The plot thickens: Jack Gentul designed the Excelsior amps.*  I'm still so startled by this twist in the road that I can only cover the few details I know so far.

I've been suspicious of these amps since I first saw one a few
months ago.  Some models had odd similarities to Hilgens - such as the carrying handle, which is, so far as I know, unique to Hilgen amps.  Common wisdom on the internet was that they were all made by either by Sano or a nameless Japanese company.  I was pretty sure that could not be accurate.  However, I already had (and still have) a huge backload of Hilgen material to investigate.  So I let it go.

Earlier this week someone who is in a position to know such things told me that he'd seen a document connecting Jack Gentul to these amps.  As fate would have it, there was an Excelsior amp for sale on eBay.  I drove about four hours to get it yesterday.

Here's the front of the amp:

So far, no resemblance to Hilgen.

Here's the back:

Thus far I have not found any Hilgen with an original Jensen speaker (although I've seen at least one replacement.) I believe this one is original.  However, that chassis is pure Jack Gentul workmanship and lay-out.  By now his wiring design and execution seems almost as distinctive as a fingerprint.  Then there are the 7591 power tubes.  The cabinet (other than the tolex) is classic Hilgen construction.

But now let's take a closer look at one of those 7591's:

Gulp.

On top of that, at least three of the pre-amp tubes are re-branded "Radio-Matic."  The amp was made in 1964.  [That fact is inconsistent with my current timeline.  However, based on other information I received last week, plus the force of inconsistencies that just won't go away, I know that my current timeline for the period after Jack Gentul left Brook Electronics has huge gaps and downright errors.  Oh well; electro-archaeology is meant to be a discipline, not a belief system.]

The control panel has some corrosion I'd like to see if I can reduce (gingerly) before I photograph it.  It is very different from the Hilgen control panel cosmetically.  It has a gold, brushed-aluminum faceplate similar to that of a Marshall Plexi, with chicken-head knobs.

Other Excelsior amps have model names, such as the "Americana." However, the only model designation on this amplifier is "High Quality Amplifier."  Where have we seen that before? 

I had thought Jack Gentul was an unsung master of amplifier design, but this is getting a little out of hand...

More to come.

*There is no resemblance between the original Excelsior amps and the Fender "pawn shop" reissues. I do not know how Fender acquired the right to the Excelsior brand, but what it purports to have "reissued" never existed. The originals are vastly superior to Fender's cynical counterfeits.

This amplifier was advertised as a Sano 16WR.  I knew that that could not be true. The seller also suggested that it might be a Hilgen.  I thought that was extremely likely. So far as I know, Sano never used this style of grille cloth, nor did it affix the brass coat of arms at the lower right corner of the grille.   On the other hand, Hilgen used this grille cloth 100% of the time, and very frequently used the coat of arms.  I have never seen the coat of arms on any amp other than a Hilgen.

And yet on another hand:

The control panel does not bear the Hilgen logo.  Nor does it use the Sano logo.  However, Sano did, on several models, place a chevron above the inputs.

And...

The wiring bears similarities to that on both early 60's Sanos and Hilgens, although it uses components that I have seen in many Hilgens but few Sanos.

However, there's no arguing with:

V.2 is an ECC82 rebranded as a Hilgen 12AU7A.  All the tubes are of similar appearance with respect to their age, and all appear original. 

The amp is a challenge to date thus far.  Remarkably, I have found no date codes or any other identifying information on the speaker.  The pot codes are atypical.  They begin with the code, "CM25880."  The internet reveals no EIA code that matches it.  Following that code are the numbers, "6430."  Typically, that would indicate that the pot was made in the 30th week of 1964, which coincides well with my working timeline for when Jack Gentul started Hilgen. 

I wonder if Jack wired this himself?  It's beautiful workmanship.

More to follow.

On June 14, 2013, I had a lengthy exchange of e-mails with Nelson Checkoway, a highly-accomplished musician and aficionado of vintage tube amps.  He's got some great old Fender and Gibson amps, but still has fallen in love with the Model 2522 Victor he recently accomplished.  He's a Hilgenite, all right.

On the page on this website concerning the 1966 Hilgen catalog, I insisted that no Hilgen amps ever had both the badge in the upper left corner of the grille and the coat of arms in the lower right corner. Yet in the photo furthest to the left above, you'll see Nelson's Victor amp brazenly displaying both insignia. The nerve of that amp.  I'm the expert around here. 

