Which Tubes do you run in VRD's & why ?

[tube fanatic]

I'm not questioning your methodology (I believe you once stated that you prefer long term evaluations of tubes).  How do you account for the normal day to day variations in our perception?  Having allergies, my ears are somewhat variable in their response.  Also, one's variations in emotional state from day to day have a profound influence on our perception of many things and accounts for why a system may sound blissful on Saturday and like crap on Sunday.  There's also the issue of our tending to equilibrate to a particular sound over time.  I find that the brain has a remarkable ability to modify its perception of things if exposed to them for long enough.

 

The SS guys must be having some good laughs over this discussion-  too bad they can't roll transistors as we roll tubes!!!

 

 

Maynard

[joessportster]

25 minutes ago, tube fanatic said:

I'm not questioning your methodology (I believe you once stated that you prefer long term evaluations of tubes).  How do you account for the normal day to day variations in our perception?  Having allergies, my ears are somewhat variable in their response.  Also, one's variations in emotional state from day to day have a profound influence on our perception of many things and accounts for why a system may sound blissful on Saturday and like crap on Sunday.  There's also the issue of our tending to equilibrate to a particular sound over time.  I find that the brain has a remarkable ability to modify its perception of things if exposed to them for long enough.

 

The SS guys must be having some good laughs over this discussion-  too bad they can't roll transistors as we roll tubes!!!

 

 

Maynard

Hey Maynard thanks for chiming in.  I will admit that in the past when it came to tube rolling I was at a loss, for the life of me there were many MANY times I tried and never could tell a difference between tube A and tube B.  MY Brain, Character, Wallet refuses to spend hundreds of dollars on this or that pair of tubes I cannot get past the fact that tubes have a lifespan and will at some point fail and knowing that little signal tube just cost me 100+ dollars is something hard to swallow.  

 

Listening with headphones did show me that tubes do sound different though I found most of those differences subtle, On the other hand some combination of subtle differences can add up to a different sound quality, something more appealing IE.... softening the trebel (which I find desirable listening to digital sources)  

 

I do take the advice I get seriously and I try and find a happy medium.  How do you choose a tube Maynard ?

[tube fanatic]

Joe, if tone shaping is the goal of tube rolling there are ways to achieve what you want without rolling any tubes at all.  Of course, this would require getting under the chassis which is not possible for everyone.  

 

Tube life is very design dependent.  The more conservatively a tube is run, the longer it will last.  This is universally accepted.  Small signal tubes, in general, can last almost "forever."  And even output tubes can provide a life span in excess of 25k hours.

 

I'm not a good person to ask about choosing tubes for a particular design as my criteria are about as far from mainstream as one can get.  In the 60s, while servicing countless radios and televisions I concluded that the best sounding audio tubes were those designed specifically for those applications.  This is just my personal bias (intended pun!).  They are not tubes which are suited to high power applications and, even if run push-pull (which I don't like), are going to be in the low power range.  And, since the audio output stages of most tube type radios and televisions were single ended, I also decided (during thousands of hours of listening) that such a mode of operation sounded the best.  Let's go to the present- the audio guys I know have budget considerations but, at the same time, want extremely good sound (the proverbial exotic champagne on a beer budget situation), extremely long tube life, very low cost of acquisition for the equipment, and the use of very inexpensive tubes in the unlikely event one needs replacement (fortunately, the radio/tv tubes mentioned above generally cost $5 or less.  When tubes start costing more than $8-10, my palms sweat!!!).  In my experience, the synergy between Klipsch speakers and such equipment is phenomenal.  As long as the person doesn't listen at ear shattering levels in large rooms, very little power is needed.  And, as I mentioned in the desktop listening thread, the guys have gone to small room systems for which higher power is simply not needed.  It's easy to put together such a system for a few hundred dollars which, in the context of what so many spend just on cables, is a good deal.  

