Hafler DH-220 as basis for guitar amp?

[bartbrn]

Hi -- I'm 62 years old and not quite senile. My background is as an experimental machinist and electronics assembly supervisor for the Inertial Upper Stage payload delivery system for the original Space Shuttle program. I am (or was) a NASA-certified and qualified microelectronics solderer.

That being said, my knowledge of esoteric audio electronics is pretty much nil.

I have, kicking around in my dangerously overloaded workshop, a cosmetically-beat but electronically fine Hafler DH-200 power amp, the first American production amplifier to use complementary MOSFETs (8 of 'em) in its output stage. MOSFETs are almost immune to thermal runaway (unlike standard power transistors then in common use in SS amplifiers).

This amp, in stereo form, is conservatively rated at 120W/ch, and bridged to mono at 300+ watts at .005% THD. I've used DH200s in several audio systems, and among the Hafler's characteristics I think would make a bridged Hafler a good candidate for guitar amplification are its high damping factor and excellent slew rate.

My electronically uninformed thinking is that my spare DH-200 might make the basis for a pretty decent guitar amp. Am I full of baloney or is this a feasible project? If it IS a feasible project, what kind, how big, and how many drivers would be optimum for a cabinet driven at this level of power, and what kind of cabinet should I be thinking about?

Another of the million things of which I'm ignorant is how guitar amps produce distortion, reverb, etc., but I was thinking about the possibility of using one of Line 6s higher-end pods as a front end, which would also provide an easy interface to my Mac and Garage Band and WireTap Studio Pro -- I use a Pocket Pod and headphones for practicing without driving my wife to homicidal urges, and even the little pocket cheapie makes some fun noises, so I assume (yeah, I know...) the more sophisticated Pods would provide some great amp modeling and effects.

Anyone have any hot tips, ideas, suggestions (please, be kind) about my ideas?

Thanks for the great forum!

Bart

[J M Fahey]

Hi Bart, good news , you have in your hands the potential for a speedy divorce or being expelled by your neighbours through the nearest state frontier.
Meaning: you can play real LOUD if you wish 
Your idea of using a POD as a preamp is excellent, your Hafler can provide the muscle, the speaker choice depends on where you intend to play plus the available storage space (and whether you need to easily transport it in your car or not).
To impress the School kids you can build a couple 4x12" cabinets.
Speakers?: you can choose Eminence Legends in a couple flavors for excellent "American" sound for a very reasonable price (visit their page where they have specs and sound samples), Celestions for a "British" sound (idem) or my favorites in the bang-per-buck competition, the Jensen MOD 1270, "american with a touch of British sound" , or so they claim. Price is most reasonable.
You also have excellent speakers by Weber, Warehouse, and a couple others.
If (as I think) you want to keep it compact, you can build a couple 1x12" very compact cabinets, easy to fit in your trunk, each holding an Eminence guitar speaker of which I don't remember the exact model now, but it's the one which stands 150W RMS.
You'll be easily heard a couple blocks away from your house or play flawlessly at mouse-sneeze levels (Family Peace).
Good luck and post your results.

[bartbrn]

J M Fahey -- Thanks for the ideas and encouragement. For right now I'm just using a practice amp (nothing remotely exotic: an eBay Crate MXR-15). I also have another possible guitar amp power source here, a Hafler TA1100 (made when they were first part of Rockford/Fosgate), which is 50W/ch into 4 Ohms and 40W/ch into 8 Ohms. It uses Hafler's "trans•nova" (TRANSconductance NOdal Voltage Amplifier) power MOS-FET Mumbo-Jumbo circuitry, and has -- unusually -- not only a gain pot, but a separate gain pot for each channel. I'm sure there's some way to bridge it to mono -- which mathematically would yield 80-100+ Watts -- but I have yet to find an article on doing so. I guess I didn't realize how much power 300+ W (the Hafler DH-200 bridged) would be for a guitar amp; what does a typical single stage amp put out?

I don't gig -- I'm old, but not old enough for THAT humiliation -- I just practice at home and mess around with Garage Band and WireTap Studio (a fantastic piece of software, IMHO, from Ambrosia, and well worth the $69 price. PPC and Intel Mac only -- and not yet "Lion" friendly -- but if you're interested, check: http://www.ambrosiasw.com/utilities/wiretap/). And no, I don't work for Ambrosia.

