Any love for the Hafler 9270?

[dogwan]

Just a little rave about this unit. I really haven't been able to read much about it out there in the wild.

I recently picked one up that need just a tiny bit of attention in the form of correct fusing and being over-biased. Once I sorted that out it appears to be very healthy. And into the closet it went.

Well, I just pulled it out and put it into rotation (replaced a DG modded Magnavox 9300 15-watter tube amp) in the living room. All I can say is wow... where have you been all my life? It is such a smooth yet heavy-hitter!

One funny thing that I wasn't expecting is the Hafler is very sensitive to the IC between the pre and itself. More so than I've ever experienced. Had to swap around through a few different IC's to get what I wanted. But once I nailed it, boy did that Hafler snap into focus. Crystalline highs, 'gasm inducing mids, and gobs of power.

The Magnavox was running alongside a separate subwoofer. It was only running a pair of Phase Tech PC-60 CA's (the 30th anniversary editions) above 100hz or so. Once I put the Hafler in place the sub was no longer needed. I don't know if it's just the amount of power (200w into 4Ω) that really drives these little bookshelf's so good. It really is surprising.

Here's a couple pics. It does run hot so I left plenty of room. The cork blocks are there to elevate the amp because my speaker cables have really beefy copper spades and the input RCA's are just above the speaker terminals. So the spades have to point down and the cables are not flexible enough to make a 90 degree bend at the height of the stock feet.

Oh, and a little sidebar: I just sold off over the summer a P1500, P5000, 9130, DH500, and a couple DH220's.
I currently still have this 9270, a PRO500, DH-220 (modded stock circuit), and a Qua-CO upgraded DH-200.
So I'm no stranger to the Hafler stable.
But so far this 9270 is turning out to be my favorite!

Why the lack of love?

Bulldog approved.

 

[damacman]

Very cool. You would also greatly enjoy the 9505. I was fortunate to work with Jim Strickland and Mark Albers for some time.

 

[dogwan]

Very cool. You would also greatly enjoy the 9505. I was fortunate to work with Jim Strickland and Mark Albers for some time.

Yeah, Strickland is the man. I have a pair of Acoustat Model X's with the original Servo-Charge tube amplifiers. They are amazing!

 

[roger2]

Which IC's worked best with the 9270? And which ones did you not like?

 

[PabloTincho]

I have the 9180 there is some hum coming from the speakers, I have to move the gain from 0 to 1/4, do you have the same problem ?

 

[dogwan]

Which IC's worked best with the 9270? And which ones did you not like?

I have a whole stash of various IC's of different pedigrees.

What has worked best so far is a DIY set that I made years ago. The recipe is single length of 22ga. Magnet wire inside a 1/4" o.d. Teflon tube for the positive. Wrapped around the outside the tube are two more runs of same Magnet wire in a double helix for the return/negative. And the whole thing is coverered in Techflex. So, suffice it to say it's a simple Magnet wire with air dielectric.

Here's an old post when I made them. I was still learning some things then (and still am today..), but whenever I pull them out they do surprise me.
https://db.audioasylum.com/mhtml/m....ssage=&sort=score&sortOrder=DESC&forum=cables

The ones I tried and didn't like with the 9270 included ...
- a pair of early Magnan silver something or others (not entirely sure what they are). Kind of rolled off at both ends and dull all around.
- a pair of early Madrigal (Levinson) HPC with Canare connectors. Oddly I was getting sibilance and distortion on the highs, which is not my experience with these cables in other setups.
- a pair of ordinary Audioquest Sidewinders. Sounded pretty good all around, but not as open as the above DIY pair.

I still may try some others I have. In particular I have a pair of older Tara Labs RSC Prime that I always thought were pretty dang good. Look forward to seeing how they do.

Like I said, I didn't expect the difference I was hearing between cables. I am a cable believer, but I am pretty realistic that as long as the cable is not a "bad" design or flawed, then degree of impact is usually very subtle. In this instance the differences were readily apparent to me.

 

[dogwan]

I have the 9180 there is some hum coming from the speakers, I have to move the gain from 0 to 1/4, do you have the same problem ?

No. Mine is dead quiet no matter where the gain pots are.

I did clean my pots with DeOxit when I got the amp just as a precaution. They are simple carbon track potentiometers. I keep mine set at 100% as a rule. In my experience Carbon pots seem to be the least detrimental to the signal flow when resistance is minimal (all the way turned up).

Does your amp only hum when the pots are at the lowest point? Or are you saying that with the gain turned up to 1/4 (or above)of the range that the music drowns out the hum?
Does the amp hum with nothing connected to it? Do you have shorting caps for the RCA's to test this out?

 

[PabloTincho]

No hum when is in the lowest point
After 1/4 that when the hum starts
Can I disconnect the carbon pots ?
No hum when the preamp is disconnected completely

 

[dogwan]

No hum when is in the lowest point
After 1/4 that when the hum starts
Can I disconnect the carbon pots ?
No hum when the preamp is disconnected completely

Hmmm, that would lead me to believe the problem is not with your amp.

Yes, you can probably disconnect the pots. But there may be issues that arise if you do. Not sure. Here's a screen shot of the schematic showing the pots (VR1 and VR101) electrically just after the input RCA's. Before disconnecting, I would try jumpering the wiper (center pin) to the input side or to the backside of R1/101. If you turn the pots all the way up and the jumper eliminates the hum that could indicate the problem is in the pots. (I think probably not, but who knows).

Other things to check:

• Are you sure Mono/Stereo switch on back panel is in the correct position?
• Have you tried a different pair of interconnects?
• Does jiggling interconnect at back of amp affect the hum (could indicate cold solder joints of the RCA inputs)
• Tried a different preamp? (if you don't have a preamp then you could use an iPod or Phone with a 1/8" to RCA cord...just be sure volume is down before you turn on amp)
• Thoroughly cleaned the gain pots and the stereo/mono switch?
• Is hum in both channels? If you only disconnect pre from one side, what are the results?

Lastly, I would suggest you start a specific thread asking for help. I'm no tech., but if I had the amp in front of me I would be asking more knowledgable people after I checked the above.

 

[dogwan]

@PabloTincho

I almost forgot, another thing to check is the wiring harness to the pots. The P5000 I had used a similar set up and one of the pots had loosened up so that it kind of just spun the whole pot instead of turning the wiper. When it did that it would twist the wires around. Easy enough to fix after re-tightening the pot in the face.

If the wires have been twisted and are starting to fray it's conceivable that you could be getting bad connections in certain positions of the gain knob range.

 

[WJE2]

On the Hafler amplifier that I owned about 14 years ago (forget the exact model number), I had some hum present on one of the channels. For me, the issue was with one of the larger filter caps. I remember locating one of the screws that held the filter capacitor in place, tightened it down, and the hum was completely gone.

 

[John Proctor]

Little late to the party but as the original post said, not a lot to read about the 9270 out there in the wild.
Picked up a lightly used 9270 several years ago that got put up on a shelf. Recently came across a Hafler 945 pre amp that was still in the original packaging, couldn’t pass it up.
Playing through 4 ohm Acoustic Research AR-3A’s, Sony CD Player and BlueSound Node. Still need to do some side by side comparisons with different amplifiers and speakers but really liking it, pairs with these speakers well. Listening to “I shot the sheriff” right now and hearing incredible detail in the music.

 

[pelerinc]

I have a 9270 and a 9290 (even more rare it seems) each running in bridged mono to drive a pair of Dahlquist DQ-10s. With roughly 400W, the DQ-10s come alive.

 

[PabloTincho]

How good is the matching preamp, the Hafler 915 ?