 

I don't roll multiple tubes when building a piece of equipment.  I simply pull what I need from the shelf.  If the equipment sounds wonderful, and measures as it should on the bench (I listen before measuring), I'm done.  Neither I, nor the guys, bother (perhaps this is a function of our being old farts) rolling tubes to try to extract a possible minuscule improvement.

 

So, I hope that answers your question to some degree!

 

 

Maynard

[dbomberger]

7 hours ago, joessportster said:

softening the trebel (which I find desirable listening to digital sources)

Interesting discussion, and to the point above, it's always interesting to me that many seem to have such disdain for Treble and Bass controls, yet a fair amount of effort seems to go into making those changes-I always like options.  It's pretty clear to me by now that everyone likes a little something different as far as listening happiness is concerned. 

[jimjimbo]

9 hours ago, Schu said:

That's just an inappropriate way of looking at data.

One CAN NOT analyze several data points and attempt to extrapolate an overall consensus... that leads to errors and distortions of the mean of information.

As usual, this makes no sense at all.

 

And secondly, how many times does it need to be said that whatever you are talking about, whether it be tubes, or SS gear, or speakers, or cables, or capacitors, etc, etc, etc.....it all depends on what YOU think sounds good.  Regardless of how much it costs, regardless of the marketing bullshit, regardless of the really swell walnut fascia on the amplifiers.  Everyone is always free to offer their opinions, and I am happy to proffer mine from time to time, but I will NEVER tell anyone that this or that is the best, or that YOU WILL think it's the best (thing) since sliced bread, or that the way that you evaluate something is "inappropriate".  Give me a break.

[joessportster]

7 hours ago, tube fanatic said:

Joe, if tone shaping is the goal of tube rolling there are ways to achieve what you want without rolling any tubes at all.  Of course, this would require getting under the chassis which is not possible for everyone.  

 

Tube life is very design dependent.  The more conservatively a tube is run, the longer it will last.  This is universally accepted.  Small signal tubes, in general, can last almost "forever."  And even output tubes can provide a life span in excess of 25k hours.

 

I'm not a good person to ask about choosing tubes for a particular design as my criteria are about as far from mainstream as one can get.  In the 60s, while servicing countless radios and televisions I concluded that the best sounding audio tubes were those designed specifically for those applications.  This is just my personal bias (intended pun!).  They are not tubes which are suited to high power applications and, even if run push-pull (which I don't like), are going to be in the low power range.  And, since the audio output stages of most tube type radios and televisions were single ended, I also decided (during thousands of hours of listening) that such a mode of operation sounded the best.  Let's go to the present- the audio guys I know have budget considerations but, at the same time, want extremely good sound (the proverbial exotic champagne on a beer budget situation), extremely long tube life, very low cost of acquisition for the equipment, and the use of very inexpensive tubes in the unlikely event one needs replacement (fortunately, the radio/tv tubes mentioned above generally cost $5 or less.  When tubes start costing more than $8-10, my palms sweat!!!).  In my experience, the synergy between Klipsch speakers and such equipment is phenomenal.  As long as the person doesn't listen at ear shattering levels in large rooms, very little power is needed.  And, as I mentioned in the desktop listening thread, the guys have gone to small room systems for which higher power is simply not needed.  It's easy to put together such a system for a few hundred dollars which, in the context of what so many spend just on cables, is a good deal.  

 

I don't roll multiple tubes when building a piece of equipment.  I simply pull what I need from the shelf.  If the equipment sounds wonderful, and measures as it should on the bench (I listen before measuring), I'm done.  Neither I, nor the guys, bother (perhaps this is a function of our being old farts) rolling tubes to try to extract a possible minuscule improvement.

 

So, I hope that answers your question to some degree!

 

 

Maynard

Thanks Maynard, I get your point and I like the philosophy I wish everything were so simple. I need to find some old fart near me that Knows how to build this stuff. I have for some time wanted to get into the build end of the hobby.  I can when it comes to speakers but when it comes to the electronics my hands simply will not allow me to do the soldering work.  My left hand gets progressively worse at shaking until it becomes almost violent  the more I concentrate my efforts the worse the result.

