Forums - 6680 Mobile Communication 12AU7A in the ‘Rock

Rivieraranch

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Posts: 2142

6680 Mobile Communication 12AU7A in the ‘Rock
05/22/25 at 17:30:34

I placed a 6680 12AU7 variant in my ‘Rock and so far it really rocks. This tube was designed for use in mobile communication and broadcast such that it maintains a steady output despite a drop in voltage. I’m not sure whether this is an end run around using a regular 12AU7 in a voltage starved circuit such as the ZRock. But the sound is very good from this tube.

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MINI TORII & ZROCK2 both anniversaried; 'Lil Audio F-15; TECHNICS SL1200MK2 KAB MODDED TT; ONKYO 6 DISC CD; MARANTZ 2226B; SCHIIT MULTIBIT DAC; SENNHEISER HD-580s

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Lon

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"Love without
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Posts: 26084

Re: 6680 Mobile Communication 12AU7A in the ‘Rock
Reply #1 - 06/17/25 at 13:29:10

Interesting, I've never tried this variant. I may soon.

I find that in my system the ZROCK3 tube is almost dictatorially influential. I have a Sun labeled Holland made 12AU7 that is just magic in the ZROCK3--even other identical tubes don't have the very same magic. I keep trying to find a better, and haven't yet in ZROCK2 or ZROCK3, and wish I could find about four more.

The ZROCK3's ability to modify the output gain is a secret weapon. Amazing what tiny adjustments can do in my system.

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HR-1,ZBIT,ZROCK3,SEWE300B,CSP3-25mod; Rega RP3 all GrooveTracer mods;PSAudio:PST+DSD, DAC Mk II, P15,NPC,PowerBases,AC-12 pwr cbls, Reference spkrcbls; Mapleshade SamsonV3; VooDoo:Cremona+Amati interconnects;Stack EQ; headphones: Sennheiser HD800S,ZMF Ori,Oppo PM1

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Lon Seasoned Member "Love without guts is worthless!" Philip K. Dick Posts: 26084	Re: 6680 Mobile Communication 12AU7A in the ‘Rock Reply #2 - 06/20/25 at 20:58:10 Wow Jim. I purchased a GE 6680 AUDIO VACUUM TUBE, GRAY PLATE, O GETTER and am listening to it now. Rich, dark, in a way that really suits my system. Thanks for that recommendation. GREAT sound with this tube in the ZROCK3 and that magic SUN/Holland 12AU7 in the SEWE300B.
Back to top	HR-1,ZBIT,ZROCK3,SEWE300B,CSP3-25mod; Rega RP3 all GrooveTracer mods;PSAudio:PST+DSD, DAC Mk II, P15,NPC,PowerBases,AC-12 pwr cbls, Reference spkrcbls; Mapleshade SamsonV3; VooDoo:Cremona+Amati interconnects;Stack EQ; headphones: Sennheiser HD800S,ZMF Ori,Oppo PM1 IP Logged

Rivieraranch

Seasoned Member

Posts: 2142

Re: 6680 Mobile Communication 12AU7A in the ‘Rock
Reply #3 - 06/20/25 at 21:26:11

Yeah Uncle Lon mine is a GE Motorola Mobile Communications 6680 from the ‘60s. Since then I acquired some European 6680 labeled International Servicemaster that I must test before using. The ZRock design revolves around a voltage starved condition in the tube. So a 6680 will maintain a stable output despite a drop in voltage.

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MINI TORII & ZROCK2 both anniversaried; 'Lil Audio F-15; TECHNICS SL1200MK2 KAB MODDED TT; ONKYO 6 DISC CD; MARANTZ 2226B; SCHIIT MULTIBIT DAC; SENNHEISER HD-580s

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Lon

Seasoned Member

"Love without
guts is
worthless!"
Philip K. Dick

Posts: 26084

Re: 6680 Mobile Communication 12AU7A in the ‘Rock
Reply #4 - 06/20/25 at 21:29:36

Nice observation and great results. I have two other GE in a lot of 23 tubes on the way to me, 15 dollars for 23 GE tubes of about ten types, but I think all the other tubes are incompatible with Decware components, but the price for those two is nothing to complain about. I have two ZROCK2 that they can inhabit . . . I have a ZROCK3 and two ZROCK2. . . an embarassment of riches.

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HR-1,ZBIT,ZROCK3,SEWE300B,CSP3-25mod; Rega RP3 all GrooveTracer mods;PSAudio:PST+DSD, DAC Mk II, P15,NPC,PowerBases,AC-12 pwr cbls, Reference spkrcbls; Mapleshade SamsonV3; VooDoo:Cremona+Amati interconnects;Stack EQ; headphones: Sennheiser HD800S,ZMF Ori,Oppo PM1

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