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Adventures with Wire....Eico HF-81.... G2 ....

Posted by drlowmu (M) on March 13, 2007 at 16:45:57

Adventures in Audio with Wire

Hi, last week I had an interesting audio experience with wire I'd like to share on-Forum. I was reworking a Eico HF-81 and listening to it on an open baffle mounted JBL D-123 with a modified ( paper, not aluminum ) dustcap. I knew from prior years of experience with the pentode 6550 Paoli 60Ms, that the Eico must also be sensitive in G2 screen implementation, ... because the Paoli pentode amp certainly was. Everything I did to the Paoli 60M's G2, was reflected in the overall amp's sound. The Eico uses EL-84s. Its output stage is NOT operated Ultra (Non) Linear, but rather, has its own screen supply, a 30 uF cap, decoupled by R = 350 ohms, from the main supply's 30 uF cap.

I jumpered a Radio Shack clip lead, from the G2 supply cap, across the stock wiring, right to the G2 point of use....viola, better sound !! I was listening in MONO to one channel BTW.

OK, one cannot under estimate the G2 requirement. So, I neatly cut and tinned THREE runs of TCSS ( Kimber Kable, 7 strands, three different diameter wires, 19 gauge, wrapped in teflon ) and hooked up all THREE runs, from the G2 cap to the G2 point of use, all three wires connected in PARALLEL.

Well folks, that paralleled set of three TCSS was quite a bit better sounding than the stock single-run Eico HF-81 wiring. I listened for a day or so to that, was pleased, and prepared another " triple " run of equal length TCSS, to go to the other channel's G2 supply. Whats the current in a G2 supply, why practically nothing !

On a whim, I added another clip lead across the first channel's run of three wires, making it four wire runs to G2. Guess what, It got better again, not enough wire !! Well, I ended up settling on SIX TCSS runs to the one P-P pair, doing G2 on my EL-84s.!!

What does "sounding better" mean?? I'd say that the dynamics and resolution, and overall clarity of presentation was way way better, it played more musical information, with a more completeness of the sound, and with better small hints, like the natural acoustic decay of struck notes. After hearing three TCSS in parallel, I could never go back to one run, and after hearing six in parallel, well, I closed up the bottom cover, smiled, and basked in the new and better sound.

My conclusion : the idea of employing a ten ampere current capability in the wire, for an audio stage operating at 1 mA ( static / quiescent ), is not far fetched at all, IF you want to maintain and properly pass the INSTANTANEOUS brief peaks of music - and not lose the musical information inside the amp, due to the amp's lackluster internal wiring. One must think in dynamic terms, rather than static measurement terms, to understand this.

This wire concept also applies "in spades" to my newly embraced Low C, HY, DCR power supply approach !!

Clip-leading in, multiple paths is easy to do on a quick experimental basis, and GOOD wire soldered-in is, of course, the ultimate answer. I like the Kimber TCSS, available from Michael Percy, on a cost / performance basis BTW.

As previously discussed in one of my earlier posts by my friend Dennis, the grounds in a SE amp are particularly critical as to both wire quality and quantity ( gauge ). I believe we can all improve our DIY amps, by experimenting along the lines I've discussed herein and encourage people to do so and report back up here. Have fun listening.

Cheers.

Jeff Medwin

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

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