But seriously, that's exactly what this site is for: to follow the evidentiary trail wherever it leads, and to abandon hypotheses when contradicted by the electro-archaeological facts.

Nelson's amp also upset an assumption that I had not expressed yet on the site: that Hilgen used only one type of control knob throughout its history.  It is still true that the overwhelming majority of Hilgens, regardless of when they were built, have the type of knobs shown in my pictures of the Swing Away and the Champion.  However, Nelson's Victor has a different style of knob, that is very similar to those used on certain Ampeg amps.  See the second photo from the left, above.

Nelson and I discussed the Victor owned by Rob Roberge and shown at  http://www.myrareguitars.com/hilgen-victor-model-r2522-amplifier.  I thought I'd already learned all I could from those pictures, but when I looked back at the photos, I saw that Rob's Victor has the same knobs as does Nelson's amp.  See the third photo from the left, above.

That I was wrong in my thinking that Hilgen amp knobs came in only one style actually came as good news for me.  I have a B2501 Basso that has exactly the same knobs. I was mildly disappointed that the amp had replacement knobs, but now it turns out that they are (presumably) original.  Much obliged, Nelson and Rob! 

However, we have a new conundrum:  why are the Ampeg-syle knobs so unusual?  Could there have been a time when Jack Gentul lost his supply of the standard knobs? Was he experimenting with new cosmetics?  If so, why did he terminate his experiment?

And we're on to an even greater mystery: is Rob's Victor in a Hilgen-built cabinet? The cabinet is shown in the photo furthest to the right, above.  Before yesterday, I would have felt entirely confident in concluding that someone had modified the original cabinet.  I have never seen a Hilgen with that style of grille cloth, and the cabinet is almost 50% smaller than the standard Victor cabinet. Indeed, no production Hilgen amp resembles that cabinet. Was this a user modification?  Or did Jack Gentul make custom cabinets as special orders? Why does Rob's Victor have a toggle power switch rather than a rotary switch?  (Hilgen used both types of power switches, but not on the same models -- as far as I know.) Tf it's a user modification, I'm impressed that they retained the white piping and that the cabinet was so neatly recovered in appropriate black tolex. I'm going to contact Rob to see what he can tell us.

Whenever I think I've seen everything, an anomaly is sure to follow.

It all started on June 14, 2013 when James Dunlap left a note on the website saying that he'd just bought a Model 2024 Challenger for $ 20, and that "everything but the tremolo works!"  I congratulated him, but couldn't help feeling the sting of knowing that I'd paid more than 10x that much for mine.  And I sure as heck wasn't going to tell him that the reverb on mine didn't work.  (I had theorized that the malfunction was caused by a bad solder joint,  a component, or the reverb itself, and that it would take some effort to diagnose.  I therefore took the only responsible course of action: I procrastinated.)

As I always do when someone alerts me that they have a Hilgen amp, I asked James to take some pictures.  He responded immediately with some clear pictures, including some of the tube array.  That was courageous of him, because James -- at that moment -- knew nothing about amp innards.

It was obvious that James's Challenger had a completely original set of tubes, including two Amperex Bugle Boys and a Mullard.  Because my Challenger also appeared to have its original tubes, I asked James to try to read off the identification numbers on the tubes.  I was assuming that our respective tube arrays would be identical.  The power tubes and rectifier matched: two 7591A power tubes and a 5URGB rectifier.  The pre-amp tubes did not:

Mine:        v1: 6C4  v.2: 12AX7  v.3 12AX7  v.4 12AU7  v. 5 12AU7
James:      v1: 6C4  v.2: 12AU7  v.3 12AX7  v.4 12AX7  v. 5 12AU7

"Only one can be correct," I thought.  Therefore, I changed my tube sequence to match James's array.  The reverb worked for the first time since I'd owned the amp.  On the other hand, the tremolo did not work -- again for the first time ever.  A lightbulb  went off in my head: "V.2 must be the culprit in James's sequence. Let's try putting a 12AX7 back in there."  I grabbed a brand new Groove Tubes 12AX7 and plugged it into V.2.  Now both the reverb and the tremolo worked!  However, the amp sounded like it had too much gain; lots of people would prefer that more conventional sound, but it no longer sounded like a Hilgen.  Because I had never seen a Hilgen circuit that had more than two 12AX7's,  I hypothesized that v.3 should be the proper location for the other 12AU7.  The theory proved correct: the reverb and tremolo were both operating, and the amp sounded like a Hilgen again.  (Back went the original 12AX7. No offense, Groove Tubes.  This is electro-archaeology.)

