HF and LF tubes

[Alf]

A while ago I made this preamp using two ecc85 tubes ( 6aq8) and it works but I am missing a bit of low frequency content in the sound. I solved this by putting an eq ( a simple boss GE-7) behind it which makes up for more low frequencies.
Someone remarked that the reason for the lacking bass frequencies was because the tubes I used were designed for High Frequency use. And it's true that this tube is used in Fm radios.
What is true about this story that I used the wrong type of tubes?
I tried this type because there is still a NOS supply of these tubes at reasonable prices

Alf

[R.G.]

No basis. There are no tubes that are good ONLY for high frequencies, especially considering that for RF tubes, audio and DC are about the same.

High frequency tubes are carefully designed to get response that **also** extends up in to RF, not to sacrifice low frequency. Tube operation is a modulated-DC operation. They have no good way to cut bass inside the tube.

[Malcolm Irving]

The Phillips data-sheet states that the ECC85 is designed for use as a radio-frequency amplifier and self-oscillating mixer, but I don't think that would affect the low frequency audio performance. Can you post a schematic of the preamp circuit? Perhaps someone here would be able to see why the bass is too low.

[Alf]

There are no tubes that are good ONLY for high frequencies, especially considering that for RF tubes, audio and DC are about the same.

Thanks R.G for clearing this up because you just confirmed what I thought.

[Alf]

Can you post a schematic of the preamp circuit?

I might do that but not yet. You could try it yourself now you know that it works.