• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Just bought a "new" amp! Fender 400PS

#43
JimmyM said:
You won't harm the speakers at all. But why 3? That amp will do that low of an impedance?
Click to expand...

I'm glad to hear that. You know...150 watts into a 500 watt capable speaker seems like I wouldn't be able to get all I could out of it. Add all of those "underpowering" posts into it, and I thought I might have an issue. I'm new to the amp game, but I think I'm learning quickly.
 
#47
I was under the impression that you had to have three cabs hooked into this (or at least three speaker loads even if they're in one cab), otherwise you're leaving some of the transformer windings looking for a load. Or in other words, operating a tube head without a load which is not good.

http://www.timeelect.com/400-faq.htm

10. Can I get all the power of the 400-PS on one cabinet?

Not without a custom-made output transformer, and/or output stage circuit modification, can it be done properly. Many amp techs have asked, why can't you use the original existing secondary windings in a series or parallel combination, and get the desired power on one cabinet. For one reason, transformer windings are NOT like resistors when you tie them in the difference circuit configurations, It simply doesn't work that way. Two 4 ohm resistors in series is 8 ohms. Two 4 ohm windings in series is NOT 8 ohms. In reality,... it is much higher, and is closer to 16 ohms. Likewise, two 4 ohm resistors in parallel are 2 ohms. Two 4 ohm windings in parallel is NOT 2 ohms. In reality,... it is much lower, and is closer to 1.5 ohms. If such were to be done, this would place a reflected load on the tubes far from the proper designed tube loading on the primary winding. Thus, the actual power yield will be far less from the output tube loading mismatch than would be expected, and there is the creation of an increased risk of fly back from the high side loading error. Now you have the smoked up tube sockets in the 400-PS without knowing why. This is sure to place blame on the 400-PS.... and not the amp tech's ERROR in thinking!
 
#49
Goodlawdy said:
Custom make a 3 speaker cab with 3 separate jacks.
Click to expand...

Yeah they cover that in the FAQ, even have a nice pic of a cab with 3 JBL K130s. That still doesn't account for the few posts before mine where people were talking about running two 8 ohm cabs off one tap for 1/3 power or 2 cabs for 2/3 power. My point was that it doesn't work that way and people are potentially doing damage to their amps.
 
#50
coreyfyfe said:
Yeah they cover that in the FAQ, even have a nice pic of a cab with 3 JBL K130s. That still doesn't account for the few posts before mine where people were talking about running two 8 ohm cabs off one tap for 1/3 power or 2 cabs for 2/3 power. My point was that it doesn't work that way and people are potentially doing damage to their amps.
Click to expand...

Maybe they had dummy loads on the other two taps.
 
#51
coreyfyfe said:
Yeah they cover that in the FAQ, even have a nice pic of a cab with 3 JBL K130s. That still doesn't account for the few posts before mine where people were talking about running two 8 ohm cabs off one tap for 1/3 power or 2 cabs for 2/3 power. My point was that it doesn't work that way and people are potentially doing damage to their amps.
Click to expand...

Yeah, that was my mistake. I reread the FAQ, and what you say is the case. Good thing I'm ordering 3 cabs then. :D
 
#52
lo-freq said:
Maybe they had dummy loads on the other two taps.
Click to expand...

Haha that's in the FAQ as well:

21. Are there any Do's and Don'ts I should know about when using a 400-PS?
1. Always make sure all speaker cabinets are properly connected to the output jacks, BEFORE turning on a 400-PS.
2. Always warm up the tubes for a few minutes before playing.
3. Always let the tubes cool to room temperature, BEFORE loading out the 400-PS.
4. Never let an amp tech without prior 400-PS experience work on your 400-PS.
5. Always use the best output tubes possible. If you have read this far, you already know which tubes they are.
6. NEVER think of using a tranny toast (power attenuator) on a 400-PS.
7. Only connect 4 ohm loads to the speaker output jacks. Otherwise, you are looking for trouble.


Not my issue, I don't own the amp, I'm just putting it out there...
 
#53
coreyfyfe said:
Haha that's in the FAQ as well:

21. Are there any Do's and Don'ts I should know about when using a 400-PS?
1. Always make sure all speaker cabinets are properly connected to the output jacks, BEFORE turning on a 400-PS.
2. Always warm up the tubes for a few minutes before playing.
3. Always let the tubes cool to room temperature, BEFORE loading out the 400-PS.
4. Never let an amp tech without prior 400-PS experience work on your 400-PS.
5. Always use the best output tubes possible. If you have read this far, you already know which tubes they are.
6. NEVER think of using a tranny toast (power attenuator) on a 400-PS.
7. Only connect 4 ohm loads to the speaker output jacks. Otherwise, you are looking for trouble.


Not my issue, I don't own the amp, I'm just putting it out there...
Click to expand...

Not talking about a power attenuator.
A dummy load is just a resistor (with a proper resistance value and adequate power rating) that you use in the place of an actual speaker load -- as long as it is chosen (and rated) correctly it should actually be safer than an actual speaker (minimal inductance/capacitance compared to a reactive speaker).
The amp would never know the difference.
 
#55
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.
 
#56
if any amp called out for a 6x10 cab, i'd think this would be it!

6 8ohm 10s, grouped into three 4ohm 2x10 pairs, each pair getting its own tap.
 
#59
KPAX said:
You're going to drop $2k on a 400PS project?
Ok, keep us posted. It certainly sounds entertaining.
I'll just put these reality check questions out there. Take them or leave them.
You've played through the amp already - right?
If so, do you like the sound?
If so, why are you going to have this guy widen the frequency response of the tone circuit? That could change the tone. If the 400PS is so good, why change the preamp?
Do you need more power? If not, why pay this guy to do even more mods? If the 400PS is so powerful, why change the power amp?
Is he going to build the original folded-horn type cabs? If so, are those the type cabs you like playing through?
Have you played through the type cabs he's going to build for you?
Click to expand...
seems like a lot of money and energy to spend on a 40 year old fender.......for that you could have 2 400+ boogies......swap the tubes and wait a while before you start hot rodding.....take some time to find out if the mods are what you need or just expensive bragging rights....
 

Latest posts

Top Bottom
Back