Monster Fender rig - 400 PS

[Pilgrim]

If you get to the point where you just need too get the amp out of there, and your regular contact is not available, just let me know. That shop is about 1/2 hour - 45 minutes from me.

It is best not to leave such things sitting too long.

[FrankieTbird]

PBG - your account of your PS400's whereabouts got me thinking - there is probably only ONE place in NJ that someone would send a 400PS for service. Is that where yours got to?

That's gotta be the guy in Union, can't remember his name anymore, been about 6 years since I lived in NJ.  He's a total tool, if it was my amp I'd get it out of there asap.

[Psycho Bass Guy]

...bigger fish to fry.  It's probably gone.

[Happy Face]

A PS 400 cab offered up the road a piece.

http://maine.craigslist.org/msg/5113251270.html

[Nocturnal]

And a 400 PS head available close to me:

http://phoenix.craigslist.org/nph/msg/5102503503.html

[Happy Face]

https://reverb.com/news/the-most-powerful-tube-amp-of-all-time-behind-the-fender-400-ps?utm_campaign=e01aae5a23-rn170502_deals&utm_medium=email&utm_source=newsletter&utm_term=0_5889ed6702-e01aae5a23-57277785

Of course, there are some obligatory "oh my back!" kinda of posts in the comments section.

[Psycho Bass Guy]

The comments about tube history in regards to the 6550A are bullshit, as are the comments about the SVT preamp rolling off bass naturally, and though it's an opinion, I would NOT describe the amp's tone on any channel are particularly "clear." Also, not using an output on the 400PS does NOT put its respective output tube pair into standby, but shorts it to ground.

Regarding the tubes, I knew the former head of QC for GE's Owensboro, KY factory; the 6550A was a US replacement for the KT88, a copy of Sylvania's 6550A, who produced ALL the tube glass envelopes for both companies. GE only made it because the envelopes already existed and they could use-off spec 6550A's, bottle and all, rebased as 6CA7's.  The 6550A had more stable screen grids than both the original small bottle RCA 6550 and coke bottle Tungsol 6550, which allowed the tube to be driven much harder for more output power. It was made to accommodate both the burgeoning hi-power hi-fi designs of the day and output power hungry manufacturers like Fender AND Ampeg. RCA, Ampeg's former favored tube maker and neighbor in New Jersey (See the 7027), had already ceased most domestic tube production by the early 70's, though it sold other makes rebranded as its own until the mid 80's. When Magnavox bought Ampeg in 1971 and moved production to East Tennessee, it leveraged its relationship with Sylvania, similarly to Fender's famous "STR" Sylvania 6L6GC's made for the also-mentioned silverface Bassman amps, to help design a higher powered 6550, though SVT's shipped with Magnavox-branded Tungsol 6550's as late as the mid 70's.

In regards to the SVT preamp, a simple perusal of Bass Gear Magazine's curve trace of the SVT preamp set flat shows a distinctive bass BOOST, not cut, or more accurately, an inherent midrange cut that could be mitigated with the active midrange control; the rest of the tone stack is passive.

It's cool to see the 400PS get some press, but though the issues I take may be details, they are important ones.

[Happy Face]

Thanks for the clarifications. 

It's still interesting to many of us.



(I deleted the rest of my comment about the people on that thread whining about the weight of the amp.) 

[Psycho Bass Guy]

I don't deny the article is a long overdue tribute to an often unknown amp, but it doesn't do anyone any favors to spread falsehoods, intentionally or not. Maybe it's the leftover bad taste of my time in TV news and seeing corners cut at the expense of the truth one time too many.

[gearHed289]

In regards to the SVT preamp, a simple perusal of Bass Gear Magazine's curve trace of the SVT preamp set flat shows a distinctive bass BOOST, not cut, or more accurately, an inherent midrange cut that could be mitigated with the active midrange control; the rest of the tone stack is passive.

So the bass and treble are passive in an SVT? And as I'm sure you know, the "ultra lo" switch is much more of a mid cut than it is a bass boost.

[Granny Gremlin]

I appreciate the clarifications as well, and there are a lot of good points in there, but, I hope you realise that this bit quoted below is a reasonably valid approximation intended for non-techie consumption and not literal interpretation; the point is the given pair of tubes is disabled.  Not a literal standby, but not properly 'on' either.  Reverb will dumb it down like that and it's not invalid if annoying for those who know better.  The rest of the inaccuracies are inexcusable though.

not using an output on the 400PS does NOT put its respective output tube pair into standby, but shorts it to ground.

Again, thanks for the clarification, from those of us who do get the difference.

[Psycho Bass Guy]

So the bass and treble are passive in an SVT? And as I'm sure you know, the "ultra lo" switch is much more of a mid cut than it is a bass boost.

The SVT was one of, if not the, first amps to feature an active EQ. However, it is only in the midrange. All the other tone controls are passive.

Re: "standby" versus ground shorting- that's the most important thing they got wrong. Fender's use of shorting output jacks to protect tube power sections is well known and there's a big difference between somehow idling the tube, like lifting the cathode ground and removing the drive signal (ala Trace Elliot) and conducting its voltage output to ground.