Ampeg Question

bluehonky · May 5th, 2006, 11:24 AM

Help me understand this thing.

I have an Ampeg Gemini VI. It has 7591 power tubes but it also has (2) 7199s.

My question is...
What exactly do the 7199s do? Can anyone enlighten me?

Check out the schem. here....
http://members.aol.com/portaflex/schems/gs-15-r.gif

trdlasvegas · May 5th, 2006, 12:31 PM

The 7199 is the PI (Phase invertor). In simple terms it splits the signal into a postive and negative phase signal in order to drive the positive and negative tubes of the push pull output.

-Tony

bluehonky · May 5th, 2006, 02:22 PM

Thanks Tony. That makes total sense. You rock.

I'm trying to lean as much as I can about tube amps and guy like you and this site make it fun and easy.

Thanks again.

Tremo · May 5th, 2006, 02:58 PM

It has TWO 7199s? Are you sure? Might someone have mistakenly put one in a 12AX7 socket? I'll have to look at Ampeg schemos again, I've not seen one with TWO 7199s. Very strange.

A 7199 is a dual tube, but unlike the common 12A?7 dual triode types, the 7199 has one triode section and one pentode section. The most common application is to use the pentode as a gain stage and the triode as a split-load PI. Alternately I've seen them used with the triode as a reverb driver, and the pentode as the reverb recovery amp.

I believe there is only one current production 7199, it's Sovtek, and it's of mediocre quality and performance. I hope JJ decides to make this type after they finish their EF86. As an alrernative, you can use types 6AN8 and 6U8, but the socket would probably need to be rewired.

bluehonky · May 5th, 2006, 03:45 PM

You're right Tremo. There is only one 7199. I was reading the schem wrong.

Still trying to wrap my brain around reading schematics.

trdlasvegas · May 6th, 2006, 03:53 PM

I'm not sure what the fancy name of this circuit is but it is definatly a Phase Inverter as the triode section of the tube is feeding the +/- output tubes, positive from the plate and negative from the cathode.

-Tony

May 5th, 2006, 11:24 AM	#1 (permalink)
bluehonky Tele-Meister Join Date: May 2004 Location: Lehigh Valley Posts: 133	Ampeg Question Help me understand this thing. I have an Ampeg Gemini VI. It has 7591 power tubes but it also has (2) 7199s. My question is... What exactly do the 7199s do? Can anyone enlighten me? Check out the schem. here.... http://members.aol.com/portaflex/schems/gs-15-r.gif

May 5th, 2006, 12:31 PM	#2 (permalink)
trdlasvegas Tele-Meister Join Date: Jul 2003 Location: Lost Wages, Nevada Posts: 205	The 7199 is the PI (Phase invertor). In simple terms it splits the signal into a postive and negative phase signal in order to drive the positive and negative tubes of the push pull output. -Tony __________________ www.trdpartsonline.com www.thermalrelief.com

May 6th, 2006, 03:53 PM	#6 (permalink)
trdlasvegas Tele-Meister Join Date: Jul 2003 Location: Lost Wages, Nevada Posts: 205	I'm not sure what the fancy name of this circuit is but it is definatly a Phase Inverter as the triode section of the tube is feeding the +/- output tubes, positive from the plate and negative from the cathode. -Tony __________________ www.trdpartsonline.com www.thermalrelief.com

May 5th, 2006, 02:22 PM	#3 (permalink)
bluehonky Tele-Meister Join Date: May 2004 Location: Lehigh Valley Posts: 133	Thanks Tony. That makes total sense. You rock. I'm trying to lean as much as I can about tube amps and guy like you and this site make it fun and easy. Thanks again.

May 5th, 2006, 02:58 PM	#4 (permalink)
Tremo Banned Friend of Leo's Join Date: Mar 2003 Location: Silicon Valley, CA, USA Posts: 3,803	It has TWO 7199s? Are you sure? Might someone have mistakenly put one in a 12AX7 socket? I'll have to look at Ampeg schemos again, I've not seen one with TWO 7199s. Very strange. A 7199 is a dual tube, but unlike the common 12A?7 dual triode types, the 7199 has one triode section and one pentode section. The most common application is to use the pentode as a gain stage and the triode as a split-load PI. Alternately I've seen them used with the triode as a reverb driver, and the pentode as the reverb recovery amp. I believe there is only one current production 7199, it's Sovtek, and it's of mediocre quality and performance. I hope JJ decides to make this type after they finish their EF86. As an alrernative, you can use types 6AN8 and 6U8, but the socket would probably need to be rewired.

May 5th, 2006, 03:45 PM	#5 (permalink)
bluehonky Tele-Meister Join Date: May 2004 Location: Lehigh Valley Posts: 133	You're right Tremo. There is only one 7199. I was reading the schem wrong. Still trying to wrap my brain around reading schematics.