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    VTA stepped attenuator in place of my PAS-3

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    RockyAM

    Posts : 26
    Join date : 2008-12-14

    VTA stepped attenuator in place of my PAS-3

    Post by RockyAM on Fri Mar 09, 2012 10:28 am

    Hey Bob, I finally got the stepped attenuator you sent me installed into my VTA ST-70 amp which I built from your kit. I use this amp in my playroom when we have people over. This is a second system and I had a basically stock PAS-3 that I was using for my preamp. I don't play records anymore and just use my CD player so I don't need the phono section on the PAS preamp. What a difference with my PAS-3 out of the way between the CD player and the ST-70! I didn't realize how much my PAS-3 was holding the amp back. The sound is now more open and bigger? with the PAS out of the chain. I put the PAS back in for about 15 minutes just to check what I was hearing. Yup .. the sound was not as good with the PAS in there. Even my wife could here the difference and she never pays much attention to the sound of our stereo. RockyAM

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: VTA stepped attenuator in place of my PAS-3

    Post by mantha3 on Fri Mar 09, 2012 4:01 pm

    Who was it that said "The Best Preamp is no preamp"....

    Captain Coconut

    Posts : 209
    Join date : 2009-10-13
    Age : 64
    Location : Great White North

    Re: VTA stepped attenuator in place of my PAS-3

    Post by Captain Coconut on Fri Mar 09, 2012 4:03 pm

    mantha3 wrote:Who was it that said "The Best Preamp is no preamp"....

    I'm pretty sure it was me. Laughing

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA stepped attenuator in place of my PAS-3

    Post by Bob Latino on Fri Mar 09, 2012 5:59 pm

    The original PAS-2, 3, and 3X were OK for their time but require heavy modification to really sound good. I agree with the original poster that an all STOCK PAS preamp will probably "hold back" any VTA amp from sounding its best. If you do have an original PAS preamp you should probably consider Roy's PAS Z-mod which is a huge improvement over the original PAS line and phono circuits. It can be had with or without the tone controls.

    On the other hand if you only have a single high level signal source like a CD player on your music system, then the stepped attenuator is an inexpensive way to get better sound out of your amp by eliminating the preamp. Below is a photo which shows the installation of the VTA stepped attenuator into a VTA ST-70 amp. This attenuator can be added to any stock or VTA ST-70/ST-120 in about 1/2 hour ...

    Bob



    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA stepped attenuator in place of my PAS-3

    Post by plexus on Sun Apr 01, 2012 10:45 pm

    I have been using a little Audio Innovation P1 preamp which is based on one 12AU7. i also have a decent quality source switch box I made. With my sources they dont really need a preamp. and logically, "the best pre-amp is no pre-amp". so i have on the way a high quality 48 position stepped attenuator from germany. i will then have no need for a pre-amp. less crap in the audio circuit the better. it took me a little bit though to grasp the idea of no preamp, much like the idea of not having a land line after having all my life was a challenge. Smile so instead of buying an SP14 I decided to put my money into a PH14/15 as my current phono stage is a weak link.

    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: VTA stepped attenuator in place of my PAS-3

    Post by tubes4hifi on Tue Apr 03, 2012 9:12 pm

    I hate to repeat myself, but I've been saying this for 20+ years, if you have a PAS3, replace it, don't upgrade it.
    Needless to say, I get way too much business for PAS3 upgrades. Much better value and quality replacing it with a modern preamp,
    or yes, if possible, no preamp at all. But the SP12 is light years better than a fully modified PAS3 could ever be, and less $$.
    And if you can afford the small difference, step up to the SP14.

    avi.inc

    Posts : 53
    Join date : 2009-08-03
    Age : 63
    Location : L.A.

    Re: VTA stepped attenuator in place of my PAS-3

    Post by avi.inc on Wed Apr 04, 2012 6:08 pm

    tubes4hifi wrote:I hate to repeat myself, but I've been saying this for 20+ years, if you have a PAS3, replace it, don't upgrade it.
    Needless to say, I get way too much business for PAS3 upgrades. Much better value and quality replacing it with a modern preamp,
    or yes, if possible, no preamp at all. But the SP12 is light years better than a fully modified PAS3 could ever be, and less $$.
    And if you can afford the small difference, step up to the SP14.

    I see that sp14 has a phono in is that for the output from a phono preamp or does the sp14 have a phono preamp on the board?

    tubes4hifi
    Admin

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    Re: VTA stepped attenuator in place of my PAS-3

    Post by tubes4hifi on Wed Apr 04, 2012 8:11 pm

    their is no phono amp inside the SP14, phono input would be coming from a separate phono preamp (such as PH14 or other)

    avi.inc

    Posts : 53
    Join date : 2009-08-03
    Age : 63
    Location : L.A.

