Will Changing my 100 Watt Tube Amp to a 200 Watt SS Amp Solve My Problem?


Hello All,  I have a 100 watt Audio Research VT100 mk II amp, with an Audio Research LS-25 preamp.  My speakers are relatively low in sensitivity, and I find that I must turn the volume up to 3 o'clock on the preamp to get enough volume for a loud listening experience.  When I do that, I am introducing more background noise.

I would like to achieve a quieter noise floor.  I am also curious about the limits of the 100 wpc amp with the Mira Monitors.  Would an older Krell 200 watt class A amp "control" the speakers better?  If so, what are the benefits of this?  There are a few amps on this site that caught my eye, all about the same value as my amp, so I can potentially make a move with very little cost.  Is this a good idea? How much wattage increase is necessary to get a significant enough difference?  Would a jump to 150 watt solid state be sufficient?


here are the 3 amps that caught my eye:

Ayre: https://www.audiogon.com/listings/solid-state-ayre-acoustics-v-5xe-amplifier-2016-02-05-amplifiers-h...

Krell: https://www.audiogon.com/listings/solid-state-krell-ksa-250-2016-02-14-amplifiers-91754-monterey-par...

BAT:
https://www.audiogon.com/listings/solid-state-balanced-audio-technology-bat-vk-250se-bat-pak-2channe...



You can see my complete system here if you want to know more about the other components:  https://systems.audiogon.com/systems/5421



Thanks!
Mark
marktomaras
Marktomaras; out of curiosity, what is your amp plugged into for power?

You posted earlier that you were having gain issues with your cartridge/phono preamp/preamp.  How was that resolved?
Lak, the amp is plugged into a Shunyata Hydra Talos.

Onhwy61, I played with the gain on the phono stage, and ultimately dropped it a touch.  This amp idea is an extension of the same issue.  I was thinking that if the power amp had more muscle, perhaps the gain on the phono stage and preamp will be just fine.  Perhaps I am asking too much from the 2 preamps, and not enough of the power amp.  What do you think?
Lak, more completely,  the amp is plugged into a Shunyata Hydra Talos, which is plugged into a dedicated outlet which has a dedicated circuit in the breaker, done when I remodeled the house and upgraded the electric service.

They should give you better control of your speakers especially the Class A Krell, which is perhaps more of a high current design than the others.

All the amps you listed have different sonic signatures so best to try them out.
Mikey8811, what does it mean exactly to have better control of the speakers? I have heard the term, but I do not fully understand the implications. 

The answer is no related to your specific complaint.  The input sensitivity of your current amp is 1.9V required to drive at full power.  The Krell KSA 250 requires even more voltage at 2.3V for full output. 

One of my amps is a VAC Pa100 which only needs .775V for full output.  So, to address your complaint of needing to crank the volume control way up which may reveal the inherent noise of the preamp, you should look for an amp which requires less voltage to achieve full power.  Tube vs solid state has nothing to do with your complaint. 

However, tubes will always be happiest driving a speaker with higher impedance.  I am unaware of how your speakers perform regarding impedance.  

Hi Mark,

If the noise only occurs when the volume control is turned up to a relatively high setting, it means that the noise is being introduced into the signal path "ahead of" ("upstream of") the volume control. A more powerful amp will often (although certainly not always) provide higher gain (the relation between its output voltage and its input voltage), which would cause you to utilize the volume control at lower settings. However the resulting noise level would be no different, since the amp is "downstream" of the volume control.

Unless, that is, the noise is being coupled into the upstream part of the signal path BY the power amp. But as I recall you’ve probably addressed that possibility already, by physically relocating the components in your setup.

Regards,
-- Al

I don't think your issue is power but sensitivity. Sensitivity in a power amp means how much power out do you get for a number of volts in from the preamp. You need either a preamp with more voltage output or a power amp with higher input sensitivity. Doubling the power will not solve your gain problem
Alan
if you don't have enough phono gain no larger amp will help.
either higher output cartridge or higher gain phonostage will cure your problem.
This is not a power amplifier issue!

This is a noise problem in the preamp. Ahendler got it right.
Ahendler got it right.
Not sure about that, Ralph.  His statement that:
You need either a preamp with more voltage output or a power amp with higher input sensitivity.
... does not appear to be consistent with what I said in my post above, and I therefore disagree.

Best regards,
-- Al

Al, when you turn up the volume and that results in noise, that is a preamplifier problem. Its true that the amp might have a certain low sensitivity requiring a higher volume setting, but even if the amp was more sensitive, you would still get the same noise even though you didn't turn up the volume as far on the preamp.


