I suspect its Hafler, I tried that.
Odd that they make the schematics available, then blank them out...
Why do the 'pro' firms print the schematics, yet the commercial hifi firms don't let you see them at all?
Credit to the pros. good for them.
Its not as though in a lot of cases the commercial ones are their own designs and in electronics, very little is new, I think its hypocritical.
Odd that they make the schematics available, then blank them out...
Why do the 'pro' firms print the schematics, yet the commercial hifi firms don't let you see them at all?
Credit to the pros. good for them.
Its not as though in a lot of cases the commercial ones are their own designs and in electronics, very little is new, I think its hypocritical.
Dunno how close this is to the schematic you're looking for, its the 9300/9500 schematic...
http://k-amps.8m.com/cgi-bin/i/PowerAmps/Semicond/hafler_915c.jpg
http://k-amps.8m.com/cgi-bin/i/PowerAmps/Semicond/hafler_915c.jpg
"Dunno how close this is to the schematic you're looking for, its the 9300/9500 schematic..."
That sure looks the same. Grounded output stage, j-fet dual comp diff inputs. A Jim Strickland design for sure.
http://patft.uspto.gov/netacgi/nph-...kland.INZZ.&OS=IN/strickland&RS=IN/strickland
That sure looks the same. Grounded output stage, j-fet dual comp diff inputs. A Jim Strickland design for sure.
http://patft.uspto.gov/netacgi/nph-...kland.INZZ.&OS=IN/strickland&RS=IN/strickland
lt cdr data said:
If that's the case, they are a bit overly concerned. It's better to have a reputation for great support and not worry about clones, since the basic topology is apparently patented. Reading the patent, it sure is broad, seeming to claim the invention of error correction for outputs (Hawksford beat them on that). I'm surprised it was allowed, since many claims appear to be prior art to me. I guess there is a trick to wording these so they can make a broad claim and get away with it.
Certainly in the pro world, manufacturers buy a test piece of virtually everything made by competitors as soon as it comes out. I know a guy who made a really good living out of that for a long time, selling say, one stack of PA, or one of every line of new amps onwards, then buying it back at a cut price six months later and flogging it on. 
I suspect the same is true in the domestic market as well!
I suspect the same is true in the domestic market as well!
hmm not familar with Jim Strickland, any info, slowhands?
I thought Herr Borbely had a bit to do with hafler? and even David Hafler himself?
Indeed, even you don't have the circuit, its not too tought to trace it out for an amateur, a big company could easily do it. So what is the point of them being cagey?
Sure they need to protect their proprietary stuff, but also, I suppose they have a duty to advance REAL innovations for the sake of science.
And which domestic companies really do come up with new innovations? they are mostly dependant upon the clever guys like Borbely, and all who went before.
I know of someone who used to put xray proof goo under a circuit to stop it being traced. Talk about paranoid.
I thought Herr Borbely had a bit to do with hafler? and even David Hafler himself?
Indeed, even you don't have the circuit, its not too tought to trace it out for an amateur, a big company could easily do it. So what is the point of them being cagey?
Sure they need to protect their proprietary stuff, but also, I suppose they have a duty to advance REAL innovations for the sake of science.
And which domestic companies really do come up with new innovations? they are mostly dependant upon the clever guys like Borbely, and all who went before.
I know of someone who used to put xray proof goo under a circuit to stop it being traced. Talk about paranoid.
lt cdr data said:
Well, here's a little history, from my recollections.
David Hafler was instrumental in so many audio advancements, from Acrosound transformers to Dynaco and David Hafler Company amps. In about 1950, he formed Acrosound and developed outstanding output transformers for tube amps, using the Williamson Ultralinear configuration. In about 1954, he formed Dynaco and released the MKII 50 watt amp, a revolutionary product in its era. This evolved to a full product line of tube preamps, tuners and amps that had excellent performance for low prices; Dynaco tube products are still cult classics today and there are companies whose sole mission is restoring and upgrading them.
In the late 60s, Dynaco began to transition its product line to transistorized design, enlisting Borbely, Bongiorno and several other top designers. Erno Borbely had a hand in the FM-5 tuner dynatune circuit as well as the cascode output stage in the ST-400. Unfortunately Dynaco went broke in about 1977, and many audiophiles were distraught. Many Dynaco products are still working today and are still considered high value for the money.
The Hafler company was formed in 1978, and Borbely rejoined Hafler at his new firm, later becoming Chief Engineer. Hafler released a series of very high performing preamps, tuners and amps with excellent price/performance; Borbely's 1979 DH-200 was amazing for its era. I believe Borbely also designed the DH220, DH500, DH280XL and DH600XL, based on similar design techniques (see articles in Audio Amateur on his 60 watt and 100 watt MOSFET designs).