    Re: VTA stepped attenuator in place of my PAS-3

    Post by avi.inc on Wed Apr 04, 2012 8:35 pm

    tubes4hifi wrote:their is no phono amp inside the SP14, phono input would be coming from a separate phono preamp (such as PH14 or other)


    Thank's

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: VTA stepped attenuator in place of my PAS-3

    Post by plexus on Thu Apr 05, 2012 11:11 am

    I've done this recently: My main sources are a Benchmark DAC1 and my Oracle Delphi turntable and sometimes my receiver for movies and tv. I was thinking about getting the VTA SP14 but then I realized I don't really need a pre-amp. I prefer to have as few things in my signal chain as possible. The DAC1 has a volume control and so does the receiver (which has a preamp out). So just the phono stage, which is the weak link in my system anyway. I had to gain up to 75dB to work with my low output MC. First thing I did was get a pair of Jensen step-up transformers so I could lower the gain on the opamp phono stage. that helped. next thing I did was order the VTA PH15 and $1000 in top quality passive parts. I also have a switch box I made a long time ago with no attenuator, so I ordered a top quality attenuator from germany. Soon once I get all the parts and build, I will have a (i hope) killer phono stage with lots of output and a killer line stage. no pre-amp.

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: VTA stepped attenuator in place of my PAS-3

    Post by mantha3 on Fri Apr 06, 2012 9:47 am

    Plexux,

    Post on the build of what you are doing if you can please. I'm 100% interested.

    I am with you on the preference to not have a preamp.

    I run with a # of sources. I also run a passive preamp. My Comcast digital cable TV receiver was a problem. The TV receiver just had a somewhat weak signal. I got a DECWARE ZSTAGE gain device I'm really happy with. This sits on the Cable TV receiver and I can use this to add a little gain (Attenuator in ZSTAGE) and it works to extend the TV receiver as acting like a high quality output stage as being a buffer/gain stage combo. Just throwing this out as it is somewhat similar to what you are doing.

    Post on what you do. I dig it.

    Thanks,



    stewdan

    Posts : 160
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: VTA stepped attenuator in place of my PAS-3

    Post by stewdan on Sun Apr 22, 2012 2:08 pm

    Hi Mantha3 --

    I also have a Comcast receiver (a Scientific Atlanta Explorer 8300HD box) with low audio output. Within the last year they gave us a new Menu System which disabled the box's front panel volume control, so no matter what Comcast does, I have very low audio signal coming out of the box.

    In my case, I am driving the RCA audio inputs of a 100 Watt/channel Home Theatre Receiver but the quality of the audio signal is terrible.

    How do you have your Zstage wired? Do you drive an amplifier directly or first go into something with a preamp?

    Please let me know,
    Stew

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: VTA stepped attenuator in place of my PAS-3

    Post by mantha3 on Mon Apr 23, 2012 3:27 pm

    I run the Motorolla Comcast box to the ZSTAGE and then I run the ZSTAGE to the Passive Pre.

    The ZStage is just a single tube buffer/gain stage. It has just one set of Input RCAs and one set of Output RCAs (no source select switch). If you get the 21 step attenuator that adjusts gain the 11th or so step out of 21 is zero/unity gain. If you put it at 14 or so then the 1.8 volt weaker signal coming into the ZSTAGE gets a gain boost up to 2.4 volts or so. It works as a buffer too having high input impedance and low output impedance so I can run on to of/by your Comcast box and push a long run of RCA cables well. This is really a beefed up output stage on the source. Ideally, the Comcast box would have this nice of an output stage built in. This can also run 12at7

    Decware is good stuff like Bob and Roys stuff.. Hand built in USA and quality. I run a nice RCA 12AU7 clear top in my ZSTAGE. The high def music channels, high def movies, palladium music channel etc. never sounded better

    Check out ECOFAN out of NewZealand.. Google "Ecofan Boostit".. Similar gain piece idea to run in front of a passive. This runs 6dj8 tubes

    Have fun
    Andy
    . Google "Ecofan Boostit".. Similar gain piece idea to run in front of a passive.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: VTA stepped attenuator in place of my PAS-3

    Post by tubes4hifi on Mon Apr 23, 2012 6:49 pm

    I really shouldn't say this . . . . but gee . . . . $600 for $100 worth of parts . . . . and I wonder where they came up with that name . . . .
    Zstage . . . . sounds kinda like Zmod . . . . but my Zmod SP6 board . . . . . for 1/10th the price . . . . .
    oh, I guess that is the assembled price though . . . . guess I'd better shut up now . . . . but watch for an SP10 model soon . . . . .

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