Does anyone have schematics for Barcus Berry model 1720? It is 70's-80's acoustic guitar combo. i've been using it for electric guitar and it has great cleans. I've tried to email Barcus Berry but can't get any answer.
Hi MTelinkangas, welcome.
A little research shows the company quit guitar amps many years ago. I've never come across the name before and a bit of Googling suggests that there aren't any circuits on line out there ('tho one of the brains trust here may have one stashed always somewhere). Not to worry, most repairs are carried out without a circuit.
What is the nature of your problem with it?
Hi, and thanks. There's no real problems, just a few broken potentiometer shaft. It can be used in that condition but i'm going to replace them some day. Just asking the schematics of pure interest.
Well the best of luck, but unless they find one down the back of a filing cabinet somewhere I think you've got Buckley's chance (http://en.wikipedia.org/wiki/William_Buckley_%28convict%29).
QuoteEnglish convict who was transported to Australia
:trouble
You mean http://en.wikipedia.org/wiki/William_Buckley_%28convict%29 ?
That's why I strongly avoid arguing with Roly, Phatt, and others.
Survival instinct, they call it.
Buckley's not around any more ..... but his lovely grandchildren seem to be happy and prospering ;)
(http://resources1.news.com.au/images/2008/10/13/1111120/495225-mad-max.jpg)
(http://www.filmosphere.com/wp-content/uploads/2012/04/mad-max-2-2.jpg)
(http://static1.squarespace.com/static/51b3dc8ee4b051b96ceb10de/t/54888f9ee4b03c0a9b8fee33/1418235809794/new-mad-max-fury-road-trailer-shows-no-mercy?format=750w)
I've seen the Documentary
;) ;)
Buckley is particularly notable for going it alone from his group of escapees who set off for Sydney, thinking it only a small distance when it was actually 1000km and some pretty tough country distant. Instead he went south west and made contact with the Wathaurung people whom he joined, learned their language, most likely the first white man ever to do so, and lived with them for 30-odd years, getting married into the tribe and having a daughter.
Koories (as southern aborigines call themselves generally) identify as "salt water" or "dry land", and the tribe that Buckley joined was coastal and less nomadic because the living was easier, however their lands extend well inland and actually encompass the Ballarat goldfields where I live. Many shellfish middens still dot the entire coastline, showing that "tossing a shrimp on the barby" long predated the coming of the whitefella.
Since Buckley eventually returned to white society, working as a translator and providing us with a unique insight in to Koorie life before white settlement, "Buckley's Chance" in Aussie vernacular is generally taken to mean "next to no chance", just possible, but highly unlikely.
Barcus Berry split in two a long time ago. Barcus Berry continued on making pickups/transducers and preamps. The other half became BBE (Barcus Berry Electronics) and made things like the Sonic Maximizer that used to be a popular unit. Their focus was the electronics.
BBE still exists. If you tried to contact Barcus Berry, it might be worth a try contacting BBE. An amplifier might be closer to their mission than to Barcus Berry.
http://www.bbesound.com/
Thank you very much. I emailed BBE, let's see if they have anything to say.
I e-mailed BBE once with a repair question regarding one of their active DI boxes and got a prompt reply; good luck.
No answer so far. Honestly I don't think that questions about amp that's been discontinued decades ago will be top priority to them. Well, there's still little hope left.
Oh well, not worse than the hundred thousands amps out there also without published schematics.
At least, being an old American amp, specially from a company which did not specialize in them, there's a great possibility that they did not go "wild" on the design but were rather conventional, some even using the straight datasheet application note or not far from it.
Which helps in servicing by comparing it to a similar one.
Just curious, if you have some free time, post a couple pictures of guts in general and a couple power amp closeups.
Sharp, well illuminated and readable so we can identify parts.
EDIT: just curious, I found a "brother" or "cousin"
here: http://forums.vintageamps.com/viewtopic.php?f=11&t=98424
It screams late70's/early80's with those aluminum domed square magnet CTS speakers and the small corner protectors (which I cloned, by the way) ; it might be very close to an Acoustic (brand) amp.
It seem that BBE won't answer... I'll try to take pictures some day.
Somewhere I read they were designed by the Standel guy ... might help understand his "style".
Every designer has his pet way to do things so often repeats some ideas in different products.
Might be a clue.
Bob Crooks definitely did design for them.