Thanks for the recommendations on drivers; can you recommend an online source or sources for these drivers and the associated hardware I'd need? I don't get out of the house much.

Thanks again!

Bart

BTW, I'm pretty far out in the country, but the guy across the street has an exceptionally annoying habit of mowing his lawn of a Sunday morning, usually about 7am. A good feedback shriek at 3am or so would remind him of the biblical injunction to stay in bed as long as possible on the Sabbath, and every other day...

[J M Fahey]

It's not an endorsement, but check this:
http://www.amazon.com/Eminence-Patriot-Texas-Guitar-Speaker/dp/B0008FUWEG
This is the 150W one I talked about, $70 each won't break your bank, and you can go to some Home Depot equivalent and buy some cut plywood (or chipboard) if you want to build a couple 1x12" cabinets (if you are so inclined) or google for some cheap ready-made 1x12" ones.
Finish is absolutely unimportant, you can use them "naked", paint them flat black with some water based (Latex/Acrylic?) paint or buy a couple inexpensive carpet-covered cabinets meant to be mounted in cars, for pennies.
Don't use your power amp bridged, hook one speaker to each channel, your POD has stereo outputs to benefit from stereo chorus and the like.
Or make an Y cord, from 1 plug to 2 plug or RCA connectors, whatever the Hafler has, if you want just to boost your small Crate to neighbour-Blitzkrieg levels.
Maybe you will be able to sleep the next Sunday mornings.
PS: even if you use your "smaller" power amp, still buy the 150W speakers, they're a bargain and, as reviewed, good for amp modeling.
Good luck.

[bartbrn]

"This is the 150W one I talked about, $70 each won't break your bank, and you can go to some Home Depot equivalent and buy some cut plywood (or chipboard) if you want to build a couple 1x12" cabinets (if you are so inclined) or google for some cheap ready-made 1x12" ones."

They look like an excellent deal, and I never even thought about the stereo chorus and how it would work with two channels -- I usually use the Pod with stereo circumaural headphones, and I really like the spacey, chimey effect in stereo.

Any recommendations on cab design -- closed, open, whatever? Never thought about the ready-made carpeted car cabs, either -- our 3 cats would be delighted to have something new to claw up!

"PS: even if you use your "smaller" power amp, still buy the 150W speakers, they're a bargain and, as reviewed, good for amp modeling.
Good luck."

Would the weak-kneed 15-Watt Crate even move the Texas Heat 12" cone? I'd love to change out the speaker. Thanks for the good lead!

Bart

[J M Fahey]

Thanks God guitar speakers are very forgiving: in open backed cabinets they sound open and airy, in closed ones focused and punchy, both sounds are valid.
Use what you get, it will work.
Your 15W Crate will not only drive 1 x 12" ... but both (since they will present the correct 4 ohms it needs) to a surprisingly high volume.
Punch its backpanel and install 2 plastic insulated jacks "Cliff/Marshall type"
and some convenient spdt switch, which will send the internal amplifier hot wire either to the internal speaker or to the jacks' hot pins.
I trust more a dedicated switch than the weak leaf switches included in jacks.
The negative jack pins go always to the speaker negative terminal.
You plug 1 12" cabinet in each jack.
PS: cats ***LOVE*** carpeted cabinets.
How do I know? Hmmmmmmmmmmmmmmm !!!!  :trouble :trouble

[joecool85]

I'm interested to see what comes of all this.  I hadn't even heard of Hafler amps before and now I want one haha.

Welcome to the board, Bart!

[bartbrn]

I'm interested to see what comes of all this.  I hadn't even heard of Hafler amps before and now I want one haha.

Welcome to the board, Bart!

Thanks for the welcome! David Hafler co-founded Dynaco in 1954, started his own company in 1977 -- the first David Hafler Co. products were the DH-200 power MOS-FET amp and the DH-100/101 (I forget the difference) preamp, both sold built, or as kits. The DH-100 and 101 preamps were good, simple, utterly conventional, and inexpensive, especially in kit form -- I built 5 or 6 of them for friends, and 2 for myself -- a couple stock, a couple with upgraded polyester and polypropylene caps, good quality wire (the stock kit wire was the worst vinyl-coated junk I'd ever seen -- don't tell anyone, but since I was workin' for Uncle Sugar's War Machine at the time, I liberated some much heavier-gauge Teflon-jacketed OFHC NASA-grade wire), gold-plated RCA jacks on PCB fiberglass mounts (I made the mounts myself -- I used to be an experimental machinist, too),  instead of the stock pre-oxidized aluminum jacks on fish-paper, which looked to be right out of an original '50s-era Dynaco etc. -- the circuit design was fine, but some of the kit components were pretty low budget.

