230 Hamburg and 250 El Dorado 'passive boost'

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230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Thu Jun 17, 2021 9:06 am

Related to the 230 Hamburg and 250 El Dorado guitars, the Tony Bacon/Paul Day Rickenbacker-book mentions a 'passive boost' for these models.

But the available schematics on the Rickenbacker-site don't reflect this; just straightforward passive Vol & Tone controls.

While 'passive boost' sounds like joking with the laws of nature, there'll nevertheless be possibilities, so curious what they've done here.

Anyone any idea if this has indeed been implemented? Anybody has a schematic, or some inside pics?

Thanks!
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (jdogric12) » Thu Jun 17, 2021 10:08 am

I had a 260 once and I don't remember a boost.
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (espidog) » Thu Jun 17, 2021 12:12 pm

Complete speculation here, but (regardless of whether it was actually put into production) "passive boost" might have been some kind of multi-tapped transformer affair, like the 3-position switch on my Epi Jack Casady bass: it changes the impedence seen by the amplifier's input stage. The result is a stepped change from clean/civilised/flat frequency response to thick/midrangey and LOUD. 8)

AFAIK it would require a specially wound and tapped pickup though.
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (teb) » Thu Jun 17, 2021 12:47 pm

250 003.jpg
I don't recall anything like that on my 250. It was pretty straightforward with tone and volume knobs and a 3-way pickup selector. Of all the Rickenbackers I've owned and sold off over the years, I probably miss that one the most. Some guitars just feel great in your hands, and that one certainly did. I sold it off to help fund a $2,700 rosewood Harrison Telecaster. It was pretty, but turned out to be a step down in terms of sound quality and playability compared to the 250.
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Sat Jun 19, 2021 5:15 pm

jdogric12 wrote:I had a 260 once and I don't remember a boost.


Thanks for the info, it then agrees with the published schematics as well, but the book-remark becoming more & more mysterious ;-) (or incorrect ;-) )
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Sat Jun 19, 2021 5:23 pm

espidog wrote:Complete speculation here, but (regardless of whether it was actually put into production) "passive boost" might have been some kind of multi-tapped transformer affair, like the 3-position switch on my Epi Jack Casady bass: it changes the impedence seen by the amplifier's input stage. The result is a stepped change from clean/civilised/flat frequency response to thick/midrangey and LOUD. 8)

AFAIK it would require a specially wound and tapped pickup though.


Thanks for the response and great & also fun to read this.

I mean, I felt free to post this 'passive boost' question also on the Facebook-version of RickResource, and replied almost an alike response as you did here.
(I happen to have a JC bass as well, and that step-up transformer is indeed a great feature, giving this bass so many possibilities, and that just with a single pickup. But hey, you know this already ;-0 )

But who knows, that Rickenbacker indeed initially considered a step-up transformer as well for the 230 & 250.

The thing is, the way the book formulates it makes one think as an alternative method of powering a circuit, i.s.o. by a battery.
This impression is strengthened by the remark that the neck-PU seems to provide enough oomph (power), but not so for the bridge-PU.
For a step-up transformer this would however be no issue at all; also for a bridge-PU it'll always work.

Bye
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Sat Jun 19, 2021 5:32 pm

teb wrote:
250 003.jpg
I don't recall anything like that on my 250. It was pretty straightforward with tone and volume knobs and a 3-way pickup selector. Of all the Rickenbackers I've owned and sold off over the years, I probably miss that one the most. Some guitars just feel great in your hands, and that one certainly did. I sold it off to help fund a $2,700 rosewood Harrison Telecaster. It was pretty, but turned out to be a step down in terms of sound quality and playability compared to the 250.


