I made an observation the other day as I was trying to figure out which amp I was going to chose for a permanent amp for my new CW3's I just purchased. I have a 6 month old VTA ST120 and a 2 year old Prima luna Prolouge 5 My preamp is a VTA Sp14 around 8 months old. Both amps are useing KT88's for power tubes with around 150 hrs and all Mullards for the pre side of the power amps, again maybe 150 hrs on them as well. My observation is that the PL is louder than the ST120! How is that possible since the 120 has more watts than the PL! I was always under the assumption that more watts would equal more loudness. But this is not the case in my setup. So is there more to it than just watts here? Now I have not put either amp on the bench to see what the output power is at a certain volume on the preamp with each amp. So for all the tech gurus out there can you please explain this to me. In my past running solid state It was always the more watts you put out the louder it was on the speaker. Like I said I have not measured any thing other than what my ears are hearing. I did put in some EL34's into the PL to see if the output would change, but I am not hearing a difference volume wise. This observation was done at low volume level at 8 or 9 oclock on the volume level on preamp. Anybody else observe this in there set up when trying to use the best amp in your collection?
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A observation I made
eminence1963- Posts : 21
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Age : 60
peterh- Posts : 1833
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Are you observing that the prima has louder volume at the same setting of volume on theeminence1963 wrote:I made an observation the other day as I was trying to figure out which amp I was going to chose for a permanent amp for my new CW3's I just purchased. I have a 6 month old VTA ST120 and a 2 year old Prima luna Prolouge 5 My preamp is a VTA Sp14 around 8 months old. Both amps are useing KT88's for power tubes with around 150 hrs and all Mullards for the pre side of the power amps, again maybe 150 hrs on them as well. My observation is that the PL is louder than the ST120! How is that possible since the 120 has more watts than the PL! I was always under the assumption that more watts would equal more loudness. But this is not the case in my setup. So is there more to it than just watts here? Now I have not put either amp on the bench to see what the output power is at a certain volume on the preamp with each amp. So for all the tech gurus out there can you please explain this to me. In my past running solid state It was always the more watts you put out the louder it was on the speaker. Like I said I have not measured any thing other than what my ears are hearing. I did put in some EL34's into the PL to see if the output would change, but I am not hearing a difference volume wise. This observation was done at low volume level at 8 or 9 oclock on the volume level on preamp. Anybody else observe this in there set up when trying to use the best amp in your collection?
pre ? That means that the prima has higher amplification then the vta, not telling
anything about max power .
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Bob Latino- Admin
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eminence1963 wrote:I made an observation the other day as I was trying to figure out which amp I was going to chose for a permanent amp for my new CW3's I just purchased. I have a 6 month old VTA ST120 and a 2 year old Prima luna Prolouge 5 My preamp is a VTA Sp14 around 8 months old. Both amps are useing KT88's for power tubes with around 150 hrs and all Mullards for the pre side of the power amps, again maybe 150 hrs on them as well. My observation is that the PL is louder than the ST120! How is that possible since the 120 has more watts than the PL! I was always under the assumption that more watts would equal more loudness. But this is not the case in my setup. So is there more to it than just watts here? Now I have not put either amp on the bench to see what the output power is at a certain volume on the preamp with each amp. So for all the tech gurus out there can you please explain this to me. In my past running solid state It was always the more watts you put out the louder it was on the speaker. Like I said I have not measured any thing other than what my ears are hearing. I did put in some EL34's into the PL to see if the output would change, but I am not hearing a difference volume wise. This observation was done at low volume level at 8 or 9 oclock on the volume level on preamp. Anybody else observe this in there set up when trying to use the best amp in your collection?
The explanation is that the VTA ST-120 has a lot less less gain than your Primaluna Prologue 5. The Primaluna amp you have only needs .775 volts in for full output while the VTA ST-120 needs about 1.4 volts. The VTA ST-120 needs a lot more input (almost double the amount) from your preamp to get the volume up there.
Bob
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eminence1963- Posts : 21
Join date : 2019-06-10
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The explanation is that the VTA ST-120 has a lot less less gain than your Primaluna Prologue 5. The Primaluna amp you have only needs .775 volts in for full output while the VTA ST-120 needs about 1.4 volts. The VTA ST-120 needs a lot more input (almost double the amount) from your preamp to get the volume up there.
Bob[/quote]
Lovely not what I wanted to hear. Thanks Bob for the explanation.
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Last edited by PeterCapo on Mon Nov 30, 2020 6:46 pm; edited 1 time in total
Roy Mottram- Admin
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especially not a problem with most preamps (such as the SP14) that puts out about 15v at max volume and even at 1/2 volume (1x gain) would be more than enough to drive either amp into overload distortion.
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eminence1963- Posts : 21
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PeterCapo wrote:eminence1963 wrote: Lovely not what I wanted to hear. Thanks Bob for the explanation.
Different input sensitivities are common in audio. In and of itself, it shouldn't be a problem. It usually means just turning the volume control higher on the preamp. Not sure why this would be seen as disappointing? Add to this that your Klipsch speakers are very efficient, and your amplifier has more power than you'd ever need, meaning that you've got lots of headroom for turning the volume control higher. I am assuming "CW3" stands for Cornwall III.
The reason I say that, is when I have my H3's running with the CW's (yes CW's stand for Cornwall's
) the H3's are way overbearing with the Prima amp. The Prima has no adjust ability for volume control. 
So the only option at this point it to use a attenuator in line to the prima amp. Which I have done already, but 6db is not enough. Have a 12 db attenuator coming in the mail, to see if that will tame it down further. I don't always listen this way, but when the time a-rises, it would be nice to not have the H3's screaming at me. I could add another preamp to the mix and have the amps on there own pre, but I cant afford nor do I want another preamp in line to the system. To be honest the Primaluna amp sounds really awful to me versus the VTA ST120 on the Cornwall's. IMHO if you want Solid state sound but like tubes get the Prima Luna Gear.
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If you need even less gain on the VTA ST-120, the stepped attenuator works well. Doesn't seem to add any noise or color the sound.
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Bob Latino- Admin
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An amp with slightly lower gain usually will have a better signal to noise ratio than an amp with higher gain. The VTA ST-70 and VTA ST-120 have a signal to noise ratio of slightly greater than 90 dB. The VTA M-125 monoblocks were tested in 2010 by a friend of mine with the proper test gear. He measured a -95 dB signal to noise ratio. Earlier this year a customer measured the signal to noise ratio of the M-125's and came up with a -99 dB signal to noise ratio. See link below ..
Measured VTA M-125 signal to noise ratio
Bob
Measured VTA M-125 signal to noise ratio
Bob
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