Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Gone_Fishing on February 03, 2021, 08:02:29 pm
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A simple question for a simple minded guy.
If I am playing my Twin Reverb build with a 4, 8, 16 multi-tapped OT and I have the OT impedance set on 8 ohms because I am playing through an 8 ohm speaker cab but I pull two OP tubes, do I switch to 4 or 16 ohms on my OT selector?
I have tried for years to understand the electionics/physics of it, but if I know what to do with my tapped OT, double or half, I’ll be happy, safe and just say, “I don’t understand it, but I know what to do”.
Thanks guys.
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If you are math inclined, think about this as an equation and the OT is the equal sign. If you do something to one side of the equation, you must do the same thing to the other side of the equation to maintain equality.
When you pull two tubes you are doubling the impedance on the primary side of the OT. Now you need to also double the impedance on the secondary side of the OT.
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Thanks Sluckey,
Math was never my cup of tea. I’m like what Mark Twain said about math, “When I die, I’m going to spend the first couple million years of my eternity learning algebra”.
**But I think that you mean increase my OT to 16 ohms, correct?**
I was confused because I have read on several forums that on a TR with the normal 4 ohm OT, you would need to disconnect one speaker to get an 8 ohm load (and I understand that) BUT, (they would then say), if you have a tapped OT, you could simply switch it to the next lowest setting, ie 2 ohm. That was screwing with my head.
Either they were wrong or my brain was still pissing into the wind.
I have a second question please.
To take advantage of the tapped OT and the half power switch, I will wire my two 8 ohm speakers in parallel for a 4 ohm load, now my question.
Is there much difference in the amp’s tone or output when running your tapped OT on 4 ohms instead of the 16 ohms?
Thanks again.
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Is there much difference in the amp’s tone or output when running your tapped OT on 4 ohms instead of the 16 ohms?
Hey, you got the amp. You tell me. :icon_biggrin:
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I’ve never rigged up my speakers for 4 and 16 ohms and checked Sluckey.
I thought maybe with your experience that you could give me a hint and save me from possibly getting another back operation.
But what the hell, I’ll risk it to appease you Sluckey ole pal.
Thanks for your expertise.
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Is there much difference in the amp’s tone or output when running your tapped OT on 4 ohms instead of the 16 ohms?
Hey, you got the amp. You tell me. :icon_biggrin:
The thing is, people disagree about whether a difference is heard, and what that difference is. It might even matter what amp is being used to try the switch.
I'm subscribed to a YouTube channel where they tried this exact thing around a year ago. The people making the video swore they heard a major difference in the room.
The channel uses excellent mic technique and audio engineering, as the channel is mostly about listening to the sonic differences in pedals, guitars and amps. But I was listening to their video through an outboard DAC, amp and reference headphones, and could not hear a difference. I normally hear major differences when they change something, and this one simply didn't come through.
:dontknow:
So no telling what your experience will (or won't) be. It's better you try it then go into the experiment with a preconception of what you "should" hear.
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Thank you very much HBPs, spoken like a true gentleman and scholar, that’s all I needed to hear.
For me, You have always proven to come through with the answer that I’m looking for on this forum, and I truly appreciate that fact, your vast knowledge and you.
My amp is an AB 763 TR clone that I built in ‘13 in a gutted Music Man chassis that had a half power switch that I wanted to use and and you answered my question then about a post on another forum about lifting the grounds and I posted on this forum and asked if that method would work.
My ears are not as keen as they used to be with the 24-7 crickets in breeding season that I continuously hear, so I’m sure that I will never hear a difference, and even more sure since you can’t.
I like to look on the bright side, it’s kinda nice to hear crickets in the winter time, plus it’s a lot more tolerable than a worn out back.
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Hearing things is often subjective ... some people swear they can hear God speaking to them personally :icon_biggrin:
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And I totally agree with you about that fact.
And there are probably more different subjective reasonings and feelings in the guitar and amp world than any other playground that I have witnessed and can think of.
But I have an open mind and realize how flawed my subjective opinion can be, unlike many who I have ran across.
I had heard many people’s differentiing opinions on my question, but I’ve found that it is always good to have another one, especially like HBPs’, who said it just like he did, gave his honest opinion, and didn’t try to color or spin it towards one way or the other.
And his answer was exactly what I was seeking and thought it probably would be, it’s all in the ears of the beholder, just like how most all people view the opposite sex as a potential love interest.
HBPs gave the only appropriate true answer, and he did so with dignity and professionalism. And that my unknown friend, is not a subjective feeling or opinion, that’s a fact.
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So if you pull two output tubes , one from each side , you would need to plug an 8 ohm speaker into the 4 ohm tap of the output transformer . Now you are reflecting 4 k ohms to the primary side . Couldn't tell from the previous posts if this is what was being said .
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correct