Hi Ralph,

Those were exactly my points! Although if I am recalling Mark’s previous thread(s) about the noise issue correctly, the noise performance of the phono stage is also suspect, as well as the performance of the preamplifier.

Best regards,
-- Al

After tinkering with the placement of the phonostage and the gain settings, I am suspecting the preamp is the culprit.

Am I wrong in feeling funny about 3 o'clock on the volume to get a rockin' experience? Seems like the high dial position is pushing the ability of the preamp too far.  One would think that my pre and power amp should be a good match though. They are both from the same era, same company, and same price point.

as it is, the sound is excellent, I am just complaint about the noise floor, which could be reduced.

Am I wrong in feeling funny about 3 o’clock on the volume to get a rockin’ experience? Seems like the high dial position is pushing the ability of the preamp too far.
No, I doubt that is the case, Mark. In fact many believe that having gains and sensitivities in a system such that the volume control is used at high settings within its range is to be preferred, assuming of course that there is never a desire to turn it up beyond the top of its range. The philosophy being that with at least some designs doing so will minimize whatever sonic effects may be introduced by the volume control mechanism itself.

Regards,
-- Al

After tinkering with the placement of the phonostage and the gain settings, I am suspecting the preamp is the culprit.

Am I wrong in feeling funny about 3 o'clock on the volume to get a rockin' experience? Seems like the high dial position is pushing the ability of the preamp too far.  One would think that my pre and power amp should be a good match though. They are both from the same era, same company, and same price point.

as it is, the sound is excellent, I am just complaint about the noise floor, which could be reduced.
What Al said, plus it might be that you have some noisy tubes.
Ok, 6 ohms isn't so bad.  However, 85db is pretty paltry.  Your AR should be able to drive almost anything sufficiently.  Although, if you do the match your max output will be about 104db-105db at 100 watts which is not close to THX or rock concert levels.  400 wpc will get you to the 110db range.  You need to borrow a pair of BIG monoblocks...

Question:  Have you had your tubes checked?  One leak/short/old tube could be adding to this if you are getting noise or harmonics when pushing it.

MARK, I agree with elevick... 85db speakers are not going to work well with tube power amps! I dont care what brand. Get a SS amp with proper input to match your pre amp and I assure you, the issue will be gone.


Matt M

Get a SS amp with proper input to match your pre amp and I assure you, the issue will be gone.
Matt, sonics **might** be better, but the noise issue (which the OP has stated is the main concern) will not be gone. See the posts above by me and by Ralph/Atmasphere.

Also, before going to a more powerful amplifier it would be prudent to research how much power the particular speakers can handle without their sonics degrading, or worse. The only relevant spec I can readily find for the Rockport Mira Monitors is a minimum amplifier power recommendation of 50 watts.

Regards,
-- Al

Mark, your ARC LS25 is a  selectable gain line stage. It looks like you can set the gain anywhere between 0 dB and 18 dB. What do you currently have the LS25 gain set at?

Cheers,
John
John, I have it set to 18db. I was told that setting is the native setting, and the lower gain settings were attenuated.

matt, I have toyed with this idea. If I were to sell my amp and preamp, and look for a similar quality / age / price solid state pair, I wonder if I would get a better performer? But then again, the ARC tube gear does sound excellent...

Mark
John, Is the adjustibility of gain is the LS25 applied after the source but before the volume control and line stage amplification (tubes).  It did on my ARC Pre (a different model). The blurb I read on this pre-amp talked about the ability to reduce source gain in the context of matching gain of multiple sources. I didn't see anything about reducing pre-amp output gain. Typically you can only change pre-amp output gain either by internal implementation of a resistor or by adding an aftermarket fixed attenuator.

 If so, then any tube noise (or any other noise for that matter) would be passed on to the amp full strength. Since Mark's noise increases as he rotates his volume attenuator, the cause of the noise  increase must originate in the pre-amps circuitry before the amplification stage or in the source, which IMHO would more likely be the phono stage which are notoriously noisy. With a phono stage the noise could originate with the design itself, of if it uses tubes, then the tubes might not be low noise enough. It could also be the phono cartridge itself. 

Mark, I haven't read the preceding posts.  I'm sure Al or someone else have already mentioned this to you. But, I would point out that the difference between 100wts and 200 wts is only 3db, i.e. not very noticible. Now if your speakers require an amp with high(er) current (i.e. they have a impedence curve dropping to 4ohms or less) this could be an exception. But even if your amp could produce 800wts at  2 ohms you still would not be solving any noise issues caused by your pre-amp's amplifications stage.

