HAFLER DH-220 ULTIMATE UPGRADE KIT. THIS UPGRADE ADDRESSES MANY ISSUES PERTAINING TO AUDIOAMPLIFIER DESIGN PRACTICE. SIMPLE UNIQUE JFET CASCODE DESIGN ALSOOFFERSCLEARAUDIBLEIMPROVEMENTS ANDINCREASED POWER OUTPUT. INCLUDES GOLD PLATED BRASS RCA INPUTS AND OUTPUT BINDING POSTSCAPABLE OF ACCEPTING 6 AWG WIRE,2 RAW PC-1 DRIVER BOARDS WITH ALL COMPONENTS, 17 PAGES OF INSTRUCTIONS AND PICTORIALS, AND ASSOCIATED WIRING.
THISPACKAGE IS DESIGNED FOR INTERMEDIATE TO EXPERIENCED KITBUILDERS YOU MUST HAVEGOOD SOLDERING PRACTICE SKILLS AND BE ABLE TO FOLLOW INSTRUCTIONS. YOU MUST BE ABLE TO READ COLOR BANDS ON 1% RESISTORS (MATERIAL SUPPLIED) AND INSTALL AND SOLDER SMALL PARTS ON PC BOARDS. YOUR TOOLS SHOULD INCLUDE:
A 40 TO 100 WATT SOLDERING IRON WITH 3/16 OR ¼ TIP WHICH CAN REACH AT LEAST 600 DEGREES F.
ROSIN CORE SOLDER (SUPPLIED)
A DAMP SPONGE OR CLOTH TO WIPE THE TIP OF THE IRON
A WIRE STRIPPING TOOL FOR REMOVING INSULATION FROM 16GA TO 24 GA WIRE
A MEDIUM-BLADE SCREWDRIVER
NEEDLE-NOSE PLIERS
SMALL DIAGONAL OR SIDE-CUTTING PLIERS
A ¼ SPIN-TITE NUT DRIVER
PLIERS, NUT DRIVERS, OR SOCKET SET FOR INSTALLING INPUT AND OUTPUT JACKS
YOU WILL ALSO NEED BOTH AN AMMETER CAPABLE OF RESOLVING 250MA DC AND A DC VOLTMETER CAPABLE OF RESOLVING 10MV DC. A VARIAC WOULD ALSO BE A PLUS BUT NOT REQUIRED.
*OPTIONAL 18000MFD NIPPON MAIN FILTER CAPACTORS AND .5 OHM INRUSH LIMITER AVAILABLE AT MY store.
POWER OUTPUT, DISTORTION, AND NOISE SPECIFICATIONS OF ORIGINAL DESIGN GUARANTEED TOBEEXCEEDED. SEE PICTURES OF TYPICAL DH-200 MEASUREMENTS. AS WITH ANY HIGH POWER APPLICATIONS,QUA-CO LLCASSUMES NO RESPONSIBILITY FOR IMPROPER ASSEMBLY,FUSING OR INSTALLATION CAUSING AMP OR SPEAKERFAILURE. IF YOU ARE INTERESTED IN HAVING THIS UPGRADE INSTALLED PROFESSIONALLY BY A QUALIFIED ENGINEERING SERVICE, PLEASE EMAIL ME FORCONTACT INFORMATION.
So what is it that allows a power amp to excel in its ability to reproducemusic? Why does Brand A power amplifier sound better than Brand B poweramplifier? Let us assume both have similar power, distortion, noise, gain, slewrate, etc. specifications. Brand A is proclaimed to be an exceptionalamp. It certainly looks better cosmetically. Does that mean itsounds better? It costs $1000.00 more than Brand B. Does that meanit is better? We read or hear about terms like triode sound, nocoloration, more natural, less fatiguing, cleaner, neutral, transparent,precise imaging, superb stage, etc., but what does it all mean? We cannotmeasure these terms quantitatively with standard test equipment. We canmake standard measurements as set forth by The Instituteof High Fidelity but that is as far as it goes. Double blind listeningtestsare the only way to proceed at this point, revealing the truth aboutyour $500 amp or your $1500 amp. Of course all testing of thisnatureis now deemed subjective, but a trained ear will fairly consistentlypick the superior amp.
So what can we surmise at this point? Why does Brand A amp own thepreferred sound? We can agree that it is surely not because it looksbetter or costs more. So what is it? What is the solution? I have concludedafter years of listening tests, circuit analysis, and endless bench testing,the answer is not as elusive or fleeting as I once felt but really what onewould expect as a now seasoned engineer.
1. Simple circuitry - This means notpushing the audio signal through more semiconductors and capacitors thanneeded. We are dealing with non-linear components and need not compromise theaudio essence with more ingredients than needed. This will only lead tounnecessary phase shift, distortion, and loss of clarity.