 

I must resign myself to using others products. If I could bring myself to live with music at a low / modest level 100% of the time I would have been happy to stick with SET amplification while most of my listening is of a mellow tone I go through spurts where I must turn on something much harder and more devious  to satisfy some emotion I am going through. when that time comes SET simply will not flip the switch. 

 

It is a compromise to some degree I look at my whole picture and attempt to put a piece into play that can fulfill both sides of my listening habits. If I were rich or had a way of dealing with audio as you are able to I could have multiple amps to satisfy the itch. Sadly I am neither.

 

I am HAPPY with the VRD's at low level they offer plenty of detail, imaging,  and sound stage and stay very musical,  when the urge hits they can become quite raucous in my space.

 

7 hours ago, dbomberger said:

Interesting discussion, and to the point above, it's always interesting to me that many seem to have such disdain for Treble and Bass controls, yet a fair amount of effort seems to go into making those changes-I always like options.  It's pretty clear to me by now that everyone likes a little something different as far as listening happiness is concerned. 

Softening the digital edge is a must for me, un-tethered Digital will lead to fatigue and a headache and ultimately I grow weary and simply wont listen. I like many others dont care for tone controls I lie to myself and make believe I am getting a purer sound quality, all the while I am choosing gear that will alter the sound without the controls. The name of this insanity should be changed from Hi-Fi to My-Fi.........................as stated everyone has a preference to what they want to hear,  and how they desire to go about getting that sound

[tube fanatic]

On 9/2/2018 at 1:44 AM, joessportster said:

Softening the digital edge is a must for me, un-tethered Digital will lead to fatigue and a headache and ultimately I grow weary and simply wont listen. I like many others dont care for tone controls I lie to myself and make believe I am getting a purer sound quality, all the while I am choosing gear that will alter the sound without the controls. The name of this insanity should be changed from Hi-Fi to My-Fi.........................as stated everyone has a preference to what they want to hear,  and how they desire to go about getting that sound

 

You raise an interesting point about high frequencies causing some issues.  For unknown reasons I, and the guys I know, have found that our tolerance of high frequency audio has actually decreased along with our ears' age related decrease in high frequency response.  Somehow, listening to equipment which is flat out to 20 kHz does not sound as enjoyable as that in which the response is down a few db at that frequency.  The "ear bleed" filter (basically a high frequency tone control) which  has been standard on my builds for quite some time sees a great deal of use by the guys.  Some are rolling off the hf response of the amps starting at around 12 kHz and loving the results.  It's interesting also because back in the day we usually designed for a flat response from around 40 Hz to 12 kHz and didn't care if it rolled off steeply above and below those frequencies.  

 

As for the usual tone controls, I don't know anyone who has a vintage tube amp or preamp which employs them who doesn't use them all the time.  It's just a matter of personal taste, as with everything else.

 

Maynard

 

 

[Audio Flynn]

The  Penta Labs KT88SC works fine for me.

Never felt the need to change the small tubes. Craig did some upgrades to my CJ preamp that were all positive.  

[derrickdj1]

I use a combination of rolling different sets every month.  Does this mean I don't have favorites.  Surprise, lol.

[Audio Flynn]

If I ever get a H H Scott 130 or LC 21 preamp I will use the tone controls. 🙂

 

[muel]

Regarding lifespan of tubes...

I bought my first VRD amp (stereo version) in 2011 along with the tubes that had been used by the original owner.  A year or so later I also got mono-blocks.  I have NEVER yet had a tube fail in these.   My power tubes in the monoblocks easily have 4,000 hours on them... I've swapped them with others a few times otherwise I'd say more like 6-7,000.   I've lost a total of 2 tubes ever since 2009!  One was a rectifier in a Scott 299b and the other was a 5670 from a DAC.  I have something running a tube in my home almost every day of the year. 

