HELP: F5T imaging is off-center

[dewdrop]

I decided to cascode my F5T to protect the JFETs. To my dismay, the imaging is slight off center towards the right now. :-(

I have biased the channels more or less to the same voltage level.

What can I do to fix this?

 

[6L6]

Swap input leads, swap speaker leads, etc... and make sure it's actually the amps.

 

[dewdrop]

I have switched the gear around and am sure it's the F5T right channel.

Bummer, any suggestions?

 

[AVWERK]

Phase is correct Left & Right ?

 

[qwertyl]

Could you measure the gain of both channels?

 

[dewdrop]

Phase is correct Left & Right ?

Yes

 

[dewdrop]

Could you measure the gain of both channels?

How do I do that?

 

[qwertyl]

How do I do that?

Not sure it is exactly correct, but I do this way:
Input - 1kHz sine wave. Output - 8Ohm resistor, about 2.83VAC. Compare input AC voltage to output AC voltage and you will have gain at 1kHz, 1W.

 

[Zen Mod]

majority of regular DVM are happy dealing with signals in range of 400-1KHz

absolute value of voltage isn't critical , just relative - comparing input with output voltage

 

[dewdrop]

Bummer, will need a sig gen to do this

 

[Zen Mod]

simple programs , free from net , will do that

all you need is any sort of computer with even crudest sound card

quality isn't important

for instance https://www.google.com/search?q=sigjenny&ie=utf-8&oe=utf-8

 

[haiqu]

Didn't think much of SigJenny I'm afraid. It wouldn't work even with a Virtual Cable program installed, kept complaining there was no wave input available. Too old tech, probably worked fine with Win95 but hasn't been updated.

 

[Zen Mod]

find another one

 

[haiqu]

Might have to write one, so far all contenders have been broken.

 

[haiqu]

This one seems to work but has no sweep function:

https://sourceforge.net/projects/audmes/files/?source=navbar

 

[qwertyl]

You can probably use virtual piano and play B5 or C6 notes 🙂

 

[coolnose]

Download the desired sine as *.wav or any other audio file and play it through your default audio player.... or am I missing something?

 

[Nelson Pass]

You can drive both channels with a common signal (music is fine) and
place any AC voltmeter across the hot outputs. If they have the same
gain then you won't read any AC. If it's only a few mV, then perhaps
that's not the problem.

 

[dewdrop]

Thanks guys. Interesting ideas, let me go figure.

 

[Sangram]

Connecting a speaker to the +outputs of both channels and play a mono signal through both channels. The speaker should be dead silent, as it is going to play any differences between the two. In practice you can still have a bit of sound, but no significant output.