Nevermind found the answer

Len058

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I'm building the EF80 Bassman Micro by Rob and nearing the end I run into an issue. I have a 16ohm Celestion Greenback, which I want to use for it. Rob only specifies an 8ohm connection. The data sheet goes to 15ohm. I know a little about impedance so I think I can get away with connecting 16 ohm to the 15 Ohm tap. But which one do I choose.
Rob says 22,5K load. I can choose 24K but I think that would be too much because the load gets higher when connecting a higher impedance speaker. I think 21,5K @15ohm will get me in the ballpark with 16 ohm connected.

Should I do something special when connecting multiple taps? I have a feeling it needs ground somewhere when one is not connected

Advice please and thanks in advanced.

Hammond_125B_Specs (1).png
 
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Wally

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@Len058 wrote: ”Nevermind found the answer”.

If you don’t mind, @Len058 and just for the edification of the curious, what was the solution that you found?
 

Len058

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@Len058 wrote: ”Nevermind found the answer”.

If you don’t mind, @Len058 and just for the edification of the curious, what was the solution that you found?
It's in red on the sheet. I copied it from Rob's site but didn't see it because I looked at the original (without Robs tekst) data sheet when I was placing the OT. And I found a thread somewhere but lost it after I read it.
 

Wally

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It's in red on the sheet. I copied it from Rob's site but didn't see it because I looked at the original (without Robs tekst) data sheet when I was placing the OT. And I found a thread somewhere but lost it after I read it.

@Len058, does the yellow highlighting indicate what you have chosen to use with a 16 ohm load? That appears to be good for an 8 ohm load…or am I missing something. Or….is that highlighting something that robrob did for another situation.
@robrob, I am curious as to why you suggest using 1/4 for a 16 ohm load in this thread but suggest 4/6 for a 16 ohm load in that chart.
It is after my lunch, and I should be in the middle of a siesta….so I might not be all here! (;^)
 

Len058

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@Len058, does the yellow highlighting indicate what you have chosen to use with a 16 ohm load? That appears to be good for an 8 ohm load…or am I missing something. Or….is that highlighting something that robrob did for another situation.
@robrob, I am curious as to why you suggest using 1/4 for a 16 ohm load in this thread but suggest 4/6 for a 16 ohm load in that chart.
It is after my lunch, and I should be in the middle of a siesta….so I might not be all here! (;^)
I chose 4-2 for eight ohm and 4-1 for 16.
It's hard to read the chart when you're in a hurry, many people have questions about Rob's designs so he's a busy man. That's why he probably also mentioned the 21500, which will lead someone who is building the amp to the right taps.
 

Wally

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Yes, I understand that.I went back to your OP and thought I saw where you are running a 6 ohm load. Hence my question about the yellow highlighted connection for an 8 ohm load. I did not review the entire thread, so maybe I missed where you went to an 8 ohm load???.

As for the question about @robrob’s two different suggestions for connections with a 16 ohm load, I was wondering if there is something special about your particular build here that caused Rob to changed from
the 4/6 24,000:15 connections to the 1/4 21,500:15 connections. Learning can be a full-time job for me.…long way to go Yet. Eeeehaw…
 

robrob

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@Len058, does the yellow highlighting indicate what you have chosen to use with a 16 ohm load? That appears to be good for an 8 ohm load…or am I missing something. Or….is that highlighting something that robrob did for another situation.
@robrob, I am curious as to why you suggest using 1/4 for a 16 ohm load in this thread but suggest 4/6 for a 16 ohm load in that chart.
It is after my lunch, and I should be in the middle of a siesta….so I might not be all here! (;^)

Either will work fine. The plate load difference is minimal between the two options.
 




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