Split load PI in Peavey 6505+ 112 Combo

[rocket]

Hi,

I am wondering why the Peavey 6505+ 112 combo amp has a spli load/concertina style PI as opposed to the LTP in the other 6505 amps and the 5150.
There is no tube saved as the 2nd half of V6 is another gain stage, that the tops don't have (an don't seem to need either).

Can anone explain this?

Rocket

[Jazz P Bass]

Huh.
I never took notice to that.
And it is the same circuitry as the 5150II.

I got this from Wiki:
"The 6505+ is a second version of the 6505 and is identical to the 5150II. It features an extra 12AX7 tube in the preampstage, to prevent breakup in the clean channel.It features separate 3-band EQ, presence and resonance controls for the 2 channels. It also feature only one input, unlike the 6505, which had two. There are bias testpoints on the back, making changes to the tubes easier."

My take on a cathodyne PI is that it is less likely to distort.
AS there are more 12AX7s in the +, maybe the designers felt that enough was enough.

[Enzo]

You say it doesn;t save a tube because the other half of the PI tube is used for something. Well, what if they want that something to be a part of the amp? If they used an LTP PI, then they WOULD have to add another tube.

[rocket]

btw: the schematic of the combo : http://www.prowessamplifiers.com/sch...es/6505112.pdf

Maybe the additional gain stage is needed to make up for signal loss in fx way and the reverb.

[Jazz P Bass]

The 1/2 12AX7 before the PI is there to enable the PI to drive the 6L6 tubes.
Without it, there would not be enough signal swing.

I still maintain that the cathodyne PI was utilized for a 'cleaner' output stage.

If you have to know, call Glen at Peavey.
I am sure he would have the answer.

[Chuck H]

I'm inclined to agree with Jazz. The Peavey MO for that amp seems to be that the preamp is the signal processor and the power amp is a reference amplifier. Ergo, the power tubes are not supposed to clip much or ever. So no greater swing from the PI is needed beyond getting the output to full power. In fact, clipping the power amp is undesirable for an amp like this. It would kill the EQ effect that is crucial to the modern, uber gain sound. The goal of that amp could be described as high gain with notable EQ control. That gets lost if you clip the power tubes. So I, for one, think this is well thought out on Peavey's part to use the extra triode for generating distortion rather than power tube drive. Where it isn't needed.