How to increase 2nd HD?

[Grant Sellek]

Hello everyone,

is there a way to slightly increase the second harmonic distortion of
a SET or similar single ended amp? Should it be done in the driver
stage or the output stage?

If you are thinking of reducing NFB, what if the amp has no NFB?

I simply want to experiment and find what differences I can or cannot
hear. However, I want to do it in a way that leaves the amp performing
at its best in all other ways.

Thanks for any help,
Grant

[Ronald]

I don't know what's best , but at least this is worth reading .....
http://www.borbelyaudio.com/15wse.pdf
(scroll down to page 3.)

"Grant Sellek" > schreef in bericht
om...
> Hello everyone,
>
> is there a way to slightly increase the second harmonic distortion of
> a SET or similar single ended amp? Should it be done in the driver
> stage or the output stage?
>
> If you are thinking of reducing NFB, what if the amp has no NFB?
>
> I simply want to experiment and find what differences I can or cannot
> hear. However, I want to do it in a way that leaves the amp performing
> at its best in all other ways.
>
> Thanks for any help,
> Grant

[Ian Iveson]

Generally, 2H cancels to some extent between driver and output stage
if the driver is inverting.

You may find that increasing the 2H of the driver actually decreases
it at the output, and vice versa.

To increase the 2H of the driver, you could add a cathode bypass cap
if you haven't got one already and can accommodate the reduction in
gain, or you could decrease its anode resistor, giving a steeper
loadline, and then relocate the operating point by changing the bias
current and HT voltage.

Decreasing the 2H of the driver via the anode resistor won't be so
easy cos you will run out of HT voltage. Unless you use an anode
choke, or a MOSFET to convert to a mu-follower (if you can find
enough HT). You could remove the cathode bypass cap if present. Or
you can change valves maybe.

Altering the distortion of the output valves might not be so easy
because you can't change the load without also affecting the final
power output and frequency response unless you change the OPT.

Perhaps more details of your particular circuit and valves would
help to produce a more focused answer.

cheers, Ian

"Grant Sellek" > wrote in message
om...
> Hello everyone,
>
> is there a way to slightly increase the second harmonic distortion
of
> a SET or similar single ended amp? Should it be done in the driver
> stage or the output stage?
>
> If you are thinking of reducing NFB, what if the amp has no NFB?
>
> I simply want to experiment and find what differences I can or
cannot
> hear. However, I want to do it in a way that leaves the amp
performing
> at its best in all other ways.
>
> Thanks for any help,
> Grant

[Ian Iveson]

> To increase the 2H of the driver, you could add a cathode bypass
cap....

> Decreasing the 2H...remove the cathode bypass cap...

oops. Opposite way round.

Ian

[Robert Casey]

Grant Sellek wrote:

>Hello everyone,
>
>is there a way to slightly increase the second harmonic distortion of
>a SET or similar single ended amp? Should it be done in the driver
>stage or the output stage?
>
>If you are thinking of reducing NFB, what if the amp has no NFB?
>
>I simply want to experiment and find what differences I can or cannot
>hear. However, I want to do it in a way that leaves the amp performing
>at its best in all other ways.
>
>
>
Take a look at http://home.netcom.com/~wa2ise/radios/cdtubedsim.gif
This is a tube cathode follower running on a low B+ source. The simulation
shows a lot of 2H. You could add this circuit to just before the volume
control of your amp. The 6111 tube is somewhat similar to a 12AU7.
Or use a 6111 submini tube, they come with long leads and are designed to
be directly wired into circuits under the chassis. As seen in
http://home.netcom.com/~wa2ise/radios/cdtubed.jpg