The DH-200 was a completely different animal -- one of, if not THE first commercial home audio amps to use power MOS-FETs for the output stage. They sold pretty much like hotcakes, as did the follow-on DH-220 and DH-500 amps, and the truly excellent DH-110 Pre-amp. The same sort of modifications were made to the DH-200 kits (especially replacing the two 10,000uF 75V output caps with bigger and cleaner units), and are still available on eBay, as are DH-200s: a lot of them were used as studio and lab power supplies, especially bridged, as the self-limiting characteristics of MOS-FETs (as opposed to the ruinous thermal runaway of typical transistor circuits of the day that required elaborate protection circuits and often fan cooling) not only allowed simpler circuits topography, but could be safely convection cooled -- check out those fins! -- not requiring noisy cooling fans. As a result, there are a lot of them around -- I just bought one used as a rack-mounted lab power supply --  cosmetically, it's not so pretty, but then, they weren't very pretty when they were brand new -- upholding the utilitarian aesthetic of Dynaco, all the early haflers were painted satin or flat black, and the pre-amps had a satin-finished black anodized front plate (if I've made any factual errors in these descriptions, let me know). In both the Hafler pre-amp and power amp kits, the circuit boards were already populated, so all you had to do was mechanical assembly and point-to-point wiring (not counting the replaced components). Not enough money in that kind of thing THESE days I guess...

My favorite CTE (Certified-Tin-Ear) audio set-up in the '80s was my (still have it!) Rega Planar 3 turntable (belt drive 1/2" plate-glass-platter-with felt-damper), Linn Basik IV arm, Orsonics head shell, and some high-end Audio-Technica mm cartridge or other, self-modified Hafler DH-101 and ditto DH-200, and a pair of my (highly subjective!) all-time favorite speakers, DCM Time Window 1s, which my expletive-deleted first wife skonkered off with after the divorce in 1987. A few months ago, I gave myself a rare monetary treat, and bought a pair of original 1979 DCM Time Window 1s from a guy in St. Louis -- bless him! -- who had taken such good care of these 30-year-old speakers, you'd swear they were new. Now if I could just find a place to put them...

Hafler sold his company to Rockford-Fosgate in 1987, which made a few Hafler-designed and badged (well, painted) amps and preamps. A few Hafler-badged products are still made, for the professional studio sound market. Hafler passed away in 2003 at the age of 83 or so.



David Hafler, mid-'50s



Hafler DH-200 specs



Hafler DH-200 schematic



Hafler DH-200 point-to-point



Hafler on the half-shell

Bart

[J M Fahey]

All I can say is:
a) WOW !!!
b) KEEP them, no matter what. :tu:

[bartbrn]

I'm actually thinking of selling the Rega Planar 3 w/Linn arm and Orsonics headshell. I just don't have enough vinyl left to give it any use, and it's in such pristine condition -- it hasn't been played since 1987, but the drive motor has recently been checked for speed accuracy, and both rubber belts (platter drive and motor suspension) are brand new -- that it would make some vinyl-phile a fantastic (and, AFAIC never significantly improved upon to this day) classic turntable that should last, with care, another 100 years. Talk about decoupling... the rubber-suspended motor, thick felt platter pad -- made by Mongolian yurt engineers! -- and 3 soft damped-rubber feet of the MDF (or whatever they called it in the UK in the '70s and '80s)-and-Formica plinth, together as an isolation system, are so effective that you could practically wail on whatever surface upon which the turntable is placed with a 10-pound post maul, and effect the stylus tracking not a whit! "Stylus tracking" -- it sounds like something out of the Pharaonic ages...

