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LTusler

New VTA ST-70

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Guest wdecho

Invert one of the speaker wires. Positive from amp to negative of speaker  and negative of amp to positive of speaker and see if it makes a difference. Just one speaker. 

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On 4/26/2018 at 7:57 PM, jvs1670 said:

 

 

I have the Khorns spaced 16ft apart in perfect corners and the room is 22 feet deep.  I really expected to be blown away and now I don't even want to listen to it without the sub on.  

 

 

When I had my Khorns in the basement, I had much better response with the Horns on the long wall. My room was 19 by 13 feet with cement floors.

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If you have the Russian PIO caps on your driver board, expect at least 200 hours before they are totally broken in and sounding their best.

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The 16 ft wall is my only option due to the layout of the room.   I had Bob Latino build mine with upgraded caps does that mean I have the Russian PIO caps?    

 

And thanks for the input Wdecho, I didn't think to try that hopefully later or tomorrow I'll give that a shot.  If that doesn't make a difference should I expect that I have a problem with the crossover?  Should I inspect the woofer and what do I look for and test for?

 

Thanks

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Guest wdecho

If the bass is better after doing the swap you can just leave it that way but put a note somewhere on the amp about the issue. To do it correctly you must change the connections on one of the OPT's of the amp but it the amp is your primary source why bother. I would not change the connections on the X-over if it played fine with another amplifier. It could very well be the problem. You should have very good bass with that amplifier so it sounds to me like the problem unless there is something more serious wrong inside the amp. 

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So I had already removed the ST70 from my Khorns downstairs and hooked them up to my Cornwalls in the living room before I had a chance to switch speaker wires and try them to see if they were out of phase.  With the Cornwalls  the amp plays great, full rich sound with plenty of volume.     Now I'm really stumped why the Khorns sound so thin, they really have almost no bass.    Should I open it up and inspect the woofer, maybe it has an issue?  These are 41 years old.     Maybe the speakers themselves are wired out of phase and are cancelling each other?   

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Guest wdecho

It sounds as though something is definitely wrong with the K-horns. Hook up one at a time and check to see if all 3 drivers are making a sound by sticking your ear at the output of each driver. If both speakers check OK by themselves hook up an amplifier and try changing the leads on one speaker as already described. It is possible that something could be wrong on the crossover network or there is a bad connection on one of the woofers. 

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^^^ This. Sure sounds like a speaker issue to me.

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I re-capped with caps from Bob Crites, so I should be good there.  I'll try and get pics to show how they are positioned and some other shots of the room too.   Did some testing a couple days ago using my Denon with an Emotiva UPA-2 amp and using the graphic EQ and some tone adjustments I  brought some better sound out.  Oddly enough if I stood at the farthest point back on the right side about a foot towards center I found the best bass.  I was the only place in the room I felt I had what I was looking for.  

 

So could it just be my room?  The front wall is 16ft across, the room is 22 ft deep.  The right side up front has a 5 ft wall that then opens up wider about another 3 feet.  That right side wall is just sheet rock and framing with nothing on the back side.   Is it my weak wall?   The other side is sheetrock against cement foundation (basement).   Should I fortify that right wall or maybe consider heavy false walls as shown in the Dope from Hope.  Maybe I'm losing all my bass into the room somehow and false walls would project the low end more effectively out into the room.   I open to all options, its a music room only an no one to shut me down.    Maybe enclose the backs with some heavy 3/4 plywood?

 

 

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Guest wdecho
On 3/21/2018 at 12:35 PM, Tarheel TJ said:

 Just wanted to hear everyone's impressions of the sonic differences between the two modes.

Do not have the VT-70 but among my many tube amplifiers I have built the difference in sound between pentode and triode becomes personal preference. I personally prefer triode but probably more to do with choice of music. With my LaScala's I have always seen the VT-70 as overkill. I have only one push pull tube amplifier and it being rather unusual in that it is run in class A with only around 6 watts of power using EL84 tubes. Plenty loud enough for me. Nothing wrong with having a Bugatti Veyron EB 16.4 and driving only 55 on the freeway though. With Klipsch speakers one is using less than 5 watts on peaks but let's not open that discussion. Dynaco clones are excellent amplifiers and I admire the builds and the fact more on this forum are getting into diy. Have tossed around in my head building one in the future myself. 

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9 hours ago, jvs1670 said:

So could it just be my room?  The front wall is 16ft across, the room is 22 ft deep.  The right side up front has a 5 ft wall that then opens up wider about another 3 feet.  That right side wall is just sheet rock and framing with nothing on the back side.   Is it my weak wall?   The other side is sheetrock against cement foundation (basement).   Should I fortify that right wall or maybe consider heavy false walls as shown in the Dope from Hope.  Maybe I'm losing all my bass into the room somehow and false walls would project the low end more effectively out into the room.   I open to all options, its a music room only an no one to shut me down.    Maybe enclose the backs with some heavy 3/4 plywood?

 

Definitly sounds like room integration issues. 

