Difference between 1977 and 90's power supply

[jackson649]

Could someone tell me if there are any advantages in using the 90's precision power supply schematics over the one used in the 1977 schematics?

[Darkbluemurder]

Do you mean the one with the "totem poles" (2 series caps at each node bypassed with resistors)? The advantages of such power supply are:

1) 2 series caps add voltage handling capacity (2 350 Volt caps can handle 700 Volts).
2) Should at any time the power supply string be broken (e.g. by a blown fuse or bad connection) there should be no residual charge in any of the caps.

You will appreciate the value of no. 2) when you worked on a Marshall with its fuse blown. The first two series caps do not have bleeding resistors, and when I checked just to make sure everything was OK the meter showed the full 500 Volts!

It should not make a discernible difference in sound.

[dogears]

There is a considerably different dropping string. That to me is the big tonal difference. The one thing we don't know is what the dropping string was on the 90s with certainty. We have an example, but it is possible the bybrid A dropping string was also used......

Could someone tell me if there are any advantages in using the 90's precision power supply schematics over the one used in the 1977 schematics?

[groovtubin]

Do you mean the one with the "totem poles" (2 series caps at each node bypassed with resistors)? The advantages of such power supply are:

1) 2 series caps add voltage handling capacity (2 350 Volt caps can handle 700 Volts).
2) Should at any time the power supply string be broken (e.g. by a blown fuse or bad connection) there should be no residual charge in any of the caps.

You will appreciate the value of no. 2) when you worked on a Marshall with its fuse blown. The first two series caps do not have bleeding resistors, and when I checked just to make sure everything was OK the meter showed the full 500 Volts!

It should not make a discernible difference in sound.

Like dogears, i`ve built almost ALL the variations, to MY ears it DOES make a HUGE diff in tone and esp string feel. Allowing the CHARGE time of a capacitor to be REDUCED produces a clearer sound. To the HIFI crowd it means BIGGER more well defined frequencies , and it does the same thing in a guitar amplifier! The overall feel is a bit STIFFER, but when you CRANK it up, hit the BOOST, STAND BACK!! try it and see what YOU think!!

[jackson649]

groovtubin, could you guys tell me which power supply you are refering to? Thanks

[skyboltone]

groovtubin, could you guys tell me which power supply you are refering to? Thanks

+1
Which one sounds fuller? without the bleeders or with them?

[groovtubin]

groovtubin, could you guys tell me which power supply you are refering to? Thanks

+1
Which one sounds fuller? without the bleeders or with them?

To ME i like using the stacked supply on a 50 watter JUST on the preamp, a 50 watter i go ALL the way, no matter which circuit, just exp and see what YOU like!

jim

[groovtubin]

groovtubin, could you guys tell me which power supply you are refering to? Thanks

97 ODS jp