However, because this tube array was different from either of the original arrays, I was still a little unsure about contradicting what seemed to be history.  Blasphemy usually gets people into trouble.

Luckily, James was at his computer much of yesterday.  I immediately sent him an e-mail in which I asked him if he was willing to try putting a 12AX7 into v.2 and to see if his tremolo came on.  I told him that, because I could not exclude the possibility that his amp might blow up, he should feel free to decline.  But I then self-servingly suggested that the odds of that happening were pretty low, given that the pin-outs for the two tubes were the same and the 12AX7 simply had more gain.  

James took a leap of faith and switched his v.2 and v.3.  Now both his reverb and tremolo worked! 

Therefore, the proper tube sequence for the Model 2024 Challenger is: v.1: 6C4  v.2: 12AX7  v.3: 12AU7  v.4: 12AX7  v.5: 12AU7  v.6: 7591A   v.7:  7591A  v.8: 5U4GB

In sum, as a result of working together for several hours, James and I (a) fixed both our amps, (b) proved what was the proper tube array for the Challenger, and (c) discovered that even if an amp has its original tubes, that doesn't preclude the seemingly unlikely possibility that someone may have taken them out and put them back incorrectly. Neither of our amps' apparently original tube arrays had been correct.  If James had not taken the time to fill out a response form and investigate this mystery as thoroughly as he did, none of this would have happened.  Thank you, James!

Now James's $20 Challenger is an even better deal.  But I'm totally delighted about that.

What a day.
What a day.

I do not have enough time tonight to describe everything I learned today from James Dunlap and Nelson Checkoway.  

Despite our lack of technical training, James and I (a) deduced the original tube sequence for the Model R2024 Challenger and, in the process, (b) fixed both our Challenger amps.

Nelson Checkoway refuted several of my working assumptions about (a) the cosmetics of Hilgen amps, (b) the relation between amp models that evolved from one-channel to two-channel versions in general, and (c) the specifications of the Model R2522 Victor amplifier in particular.

I had hoped that the website might work this way, but I had not dared hope it actually would.  I am in awe at the generosity, enthusiasm, and technical competence of the folks who are contacting me through the site. I am convinced that, together, we are actually going to solve the mysteries of the great but unsung Hilgen amplifiers and their designer, Jack Gentul.  Plus, the story is turning out to be far more intriguing than I would ever have supposed.

Thank you all, my esteemed fellow electro-archaeoligists.  More detail tomorrow about the happenings of today.

John

I now know that I do NOT know what the chassis codes mean.  

Based on the history available to me so far, distinctly Hilgen amps were made only from 1964 through 1967.  I had run into a string of 1965 and 1966 models that had chassis codes that ended appropriately in 5 or 6.  Hence I tentatively concluded that the last digit was the year of manufacture.  Since then I have found chassis codes with final digits that cannot possibly be the build date, and others where NONE of the digits could be year codes. 

The letter preceding the number is proving no more consistent.  Thus far I have seen chassis codes beginning with the letters B, C, D, G, and K.   Unless there is some startling new information out there, there are already more letters than there are possible years of manufacture.  I suppose the letters could indicate the month, but it seems odd that Hilgen would keep track of the month but not the year.  The letters definitely do not signify a model number, because I have found multiple different models with chassis codes that begin with B. 

Here is a good example of a question that cannot be answered without data from other Hilgenites.  I presume that if we obtain enough chassis codes from amps that are capable of being dated from speaker, pot, or other date codes a pattern will emerge.  If it were purely random, why would Hilgen bother to stamp alphanumerical codes on their amps at all?

On the plus side, today I had the good fortune to purchase on eBay an amplifier that is obviously a Hilgen but that does not have the "Hilgen" badge in the upper left corner of the grille cloth or the Hilgen name on the control panel.  However, it has to be a Hilgen because it has grill cloth and other cosmetic appointments that are unique to Hilgen and -- perhaps most importantly -- bears the brass "coat of arms" that Hilgen (and Hilgen alone) continued to use on some of its production bass amps.  It has no Sano markings whatsoever.  My present hypothesis is that Mr. Gentul built the amp before he had formally severed his legal ties to Sano, and thus could not put his name (or any other overt brand name) on it.  Perhaps it was built in Jack's father's basement.  Perhaps Jack wired it himself.  All speculations, but plausible ones.

In any event, I believe I've found significant evidence of how Hilgen Manufacturing Company evolved out of Sano.