 

I would suggest if you can that you try placing the speakers along the side wall (with the concrete basement) since it should have the best reinforcement for the bass. Start with them in the corners and see how that sounds and if necessary you can try moving them closer together and out of the corners to see how they interact with the room modes for better sounds at your listening location 

 

miketn

 

 

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Hook the ST-70 up to the bass cabinets direct by themselves and no crossovers in line if you haven't already.  Has anyone been inside the bass bins?  Something internal could potentially be out of phase.  It sounds like you can rule out the amp having an issue since it seemed to sound fine on the Cornwalls.  Always check polarity when hooking up to older cabinet...then check it again.  But if you hook the amp up to the bass bins by themselves, with correct polarity, and  the bass is still thin, reverse one side and see what happens.  In 41 years, someone could have been inside one of those bins and swapped something out.  Who knows.  

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On 3/21/2018 at 10:34 AM, Tarheel TJ said:

Just got mine finished up last night.  Fired right up on the first try!  Played it for a couple hours on the Heresys to confirm function.  It was interesting playing with the pentode/triode switch.  To my ears, it sounded much better in pentode mode.  Much better bass and more balanced sound.  Triode mode was way too "midrange forward" for my taste, at least while playing rock and roll.  It will be interesting to hear the difference once I incorporate it into my main system as it will only be driving 500hz and up on my bi-amped mains (2" B&C drivers over La Scala bass bins).

IMG_2585.JPG

 

 

This Triode/Pentode crap with Bob Latino and others just drives me crazy.... the amp does not operate in Pentode mode. It operates Ultra Linear which is more similar to Triode than Pentode. I have no clue why Bob calls it Triode/Pentode switch.

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On 3/21/2018 at 1:35 PM, Tarheel TJ said:

Glad to see I'm in good company.  Anyone else have thoughts on triode vs. pentode operation?  I will be using mine with a MiniDSP in the main system, so I should be able to EQ it flat regardless.  Just wanted to hear everyone's impressions of the sonic differences between the two modes.

 

How are you liking the combination of miniDSP and VTA70? I have both as well and am still getting used to what the miniDSP can do. I am only running 2 ch system so no crossover functions enabled, just PEQ. After a week or so of evaluating I have found some pretty good room corrections, but I can't help wondering if the introduction of all this digital processing is degrading the sound more than it is helping the frequency response. I suppose it is always a trade off.

 

It is nice that it is possible to send digital digital input to the miniDSP directly from my computer/iPhone as this eliminates one stage of D/A and A/D conversion. I wonder if the final D/A in the miniDSP is as good as the iPhone.

 

In any event, it is an extraordinarily powerful device and a lot of fun to play with. I have the 2x4 HD version and the UMIC-1 with REW.

 

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Btw, I had the amp on the bench for some sweep testing last night and I am amazed at the performance I am seeing. The frequency response is perfectly flat from 20-20K. In fact, it's pretty much flat from near DC to over 30Khz. The NFB seems to be implemented perfectly.  10KHz square wave presentation is textbook perfect. No ringing, nice and square. 40Hz square wave looks as good as the advertised specs for the new ST70 gen3. The slopes are only slightly tilted down. This thing can really sustain some low end energy! I don't have a distortion analyzer, but I am seeing a solid 38 watts RMS per channel with both channels driven at 1KHz into 8 Ohms before any clipping is visible. At this level I see no signs of crossover distortion or caving of the sinusoid shapes. I think it's a keeper!

 

Here is a pic. The purple wires are for a volume control pot I installed. May move to a stepped attenuator later. PIO caps just arrived from Ukraine so I'll be putting them in soon. This was so much fun to build :)

IMG_0901.jpg

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@jvs1670  Did you ever get this figured out?  I would believe that if the Cornwall's sounded good with the ST-70, then the Klipschorns should definitely have bass.  Did you hook the amp just to the bass bins only and check phasing?  Hook it up and if it sound thin in bass, swap one speakers' + and - and see what happens.  Klipschorns aren't known for having anemic bass unless a room is totally awful, woofers out of phase, or just mediocre equipment (maybe).  But I've heard Klipschorns hooked up to an iPod output for testing and they had bass with that little of voltage.  I'm just curious...

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12 hours ago, rjp said:

 

How are you liking the combination of miniDSP and VTA70? I have both as well and am still getting used to what the miniDSP can do. I am only running 2 ch system so no crossover functions enabled, just PEQ. After a week or so of evaluating I have found some pretty good room corrections, but I can't help wondering if the introduction of all this digital processing is degrading the sound more than it is helping the frequency response. I suppose it is always a trade off.

 

It is nice that it is possible to send digital digital input to the miniDSP directly from my computer/iPhone as this eliminates one stage of D/A and A/D conversion. I wonder if the final D/A in the miniDSP is as good as the iPhone.

 

In any event, it is an extraordinarily powerful device and a lot of fun to play with. I have the 2x4 HD version and the UMIC-1 with REW.

 

 

RJP, I am loving the MiniDSP and ST-70 combo.  Like you, I am still dialing in my settings.  However, compared to my stock LaScalas, it is a monumental improvement!  I am hearing the best hi fi I have ever experienced, including unobtainium setups at high end audio dealerships.

 I too worried about losing fidelity to the AD/DA conversions.  However, what I am hearing is so good I have forgotten all about that.  Maybe you could best this with a really high end all-analog setup, but I would hate to see the price tag.

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