resistor types

[Jazz P Bass]

Post the manual!

[TompaTheMan]

please be gently when asking for stuff!

[Jazz P Bass]

Got it.
LINE 6 ALCHEMIST SM Service Manual free download, schematics, eeprom, repair info for electronics

[TompaTheMan]

A simple thank you would be nice!

[Jazz P Bass]

Ooops!.
Sorry for being rude.
Thankyou for the information.
I still think you are in for a rough road modding this amp.
There are numerous jacks on the two channels.
Have you tried an offboard EQ in the EQ Send/return jack?

[TompaTheMan]

yes... and no I found a bad cable inside it just where the input for the guitar is..I'm trying fix it now

[bob p]

How come it's described as a pseudo-UL arrangement? I seem to remember that the UL taps are more like 20% than the more conventional 40% but it still conforms to the UL concept.
Pete

Sorry for the late reply, but I've recently been reading a bunch of old UL articles (thanks Gingertube!) to get a better handle on how the STR is set up. I took measurements of the OT, and the screen taps are at a much lower level than I've ever seen in any other examples of UL operation -- 12.5%. The most popular screen tap, coming from the HiFi world, appears to be about 40-45%, which is the point for minimum distortion. Going higher takes you closer to triode operation, going lower takes you closer to pentode operation. Mullard was famous for the 20% value, which is generally accepted as the highest power operating point for UL operation. I'm sure that you already knew this, but what struck me as odd was Fender's decision to tap at 12.5%, which is much lower than normal range for UL operation.

What's most interesting about the 12.5% choice is that distortion increases remarkably when UL taps are chosen at operating points below a 20% turns ratio. For the STR, Fender chose a very low UL tap ratio to make the amp operate more closely to pentode mode, with markedly higher distortion than any UL setup I've ever seen. It seems that the choice of a extremely low tap point for UL operation was deliberately chosen to keep the amp from operating too cleanly, while also maintaining the tube life prolongation advantages that come with UL operation at extremely high plate voltages at or above 500VDC. After quite a bit of reading it appears obvious that this amp was designed in a "pseudo-UL" implementation to make the amp sound like a pentode amp while giving the high voltage tube lifespan of an UL design.

There are a lot of odd implementations in this amp, which aren't always obvious or easy to understand without detailed study. The amp uses design features that are subtle, and they're the kind of things that most people are likely not to understand unless they do some detailed study and analysis of the circuit; the tendency for people not to do that often prompts them to modify the circuit to go with more traditional (BF/SF) implementations, which ultimately results in reliability problems. The more that I study this amp the more that I realize that the guy who designed it was one sharp cookie, and the less inclined I am to make the kinds of changes that seem tempting at first glance.

[dumbassbob]

Sorry for the late reply, but I've recently been reading a bunch of old UL articles (thanks Gingertube!) to get a better handle on how the STR is set up. I took measurements of the OT, and the screen taps are at a much lower level than I've ever seen in any other examples of UL operation -- 12.5%. The most popular screen tap, coming from the HiFi world, appears to be about 40-45%, which is the point for minimum distortion. Going higher takes you closer to triode operation, going lower takes you closer to pentode operation. Mullard was famous for the 20% value, which is generally accepted as the highest power operating point for UL operation. I'm sure that you already knew this, but what struck me as odd was Fender's decision to tap at 12.5%, which is much lower than normal range for UL operation.

What's most interesting about the 12.5% choice is that distortion increases remarkably when UL taps are chosen at operating points below a 20% turns ratio. For the STR, Fender chose a very low UL tap ratio to make the amp operate more closely to pentode mode, with markedly higher distortion than any UL setup I've ever seen. It seems that the choice of a extremely low tap point for UL operation was deliberately chosen to keep the amp from operating too cleanly, while also maintaining the tube life prolongation advantages that come with UL operation at extremely high plate voltages at or above 500VDC. After quite a bit of reading it appears obvious that this amp was designed in a "pseudo-UL" implementation to make the amp sound like a pentode amp while giving the high voltage tube lifespan of an UL design.

There are a lot of odd implementations in this amp, which aren't always obvious or easy to understand without detailed study. The amp uses design features that are subtle, and they're the kind of things that most people are likely not to understand unless they do some detailed study and analysis of the circuit; the tendency for people not to do that often prompts them to modify the circuit to go with more traditional (BF/SF) implementations, which ultimately results in reliability problems. The more that I study this amp the more that I realize that the guy who designed it was one sharp cookie, and the less inclined I am to make the kinds of changes that seem tempting at first glance.

I hope thats all thats wrong with mine