Fender 400-PS  Ed Jahns Comment Page


If anyone would like to share their experiences with Ed Jahns, his 400-PS, or in some way contribute my effort to make known to the world the man who created the most amazing amplifier, please leave me an e-mail as you would have it appear here.  Any pictures will be greatly appreciated.

Many thanks in Advance,

Richard K. Koerner

Fantastic account of Ed on your web site.  I was speaking to folks recently about my time working in R&D back in 69-70s.  there were giants in the land back then: Ed was on of them.  I had forgotten his last name, but knew him by Ed. I was there when he designed his 6550 tube amp you show on your site. I was just a kid of early 20s then; designed and worked on CBS/Fender synthesizers with patch cords and all.  Great place to work and meet people in music industry as well.
Ed was quite a nice person; remember his saying he used to design at Philco and Pilot.  He must have been in his 60s when I was there; assume he's gone by now.

best regards,
Rick Vogel
KVRZ-FM president


I enjoyed your web site article on the Fender 400-PS, and it brought back some
recollections for me.

I "met" Ed Jahns by phone in 1978 when I worked the repair shop for a music
store in Charleston WV.  I immediately came to appreciate the designs,
construction, and customer support of Fender [CBS] Musical Instruments.  Our rep
had given me the super-secret instructions on calling for Fender Tech Support.
First, you placed a person-to-person call to Joyce Patterson, who was always in
a meeting or unavailable.  Now Joyce was a real person, but she would never
return the call.  Instead, a tech would call back on their WATS-out line and
presto - toll-free support!

Over the 2 years at the store, I talked with Ed on various troubleshooting
problems, ECOs, and some custom work I was asked to do.  I probably touched some
aspect of every tub amp that ever had the Fender logo.  There was something
educational in every conversation.  I learned - across several occasions - why
(and how) Ed had redesigned the 6L6 tube for the Twin, what causes scratchy
level controls, why a 7025 and a 12AX7A are NOT the same tube, and a number of
other great tips.  He and I both marveled at how the best efforts of circuit
designers to build true, clean amplification were being hammered by the
Marshalls and the Mesa Boogies of the time.  Effects makers were having the
darnedest time getting the Fenders to overdrive an amplifier stage.

Thanks for a great writeup on the 400.

BTW, I enjoyed this article on Harold Rhodes

These two should also be considered among the greats of Rock & Roll !!

Ronald Garrison


Remembering Ed Jahns

I worked at CBS Musical Instruments from 1970 through 1974 and worked with a man who designed many of the amps that make the name “Fender” memorable to this day. Of course, that man was Ed Jahns. I suppose his most memorable achievement was the 400 P.S. Bass Amplifier. The 100 watt Twin Reverb was also a gem and as I recall was a best seller for many years. The 400, however, stands out as a product that was way ahead of its time in terms of utilizing tube design to the ultimate in achieving stunning performance. Raw power. Another challenge at the time was how to harness all that power without smoking the speakers that all that power was being channeled to. It ultimately took 3 separate enclosures using state-of-the art speakers from both JBL and Vega to soak up about 150 watts each. The result was awe inspiring. If you were ever at a venue where the 400 along with the 3 speaker enclosures were being used – it was an experience of a lifetime. I always had empathy for the performers on stage who were so close to those deafening decibels.

I was Manager of Electronic Design at the time and thought I was pretty savvy about circuit design until I’d watch Ed start to design a new circuit. Forget about pencil and paper and sketching out a circuit – Ed would start soldering components together back-to-back, making measurements from time to time, while wearing his fedora and smoking a cigarette in his signature black cigarette holder. Only when he was done and satisfied with his work would it be committed to paper. I’ve never seen anyone else work like that! Ed was a stickler for using quality components even though there was extreme pressure from management to keep costs to a bare minimum. I recall more than one amplifier design never making it to market because the ROI didn’t meet the stringent corporate requirement – and I’m talking pennies!! Ed was forced to use 10% to 20% components to keep costs down. However, this also caused  a bit of a stir on occasion when a customer would come in and complain that his 100 watt amp was only putting out 80 watts or so. On the flip side, customers would occasionally come in and ask how come we were only advertising 100 watts when his amp was putting out 120 watts. And of course, Ed would explain this apparent controversy and for those whose amps were putting out less, he would “tweak” the amp to get the promised 100 watts. Most folks did not appreciate what it took to get Underwriter Laboratories (UL) approval for designs made for a mass market! There were always ways to get more power output – but not in a consistently “safe” manner.

Back to the 400 P.S. After Ed had a working prototype and 3 enclosures with speakers that would handle the task – Ike Turner and his crew were called in to give the amp a test run. It was set up in the sound room and after getting all the proper connections made, they started to jam. WOW! The entire complex descended on the area because you could hear it wherever you were at. Ike and his musicians were ecstatic and I believe they were one of the first to own a production set. Bringing in musicians to test new products was standard fare and was crucial to get the feedback necessary from the end-users to make the product stand out compared to the competition.

Ed was “old school” in his approach to electronic design but he had a natural ability or vision when it came to tubes. His knowledge of how to get the absolute most out of a particular tube type was uncanny. He was known to work with tube manufacturers to maximize tube performance – as was the case with the tubes used in the 400. I didn’t personally witness this, but there are others who can testify to the collaboration with tube vendors in this regard (e.g. General Electric).

These were the days when folks such as Freddy Tavares, the “golden ears” for guitar sound quality, Gene Fields working on state-of-the-art steel guitars, Harold Rhodes and his 73 and 88 key electric pianos, Seth Lover working on the ultimate hum-bucking guitar pickups were plying their trade. What would the Fender name be without the talents of these and others whose names I can’t recall?

Ed was always the gentleman when asked for technical help. Those were the days when he would drop everything to get the customer what he needed – and of course at no cost. Try getting that today! I wish I could recall more detailed memories of those days!

I only knew Ed for about 4 years, but he has left a lifetime impression on me and I would venture on those who had the opportunity to even know him a little bit. He was “one of a kind” and will never be forgotten. God Bless . . . . Ed.

John Sennikoff


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