Design and OPT for SET high frequency amp

[levimax]

I have a tri-amp system and I would like to build a SET amp preferably using El-34's and 6SN7's because I have some. I know OPT are the most expensive part of a SET build and I know much of the expense is trying to get the OPT to cover the 20 to 20K range. If I could live with -3 db @ 1 Khz with flat to 40 KHz is there a cheaper OPT I could use that would be optimized for this frequency range? Is there an existing design for an amp like this that you could point me to?

Is it even worth thinking about an amp l like this or am I better off just building a "regular" 20 to 20 Khz one.

I tried to search SET and high frequency and didn't get very far.

Thanks

 

[audiowize]

Yes, there are lots of single ended OPTs that don't give much bass response. Edcor and Hammond make some that don't do a lot below 100Hz. If you have a 2 stage cap coupled amp, you can build in a first order high pass filter at 1kHz pretty easily.

 

[Tubelab_com]

I built a small SE tube amp that was built with "full range" capabilities. I used the Edcor XSE 15-8-5K driven by a triode wired 6V6GT. Output power is about 2 watts, and the response at 2 watts is flat from about 40 Hz to nearly 40 KHz. I did have this amp driving the tweeters in a 2 way system with a push pull 300B amp handling the woofers. An active solid state crossover was used. The 300B amp died several years ago, but it will be rebuilt soon. The little Edcors excel when not pushed hard, and I wouldn't hesitate to use them in a similar application.......they work pretty good with a 45 DHT too, but it just doesn't sound right to spend more on the tubes than the OPT's.

 

[levimax]

Yes, there are lots of single ended OPTs that don't give much bass response. Edcor and Hammond make some that don't do a lot below 100Hz. If you have a 2 stage cap coupled amp, you can build in a first order high pass filter at 1kHz pretty easily.

Thank you! Looking at the spec sheets the cheaper OPT that have less LF response also have limited HF response... looks like if I want good HF I am going to have to buy a good OPT

 

[levimax]

I built a small SE tube amp that was built with "full range" capabilities. I used the Edcor XSE 15-8-5K driven by a triode wired 6V6GT. Output power is about 2 watts, and the response at 2 watts is flat from about 40 Hz to nearly 40 KHz. I did have this amp driving the tweeters in a 2 way system with a push pull 300B amp handling the woofers. An active solid state crossover was used. The 300B amp died several years ago, but it will be rebuilt soon. The little Edcors excel when not pushed hard, and I wouldn't hesitate to use them in a similar application.......they work pretty good with a 45 DHT too, but it just doesn't sound right to spend more on the tubes than the OPT's.

Thank you for sharing your experience! I will check out the Edcors

 

[mctavish]

Have a look at the "Robin Hood" series from Magnaquest... They sound EXACTLY like what you are looking for and lack nothing in the quality department

 

[Tubelab_com]

I will check out the Edcors

I ran a frequency response test with these OPT's about 10 years ago. Granted it was done with a 300B SE amp, but the -3db point for HF is about 45KHz. The results are on my web site about halfway down this page. Expect to lose a bit if driving the OPT with a tube that has a higher plate resistance.

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