 

People talk about tubes as if they are light bulbs designed to burn out.  I don't think that is a completely valid comparison especially for tubes built for military or hospital equipment.  By the way, I have incandescent bulbs in my house that have never been replaced in 21 years.  The rest have been replaced with CFL's or LED bulbs and many of them have been replaced more than once.   Tube lifespan just doesn't appear to be much of a concern. 

 

[jimjimbo]

If you are fortunate enough to find and use military or hospital grade tubes, then lifespan/ruggedness/viability is not as great an issue as "normal, consumer" grade tubes, and, it is certainly dependent on whether you are talking power tubes, rectifiers, or small signal tubes.  There is a reason why folks look for "matched section" tubes, and there is a reason why tube testers employ "life tests".  A tube may have something of a future lifespan overall, however, the actual strength of each section may be in question, and is very important.

[tigerwoodKhorns]

Old thread.  Need some info.

 

Can anyone supply a scan of the VRD owner's manual? 

 

I am new to this.  I bought some KT150s.  I understand that they will only produce as much power as the amp will allow, but are they in the correct range if used in the VRDs?  (will the VRDs provide enough voltage to drive them properly).  I'd prefer to underdrive them to make them last longer, but I need to understand how this works.  @tube fanatic

 

I need a lesson in tube curves and more info on VRDs.

 

Thanks. 

[henry4841]

Am I correct that the VRD is a EL-34 PP amplifier? Kt-150's might work but not to it's their full potential. This is from just looking quickly at the data sheets the pinout is much the same except for G3 which is tied to the cathode internally on the KT-150. The KT-150 should at least make some music. Both are true pentodes with much the same pinout. For the KT150 to work the best it is capable of the current in the tube should be increased. That is if the plate voltage is close and the PS transformer is capable of producing enough ma.  

 

https://frank.pocnet.net/sheets/084/k/KT150.pdf

https://frank.pocnet.net/sheets/030/e/EL34.pdf

[tigerwoodKhorns]

9 minutes ago, henry4841 said:

Am I correct that the VRD is a EL-34 PP amplifier? Kt-150's might work but not to it's their full potential. This is from just looking quickly at the data sheets the pinout is much the same except for G3 which is tied to the cathode internally on the KT-150. The KT-150 should at least make some music. Both are true pentodes with much the same pinout. For the KT150 to work the best it is capable of the current in the tube should be increased. That is if the plate voltage is close and the PS transformer is capable of producing enough ma.  

 

https://frank.pocnet.net/sheets/084/k/KT150.pdf

https://frank.pocnet.net/sheets/030/e/EL34.pdf

 

I think the VRDs are optimized for KT88s.  This guy is gettign 80 wpc but these might be custom amps. 

https://www.audiocircle.com/index.php?topic=127465.0

 

Do you have a link to a tutorial as to how to read these graphs? 

 

[henry4841]

1 hour ago, tigerwoodKhorns said:

 

I think the VRDs are optimized for KT88s.  This guy is gettign 80 wpc but these might be custom amps. 

https://www.audiocircle.com/index.php?topic=127465.0

 

Do you have a link to a tutorial as to how to read these graphs? 

 

The correct bias for a KT-88 would be very different from the KT-150. There is a guy on the PrimLuna thread saying he thinks it has an automatic bias circuit. Not so sure myself but if so it would have to involve some SS components to my way of thinking to achieve that along with some sensing devices. 

 

One really needs an electronic background to understand the info on a data sheet. That being said though most of the info provided is for someone designing an amplifier. What we are discussing is bias so there are a few things that are important to us. To simplify this lets use this tube for an example. 

https://frank.pocnet.net/sheets/163/e/EL34.pdf

This JJ EL34 tube is rated for 25 watts. To make for a long tube life we only want to use around 80% of that value, lets say 20 watts to make it simple. There are only two things we can play with to achieve running this tube at 20 watts, volts V and amps, milliamps in this case ma. On this data sheet the typical characteristics is shown. They quote 250V's and 100ma of current. Using ohms law you will find using those figures a wattage rating of 25 watts, the limit of the tube. Ug3 is negative so no voltage typical. G2 typical is 265V so with a plate voltage of 250v G2 is plenty good enough. G1 has to be more negative than ground to put the brakes on the tube. Ia is the typical current of 100ma which is much higher than I would run any EL34 but that is what is on the data sheet. What try to run on my SET EL34 builds is around 400V on the plate and run approxiamantly 52ma of current for 20.8 watts. 

