Mic pre question

[brianqq]

Hi,
I have a question about the Altec 1566 mic pre.
Looking at this schematic http://www.tangible-technology.com/tubes/1566/1566.html I am a little confused. And I have seen the original that shows it wired with the input transformer (not much better).
My question: is the signal from the input jack / input transformer also being connected directly to the volume pot?

I am building a preamp loosely based on this. I have taken the first stage of the 1566, and the rest is a 3 stage tone buffer.
It ends off the cathode like the 1566, but I don’t have an extra triode to double up with. It is finished, but the power transformer can’t handle the circuit. I am waiting for a new one to come in the mail. I hope it sounds good.

Brian

[MarcelvdG]

According to the schematic, the transformer is only connected to the potmeter when you select the low-gain mode and don't plug in an instrument. In high gain mode without an instrument, it is connected to the leftmost valve section. When you plug in an instrument in the jack input, the input transformer's secondary winding isn't connected at all.

[brianqq]

So the answer is the input signal is always connect to the volume pot
regardless if the transformer is being bypassed or not.

I know I can eventually find out when I start playing with it, but
what do you think the difference in noise would be with Hi vs Lo gain modes?

[Wavebourn]

Originally Posted by brianqq

So the answer is the input signal is always connect to the volume pot
regardless if the transformer is being bypassed or not.

No, It is connected directly to the pot only and only when gain switch is in the low gain position.

Te minus of this amp is phase inversion in different positions of the gain switch.

[brianqq]

Originally Posted by Wavebourn

No, It is connected directly to the pot only and only when gain switch is in the low gain position.

Te minus of this amp is phase inversion in different positions of the gain switch.

"Te minus"?
I don't know what that means.

Are you refering to the grey line, because that is what is confusing me.
I can see the different positions of the switches, but the grey line shows it connected at all times. It is very missleading.

[Wavebourn]

That means "te typo". My keyboard swallows symbols sometimes. I expect you to excuse typoos and misspelilngs when people help you, especially on international forum where people speak many different languages.

That line is not electrical. It means mechanical connection between sections of the switch. Like in that anecdote, "Sir President, that Ooooo means Olympic Emblem, you should not read it, the text of your speech is below it".

[brianqq]

I was just asking a simple question, I could not put the typo into any context. You should listen you your own advise.

I would like to thank every body for the help.

Brian

[Wavebourn]

You've got the right and comprehensive answer long time ago, actually. With no typos at all.

This one:

Originally Posted by MarcelvdG

According to the schematic, the transformer is only connected to the potmeter when you select the low-gain mode and don't plug in an instrument. In high gain mode without an instrument, it is connected to the leftmost valve section. When you plug in an instrument in the jack input, the input transformer's secondary winding isn't connected at all.

[ruffrecords]

The grey line that is confusing you is simply meant to indicate that the two switches are ganged i.e. are part of one switch. A agree it is badly drawn and could be confusing to a newcomer. Usually such a line is drawn dotted and connected at each end to the arm of the switch and not to one of the pins of the switch which IS misleading.

Cheers

Ian