Hafler DH-100 upgrade

[Feanor]

Very recently I notice a Hafler DH-100 preamp for sale here in Canada on eBay; since I had no back up preamp, I decided to bid for it. At the same time I knew that I could by an upgrade kit from another eBay seller. Once I'd got the preamp home and it tested OK, I ordered the upgrade kit from ray17760 ... here.

I didn't audition the preamp much before doing the mods, just enough to get rough idea of the sound. The upgrade kit consisted entirely of capacitors, viz. the major ones in the power supply and most in the line stage signal path; (not all, but the seller insists the originals are as good as any). Kit contents ...



The kit included desoldering wick and rosin solder, but I had my own solder sucker and silver core solder which I used instead.

The upgrade sound was basically as advertised though "dramatic" might be a slight hyperbole. Nevertheless the new sound as detailed, reasonably spacious, with a slight prominence in the low-mid bass vs. my main preamp. The highs pretty grain-free but tiny bit bright or shrill.

But lo! I figured I might have the solution for the slightly bright highs in a couple of OPA627 opamp pairs. These I had abandoned from an earlier project; they were from Gigawork, a eBay seller in China ... here.

I installed the OPA627's for a significant (but not "dramatic") smoothing of the highs. Now I have a very tolerable backup preamp! Also some fun and a total cost under $175. The modded Hafler DH-100 preamp vs. my Sonic Frontiers Line 1, (final MSRP $3500):

• Slightly warm low-mid bass, otherwise a neutral balance
• Clean, non-grainy sound
• Very good detail & resolution, close to, but not as good as the SF
• Smooth highs with the OPA627 opamps, though not as refined as the SF
• Acceptable soundstage & depth, but much inferior to the SF -- this is where the latter rules big-time.

My upgraded Hafler DH-100 ...