Skyliner Tonestack Questions

[exocet]

I have a couple of Skyliner Tone Stack questions that I've been holding on to for months thinking that I might be able to work out the answer myself but to no avail.

1. What does Skyliner mean? I know it's just a made up term and have also seen references to 'scoping the output' to see a 'skyline' what does it mean and how different is the frequency response compared to a 'standard' Fender Twin tone stack. I've tried to use LTSpice but am not clever enough!!

2. What purpose does the 1n cap across the Bass Pot serve? If you decrease this value what happens? I know that in a standard TMB stack, you have 3 capacitors and that C3 feeding the Mid Pot effectively controls the upper range of the Bass control frequency response. C2 (feeding the Bass Pot) could be any value as it only has to block DC from the Pot. C1 sets the lower end of the treble control range. When the mid control is split away from the 'stack' as per Dumble architecture, I'm lost!!

[talbany]

1. What does Skyliner mean? I know it's just a made up term and have also seen references to 'scoping the output' to see a 'skyline' what does it mean and how different is the frequency response compared to a 'standard' Fender Twin tone stack. I've tried to use LTSpice but am not clever enough!!

There is more to the Skyliner than just the clean tonestack

Skyliner Amps - Skyliner amps can either be with or without the post overdrive stack. (The word skyliner refers to the clean tone stack). This stack has a bass knee of around 80 hertz and gives a slightly harder attack on the bass notes. The middle control is centered at or around 400 hertz as this provides the more pronounced upper mids that many folks talk about. Skyliners in general also used a negative feedback circuit between the plate and the grid of V1b..(Although some amps like 183 did not use this circuit I consider it part of the Skyliner upgrade in a pre classic)


The skyliner also had a PA boost circuit that breaks the connections between the treble and the bass controls as well as the top of the bass control to the wiper of the bass.(in Rock mode)This gives about 10+dB of boost on the top end with a gradual rolloff in response starting at around 600 to 800 hertz. This helps the bottom end from going loose especially with higher output buckers..

2. What purpose does the 1n cap across the Bass Pot serve? If you decrease this value what happens? I know that in a standard TMB stack, you have 3 capacitors and that C3 feeding the Mid Pot effectively controls the upper range of the Bass control frequency response. C2 (feeding the Bass Pot) could be any value as it only has to block DC from the Pot. C1 sets the lower end of the treble control range. When the mid control is split away from the 'stack' as per Dumble architecture, I'm lost!!

The bass control configuration (cap and resistor) in the Skyliner amps is part of whats known as the James configuration..You can download the Duncan TSC here and run some simulations..

http://www.duncanamps.com/tsc/

Take some time with the search function at the top of the page as there is a wealth of info on the skyline TS buried within this forum..
Hope This Helps!!

Tony

[Max]

Skyliners in general also used a negative feedback circuit between the plate and the grid of V1b..(Although some amps like 183 did not use this circuit I consider it part of the Skyliner upgrade)

Hi Tony,

AFAIK the V1b LNFB circuit is already the usual configuration for the transition generation and 4th generation "classic" amps. So AFAIK this V1b LNFB circuit is no part of a skyline update of a "classic" amp. Such a V1b LNFB loop would only be a part of a skyline update of a "pre-classic" amp.

All the skyline amps - original or updated - have a mid switch instead of the "pre classic" and "classic" deep switch.

A good example for what AFAIK makes a skyline amp a skyline amp are all the differences between the updated skyline version of #124 and the original "classic" version of #124.

original "classic" version of #124: https://tubeamparchive.com/viewtopic.ph ... 262#140262

updated "skyline" version of #124: https://tubeamparchive.com/viewtopic.php?p=55006#55006

All the best and take care,

Max

[talbany]

Max
Thanks for the clarification..

Be Well!!

T