little tech questions from your day

Postby biscuitdough on Sun Jan 14, 2018 11:42 am

TomWanderer wrote:..And now I see that the current version of the Signal Flex SF-8060 requires only 12v, not 15...


The current Rolls model seems to require 15v.

I think you found a glitch in the matrix.
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