If anyone is interested, there's a period (1980) review of the Hafler DH-200, by the legendary op-amp and analog audio guru Walt Jung from the venerable audiophile magazine TAA (The Audio Amateur):

http://www.nulltime.com/DIYAudio/projects/DH200/DH200review.html

To my astonishment, The Audio Amateur is still plugging along, under another name, AudioXPress:

http://www.audioxpress.com/

Ahhh, reading that old TAA review -- that and Stereophile were the only audio mags I ever subscribed to -- brings back memories of the great audio debates of the '70s and '80s, before CDs changed the audio world: moving magnet or moving coil stylus? S-shaped tone-arm or straight? Solid-state or tube components (that one continues unabated even today), what was the best speaker wire, the '80s British vogue of 12- to 8-gauge single-strand, two-conducter stove wire of the type you'd see in multi-strand 2" 600V and up transmission line (try shoving THAT in your banana jack!) or the similarly-heavy-gauge multi-stranded OFHC glorified zip-cord of the "M*nster Cable" type. Anyone who wants to explore THAT particular esoterica should check out:

http://www.roger-russell.com/wire/wire.htm

My favorite "'80s audio excess of stupendous proportions" was a guy who insisted upon (and built) a HUGE listening room that was entirely poured, re-barred, and formed concrete down to 18" or some crazy depth below ground-level, with integrally form-poured concrete plinths for each component and each speaker, and curved, off-angle, and stepped-surface walls and ceiling to avoid standing-wave formation. Those were the days! Still are: one of my best friends has two near-7-foot-tall (29'' x 79'' x 2-1/2'') Magneplanars, each one weighing 140 pounds, driven by two mono-monster 150+W McIntosh tube amps that themselves weigh well over 50 pounds, serving the double function of driving the Magneplanars and heating the house.

At age 62, my hearing -- and I just took a test to verify it -- is dismal: I can barely hear anything under 100Hz, or over about 12KHz (too much live rock standing with my head practically IN one of the amp stacks), so hi-fi to ME these days is MP3s through some cheapo ear buds. Kids, if you want to be able to hear in your "Golden" (they ain't) years, don't be driving around playing some god-awful bass-cranked-WAY-past-11 hip-hop at a decibel level that actually makes the rusted rear fenders of your bitchin' chort flap in and out like elephant ears...

Anyway, enough off-subject stuff. Just an old ex-hairbag hippie reminiscing...

Peace & Love

Bart 

[joecool85]

Good times, Bart huh?  I'm only 26 but I have already noticed some of my peers can't hear things as well as others.  A good example is my bass player brother, he's only 23 but has played a lot of shows and frequently is near the drummer.  Between that and his bass rig his hearing isn't what it should be at only 23.

I actively make sure I'm not over-cranking my radio to make sure I'm not damaging my hearing.  Seems like everyone I know listen to their radio and TV louder than I do now.

[bartbrn]

"A good example is my bass player brother, he's only 23 but has played a lot of shows and frequently is near the drummer.  Between that and his bass rig his hearing isn't what it should be at only 23."

Ain't it the truth? Another close friend of mine who's the same decrepit age as I am (we graduated high school together in 1966; electric light had just been invented) spent the 5 or 6 years in his last year of high school and all through college (RSDI) playing with his band "Rasputin and the Mad Monks" (one of the down sides of the '60s was truly lousy band names). They played all over Upstate NY, RI, Ontario, and Quebec. He was in exactly the opposite situation as your brother -- he was the drummer for "Rasputin" (which everyone called the band anyway, and it would have been a slightly less-annoying name), and their bass player stood to one side of him, and one of the stacks was on the other, and the bar/club stages they played on were about the size of a postage stamp.

He took up playing again in his 40s and did a few local (beautiful, exotic Utica, NY) jazz and rock gigs; somehow he became friends with Pat Benatar (did you know her birth name was Patricia Mae Andrzejewski? Just found out on Wiki-P) and her hubby Neil Giraldo, and my friend is now totally deaf in his left (stack side) ear. Sacrifices MUST be made!

Boy, bad band names... I ought to open a discussion in "Player's Corner" about bad band names -- kinda like rockandrollconfidential.com's "Hall of D*uchebags, which, if you've never seen it, has some hilarious-and-embarrassing-but-true stuff, especially promo and CD art band photos guaranteed to make you wet your pants.

Peace, love,and soouuuullll!

Bart

[joecool85]

You should start a "bad band names" thread, it's be fun!

[bartbrn]

I posted a new topic in "The Player's Corner" called "Lousy Band Names." I kinda ran out  of steam in this ungodly heat, but I'll remember more. Meanwhile, check it out and please contribute any lousy band names and stories...

Bart