[chasm3940]

Recently had to replace my speakers (new Martin Logan Clarity's), and am now looking at the rest of my old equipment.  Current amp is a Hafler DH200, so I read with interest about AVA's re-cycle of this chassis.  But I have also seen criticism of the original Hafler concerning its inadequate power supply.  I see that the AVA rebuild retains the old power supply.  Could you please comment on this for me as a novice?

[OldCoder]

I've owned two MOSFET versions of them for quite a while, and I have been very happy with them.

While they do not hold a candle to the new designs that Frank offers, I never felt that the power supply was a limiting factor, nor did I notice problems with creating volume (I am a WHO fan), or get the sense that the power supply was inadequate in any way.

Of course, once I heard Frank's Omegastar and Fet Valve amps, I did want to upgrade....and have.  But that doesn't diminish the regard I hold his DH 200 upgrade in.  Still use one for my subwoofer.  Frank did have to replace the power switch on it once, after I managed to weld it open (like I said, I like the Who!).

[Zheeeem]

I still have an AVA MOSFET version of the DH-220 in operation, driving the notoriously inefficient Magnepan Tympani 1(U) to ample levels.

If you are worried about having a large enough/stable enough power supply, talk to Frank before the upgrade to see what he can do.  Alternately, you might want to think of selling your DH-200 and buying an Omegastar 260EX (or FET-Valve 350 if you can spring for it).  Both are outstanding.

[skrivis]

Recently had to replace my speakers (new Martin Logan Clarity's), and am now looking at the rest of my old equipment.  Current amp is a Hafler DH200, so I read with interest about AVA's re-cycle of this chassis.  But I have also seen criticism of the original Hafler concerning its inadequate power supply.  I see that the AVA rebuild retains the old power supply.  Could you please comment on this for me as a novice?

Someone told me that they used the identical power transformer for the DH-200, DH-220, and XL-280. It's a _very_ robust transformer. The bridge rectifier in the 200/220 is quite sturdy. My DH-220 had a pair of big soup can filter caps originally.

I really don't see that the power supply in these amps could be considered to be inadequate.

The only problem with the Hafler chassis is that the circuit boards mounted on the heatsinks are close to the transformer. According to AVA, this can cause some problems. The new AVA chassis keep the power supply well away from the signal circuitry.

I had my DH-220 upgraded to a Mosfet 250 C, and then more recently to an OmegaStar. I'm going to be sending it back to AVA pretty soon to get the EX output devices put in.

I have never been unhappy with this amp, in any of its incarnations. I don't notice any hum or noise, so I'm not sure how much of a factor the cramped case is. Output power is more than sufficient for anything I've ever done with it.

I think you get a bit more amp by upgrading your DH-200 than by buying a new OmegaStar 240EX. But it's a bit more expensive too. (And don't forget that you can sell your DH-200 if you buy the 240EX too.)

In my case, it was most cost-effective to upgrade my old amp, because it was already a Mostfet 250 C, and it wound up being cheaper than buying a new amp.

If I were doing it now, it would be $899 to go from Mosfet to OmegaStar EX.  I would be very tempted to get the 240EX instead. (I think "very tempted" may not be strong enough. How about "highly likely?")

[avahifi]

The only people who will tell you that the original Hafler DH series amps have inadequte power supplies are those that want to sell you new power transformers in the process of taking out the bad sounding parts and installing good sounding parts in the same old tired slew rate limited audio circuit.  They do this because it is all they can do, they have no clue as to what the worst case problems with the amplifier is, or how to design a new ultra wide band super clean audio circuit from scratch.

Oh well.

The original Hafler power transformers and diode bridge are way more than adequate to sustain full power of the amplifiers indefinately, and we have never had one fail.  Thus they are absolutely the last thing we would suggest you pay for in upgrading the amplifier.  It would be like telling you that the best way to get better performance from you VW Beetle would be to replace the gas tank and seats.

Oh well.

So much snake oil out there, so little good engineering.

Frank Van Alstine