 

Decrease the current run more voltage. Increase the voltage run more current. As long as one does not go over 25 watts for the JJ EL34 the tube should be OK but as I said most do not run a tube at max. 

 

If you compare the two tubes the KT88 is a 40 to 46 watt tube whereas the KT150 is rated at 70 watts. Pretty big difference is you want to get the most out of the KT150. 

 

I hope this helps some but if really interested an online electronic course is the way to go. I do not see where it will hurt anything to try the KT-150 in the VRD without changing a thing but if the amp is biased correctly for the KT-88 tube one should re-bias the amplifier to run more current for the KT-150. Also the KT-150 is going to drop the plate voltage some as well. 

[tigerwoodKhorns]

@henry4841

 

My understanding is that the Prima Luna will allow you to plug in even mismatched tubes and will adjust itself to correct.  I saw a video where Kevin deal mentioned this stating you don't even need to match the quads and you can run from the EL34 up to the KT150. 

 

I really appreciate the info that you provided.  I took some electronic courses in undergrad 30 years ago when I was getting my engineering degree and really want to be knowledgeable on this. 

 

To cut to the chase, I can run the KT150s but will not get the full power output from them. That is fine, but I imagine that there is a range on those graphs where the tube is designed to work and if you get outside of that area in any direction it is not ideal. 

 

Here is a great video where he goes through the simple calculations to get full power form the tubes.  About 14 minutes in he shows that if you run at lower current than as designed, the curves are steeper and it is easier to clip moving down the load line.  I will not pretend to completely understand the chart, but I have seen many similar charts where you move out of the optimal range and things do not work correctly, safety factors decrease, etc. 

 

 

 

 

 

Here is an initial question.  This chart is from the video.  If the VRDs run at 1.6A heater current, is that too low as it is below spec?  I just noticed that he does mention this at the end of the video.  The other items are all stated as 'max' voltage current and dissipation so I assume that these are OK so long as everything is run in a balanced fashion. 

 

The person who sold the VRDs had used KT150s and loved them, that is why I picked up a quad of them.  I should have done a little more research on them but they are not that easy to find so I jumped when they went on sale. 

 

Here is a good link that I will need to study, but unfortunately I don't have the specs for the VRDs. 

 

https://robrobinette.com/Drawing_Tube_Load_Lines.htm

 

 

 

I'll ping Craig on this one. 

 

 

 

[tigerwoodKhorns]

@NOS Valves

 

Craig,

 

deleted - Craig, I sent you am email with a few questions on the VRDs. 

 

 

[richieb]

This is interesting. I’ve owned VRD a couple times, always ran KT88’s.

So for opinions - do you think an amp that can run damn near any tube that’s fits the tube socket is a compromised design 

opposed to a manual bias and limited tube application?

[tigerwoodKhorns]

1 hour ago, richieb said:

This is interesting. I’ve owned VRD a couple times, always ran KT88’s.

So for opinions - do you think an amp that can run dam near any tube that’s fits the tube socket is a compromised design 

opposed to a manual bias and limited tube application?

I am not qualified to answer, but the Prima Luna does not look like a compromise to the extent that is can adjust to account for just about anything.  Tubes meet high tech. 

 

https://www.primaluna-usa.com/primaluna-evo-400-tube-integrated

 

Watch the video above on the KT150s, if the voltages and resistance can be adjusted by a microprocessor in the Prima Luna, where is the compromise?  It will optimize for each tube.