Slagleformer Preamp

Discussion in 'Everything Audio' started by marantzfan, Nov 10, 2017.

  1. marantzfan

    marantzfan Administrator Staff Member


    I’m starting to look at these little fellas more seriously. There is a good chance in the coming months that I’ll finally get off the fence and build one.

    There looks to be quite a few options available.. any tips?

  2. Redboy

    Redboy Knobophobe

    I'm kinda familiar with these.

    You'll get the Slagle magic with any of them; the secret sauce is in the magnetics, and that doesn't change from model to model.

    What does change is the number of steps you get (bigger jumps of attenuation with the lower cost modules offer less fine tuning) and the brand of switch used. Those plastic-bodied switches are high quality but sorta cheesy feeling (IMO) Lorlin models, while the metal ones are the incredible Elma switches. The only switches I like better are Seiden's high end offerings.
    marantzfan likes this.
  3. inthewoods

    inthewoods AARP Member

    I use his TVC modules
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  4. mhardy6647

    mhardy6647 Señor Member

    sorry, I can't but think of Bowie whenever I hear or see "TVC"...

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  5. marantzfan

    marantzfan Administrator Staff Member

    Come on Mike. Not letting you off that easy.. tell me more. ;)
  6. JohnVF

    JohnVF Administrator Staff Member

    As an owner of a Redboy Audio slagleformer preamp I can say yes, you should do this
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  7. ejfud

    ejfud Junior Member

    They are the best. Do it.
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  8. mhardy6647

    mhardy6647 Señor Member

    I have -- umm -- some sort of AVC or TVC thingie from Redboy's Early Period. I figure it'll be worth big bucks some day; you know, Portrait of the Artist as a Young Man and all that sort of thing.

    [​IMG]010 by Mark Hardy, on Flickr
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  9. mhardy6647

    mhardy6647 Señor Member

    PS I wish when I bought that Azden switch from my son's high school photography teacher at a school fundraiser fleamarket (many years ago) -- that I'd have bought both of the ones he had. :frown:

    EDIT: sorry about the atrociously constructed sentence above. I must not have had enough coffee yet this morning...
    I am going to let it stand as an example to others to avoid my path. You know, like the corpses hanging near the quay at the beginning of the first Pirates of the Caribbean.

    pirates beware.jpg

    Last edited: Nov 11, 2017
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  10. marantzfan

    marantzfan Administrator Staff Member

    So... in looking at these options, I’m leaning away from the basic module that has the coarse and fine tuning volume adjust for each channel.

    Ain’t nobody got time for that four knob action just to turn it up and down. ;)

    I could live with one knob per channel, although I’d prefer just one volume knob for both channels... but it seems that in Slagleland, the less knobs you get the more expensive. I guess less really is more sometimes.. ;)

    Typically I have been ok with three inputs, but why not add a few more on this build just for future flexibility. I’m leaning towards 5-6 total. I’ll also need a least two pairs of outputs since I run subwoofers. A really nice feature would be a summed mono output as well, but I’ll have to look up how one does that.

    A remote would be nice too, but apparently that option from Bent Audio is no longer available to the public. Is there another option available?
  11. billfort

    billfort Administrator Staff Member

    Looking forward to seeing where you go with this Anthony – should be interesting.

    I thought I'd share some of my thoughts on this approach as I keep coming up against hurdles every time I've considered building one of these.

    If I could build one to fit my system and needs, it would end up pretty expensive, and considering what it would replace, I'd need to hear what it can do before committing. I know several here who's ears I've come to trust rave about them, but I haven't tried a TVC. My experience with simple level pots has not been good and I actually find things sound better without them (along with a good pre-amp). I built fancy Alps pots into my 2A3 amp and even tried them in hot-rod shunt-bypass mode to see where this 'less is more' approach could go – and they are now out of circuit and just fill the top plate holes. Simpler amp circuit on a good active pre-amp sounds better to me.

    I also tried stepped attenuaters of various flavors including a very nice DACT CT2 24 postilion. I had a problem with the 'steps' and even if you could use all 24 positions in your listening range (I couldn't), I sometimes felt it was just too quiet or too loud. Even when this was not an issue though, I still found a good pre-amp had more drive, dynamic contrasts and just balls (I'll call it...); the attenuator was super clean, detailed and airy, very 'hifi', but I liked listening to music better with the pre-amp.