Thanks for the response & nice picture. Too bad the Tele turned out a bit less.... FWIW, as I thought to have understood it Rossmeisl was involved in that one, and not in those 230 & 250 from later years.
Hope you still have the other Rick on the photo?
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (teb) » Sat Jun 19, 2021 9:13 pm

Yes, I still have my modified 2030 bass, though that was the first body I built for it and it's sitting somewhere in the basement. The current body is the second one I built with a few minor changes to the shape and it is top-bound (lower right in the second photo). I go back and forth on it between flats for old time rock and roll sounds and half-rounds which can sound kind of like a really good (better than real life) acoustic bass guitar.
sound clip:
https://www.broadjam.com/songs/toddbrad ... drive-in-d

2030k.jpg


009a.jpg
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (espidog) » Sun Jun 20, 2021 5:02 pm

Really enjoyed that soundclip, Todd - what a gorgeous tone you've got going there. 8)

And as for the top-bound modified 2030... that's as pretty as! Wake up, RIC - you're missing a trick here!
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Sun Jun 20, 2021 5:06 pm

teb wrote:Yes, I still have my modified 2030 bass, though that was the first body I built for it and it's sitting somewhere in the basement.]


Oops, I hadn't watched that 1st pic in full detail the first time, it'sssss a bass!! And as I understand it it's all 'original', but you made/modified/in-fact-replaced the body? (And didn't stop there :D ) Nicely done!

I'm at home with electronics, but wouldn't easily tackle the woodworking side of things... Having great respect for folks that do.
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Sat Jun 26, 2021 8:45 am

4000 wrote:
jdogric12 wrote:I had a 260 once and I don't remember a boost.


Thanks for the info, it then agrees with the published schematics as well, but the book-remark becoming more & more mysterious ;-) (or incorrect ;-) )


FWIW, as it seems then, only the first/early versions of the 230, 250 had the 'passive boost', but later on this was changed into the more conventional circuit, as also reflected by the schematic on the Rick website.
I read this 'change to normal' elsewhere (further on) in the Richard R. Smith book.
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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (soundmasterg) » Thu Jul 01, 2021 6:17 pm

I have a 1989 230 and I talked to John Hall through email maybe 10 yeas ago about it because I was refinishing the guitar and had some questions about it and about the pickups and the circuit in general. Here is some of what he said about it.

In the Rickenbacker sales brochure it talks about a semi-active circuit. John said "Those capacitors and resistors ARE the semi-active design." Basically they tap off some of the signal to give a mid boost. It works better with the neck pickup than the bridge pickup as there is more signal to draw from. Being an electrical engineer, I can tell you that there is no semi-active about it technically. It is a cool circuit to give a little boost to the signal but it is just a circuit with no active components in it that add gain, so it isn't active or semi-active. It is just sales gebblygook. :)

When I refinished my 230 to Blue Boy I rewired the circuit from the circuit board to individual pots and used the Gibson control arrangement. I added that same circuit in with discrete resistors and caps and it performs the same as the one they had on the circuit board. I used to have a schematic around somewhere, but I just moved and wouldn't be able to find it for months. It isn't very complicated though....just a couple resistor and caps. If you want a copy of it or a description of what they were doing, then give me a couple months and then send me a PM and I can see if I can find it for you.

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Re: 230 Hamburg and 250 El Dorado 'passive boost'

Postby (4000) » Thu Jul 01, 2021 8:01 pm

Thanks Greg, this the missing piece of the puzzle, thanks for sharing this info!
And all laws of nature are applicable again ;-)

Sure interested in having a look at the schematic some day, not in a hurry, glad already this info came around.
I'll PM you in a few months, thanks already.

And interesting to hear that you considered the circuit usable enough that you added it again after your guitar upgrade.

W.r.t. 'sales gebblygook', can imagine it being just that, and makes me think of this description that was used for
some old solid state Rick amp (so called bounce-back power supply, but inspecting the schematic doesn't seem to
reveal anything out of the ordinary) - but Rickenbacker obviously not the only brand using 'special descriptions' for in essence conventional stuff.

Thanks again!

Peter
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