Hafler gradually moved into pro audio amps (which have different requirements such as balanced inputs and level controls), and became successful there. Their early pro audio products were the original consumer amps with bolted-on pro preamps (P500 is a good example, it used the DH500 chassis, transformer, boards, relays, everything, just crammed in the front end for pro use). With the pro product portfolio and an excellent reputation for building solid amps, David Hafler Company became an attractive acquisition target.
Rockford picked them up in 1988. The emphasis on home audio has shifted to pro audio. Strickland is Chief Engineer, and has several audio patents including the one for the 9303 and 9505 grounded output stage, which by the way is simply an output stage with voltage gain, duh. But with the right marketing mumbo jumbo, the amps are selling.
)To be fair, the product quality is very high and the designs are competent performers. I'm glad, because they are designing and building in Arizona, and those folks need the jobs.
I agree it is possible to reverse engineer the circuit and get the design. I don't want to spend the time. I need to fix it or scrap it.lt cdr data said:
lt cdr data said:
The missing schematic may be simply an error, or a conscious deletion. I don't know, but it's frustrating.
You raise some good points about innovation. We don't see much of it in today's products. I suspect that creative guys don't always achieve business success, for reasons often beyond their control. Dynaco's demise is a perfect example. Here was a company with great products and a loyal customer base, but they fell to the assault of Japanese consumer audio makers in the late 70s, like Marantz, Fisher, Scott, and others....
Life's tough and then you die.
slowhands,
Nice reprise on the history of Dynaco and Hafler. Thanks.
One slice of it not included is the acquisition of Acoustat by David Hafler. Acoustat had some really innovative technology developed by Jim Strickland, who also had some patents on this technology. This occurred in the late 70s and early 80s. Unfortunately Stickland's work was not backed up by a competant business manager and Acoustat fell on hard times, hence its acquisition by the Hafler Co.
Then, when Rockford/Fosgate absorbed the then Hafler company it got Strickland. At that time I believe the production remains of the Acoustat speaker line was sold to an Italian firm. But, Strickland remained with Rockford/Fosgate to design amplifiers.
This transistion occurred around 1989 as I recall. From then on "Hafler" amps were mostly professional types and were the property of Rockford which only used the Hafler name for marketing purposes. The Transnova amps, and some others now bearing the Hafler name, were designed by Strickland and are very similar to the original Acoustat TransNova TNT-200 amp.
For several years Rockford/Hafler provided absolutely no technical support to the previous (mostly kits) Hafler amps of the early 80s and pre-Rockford acquisition. Then, a few years ago, the "new" Hafler company did at least begin a Technical Archives section to at least present to the public original construction manuals for the early kit models. But now this last Hafler amp business has ceased to do business. End of a saga.
Nice reprise on the history of Dynaco and Hafler. Thanks.
One slice of it not included is the acquisition of Acoustat by David Hafler. Acoustat had some really innovative technology developed by Jim Strickland, who also had some patents on this technology. This occurred in the late 70s and early 80s. Unfortunately Stickland's work was not backed up by a competant business manager and Acoustat fell on hard times, hence its acquisition by the Hafler Co.
Then, when Rockford/Fosgate absorbed the then Hafler company it got Strickland. At that time I believe the production remains of the Acoustat speaker line was sold to an Italian firm. But, Strickland remained with Rockford/Fosgate to design amplifiers.
This transistion occurred around 1989 as I recall. From then on "Hafler" amps were mostly professional types and were the property of Rockford which only used the Hafler name for marketing purposes. The Transnova amps, and some others now bearing the Hafler name, were designed by Strickland and are very similar to the original Acoustat TransNova TNT-200 amp.
For several years Rockford/Hafler provided absolutely no technical support to the previous (mostly kits) Hafler amps of the early 80s and pre-Rockford acquisition. Then, a few years ago, the "new" Hafler company did at least begin a Technical Archives section to at least present to the public original construction manuals for the early kit models. But now this last Hafler amp business has ceased to do business. End of a saga.
Dick West said:
wrong language
not Russian,djoksim is from Serbia.
to djoksim:
it's nice registering today and wandering through old threads,trying to sold what you have...?
what is with "DIY" in title of this forum?
better go to trade area of forum and try there to make money.
btw I have 9505 schmtc and I payed it zilch,zero,nothing .
I earned that shmtc with favors I made to other ppl
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