FWIW. Forgive any redundancy created by existence of preceding posts.
Mark, your ARC LS25 is a  selectable gain line stage. It looks like you can set the gain anywhere between 0 dB and 18 dB. What do you currently have the LS25 gain set at?
The line stage gain will not make any difference. The volume control won't affect the noise of the line section. The only thing it can affect is how much noise is present from sources, like the phono section. Its my opinion that this is where the problem lies. It might simply be noisy tubes and it could also be that the phono cartridge has output slightly too low for the phono section to work with gracefully.


Do you think my Whest PS .30R is the culprit here?  I can definitely say that my PS Audio DAC does sound quieter than the analog, both driven through the ARC preamp.  I was under the impression that the Whest is quite a capable phono stage, with ample gain and balanced circuitry.  It is definitely a confusing process to determine how components play well together!
Maybe I should sell all of my components and get a used Devialet!
Does it have a quiet phono stage? Or you could buy a gun. Personally, I I had to go solid state I think I'd choose the latter! :-)
Ha!  Newbie, I love the tube devotion.  I am wondering if I am a fool for considering it.
Hi Mark,

I have no experience with the Whest phono stage, but based on all that I’ve read about it I too would expect it to be very quiet with a Lyra Delos, which is rated at 0.6 mv output under the standard test conditions. And since the phono stage is solid state, noisy tubes are not an issue with it.

Also, the circuitry in the front end of your ARC LS25 preamp, up to and including both the gain select circuitry and the volume control circuitry, is all solid state (as can be seen in the schematic at arcdb.ws). So noisy tubes are not an issue there as well.

And you’ve already done significant re-shuffling of how your components and cables are physically positioned, to minimize any noise coupling that may be occurring as a result of how everything is positioned.

So regarding the noise issue I’m pretty much out of ideas at this point. Other than to suggest that if you already haven’t you try unplugging all of the digital stuff from AC power, to verify that digital noise is not radiating or otherwise coupling into the analog front end.

Regards,
-- Al

Al,

Indeed I evaluated the system with digital components off completely.  Just curious as this may not be the way I will go, but how would you expect a high end integrated unit to work in this regard?  Something like a $13k Jadis tube integrated with phono stage or a similarly priced Deviate with phono stage?  Would the lack of cabling and assumed synergy between the internal components in such a unit provide a quieter, higher performing system? 
I don't know the answer to that question, Mark.  In part because I have no experience with integrateds in recent times, and never in that kind of price range.  And in part because we haven't been able to arrive at an understanding of what is presently causing the noise issue.

Best regards,
-- Al
 
Mark, Maybe a dumb question, but exactly where are you when you can first hear the noise? When you are in your listening chair? 6' from your speakers? 6" from your speakers? I know some folks, of the anal sort, like me perhaps, who put their ear right up to the tweeter and judge by this. Does this noise really intrude on the allusion of a black background when music is playing? Is the background noise a hiss or a hum?
Sorry, another question.Have you disconnected all of your sources from your pre-amp, in fact unplugging them is best, and then rotate your volume control to its 3 o'clockposition and see if you still have the noise? Rotate to max, any noise then? If the answer happens to be 'no noise' then add your sources back, one at a time until you find the one which starts the noise as previously described.

 If the answer is there was no change from your fully connected system then you have either found the noise floor of you pre-amp or that you have something in the circuitry in the pre-amp prior to the amplification stage which is causing it. You might then contact ARC and ask their service department techie.
Are you running a low output MM or MC? It sounds like you need a head amp or a SUT to improve the gain. I think your ARC tube amp is fine.
I still really think you need to either borrow gear from a dealer or friend.  You have 2 issues:  Noise and lack of volume.  A pair of 400 watt monoblocks will cure that.  Curing the noise issue might be trickier unless excess power solves all.  And yes, the Devialet might do it. However, it's going to be cheaper to buy new speakers...
^^ bigger amps won't cure this problem as it is not caused by amplifier power or the lack thereof.

I have seen problems with cartridges where the magnet structure was damaged and has caused low output in both channels. The Whest, while not my favorite phono section, is not known for noise, so right now I am suspicious that the cartridge might have taken a hit somehow and is not making the proper output voltage- hence the noise.

I would try a different cartridge to test this theory.
"minimum amplifier power recommendation of 50 watts."

AL, What speaker manufacturer does not say this..?? ROFL.
(please dont answer that)


All I was saying is that Mark should try a SS amp (of course one that will drive the speakers) .

