The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all products and all products



    Posts : 76
    Join date : 2015-01-25
    Age : 60
    Location : Northern Ontario


    Post by tubenutr on Wed Feb 17, 2016 9:28 pm

    Does anyone use a ss subwoofer with their zmod PAS3 or other tube preamp?
    Is so, how does it sound or interface.




    Re: Question????

    Post by Guest on Wed Feb 17, 2016 9:29 pm

    Eskimo wrote:Does anyone use a ss subwoofer with their zmod PAS3 or other tube preamp?
    Is so, how does it sound or interface.



    is it a stand alone powered sub? What do the sub's instructions say about connecting it?

    Posts : 65
    Join date : 2015-07-15

    Re: Question????

    Post by GreggW on Wed Feb 17, 2016 9:38 pm

    I have a Velodyne powered sub connected directly to the ST120 speaker outputs, then to a set of Polk towers. The preamp, a fully modded PAS 3, never "sees" the sub as there is no direct connection. There is no extra rumble, hum, or unusual sounds out of the sub or speakers. Honestly, for a lobuk speaker system it sounds really good to these old ears.

    Posts : 72
    Join date : 2012-07-08
    Age : 58
    Location : Livermore, CA

    Re: Question????

    Post by aguaazul on Thu Feb 18, 2016 2:09 pm

    Hey Eskimo,

    Before I had speakers that had some good bottom end I played around with a powered sub.
    I started out with a PAS3 and an ST-70, both refreshed to stock in by Joe Curcio (Dynaco Doctor). He lives within 1 hour driving distance; he’s a good fellow, took his time with me and really helped me get started.

    I wanted to hear what they sounded like in their basic form. He did bypass tone controls in the PAS3, fixed the RIAA on the phono stage and he strongly suggested that I dump the 7199 tubes on my amp that were out of spec  for the SA-6GH8A 9 PIN Socket adapter with some 6GH8A’s.  His advice from the cost & sound standpoint did not steer me wrong.

    I listened to that set up for a couple of years. Just running some homegrown speakers that I had laying around, even though they had been sweetened up with super tweeters & crossover upgrades, they were nothing special.

    When I was leaving Joe’s shop one day, he knew what my setup was like, I asked him what speakers I should try to learn the sound of my gear, he pointed up to a pair of Dynaco A-25’s and said why don’t you  try a pair of those… good advice.

    Year later, looking for some more bottom end…  I picked up a pair of Klipsch Hersey’s.  Great speakers, super soundstage, imaging, still not hitting the bottom end I was looking for… even after I did the top of the line crossover rebuilds… still not getting the big bottom sound I was looking for.

    I then decided that I needed to add a subwoofer to the Hersey’s because I could not afford any other speakers with that sub 50 Hz frequency responses.
    So I picked up an ENERGY EAC electronic crossover. But the PAS3 could not work with it connected up to the RCA jacks due to the impedance mismatch (that issue you will not have with your ZMOD boards by the way), so…

    Back to Joe (Dynaco DR), he installed a tube Cathode Follower Mod into my PAS 3. Sha-zam, I could use the subwoofer that I have for the home theater system with the vintage tube stereo system, getting the bottom that I was looking for!

    It was a huge success.  

    Luckily I fell into a pair of 1972 Bozak Symphony Speakers with the N-106B Active Bi-Amp Crossover network with the N-104 & N-107 crossovers and a pair of Bozak B-313’s.  These were gifted to us from a wonderful family for a charitable donation to a charity of my choice! These speakers fill in the bottom end without any extra subwoofer or any other accouterments.

    So I no longer use the EAC, Dynaco A-25’s or the spiffed up Klipsch Hersey’s, the old home grown speakers are in the shop used for testing… I still have the ENERGY EAC electronic crossover, it’s hanging around, waiting for the next system it could be used for, or for somebody who needs it.  

    I did the ZMOD mod to the PAS3, liked it, but decided I missed tone controls with the Bozak speakers, so I went with the TCLA setup. The ZMOD line board lives in a tricked out PAT-4 case. My ST-70 runs the VTA70  ‘classic’ driver board. My Symphonies are Bi-Amped using the Bozak N-106B crossed at 400Hz with a SS Carver A-220 running the 4 - 12" woofers.

    At this time I’m playing around with DACs. I’m tuning up a Lampucera1.0 + Lampizator CS8416 + CS4397 kit, I can choose to use it with or without the tube stage, looks promising.

    With a Red Baron V5 & Tube-I-zator V3.1 build on the horizon. There are pictures of all of this on my Google+ profile.



    Posts : 959
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Question????

    Post by peterh on Thu Feb 18, 2016 3:40 pm

    Sounds complicated.
    A use a PAS3X + VTA70 and opus3 transmission line speakers. Made in concrete heavy as (..) but
    covering the audible spectrum. No mods, only a homebuilt cathode follower box that interfaces
    to my computer ( the pas needs this to drive low impedance inputs), and contains a remote volume.
    I'd likely keep this exact set for another 10 years, can't improve the perfect :-)


    Posts : 792
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Question????

    Post by GP49 on Fri Feb 19, 2016 1:43 am

    I use a modified PAS. Like a stock PAS it is sensitive to output loading. I also use a Dynaco Stereo 400 to drive AR-3s (midrange and tweeter disconnected, so they are instantly restorable to stock) as subwoofers, through an electronic crossover of my own design (actually a cookbook design with filters selected for the response I want). Even though solid state, the input uses FETs so the impedance is high, suitable for the PAS driving them and a pair of modified Mark IIs.

    Why the ARs and Dyna power amp instead of a dedicated subwoofer or a pair of them? I feel that this combination is faster and more dynamic than the usual subwoofer, which is designed for cinema, not music. Many are BOG SLOW. This combination better matches the main speakers.

    Posts : 91
    Join date : 2011-09-20

    Re: Question????

    Post by kaner on Fri Feb 19, 2016 10:26 am

    I use a DIY passive pre into my VTA ST70. The sub (Monitor Audio) is fed off of the speaker jacks of the ST70, and run at fairly low levels. It does a nice job of filling in the bottom end without getting flubby.

    I occasionally use a blue ray player into that system to watch movies. Then I'll turn the sub up a bit.

    I'm building a Pass B1 buffer to replace the passive pre. It'll be interesting to see if that brings out more low end without the sub.

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    Re: Question????

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