I have been somewhat interested in design details of these amps because likely related Barcus Berry patents feature some neat inventions : "Load correction" - more specifically, several embodiments of it - obviously had something to do with reactive speaker loads, but the patents are somewhat obscure in whether BB tried to compensate/eliminate the reactive nature of speaker loads or simply enhance it similarly to modern "mixed mode feedback" schemes. Then there are others too, like a nice notch circuit for feedback or hum elimination.
This in an era when most solid-state guitar/acoustic amp designers were still unaware that such features should perhaps even be developed.
Haven't seen schematics. Circuitry patented by Bob Crooks / Barcus Berry, however, is something I have never encountered in Crook's earlier work with Standel, Randall, SG Systems, Gibson, etc....
On that note... I never got to try any of these but I always wondered about the "Accent" controls: How exactly do they work? Low-band / High-band distortion? Post-distortion tone controls in addition to other tone controls? Something else...?
There's not much information around about these amps so every little bit helps all others who are interested in them.
Edit:
http://patents.justia.com/inventor/robert-c-crooks
Thanks Teemu for the search effort and links provided.
I quickly browsed those Patents (each one requires re-reading a lot of times to cut through the Legalese :P ) and found that he basically patented current drive in 1979
Quotemeans and method are provided which correct for variations in an amplifier load such as a speaker by sensing the load current, developing a feedback signal related to the load current, comparing this feedback signal with the amplifier program, and instantaneously adjusting the gain of the amplifier to compensate for load current deviations from the program applied to the amplifier.
and later ones were tweaks on the basic first one, to which he constantly refers.
He
seems to be trying to get full, flat frequency response from full range drivers, up to 20 kHz :o and recognizes that adding crossovers and tweeters complicates the issue.
Then he talks about fast rise time amps as being better, which is true.
At least, can't hurt, at all.
And then mentions an issue which has been intriguing me, since I saw it in an "Exciter" pedal: he claims that by advancing phase up to 180 degrees "high frequencies separate and become easier to hear" relative to"muddy" mid frequencies.
I'm not so sure I buy such a simplistic explanation (human ear is quite insensitive to absolute phase), but all said pedal (I can post the schematic if you wish) does is first passing highs through a single phase shift cell (think any classic guitar Phase Shifter) and then mixes it with original signal.
There's a switch to mix in/out of phase.
Net effect is a
strong treble boost ... so maybe that's what Mr Crooks is hearing.
Mixing out of phase gives the classic Phase Shifter response: values are chosen to provide a notch at 5kHz (might be good to tame some annoying speaker peak) while the peak at 20 kHz is perceived as strongly rising treble up to the limits of audibility.
Mixing in phase provides just a shelf type boost above 5 kHz .
In both cases, a single speaker will be perceived as "more transparent sounding".
So
maybe the "Accent" control is some of that.
The idea is interesting and has great potential, but maybe didn't go further because doing it in "hardware" (adding anything from a cheap Piezo to an expensive driver or bullet) provides more and truer highs than EQing a "guitar speaker" which typically drops at 18 to 24dB/oct above some 3500 Hz
I'm somewhat familiar with early BBE "Enhacers" and later BBE "Sonic Maximizers".
The phase shift idea... I think it's nothing but common "time alignment" thing: Introduce electrical phase shift to compensate the acoustic one created by the loudspeaker system.
I'm not too familiar how all this "phase" stuff behaves in practice so I can't comment on whether BBE's "enhancer" idea works like it's claimed to do, but I do know that time alignment with phase shift or phase lag filters is extremely common design practice and in practice one can make it work effectively.
...But I would think you need to match it to specific drivers though, not offer it in some mysterious "black box" that approximates some generic phase lead/lag behaviour.
Edit: Refreshed my memory and took a glance too:
- Amplifier load correction system, US 4260954, is a generic mixed-mode feedback scheme. Note's are made about the scheme correcting phase errors at certain frequncies. Never investigated that.
- Method of correcting for variations in a load driven by a power amplifier, US 4482866, is a scheme somewhat "external" to power amp. Instead of sampling loudspeaker load current the circuit senses an approximated load current from a reactive circuitry that emulates characteristics of a real loudspeaker. Now current feedback can be applied in earlier, low current stages, indenpendent to the load. At least that seems to be the idea by quick glance...
- Reference load amplifier correction system, US 4638258, continues based on earlier patent's ideas.
- Notch filter system, US 4496859, is a resonant filter (with gyrator) that notches deep at 60 Hz.