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Just bought a "new" amp! Fender 400PS

#64
johnk_10 said:
in build quality, quality of components, power output, and tone. its quite a bit stronger than any of the 15 vintage SVT's that I've owned, including my current two. its tone is more transparent and clear, like a gigantic fender dual showman, but with alot more low end.
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did they sell fairly well..i've never seen one used,and around the time guys here were able to afford the bigger fenders most of them got svt's
 
#66
johnk_10 said:
I don't think that they did. one reason might have been because of the need to always run 3 cabs to tap its full output. but i have seen quite a few of them in my day and have owned a total of three heads.
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up here we have a market of 10% of the american ......and if they do the math sometimes makers don't even bother selling here......but i've seen so many svt's i gotta wonder where they all went
 
#67
cripula said:
Coreyfyfe, I was always under the impression that one 4ohm load would deliver 145W, 2 290W, and 3 the entire 435.
What you posted form Rich's FAQ is a bit over my head, but I believe he's talking about trying to get 435W out of 1 output, which you can't do.

I was under the impression it functioned as 3 separate 145W amps and was safe to run one or 2 cabs, you just wouldn't realize the full potential of the amp. Hopefully someone like Johnk_10 will step in and explain it for us.

FWIW I haven't run mine that way, only when I went to try/buy it. And it was still killing with only 2 4 ohm cabs.
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If you are running it that way, you are essentially leaving taps from the transformer without a load, or to be technical about it with an infinite load, which is not good for the transformer. It may function as three separate amps, but if they're all controlled by one standby, then you're running them all, not just the ones you plug in.
 
#68
I was interested enough to post the question to the 400PS yahoo group. Rich says it's fine to use one, two, or three cabs, as long as it's one per output jack and they're 4 ohm cabs.

Searching the archives I found a post referring to the 400's output transformer having 3 separate output windings, one for each jack.
This was interesting too:

"The PS400's 3 output jacks are unusual compared to nearly all other tube amps in that they each have a switch that "turns on" a pair of output tubes. Plug in one cab you get one pair of tubes; 2 cabs, 2 pair of tubes; all 3 outputs plugged into and you get all 6 output tubes operating. The 3 output jacks are all the same in how they work, so you can pick any combination of jacks you want and the PS400 should be happy"

Check out the original ad - the amp came with one speaker. The copy sure reads like it'll work fine with only one cab, and add more if you need it.

Link Removed
 
#69
cripula said:
"The PS400's 3 output jacks are unusual compared to nearly all other tube amps in that they each have a switch that "turns on" a pair of output tubes. Plug in one cab you get one pair of tubes; 2 cabs, 2 pair of tubes; all 3 outputs plugged into and you get all 6 output tubes operating. The 3 output jacks are all the same in how they work, so you can pick any combination of jacks you want and the PS400 should be happy"
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Ah, well there is the answer then. If the three sets are turned on/off by the presence of the cab then that's different. I don't own the amp, so it's not something I can see/test that's why I posed the question. I hadn't read anything like this anywhere, just that you needed to have three outputs going simultaneously (whether thats one cab or three is something different).
 
#71
cripula said:
I was interested enough to post the question to the 400PS yahoo group. Rich says it's fine to use one, two, or three cabs, as long as it's one per output jack and they're 4 ohm cabs.

Searching the archives I found a post referring to the 400's output transformer having 3 separate output windings, one for each jack.
This was interesting too:

"The PS400's 3 output jacks are unusual compared to nearly all other tube amps in that they each have a switch that "turns on" a pair of output tubes. Plug in one cab you get one pair of tubes; 2 cabs, 2 pair of tubes; all 3 outputs plugged into and you get all 6 output tubes operating. The 3 output jacks are all the same in how they work, so you can pick any combination of jacks you want and the PS400 should be happy"

Check out the original ad - the amp came with one speaker. The copy sure reads like it'll work fine with only one cab, and add more if you need it.

Link Removed
Click to expand...

That sounds a lot more sensible!
 
