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EL34/6L6GC Differences & Ampeg B-15R
- Thread starter gstaats
- Start date
Hello…
I know this is an older thread and this subject is in a few places on TB. I just can’t find it. Connecting a B15R with a B15E should be done cab to cab right? Changing amp from 8 to 4ohms?
Another reply more on this threads subject. I am running a 6CA7EH in my B15R. Sounds big and deep
Thank you again! What is the correct way of adding in the B15R?
That is how I do it. The outputs on the B-15R are parallel - you could do it either way. The B-15R stock is 8 ohms, and the b-15e is 8ohms. Set the amp to 4 ohms and you're good to go.
Yes. The manual can be found here: B-15R.PDF (ampeg.com)
Speaker out on amp:
Internal speaker jackplate:
Jackplate on B15E appears to match above:
I had a tech put in the 6CA7. I had considered KT66 but am not sure if that would be wise. Has anyone tried that?
No experience with KT66. Before trying it, the wiring of the tube sockets should be inspected to make sure there are no illegal connections (I.E. compare the wiring of the socket to the tube pin out). Also it may be wise to adjust the value of the screen resistors. And of course, check/reset the bias.
Since EL34/6CA7 are common, I would just stick with the original tube type.
The bias voltage in a fixed bias amp should normally be checked when the power tubes are changed.
In the B-15R, the bias was set at a conservative level for both the 6L6GC and EL34 tube switch settings. The logic was that the two bias settings would be good for a range of the two tube types.
With the high cost of tubes today and the lack of tight tube production tolerances, the options are to offer either pre-screened tubes for an amp so they would be plug and play, or checking and adjusting the bias when the power tubes are changed to optimize the bias.
Sweet. I have one too. Hang on to it. Only 97 of them were ever made. While they aren't anything exceedingly "special", they are super rare. I did replace the stock drivers with Eminence Delta Pro 15A drivers. The stock drivers are known to fail. Improvement in low-end handling with new drivers.
Back in the day Groove tubes sounded great, I think they're the company that made bassists and guitarists think about matched sets instead of just throwing in a tube when one went bad, course they were all American tubes back then.
Think he was asking the correct way to connect ext cab to combo.
As long as amp is set to 4 ohms, one can connect the ext cab either via 'daisy chaining' from the speaker box of combo or going straight outta the amp with, in this case, one speakon loaded cable, and one jack speaker cable
Yes, that’s how it is done.
As others have explained, I'll add....The amp's speakon and ¼" jack are wired in parallel, so either or both can be used with the impedance switch set to 4 ohms. The speaker cabinet input ¼" jacks are also wired in parallel. With two cabinets, you can run two cables, one to each cab, OR you can run one cable from the amp to a cab and a cable daisy chained from one cab to the other. The two ways of connecting the cabs are equivalent. Speaker cables should be used, not instrument cables.
Amp's speaker output.
Cabinet speaker input.
