Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on February 16, 2025, 12:11:07 pm
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do i connect the 8 ohm OT tap to a 16 ohm cab to accomplish this?
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
really?. ok so i'm using a pair of EL34's with this 8K CT OT. i would use an 8 ohm speaker connected to the OT''s 4 ohm tap?
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
really?. ok so i'm using a pair of EL34's with this 8K CT OT. i would use an 8 ohm speaker connected to the OT''s 4 ohm tap?
NO!
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
really?. ok so i'm using a pair of EL34's with this 8K CT OT. i would use an 8 ohm speaker connected to the OT''s 4 ohm tap?
You have it backwards.
He wrote; "...connect a 4Ω speaker load to the 8Ω OT tap."
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
you are wrong!
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
??
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Well, I tried. It was a simple question and I gave a simple answer. Maybe one of the smart guys will straighten us out.
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Guys, Joe is trolling you.
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Haha
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not trolling. trying not to blow up my amp. SEL may have had it right. This is from the Robinette site for the 800 using a 7K OT.
(https://i.ibb.co/wZDz21GG/gfg.png)
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He says ‘8 ohm speaker to 16 ohm jack’
(Which is equivalent to ‘4 ohm speaker to 8 ohm jack’)
So if you have a speaker cab with 8 ohms impedance, connect it to the 16 ohm output jack on your amp. But if you have a 16 ohm cab, you’ll be looking for a 32 ohm output jack on your amp. And if your amp only has an 8 ohm output jack and a 16 ohm output jack, you’ll want to rewire the cab to make 4 ohms or 8 ohms respectively (if you can). Otherwise not.
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to wrap up. my amp has a 4 ohm speaker. my OT is 8K ct. i will use 2 x EL34. I will connect the 4 ohm speaker to the 8 ohm OT tap. If anyone objects to this please state your case now or forever hold your peace.
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Try/test each tap briefly and decide which tap sounds best and come back later and ask if it's safe.
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The details matter. To be precise all the taps need to be measured to find each taps turns ratio.
Phase matters and phase calculations include an inverse.
OR
Try/test each tap briefly and decide which tap sounds best and come back later and ask if it's safe.
Also, power handling and power output also matter (because if it’s a 15 or 20W OT, it might not last as long with 30 or 40W being pumped through it)
And voltage and power matters for determining an optimal/target reflected load (to get maximum efficiency and output power).
And bias and phase inversion matters for determining operating class and output power.
But I think he just wants to wrap it up and plug it in. So be it. Or not.
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to wrap up. my amp has a 4 ohm speaker. my OT is 8K ct. i will use 2 x EL34. I will connect the 4 ohm speaker to the 8 ohm OT tap. If anyone objects to this please state your case now or forever hold your peace.
You're the only one who ever had any objections. :icon_biggrin:
But, as tubeswell said, there are other things to consider, rather than just matching Zs.
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i knew this forum would bring clarity
(https://media0.giphy.com/media/v1.Y2lkPTc5MGI3NjExcW9jMXRpc21sZHo1MnFsaTFpOWY2N212NW82bjJ0OW95dzF0eWFlMCZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/VBUIvFMG4eEOQ/giphy.gif)
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PP 6v6 amps sometimes use an OT with 8k primary and single 8ohm tap and that means connecting a 4ohm speaker results in 4k reflected primary.
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No. You need to half the primary z so you would also need to half the secondary z. IOW, connect a 4Ω speaker load to the 8Ω OT tap.
This is actually one of the best explanations I've seen on how to tweak the OT to fit with a different tube primary impedance. Usually I'll watch the Uncle Doug video a couple of times to end up at the same result.
Including the voltage and bias considerations from the datasheet of course.
Things may or may not get murkier when talking about vintage Marshall OT with supposedly 8k primary vs modern OT's that have multiple secondaries that use different size wire so all secondary taps reflect back the same primary z.
Well, that's an interesting thought.
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Well, that's an interesting thought.
if you're bored read up on something like "Effects of AC signal in a reactive circuit" read the one's from Universities you find full of equations :icon_biggrin:
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Not to belabor this
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yep, that's the page, after doing thousands of hours worth of math like that, I've concluded that Mathematicians are sadistic
physics is laid back chill'n til math walks in the room and nobody can have nice stuff til the math is satisfied. :icon_biggrin:
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Well, that's an interesting thought.
if you're bored read up on something like "Effects of AC signal in a reactive circuit" read the one's from Universities you find full of equations :icon_biggrin:
If I'm that bored, I'll just watch Uncle Doug's video again and figure out the ratios for each secondary by practice. It's more funner that way.
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Things may or may not get murkier when talking about vintage Marshall OT with supposedly 8k primary vs modern OT's that have multiple secondaries that use different size wire so all secondary taps reflect back the same primary z.
I think that for clarity an
If the proper speaker is connected to the proper tap
Must be added
Franco
p.s.: the use of different size wire on different secondaries is not mandatory, what is important is the turn ratio of the windings
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project scrapped. no clear answers here. gonna go in a different direction
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no clear answers here.
No, you got a clear answer, you just didn't like it.
And you came up with a search that backed what was said.
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Calboy - you're distracting from the converstaion and NOT helping. Go away.
joesatch - you're being rude and difficult. You have your answer, use it or not. Stop your BS, went from ignorant to stupid. Don't like it? Too bad. Go away.
Guys, you can lead a horse to water... (do not beat this dead horse, it has died. lol)