I think George would agree that 4.7k is close enough, but I do not like to speak for him.
If you look here Tubes and Applications | Tubelab you will see that George ran simulations (with SE Amp CAD) for various scenarios. He posts results based on various tubes, at both 5k and 3k OPT impedance.
With 3k impedance, output power of the amp is higher, but so is distortion. You can look at the numbers to get an idea how this scales.
So 4.7k will result in very slightly higher output power and distortion. I believe measurement gear would be required to tell the difference.
I wouldn't hesitate to use 4.7k OPTs in an SSE build. Especially ones of such high quality as the Lundahls. The spec sheet for the LL2769 even states they are intended to be used with EL34, KT-88, KT-150 ... which is exactly the class of tubes the SSE is intended for.
I would bet a lot of money they sound better than a Hammond 5k. 🙂
If you look here Tubes and Applications | Tubelab you will see that George ran simulations (with SE Amp CAD) for various scenarios. He posts results based on various tubes, at both 5k and 3k OPT impedance.
With 3k impedance, output power of the amp is higher, but so is distortion. You can look at the numbers to get an idea how this scales.
So 4.7k will result in very slightly higher output power and distortion. I believe measurement gear would be required to tell the difference.
I wouldn't hesitate to use 4.7k OPTs in an SSE build. Especially ones of such high quality as the Lundahls. The spec sheet for the LL2769 even states they are intended to be used with EL34, KT-88, KT-150 ... which is exactly the class of tubes the SSE is intended for.
I would bet a lot of money they sound better than a Hammond 5k. 🙂
A mismatch of 10% or less will not affect anything. An SSE with KT88's will work fine with anything from 4 to 6K ohms. Some people even run them as low as 3K, which will produce a bit more power, at the expense of higher distortion a a poorer damping factor.