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Thread: Modded SET amps

  1. #1
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    Modded SET amps

    Hi, who has, or has had, modded their SET amps to much better heights than stock - either through tube rolls and/or by getting a techie to change parts. There are many amps like Cary 805 and Viva Verona that come used at nice prices but have stock tubes. The Viva 845s seemed to be voiced to the shuguang, but all other amps have 211s and 845s and other driver tubes can that can be modded. Any such cases around here?
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    I modded my personal 805AT based SET monoblocks from Arte-Forma. Amazing results, but this is only for my own use. It included rewiring the entire amp, new binding posts, upgraded caps, added decoupling caps for HF and inrush limiters to extend the life of the output tubes. Not my business to mod anymore.

    I also rolled the tubes many times to get to the most transparent and fast combination, Russian military tube for input, Genelec KT-88 for driver and Chinese 805AT for output. I feel they are the best amps I have ever heard now, and I hear amps at a lot of shows. I need really revealing amps to hear improvements in my converters and DACs.

    The unique thing about these Arte-Forma monoblocks is 30-35W per channel all DC-coupled. Excellent output transformers too.

    Steve N.
    Empirical Audio
    Last edited by Empirical Audio; 11-27-2017 at 02:15 PM.

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    Thanks Steve.
    Audition recordings: Zero Distortion Link; Reference Components: Zero Distortion Link; Own: Lampi GG One-day-to-get: Apogee Scintilla, or a horn (with Tenor 75 OTL ), Preamp to be fit in to suit the gain and drive the power amp. Analog: TBD

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    I have built at least 10 amps, preamps and DACs from kits—stock parts first, then one-at-a-time modifications. Output transformers, resistors, and capacitors. It has usually been easy to hear the changes, especially in a SET amp, although the magnitude of the change depends upon what is replaced by what.

    Haven’t owned or tried this in an amp with very high plate voltages like an 845 or 211—just 300B, 2A3, EL84 and EL34 amps.

    Dave

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    [Industry Expert] Addicted to Best! DaveC's Avatar
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    I've re-built my SET amp many times over the years, the current configuration is relatively high gain for covering >400 Hz on my 3-way horn hybrids. It currently has an input and driver section with it's own power supply, 6SL7 in, 6SN7 out and a separate EL34 SET power section with James OPTs.

    I'd guess most any commercial SET amp could be significantly improved as the best parts to use in a tube amp cost a fortune and very few mfg'ers will use totl parts.
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    If you do go to those lengths, I'd start with an amp that has great transformers first. This is the area with SET that has the most influence and modifying an amp with TOTL parts that has mediocre transformers will likely never compete against a stock amp with superb transformers.
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    I modified my two Wavac SET stereo 572 amps (rated by Wavac as 50w per channel but probably more like 40) to anode capped 572B. The original 572 tubes were not anode capped, but Svetlana stopped production of them. The 572b anode capped tubes are in every way the same tube in specs as the 572-160 except for the anode cap. Also, the 572b tubes are still in production and used widely for radio frequency applications. (Note this refers are the 572-160 tubes. Svetlana made a range of about four 572 tubes without the anode cap with different specs i.e. 572-30 etc.)

    The better thing about the 572b tubes is they are larger and have thicker glass envelopes than the original 572 tubes, plus the anodes are a lot sturdier and take the high currents better. The 572b last longer and to me the Svetlana 572b sound better than the non-anode capped 572s that it used before. There are some NOS 572bs that can be used, as well as Chinese 572b tubes, so there is more flexibility with 572b tube rolling. Also, re-tubing the amps is very economical compared to other SET amps that put out relatively high power in the 35 to 50 watt range per channel.

    I'll be selling one of the 572b Wavacs when I get around to it, and keep the lesser sample because it is the best Stax headphone amp (when coupled with Stax transformer box) I have ever heard, amazing headphone sound.
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    my friend with Audion Black Shadows upgraded his power supply caps - work done by Bob Hovland. Much quieter and now I believe standard on Audions.

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    [Industry Expert] Addicted to Best! DaveC's Avatar
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    Quote Originally Posted by DSkip View Post
    If you do go to those lengths, I'd start with an amp that has great transformers first. This is the area with SET that has the most influence and modifying an amp with TOTL parts that has mediocre transformers will likely never compete against a stock amp with superb transformers.
    I agree... SETs are simple enough most everything matters but the trafos are the most expensive parts that make the most difference.
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  10. #10
    Yes, I have had a couple. The Border Patrol P20 had Blackgate psu caps / silver ribbon signal wiring / teflon tube sockets / nextgen rca jacks / eichmann binding posts / shielded umbilicals as well as the factory EXD mods. The Audio Mirror 6c33 monos had clarity mr intrstage coupling caps / teflon tube sockets / fast recovery diodes / nextgen jacks / eichmann binding posts / furutech iec inlets. All of these mods were worthwhile and in addition to tube rolling / fuse upgrades.
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