#72
cripula said:
I was interested enough to post the question to the 400PS yahoo group. Rich says it's fine to use one, two, or three cabs, as long as it's one per output jack and they're 4 ohm cabs.

Searching the archives I found a post referring to the 400's output transformer having 3 separate output windings, one for each jack.
This was interesting too:

"The PS400's 3 output jacks are unusual compared to nearly all other tube amps in that they each have a switch that "turns on" a pair of output tubes. Plug in one cab you get one pair of tubes; 2 cabs, 2 pair of tubes; all 3 outputs plugged into and you get all 6 output tubes operating. The 3 output jacks are all the same in how they work, so you can pick any combination of jacks you want and the PS400 should be happy"

Check out the original ad - the amp came with one speaker. The copy sure reads like it'll work fine with only one cab, and add more if you need it.

Link Removed
Click to expand...

Of course you could run any combination of cabs as long as you end up with each tap seeing a 4ohm load -- imagine six 8ohm 410 cabs!!!
I'd love to hear one hooked up to three Bergantino NV610 -- make a vertical stack but have the cabs on their sides.
 
#73
lo-freq said:
I'd love to hear one hooked up to three Bergantino NV610 -- make a vertical stack but have the cabs on their sides.
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I can tell you it's pretty jaw dropping with an NV610, NV215, and ampeg 8x10...
I do want an NV412 to complete the NV/400PS setup. I have an inkling that may turn out to be the best bass rig on planet earth. Unless I have to carry it... :D
 
#74
Heh, yeah, 400PS is very powerful amp, but 435 watt it is peak power (amplitude of voltage multiplied by amplitude of current). RMS power is twice lower 217.5 VA.

Anode voltage of 400PS is 700V. Maximum cathode current per 1 good 6550 tube is 0.22-0.23 A.
So max RMS power of this amp is Prms = Vrms * Irms = 0.7*650V * 0.7*(3*0.23A) = 219.7 VA
Or 219.7 * 2 = 439.4 watt peak power.

If you want more power you need more anode voltage swing and/or tube that can conduct more cathode current. But 660V/0.195A is datasheet limit of 6550. This is why this amp need very good GE6550A tubes, they work in very extreme condition. General KT88 would work in 400ps not so hard, because have 800V/0.23A specs.
 
#75
No. The 400PS is 435 watts RMS, not peak power ( it has 3 separate outputs @145 watts each). i measured eack of my outputs and it was putting out 147 watts RMS. With all of the loads hooked up into cabs, the amp feels stronger/louder than either of my SVT's. And GE 6650A's hold up very well in them.
 
#76
Hm, interesting. If a pair of 6550 puts 145W RMS, then cathode of one tube conducts 145Wrms/455Vrms = 0.31A RMS, or 0.31/0.7 = 0.45A peak. It is two times greater than nominal max current. It seems, than such doubled current is allowed because tube is resting second part of a period.
In any case such currents better suits for KT88. But, from other side, music is not pure sine wave, so you didn't really get constant max power when playing.
 
#78
If I could figure out how to rip a still from a dvd, you would all be looking at my 1988 RIG OF DOOM.

It was a Fender 400PS, restored and reworked by Dave Hicks, of Fender Mender fame. Mainly known for his guitar amp work, he did a mean job on the 400PS, and I couldn't have asked for a better amp.

It powered the original folded 18" horn, laying on it's side, and topped by an Ampeg SVT 8x10, also on it's side.

Sitting on top was my trusty Blue crystal 400PS, with white piping around the grill cloth. I only used two outputs, though I switched them around a little bit. And with that rig I never, and I mean NEVER needed PA support.

The rig was much louder than the house bands we played with most places, and would smoke any two cabinet SVT it came up against. Both volume, clarity, and when it got nasty, distortion.

G.A.S. got me one day, and the refrigerator cabinets got a little old. So I sold it, and have regretted it every day since. The Eden stuff I had was nice, but it was no 400PS.

Anybody know how to rip still from a dvd? You have GOT TO see that rig.
 

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