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Posted

I think you can use any of those valves as an input but they have different output & hence different the amp will have different gain, depending upon which.one you use.

In Turning Japanese case he is using a low gain valve & the amp is clipping. His speakers might be inefficient?

Herby

 

Posted

I think you can use any of those valves as an input but they have different output & hence different the amp will have different gain, depending upon which.one you use.

In Turning Japanese case he is using a low gain valve & the amp is clipping. His speakers might be inefficient?

Herby

 

Posted

Yes, you speakers may be efficient but how big is your room? How loud do you play it?

The point is you are using the lowest gain input valve that the Cymer 13E1 can operate with.

Try the 12at7, much higher gain & hence higher output.

I used my Cymer 13e1 on some Magnepans, which love a bit of power & current & they worked. Not optimal but you could.live with.it & they didn't clip.

 

 

Posted (edited)
2 hours ago, Herbyj said:

I think you can use any of those valves as an input but they have different output & hence different the amp will have different gain, depending upon which.one you use.

In Turning Japanese case he is using a low gain valve & the amp is clipping. His speakers might be inefficient?

Herby

 

 

It's not just the amplification factors that are different. The transconductance/mutual conductance and plate/anode resistance values of those 3 tube types are also different. That would throw out the bias points and cause the distortion issue encountered above in Turning Japanese's amp. Please see comparison below.

 

12AU7:

 

Screenshot_20241212_212437_Drive.jpg.50c78ea1cd6b6b58f237b5eb4a75a476.jpg

 

12AT7:

 

Screenshot_20241212_212329_Drive.jpg.42f26ee6624a32b7a3dd98849ac0be7a.jpg

 

12AX7:

 

Screenshot_20241212_214243_Drive.jpg.ad0dd929402f4531a5f310ac6e38a8e4.jpg

Edited by xlr8or
  • Like 2

Posted
1 hour ago, xlr8or said:

 

It's not just the amplification factors that are different. The transconductance/mutual conductance and plate/anode resistance values of those 3 tube types are also different. That would throw out the bias points and cause the distortion issue encountered above in Turning Japanese's amp. Please see comparison below.

 

12AU7:

 

Screenshot_20241212_212437_Drive.jpg.50c78ea1cd6b6b58f237b5eb4a75a476.jpg

 

12AT7:

 

Screenshot_20241212_212329_Drive.jpg.42f26ee6624a32b7a3dd98849ac0be7a.jpg

 

12AX7:

 

Screenshot_20241212_214243_Drive.jpg.ad0dd929402f4531a5f310ac6e38a8e4.jpg

The big question for me is which one was it designed for? The review doesn’t help as it’s the 45 driver so input valve is likely to be different, herby bought from new and has the 99 valve so his bring 12at7 suggests that is what mine is

 

Looking forward to trying it when the at. Valves arrive later today, will be cool to see the inside of your amp herby when next st home if you can help with that please

 

cheers

darren

Posted

well the good news is putting the right valve in certainly improves the sound - pair of cheap  and not well matched valves in for now is very promising so will have a mooch for a better matched pair after xmas

 

many thanks for your help guys

 

darren

  • Like 1
Posted
On 17/12/2024 at 9:42 PM, Herbyj said:

These are the GE 12AT7 that came with my Cymer 13E1 amps which I bought new from Elson.

 

https://www.tubedepot.com/products/12at7wc-jan-ge

They sound great and aren't too expensive for NOS valves.

 

I am still in Japan but home just before Xmas. I'll post some pictures of the internals of my amps then.

Cheers

Herby

 

 

thanks for the tip - got a pair of matched and balanced from langrex here in the uk and they sound a couple of notches better that the other ones I bought as a starter for ten. light up brighter as well so bargain for £40 posted

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