Hafler XL-600.....The Eviction Notice Amp
- Thread starter Son-of-Vere
- Start date
Stavro
Active Member
They didn’t recap. It didn’t need a recap. I bought it from eBay with a blown left side. It needed 3 FET output transistors (2sj49) and another feed transistor (25k246). $120 in parts and $470 labor. I swear by these guys. Yours may just need a bias adjustment or an alignment of the one variable capacitor in the signal path.
The large filter caps often don’t need to be replaced. Those can usually be reconstituted with a variac. I have done it many times with my old DH-220 that I have had since the 80’s just after college. Now my son uses it in his rig with the original caps.
I have to say the 280 sounds phenomenal. It sounds like my 600 - just a little less power. The 220 sounds different due to the different input circuitry.
Thanks for the referral. Seems well worth it. On a related note, I resurrected my old Parasound C/DP 1000 CD player today. Replaced a dried out drive belt ($8 fr Amazon) for the drawer. All by myself.
Stavro
Active Member
Ok - update here. I was bored during Covid, and I went out and bought a second XL-600. I'm now running them in mono. It isn't the power - my speakers can only handle 200 watts. The separation and imaging are stunning! The sound is just there - effortless and light. I can't really explain it. I will also say that since the amps are in push/pull mode, there is a 6db gain. The only warning I can say is don't turn them on at the same time. The line conditioner almost blew the breaker.
Attachments
ouimetnick
Hafler Fan!
I have one that I use occasionally. I actually prefer the sound that Musical Concepts PA-4 boards put out. I have those installed in my XL-280. Planning on getting rid of the stock PC-40 boards and putting in some new MC ones, just not in a rush to do it.
Binkman
Lunatic Member
thank you @merlynski for the 'like'. Was hoping this thread came up because of the unique 'V-8' amp. design.
Wonder if @Son-of-Vere still has it?
Wonder if @Son-of-Vere still has it?
merlynski
Curmudgeon Electronicist
That photo of the heatsink caught my eye. I used to work on a power supply for a commercial video/audio recorder that had a 1.5KW power supply. It had 3 similar heatsinks on it, about 25% bigger than that.
Stavro
Active Member
Actually it’s more like a V16
A friend brought an XL600 here for an audition. I set it up with my recently repaired NAD 3155 integrated running in preamp mode and my dbx CD player for a source, driving some Polk RT5 minis that I've had laying around. I have the speakers set up in my garage on a tool bench about 5.5 feet wide, one s[ealer at each of the back corners on the bench. No isolation pads or spikes or anything else. Even with that crappy setup this really sounds good. I tried to challenge it and it laughed at everything I gave it, from jazz to folk to rock. I even tried an ancient recording of Yves Montand singing some song in French, but it put his voice right in the center where it should be, surrounded by air. Sonically it is very close to the XL280 amp, as others have said, but far more forceful when needed.
Everything was great until about 45 minutes in to the listening session. The sound cut out and then back in, then back out, and when it came on again it sounded incredibly odd. I thought the woofers in the Polks went, but they were ok. I can't explain how weird it sounded, except it was like the bass was greatly curtailed, like the woofers were crossed like midranges. The volume was down too. I figured it was some fault that I'd need to fix and thats why the thing wound up at my house.
I just tried the amp out now after letting it rest all day, and its playing perfectly. I noticed the fan kicked on right away, but it was low enough that music at just below speaking level drowned it out, for about 8-10 minutes or so. Then I had to turn the music up to speaking level. I quit listening about 10 minutes after that, and the amp fan was loud enough to sound like an old microwave oven.
I guess this thing is running hot and probably needs at least some adjustment if not outright service. DC offset was looooow when I first fired it up, probably in the 10-15mV range. Don't AB amps run hotter the closer they get to 0mV DC offset? Would doing that Excelinear adjustment help this heat issue?
Everything was great until about 45 minutes in to the listening session. The sound cut out and then back in, then back out, and when it came on again it sounded incredibly odd. I thought the woofers in the Polks went, but they were ok. I can't explain how weird it sounded, except it was like the bass was greatly curtailed, like the woofers were crossed like midranges. The volume was down too. I figured it was some fault that I'd need to fix and thats why the thing wound up at my house.
I just tried the amp out now after letting it rest all day, and its playing perfectly. I noticed the fan kicked on right away, but it was low enough that music at just below speaking level drowned it out, for about 8-10 minutes or so. Then I had to turn the music up to speaking level. I quit listening about 10 minutes after that, and the amp fan was loud enough to sound like an old microwave oven.
I guess this thing is running hot and probably needs at least some adjustment if not outright service. DC offset was looooow when I first fired it up, probably in the 10-15mV range. Don't AB amps run hotter the closer they get to 0mV DC offset? Would doing that Excelinear adjustment help this heat issue?
Stavro
Active Member
No - your bias is probably high. It should be 400ma for each side. When I put mine up to 500 and higher I could hear the fan. When I brought it down the fan (dc and continuously variable) slowed. It also explains the cutting out. You may have tripped a thermal breaker given the high bias and high volume. Congrats on the find. I love both of mine (dual monobloc mode).
Just how do I set the bias on this thing? I looked through the supporting documents for both this amp and my XL280 and found nothing about bias.
Stavro
Active Member
Ok - disconnect speaker leads and inputs from the amp. Be careful in there - one section has 90V and the other 100V. When you open it up you will see the heat sink block with the mosfets. On either side are the driver boards. They have 4 10amp fuses. Pull one fuse and put a multimeter in amp mode (preferably with alligator clips) on the two sides of the fuse clips. When you turn it on, it should go up to about .4amps or 400ma. If it goes higher, then you have to trim it back. Be careful not to trim the variable capacitor (it has a copper screw head and a green ish body) you want the trimmer pot that is black. There is only one per side. Small adjustments only. After it settles to where you want it, then power down, wait for the amps to go to zero, put back the fuse and do it to the other side. Depending how you have your leads hooked up it could be positive or negative. It doesn’t matter. It is DC amps we are measuring. Also you know have to do it to the fuses up top since the bottoms are a mirror.
Does it make sense?
Does it make sense?
Stavro
Active Member
I figured out how by first biasing my DH-220. Basically the same.
Perfect sense. Far better sense than the Excelinear adjustment. I've read that a few times and still can't understand it.
What is the resolution on the bias pot? Is it single turn or multi-turn? I'm guessing that its single turn because you said to use small adjustments.
I had one of those new in the late 80s. It was one of the dullest amps I've ever owned. Nowhere near the sound of the XL280. I have an SE240 here thats got a sound similar to the DH220, but it still sounds more detailed to me than the 220. I still with I'd kept the DH220 because its a great project amp.
Stavro
Active Member
Yes single turn.
I still have my 220 - all stock and original - actually it sounds almost as good as my 280 - not as good but - almost.