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PostPosted: Wed, Jul 08, 2020 10:21am 
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Captor 8 attenuation input - is that ok to use 16Ohm cabinet if not going to use THRU at all? Using at home for silent recording and attenuation only. Amp switchable, I have 2 cabs (8 and 16) and would like to switch cab from time to time.


Last edited by Sergii on Wed, Jul 08, 2020 1:01pm, edited 1 time in total.

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PostPosted: Wed, Jul 08, 2020 10:47am 
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Any quality TUBE amplifier can mismatch Ohms by 100% with no damage. A Solid State amplifier must match Ohms. So, an 8 Ohm TUBE amp can use 16, 8, or 4 Ohm cabs. A 16 Ohm TUBE amp can use 16 or 8 Ohms but not 4 Ohms. A 4 Ohm TUBE amp can use 8 or 4 Ohms but not 16. That information came from Skip Simmons, a well known and regarded tube amp tech, on "The Truth About Vintage Amps" podcast.

Two-Notes is covering themselves by requiring an exact match, imo. If someone used a cheaply built amp and mismatched Ohms, they would say their amp was damaged by Two-Notes.

Having said that, I would not be afraid to mismatch at 100% but if something happens don't blame Two-Notes. They said specifically to match the 8 Ohm load so the decision is completely up to the user.


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PostPosted: Wed, Jul 08, 2020 12:19pm 
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I've read about mismatch one step and so on. But here question is more like – as I understood impedance is crucial factor for an Amp but not for speaker. I've asked earlier about Captor X and got an answer than yes, until your amp sees impedance of a Captor X you safe to use any cab. The same in Torpedo Reload, it's even written in manual that you can even combine different impedance cabs with it. It has two inputs marked 4/8/16 and 8/16, basically you set impedance for amp and plug any cab there. And since there is no THRU it's safe all the time. With Captor X it's totally fine until you turn off attenuation and Amp is starting to see impedance of a real Cabinet via the same input. So let say if you forgot that there is mismatch, it's your problem.

So I just wondering if it's true for Captor 8 as well. Until I use attenuation input and 8 ohm Amp - it's basically doesn't matter which cabinet is plugged, right? I'm asking from the perspective of sound quality as well.


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PostPosted: Thu, Jul 09, 2020 4:58am 
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Sorry torrent61, but you mixed up tube amps and solid state amps, correct is the opposite way

Tube amps cannot mismatch impedance (or just in a certain grade)
and solid state amps can !

Tube-amp:
If speaker impedance is higher than amp impedance, the amp can’t give away all its power. Part of it gets reflected back into the amps output transformer, heating it up. If speaker impedance is much higher than amp impedance (infinite for nothing connected), all power gets reflected back into the amp causing serious damage to the output transformer.
If speaker impedance is lower than amp impedance, the amp needs to work harder to get the same output level as with an impedance match. Since a tube-amp is limited to how much power it can give, it can never damage itself. The tubes get worn out faster (since they have to work harder) and the amp won’t seem to be as loud as with an impedance match.
As a precaution, most tube-amps automatically short circuit (impedance of load is 0) there output when no jack is connected. This is to make sure that if the amp were to accidently turned on with nothing connected, it wouldn’t cause damage to the output transformer. Just make sure you don’t have a cable without a speaker connected to the output of the amp, as this would bypass the safety precaution!
You can get away with a ½ mismatch for tube-amps. For example, you can connect an 8 ohm output of a tube-amp with a speaker cabinet of 4 or 16 ohm without causing too much harm. But you will lose power and bandwidth causing the guitar to sound thinner and less defined. Never connect a 4 ohm output to a 16 ohm speaker cabinet.
If you need to make a mismatch it’s better to have the speaker impedance lower than the amps impedance (as described above).