Matt

I personally love anything Ayre makes...all my electrical components are Ayre ....extremely pleased.  However....It seems to me that your problem is not with your amp.
I just mounted a new Dynavector 20X2 on my Xtension 10 and I have noise too! :-( I really dont think its the cartridge...or my Chinook phono pre...or my Manley Jumbo shrimp linestage, nor is it my amplifier. I think noise is getting in from the house electrical system. All I know is that it sux major *(&^. otherwise my system would be awesome sounding. Now im looking at power conditioners (yuk).

Matt M
AL, What speaker manufacturer does not say this..?? ROFL.
(please dont answer that)

All I was saying is that Mark should try a SS amp (of course one that will drive the speakers) .
And all I was saying is that:
... before going to a more powerful amplifier it would be prudent to research how much power the particular speakers can handle without their sonics degrading, or worse. The only relevant spec I can readily find for the Rockport Mira Monitors is a minimum amplifier power recommendation of 50 watts.
My comment being inspired in part by someone else's mention of 400 watt monoblocks, in the post just above the post you made yesterday.

Glad my comment provided you with some amusement.

Regards,
-- Al
I'm coming late to this discussion, so I'll try to be succinct. One of your problems has already been identified: the preamp, for whatever reason, has a poor signal-to-noise ratio. This could be due to mediocre original design, but it could also be due to deterioration of some of the internal electronic components. It would make sense to get a good technician to diagnose the preamp and make any indicated repairs.

The other relevant point is that increasing the amplifier power from 100 watts to 200 watts will not have much effect. Doubling the output power of the power amp will only increase the maximum audio signal level by 3db, which is discernable only as a slight volume increase. Your AR VR100 amp is a fine unit, but it needs to be paired with more sensitive speakers if you want to listen at high decibel levels. As a rough rule of thumb, I like to pair low to moderate power tube amps with speakers rated for 90-92db sensitivity or higher.

Just my 2 cents, FWIW.
Thank you all.  There are a lot of good info and ideas here.  I am interested in what sdcampbell said about the poor signal to noise ratio.  Perhaps that is worth investigating.  Newbee, I have tried what you suggested, but I think I need to refresh my memory by doing it again.  Saturday Morning is listening time for me, so I'll tackle that in the morning.  By the way, I just listened to some Ella Fitzgerald on vinyl at low volume and it is excellent.  No hiss, no problem.  But that was at a volume level one could have a conversation over...
If you do decide on the Krell amp, I have a much nicer specimen and it has also been upgraded to a 250S.
I have had the following problems in the past. 1st: I had a classe preamp driving a mcintosh amp and I had to turn the volume up almost all the way to get the volume I wanted. It was a mis match between the preamp and amp voltages and classe told me they could modify the preamp to make it compatible with the mcintosh, so I ended up with a classe amp and I was driving the same setup at around 10-11 o'clock on the preamp.
2nd issue: I had a rogue magnum integrated tube amp with the it-120 tubes and it didn't control the speakers very well. I changed the wiring inside for 4 ohm tap and it was much better. 
I have had the following problems in the past. 1st: I had a classe preamp driving a mcintosh amp and I had to turn the volume up almost all the way to get the volume I wanted. It was a mis match between the preamp and amp voltages and classe told me they could modify the preamp to make it compatible with the mcintosh, so I ended up with a classe amp and I was driving the same setup at around 10-11 o'clock on the preamp.
2nd issue: I had a rogue magnum integrated tube amp with the it-120 tubes and it didn't control the speakers very well. I changed the wiring inside for 4 ohm tap and it was much better. 
1 more thing. Even running with the 4 ohm, the 100+ watts wasn't controlling the low end enough for me, and in some cases I had to get the volume setting to around 2 o'clock for the output I wanted. I ended up buying a 250 watt Hegel integrated and night and day difference IMO. Never go above 50 out of 99 for volume and the speakers don't sound as wholly. i liked the rogue very much but I would have had to get a larger tube amp but even then I'm not sure it would have helped to control the bass. the best of both worlds could be using a tube pre with a ss amp.

Update,

I tried listening to the noise of the preamp on its own.  I powered on the phono pre, the preamp, and the power amp.  I then put the volume at maximum, with no source playing.  I began with the phono selector on the preamp.  At full volume, the hiss+subtle hum is fully audible at the listening position.  Then I tried the other inputs on the preamp, beginning with the input for the DAC, powered on, no music playing.  Followed by all of the other inputs.  Even at full volume, only the input connected to the phono stage produces the noise.  The other inputs, including the connected DAC input are extremely quiet, even at full volume with my head near the speaker.  I can hear noise, but it is subtle, and my head is near the speaker at full volume!