    I keep harping on good pre-amp because that's a big factor for me; I spent many years on the pre-amp merry-go-round before settling in on the Joule Electra I use. I kind of lost count of how many but I owned, borrowed, or demoed many tube, SS and hybrids over a 15yr period and lived with them in my system before settling on the one I now consider my end-game – haven't touched it in about a decade.

    If I could somehow hear a TVC and thought yup, I gotta have one, the usability issues I'd have to contend with would be;

    As many 'steps' as possible and hopefully, they are all mostly usable in my listening range.

    I never thought much about a 'balance' control but do adjust it sometimes – I'd miss this but could probably live without it.

    I need multiple inputs – currently have 4, use them all and sometimes would like more.

    I need multiple line-outs – 1 to connect my main amp/speakers un-molested and 1 to connect the active/eq'd/SS bass fill pieces. Actually I'd like to have 3 – I have a headphone amp I'd like to connect without unplugging something else.

    Remote volume control – never thought this was a big deal but now that I have it, I love it and wouldn't want to do without anymore.

    So a tough leap for me; would it be 'better' (back on the merry-go-round I got SO tired of), could I get the functionality I'd like and could I actually build and afford what I'd be happy with? Maybe you'll convince me. :)
    marantzfan likes this.
  12. JohnVF

    JohnVF Administrator Staff Member

    I’ve used a passive attenuater and the TVC is nothing like what I heard with that. It was clean and clear but lacked drive and dynamic contrasts. The TVC really maintains clarity and tone while delivering striking dynamics. I believe if they were more common and cheaper/easier to make that they’d be the way many in this hobby controlled volume. The confusion between them and other passive devices, I fear, is keeping many from an enlightening experience.
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  13. marantzfan

    marantzfan Administrator Staff Member

    I’m really interested to see how these sound (or don’t) in my system. My concern with any passive design has been that I’ll lose drive and dynamics but all feedback I’ve heard on these is the opposite.

    Only one way to find out right, get my ears on some. ;)
  14. Prime Minister

    Prime Minister Site Owner Staff Member

    My limited experience has shown you lose nothing in drive and dynamics. At all.
    marantzfan likes this.
  15. marantzfan

    marantzfan Administrator Staff Member

    Getting a little excited about this project. Gotta be honest. :)

    Any recommendations for a quality source selector switch?
  16. JohnVF

    JohnVF Administrator Staff Member

    Do those of you who use SUTs for LOMC think they squash dynamics? I really want to scream it from the hilltops. All passives are not remotely the same. Instead I’ll just plead for those who are curious to find one and try it. I’ve used many high quality preamps. VAC, Klyne, Marantz Reference, Primare, early tube based Bel Canto SEP... the TVC does some things better than all of them. It’s not better at everything but on the average it bests them all. A truly open window to the music.
  17. Redboy

    Redboy Knobophobe

    Methinks @billfort Bill thinks too much... :)

    Bill, we've got to get you some ears-on experience with these! You can keep the Joule Electra preamp - just swap out the pot in that thing for some autoformers, mang!

    Since we're already talking transformers here, you'll want to check this out:

    If you go whole hog on the autoformers and buy the swanky ones, you'll want to use this switch (and pcx is having a 25% off sale now thru the end of the month):
    marantzfan likes this.
  18. marantzfan

    marantzfan Administrator Staff Member

    Now that is interesting; using a matching transformer to sum the channels.

    I'm trying to fight the urge to buy the top-o-the-line Elma module and the switch you linked above... Good thing is, I need to refill the coffers before I'll be able to allow the impulse to overcome me. It's quite likely though that is exactly what I'll do. Go big or go home, right? ;)

    So, the next issue on the docket for me is appearance. I'm thinking of how to tie this in aesthetically to my newly constructed Simple 2A3 amplifier.

    I want to use the same color scheme of cream, hammered copper and walnut...

    Maybe a cream colored face with walnut case? Or, hammered copper face with cream colored chicken head knobs? I've got a little while to figure that out... :)

    Seen any cool looking preamps that use wood that I might replicate?
    Chops54 likes this.
  19. TubeHiFiNut

    TubeHiFiNut Administrator Staff Member

    You guys have sold me on the idea. I've decided to replace the stock Alps pots on my Quicksilver Line Stage preamps with the Slagle Autoformers.
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  20. Redboy

    Redboy Knobophobe

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