Ceriatone C-Wreck vs Rocket

[norburybrook]

The switch is a mod Ken Fischer put in at least one Rocket. I also put it in my Rocket clone. To my ear there is a bit less gain when the voltage divider and 25uF cap are engaged. The cap does increase the gain but the voltage divider reduces it.

The switch to me is a humbucking/single coil switch. The Rocket in it's normal state suits single coils a little more. The cap with the voltage divide seems to my ear to cut the mids in the Rocket making it more suitable for humbuckers.

Mark,

Strange as I get completely the opposite , the amp as a Z wreck with the divider and cathode cap is gainy and with them lifted, in Rocket mode, it's a lot cleaner and less gainy.


I've just ordered some more electrolytic caps to see what the extra filtering of the rocket does to the sound the wreck only has 8uf on the pre amp stages where the rocket has 22uf that's quite a difference.


M

[Mark]

Marcus are you lifting the 220K to ground of the voltage divider?

[M Fowler]

Dr Z later changed that low filtering to a more reasonable/standard uf.

[norburybrook]

Marcus are you lifting the 220K to ground of the voltage divider?

yes, I've got the 250k voltage diver resistor and the cathode cap wired to a SPDT switch so they come in and out together. it's entirely possible I've cocked it up though

Basically I lifted the ground end of the divider and the ground end of the cap and took that to the top of the switch and then the center of the switch goes to ground. So they're either floating or grounded.

From what i read up to doing this, the Z wreck had more gain than the rocket so that's the expected result no?


M

[telekasper]

Sub a 100k for the 220k plate load resistor on v1 and change the voltage divider at the phase inverter from 220k/220k to ground to something like 100k/470k to ground.

Ok, spending more time with this amp I have come to the conclusion that the lower headroom is directly related to the power tube section. I tried all 12at7's in the preamp and phase inverter and really the amp sounds better with 12ax7's and the lower headroom really didn't improve. Any suggestions for getting more headroom out of the power tube section? The amp has a matched quad of Russian 6p14p valves and a ppimv. It seems to gain a little headroom using the lower voltage side of the 260v/290v comfort switch.

[M Fowler]

Change the 220k plate resistor to 100K or 120K or 150K or 180K anything but higher gain 220k

remove the 220k/220k voltage divider only need the 220k input to PI off the treble pot wiper.

[telekasper]

Change the 220k plate resistor to 100K or 120K or 150K or 180K anything but higher gain 220k

remove the 220k/220k voltage divider only need the 220k input to PI off the treble pot wiper.

Thanks!
Ok, I have done a 100k plate resistor sub. So just to be clear, the 220k resistor that goes to ground can just be removed, keep the one to the treble pot?

[Colossal]

Change the 220k plate resistor to 100K or 120K or 150K or 180K anything but higher gain 220k

remove the 220k/220k voltage divider only need the 220k input to PI off the treble pot wiper.

Thanks!
Ok, I have done a 100k plate resistor sub. So just to be clear, the 220k resistor that goes to ground can just be removed, keep the one to to the treble pot?

Yes. Keep the series 220k. Remove the 220k to ground. You could also put that ground lift on a switch and be able to A/B it.

[2tone]

How does removing the 220k resistor to ground decrease the gain? I would think it would send more signal to the PI, whereas the voltage divider takes away some signal, sending it to ground, which should lessen the gain?

[Colossal]

How does removing the 220k resistor to ground decrease the gain? I would think it would send more signal to the PI, whereas the voltage divider takes away some signal, sending it to ground, which should lessen the gain?

2Tone, I have seen this mod when there is no bypass cap on the second stage. With the 220k/220k divider in and no 25uF cap on V1b, that is the lower gain setting. The Rocket has no bypass cap and only the series 220k in front of the PI. The ZWreck has the 25uF cap and the divider.

[2tone]

Thanks Colossal..I have done the mod to my Rocket in the early days...I put in the bypass cap and I put in a 220k with a switch to ground for both the cap and the 220k> BUT, I still am confused as to how putting in the 220k/220k voltage divider, which will lessen the volts to the PI, will increase the gain?? I see how the bypass cap will increase the gain, but this voltage divider eludes me on the theory.. I found that in my Rocket, after putting in the extra 220k and the bypass cap, both on a single switch to ground, that the overall volume and gain of the amp was only slightly changed, maybe a hair dirtier..

[telekasper]

It does appear to me that the resistor to ground would bleed off some signal or voltage, and removing it would increase the gain? Does it have some effect on stability? I'm here to learn something so please explain if you have a chance!
I will leave that split alone for the time being.

[norburybrook]

Thanks Colossal..I have done the mod to my Rocket in the early days...I put in the bypass cap and I put in a 220k with a switch to ground for both the cap and the 220k> BUT, I still am confused as to how putting in the 220k/220k voltage divider, which will lessen the volts to the PI, will increase the gain?? I see how the bypass cap will increase the gain, but this voltage divider eludes me on the theory.. I found that in my Rocket, after putting in the extra 220k and the bypass cap, both on a single switch to ground, that the overall volume and gain of the amp was only slightly changed, maybe a hair dirtier..

the 220/220k DECREASES gain but that's because the 25uF cathode cap INCREASES gain so it needs to be balanced out. Hence overall there'a not a lot of difference. The Z wreck has slightly more gain IMHO than the rocket.


I'm going to add the Rocket filtering this week to my Wreck, so I'll post back how that goes.

M

[telekasper]

Thanks Colossal..I have done the mod to my Rocket in the early days...I put in the bypass cap and I put in a 220k with a switch to ground for both the cap and the 220k> BUT, I still am confused as to how putting in the 220k/220k voltage divider, which will lessen the volts to the PI, will increase the gain?? I see how the bypass cap will increase the gain, but this voltage divider eludes me on the theory.. I found that in my Rocket, after putting in the extra 220k and the bypass cap, both on a single switch to ground, that the overall volume and gain of the amp was only slightly changed, maybe a hair dirtier..

the 220/220k DECREASES gain but that's because the 25uF cathode cap INCREASES gain so it needs to be balanced out. Hence overall there'a not a lot of difference. The Z wreck has slightly more gain IMHO than the rocket.


I'm going to add the Rocket filtering this week to my Wreck, so I'll post back how that goes.

M

So are you saying Its necessary to remove the 25uf cap and the 220k to ground?

[norburybrook]

Thanks Colossal..I have done the mod to my Rocket in the early days...I put in the bypass cap and I put in a 220k with a switch to ground for both the cap and the 220k> BUT, I still am confused as to how putting in the 220k/220k voltage divider, which will lessen the volts to the PI, will increase the gain?? I see how the bypass cap will increase the gain, but this voltage divider eludes me on the theory.. I found that in my Rocket, after putting in the extra 220k and the bypass cap, both on a single switch to ground, that the overall volume and gain of the amp was only slightly changed, maybe a hair dirtier..

the 220/220k DECREASES gain but that's because the 25uF cathode cap INCREASES gain so it needs to be balanced out. Hence overall there'a not a lot of difference. The Z wreck has slightly more gain IMHO than the rocket.


I'm going to add the Rocket filtering this week to my Wreck, so I'll post back how that goes.

M

So are you saying Its necessary to remove the 25uf cap and the 220k to ground?

if you want it to be like a rocket then yes. I find this has slightly less gain. I put them on a switch if you have them in circuit then it's a 5 minute job and you can have rocket/ Z wreck switch

M