I tried moving the phono stage to another input, to see if there was a problem in the input circuitry.  This is not the case.  The same noise simply moved over to an aux input, and the phono input went quiet.

Interestingly, but probably inconsequential, is that the unused CD input has a little hum to it at full volume, whereas the other inputs do not.  This is just a little side note.  

So, does this experiment show that the preamp is quiet and the phono stage is noisy?  Or, is it still the preamp somehow, and the higher gain of the phono stage is bringing out the inherent noise in the preamp somehow?

Lastly, I found some tubes that I bought years ago, and never used.  They are NOS 6H23P-EB (Premium) tubes.  http://www.thetubestore.com/Tubes/6922-E88CC-Tube-Types/6H23n-EB-6922

I was thinking to try them out to see if there is lower noise, but after this experiment, I don't think it will do much, it seems that the culprit is the phono stage.  

What do you think?
Update 2.

After the above experiment, I followed the idea that the preamp is actually quiet and that the phono stage is causing the noise.  I lowered the gain on the phono stage from 55 to 50db.  The theory is that I can turn the volume high without much issue on the preamp.  I did this, and indeed, with the lower gain on the Whest, I had to raise the volume quite high to get a lout experience, but I was not maxed out.  Before I played the music, I listened to the noise at full volume, with the newly lowered gain on the phono stage.  The noise was lower, as expected, but not by a huge amount.

I played Miles Davis Kind Of Blue.  I listened to the noise at full volume with nothing playing to familiarize my mind and ears, then I lowered the volume and played the record.  As the needle began to play, I immediately heard a fairly considerable amount of noise.  But this I felt was in the recording, not due to my amplifiers.

The sound was excellent by the way, but that noise is still there a bit.

Then I fired up the PS Audio Perfectwave DAC mkII and played the same track.  I use the balanced connections on the DAC and I also turn the volume to full as I was instructed by some of the aficionados of this product.  The result is that the output is much higher than that of the phono stage, so my volume control on the ARC preamp is far lower, dropping the noise floor even lower.

To finish the comparison of Miles Davis, the noise in the recording that I heard on the vinyl was also there on the digital.

I am looking forward to hearing your thoughts on these new tests.  Please let me know if I am drawing the proper conclusions.  Perhaps I need a quieter phono stage.  Maybe I do not need a ton of gain.  50db is working, though I am still at the top of the volume control.  If I could have a dead quiet, phono pre with 55 db of gain, that may be the perfect accompaniment to this system, that is, if I am interpreting the experiment properly.
Hi Mark, It appears that you have sourced your problem correctly to your phono stage and/or cartridge. To determine whether its is the phono stage or the cartridge or both in combination, disconnect the IC from your TT to the phono stage and just listen to the phono stage at various gain levels and with your pre-amp VC . If there is no noise (as I suspect there will not be) then you have either a mismatch with the cartridge due to the inherent noise floor of the cartridge, something mechanically deficient in the cartridge or its set up. I'm not familiar with your phono stage or cartridge so I can't help you on this issue.

I'll save your eyes a bit by not amplifying on these comments but I would be happy to explain my conclusions if you ask.
1) There is nothing wrong with your pre-amp.
 2) There is nothing wrong mechanically speaking with its tubes.
 3) There is nothing wrong with having to listen with your volume control at 3 o'clock or even wide open if that is the position that meets your needs. Remember, all a volume control does in your pre-amp is lower the strength of the signal from the source before it reaches your volume control.. That's all. It does not lower the strength of the output from the pre-amp's tube section which is seen at a constant level by your amp.To some degree its function is redundant to the other options your have to reduce source output strength.

BTW, re the hum on the unconnected CD input selection. Small hums can be very difficult to trace. But before you conclude that this is a problem try connecting your dac to this input and see if the hum goes away.

Hope this helps a bit. Perhaps others can comment on your phono stage/cartridge/set up issues. 
Newbee,

I think it's time to change your handle to old pro!
Ok, so I tried a quick test, I listened as I did before, to the phono stage with the volume all the way up, and then I muted the preamp, removed the IC from the table to the phono stage, and unmated the amp.  The noise was the same.  Changing the gain means pulling the phono stage from the rack, unscrewing a panel, flipping some dip switches, and reassembling, so I cannot do it on the fly.  If the noise is the same at 50db gain setting, with or without the turntable connected, is that conclusive enough?  What is my next step?