2. Good design practice - This iswhere many amplifier designs fall short. The first problem area overlooked isPC board layout. It is crucial that 2 layers or multi layer PC boardshave minimal or no track crossover from layer to layer. This will tend toinject capacitance into unwanted areas and cause instability. In turn,this leads to the addition of more capacitors to stabilize circuitry,effectively robbing bandwidth and introducing additional phase shift. The ampdesign is now flawed by poor PC board layout. Amps that have multiple smallvalue pF caps or caps tacked on to the foil side would be suspect of thisflaw. The second problem area and one that will corrupt the sound of eventhe best amp designs is proper grounding technique. Input, output, andpower supply grounds must follow the star ground scenario. For some reason,many manufacturers still to this day do not seem to get the importance or takegrounding serious enough. Ground is ground. Period! It drives me crazy when Isee resistors in the ground path to balance out ground loop situations ordaisy-chaining unrelated grounds to save 12 inches of wire. These acts willmuddle the audio content and ruin what we are trying to accomplish. If you haveany of these situations, correct them or save your money and go buy a $159receiver. When evaluating a design, look at the B+ and B- rails in relation topower supply and signal grounds. Then, try to visualize the circuit backwardswhere the grounds now become the B+ or B- and the B+ and B- become the grounds.This look can be very revealing. Would you insert current limiting on powersupply rails and expect music to sound dynamic and accurate. I already have aproblem with fuse resistance in the rails skewing dynamic capacity andincorporate bypassing measures when required but that is a topic for adifferent discussion.
3. Quality parts - Audio engineersare often limited to the final costs requirements of a new design.Unsurprisingly, the first parts to be downgraded to save on cost are capacitors.(Except for their own unit of course) This is a poor choice. Even under thedouble blind listening test, most audiophiles can consistently pick out thedifference between quality polypropylenes and inexpensive metal films.Semiconductors should also be of good quality with low noise and distortioncharacteristics. Now all that is needed is a properly sized power transformerand main power supply filtering capacitors along with some desirable bypassing.
Pure amplification does not have to be elusive. Listen to simplicity and enjoy.
PC-1 DESIGN GOAL REALIZATION
A. Precise PC board layout with notrack crossover.
B. First stage single endedJfet/bipolar cascode differential amplifier with CCS regulation. Jfetsincorporated are genuine Toshiba 2SK170BL devices with IDSS closely matched. Ifyou know anything about this Jfet, I need not say anything else. High inputimpedance, high gain, tube like presence, and eerie low noise in listeningtests makes it a no brainer. Cascode configuration reduces Miller effect,drastically increasing bandwidth and lowering distortion. This all importantfirst stage configuration eliminates the need for massive gain and responseused in many amps to cover up distortions and design flaws.
C. Second stage also uses SE bipolarcascode amplifier with CCS regulation. Again, Miller effect is reduced andbandwidth is not compromised.
D. Simple bias control and emitterfollower circuit to drive output stage is added and all that is needed tocomplete the design goal. Clipping now occurs at 150-160 watts into 8 ohmsinstead of the 110-115 watts from original PC-6 or PC-19.
E. Polypropylene capacitorsthroughout with all HE electrolytic caps bypassed with polypropylenes
F. Vital star grounding realizedwith pictorial showing proper wiring arrangement
SPECIFICATIONS
Signalto Noise Ratio, unweighted:
Exceeds100 db referred to100 watts into 8ohms106 dB Typical
TypicalTHD at100 watts into 8 ohms:
20Hz: 0.002%
1kz: 0.002%
20kHz: rms for 100watts into 8 ohms.
FrequencyResponse into 8 ohms:
-3 db, 4.8 Hz to 225 kHz at 1 watt.
SemiconductorComplement per board:
9transistors, 2 Jfets, 5 diodes, 4 zener as advertised. Well packed. Very fast shipping. Great transaction!
Excellent service and support
Fast shipping. Amp adjusted and tested. This is an an outstandiing product.
I listened to the JFET cascode kit in the DH-200 today. Holy cow !!! I compared it against an original DH-200 using one channel from the original design and one channel from another DH-200 amp with your new driver boards with the preamp in mono and adjusting the balance back and forth. All I can say is WOW ! I didn\'t expect to hear that much of a difference. Stereo Imaging is better. switching both channels to the new amp you can close your eyes and place some sounds in a very, very specific front/back left/right space. There is a sense of ease and the music seems to have more depth and space.It\'s hard to believe how good the DCM TF350 speakers sound with this new amp. They are pretty good speakers but nothing that exotic. The lows are quite a bit better as well maybe some of which is due to the original amp having original power supply caps. The original amp is one that you repaired for me and has a capacitor upgrade kit so I know it\'s working correctly and is a good comparison. D***, now I won\'t want to use the old amps until I upgrade them.
Many thanks, again, for your excellent designs. I just installed the Hafler DH220 get cascade boards and upgrades, filter caps and inrush suppression. The result is spectacular. This will force retirement of my EL34 upgraded ST-70 type amp. The upgraded DH220 has I ncredible resolution and transparency without some of the fatiguing qualities of bipolar designs. Took a scant 2 evenings to complete the work.
Wow it gives me goose bumps its amazing performance. Not only did I install your cards but added 4 Nichicon 33,000uf power caps with soft recovery rectifiers along with dual mono torodial transformers. This jumped several levels in performance believe I\'ll have this amp until I die. align=\"left\">