Transistor/solid-state amp:
If speaker impedance is higher than amp impedance, the amp won’t produce more power than it can give away. It’s therefore safe to turn on a solid-state amp with noting connected to it (infinite impedance). PA technicians sometimes confuse tube-amps with solid-state amps and tell guitar players that it’s okay to turn on their guitar amp with no speaker connected to it, but this can be very dangerous as described above.
If speaker impedance is lower than amp impedance, the amp will increase its output power to drive the bigger load**. Since there is no theoretical limit to how much power a solid-state amp can give, it will simply blow-up when you short circuit (impedance is 0) the output of the amp. Luckily most amps have fuses and short-circuit protection build in.

source: https://www.n-e-l.be/single-post/2016/09/28/The-dos-and-donts-of-guitar-amp-impedance

br
Mario


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PostPosted: Thu, Jul 09, 2020 11:40am 
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Thank you for the wise information.. But the question is - ATT (attenuation) input in Captor. So you feed your amp with the impedance of Captor, and can even use it with no cab. But what is happening using attenuation input? It's a reactive load, so what is going out from Captor to Cab in this situation?


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PostPosted: Fri, Jul 10, 2020 3:00am 
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Sorry Sergii, I do not own a Captor, therefore I cannot help you in this matter.
I own a Torpedo Studio which has no attenuation but a load.

If you do not get a response from any other member of this forum, I would recommend to contact the Two Notes support.

br
Mario


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PostPosted: Mon, Jul 13, 2020 5:17pm 
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mariosr wrote:
Sorry torrent61, but you mixed up tube amps and solid state amps, correct is the opposite way

Tube amps cannot mismatch impedance (or just in a certain grade)
and solid state amps can !

Tube-amp:
If speaker impedance is higher than amp impedance, the amp can’t give away all its power. Part of it gets reflected back into the amps output transformer, heating it up. If speaker impedance is much higher than amp impedance (infinite for nothing connected), all power gets reflected back into the amp causing serious damage to the output transformer.
If speaker impedance is lower than amp impedance, the amp needs to work harder to get the same output level as with an impedance match. Since a tube-amp is limited to how much power it can give, it can never damage itself. The tubes get worn out faster (since they have to work harder) and the amp won’t seem to be as loud as with an impedance match.
As a precaution, most tube-amps automatically short circuit (impedance of load is 0) there output when no jack is connected. This is to make sure that if the amp were to accidently turned on with nothing connected, it wouldn’t cause damage to the output transformer. Just make sure you don’t have a cable without a speaker connected to the output of the amp, as this would bypass the safety precaution!
You can get away with a ½ mismatch for tube-amps. For example, you can connect an 8 ohm output of a tube-amp with a speaker cabinet of 4 or 16 ohm without causing too much harm. But you will lose power and bandwidth causing the guitar to sound thinner and less defined. Never connect a 4 ohm output to a 16 ohm speaker cabinet.
If you need to make a mismatch it’s better to have the speaker impedance lower than the amps impedance (as described above).


Transistor/solid-state amp:
If speaker impedance is higher than amp impedance, the amp won’t produce more power than it can give away. It’s therefore safe to turn on a solid-state amp with noting connected to it (infinite impedance). PA technicians sometimes confuse tube-amps with solid-state amps and tell guitar players that it’s okay to turn on their guitar amp with no speaker connected to it, but this can be very dangerous as described above.
If speaker impedance is lower than amp impedance, the amp will increase its output power to drive the bigger load**. Since there is no theoretical limit to how much power a solid-state amp can give, it will simply blow-up when you short circuit (impedance is 0) the output of the amp. Luckily most amps have fuses and short-circuit protection build in.

source: https://www.n-e-l.be/single-post/2016/09/28/The-dos-and-donts-of-guitar-amp-impedance

br
Mario

No, I am correct about tube amps. I know this for certain. Source: http://blog.hughes-and-kettner.com/ohm- ... impedance/ Source: https://youtu.be/TVVRFv3A-C0 (on this one, he mentions going from 8 Ohm to 16 Ohm and gives it an okay and he mentions 16 Ohm to 4 Ohm and gives it a thumbs down, just like i said, but he doesn't mention going 16 Ohm to 8 Ohm)
Source: https://youtu.be/sdGxVP_ju30 Source: https://youtu.be/bTcx-f1PIJU (this one from Ampeg talks about mismatching solid state output power amps and says you'll burn them up if you go 100% mismatching DOWN, i.e. 8 Ohm to 4 Ohm)


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