Tubes Asylum

Questions about tubes and gear that glows. FAQ

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

Serious Micro-Phonics and Hum from Citation V

Posted by mr9iron on July 7, 2012 at 01:06:10:
Inmates,

have been testing a Citation V on and off over the last month or so. I re-built it with McShane kits. All new tubes, new input jacks. All new resistors replaced with the resistor kit, choke, In- rush limiter, New McShane power supply kit all new caps......

This amp seems to be running fine and has seriously strong output and bass response. I can detect no "power leak" or weakness sonically of any kind. .... but this amp is very seriously micro-phonic.

It's so micro-phonic that you can hear the grids in the tubes pinging with the heating and cooling. If you gently tap the chassis or even walk across the floor it transmits and amplifies it like a microphone.

Every tube is micro phonic. If you tap the input tubes, or driver tubes, or output tubes, they will all thud and ping very loud. Tap any of the transformers, it's like a mic being broadcast.

I changed out every tube with another new quad and every 12by7a and 6cg7, still the exact same result. I somehow doubt every tube is micro phonic, and that every replacement tube I switched out is also micro phonic.

The Amp also exhibits a fairly decent hum, however, I think the hum is just the minor transformer hum that is being picked up and transmitted like every thing else. So I want to say it's the same problem as the micro phonics.

Someone suggested this can happen as the result of lose or bad tube sockets. I checked all of them (and de-oxed them) they are tight and secure. Again I doubt all 8 sockets are bad.. I want to say this has to be something bone-headed and simple. Something I did on the restore....

Could this be a bad ground? The re-build calls for a ground bus to be made and all the PS caps to be run to that ground on the mounting bracket, which I did do..

I am terrible at trouble shooting and I am not sure where to start.. Any suggestions welcome as usual..

thanks in advance!

Jeff