Two bad tube experiences

[amirm]

Oh boy. I used to have nice memories of tubes but they are almost erased with two recent lousy experiences.

First it was the tube in the Nova DAC. When I turn them on, it just added gritty distortion -- something I don't usually associate with tubes.

Recently we got an audiophile tube power amp. Boy, did it sound bad. It had the same gritty character and no bass to boot. I mean almost zero bass response! You had to squint to hear any.

Didn't think it was so easy to make a bad tube stage/amp. But I guess it is.

Others have similar experiences?

I need to go visit Steve to remind myself of good tube sound again .

 

[DaveyF]

Amir, I kind of think of tubes as akin to carburetors in cars... They can work very well, but usually need far more care and maintenance than their newer counterparts. With that in mind, I wander if the components that you were listening to were correctly set-up. Were the tubes in clean sockets, were they not used up, were they biased correctly, etc.
With a ss amp, you can pretty much turn it on and you're good to go, that is occasionally not the case with tube gear IME...

 

[amirm]

I assume they were set up properly. I actually met the designer of the power amp, gave him feedback and he came back with a modification which made it worse. The unit looked beautiful btw so the build quality was there. The Nova DAC came from factory so I assume that was also in good shape.

 

[Orb]

I will need to try and find it,
but one of the audio magazines were critical of the tube-related circuity of the Nova DAC themselves.

Cheers
Orb

 

[LL21]

and i still gotta a SS Class A that has been buzzing mysterioiusly for 18 months...and its back under warranty as of Tuesday with the guys who replaced the capacitors...no technology is perfect..and a lot of diff approaches (tube and ss) when done well can be both reliable and exquisite...i have (so far!) not had any problems with 5 different tubed equipment in over 12 years...go figure!

 

[FrantzM]

Amir, I kind of think of tubes as akin to carburetors in cars... They can work very well, but usually need far more care and maintenance than their newer counterparts. With that in mind, I wander if the components that you were listening to were correctly set-up. Were the tubes in clean sockets, were they not used up, were they biased correctly, etc.
With a ss amp, you can pretty much turn it on and you're good to go, that is occasionally not the case with tube gear IME...

There iare many reason why cars no longer use carburetors ... as for tubes in electronics .. let's leave it there

 

[Phelonious Ponk]

I like Davey's analogy -- good SS is to tubes as modern fuel injection is to carbs. And I have very fond memories of a 57 Chevy ragtop, 283 bored out to 302, 3/4 race cam, to four barrels in line....sigh....But tubes certainly don't have to sound gritty. Did they have enough power for the speakers they were trying to drive?

Tim

 

[RogerD]

Brand new out of the box? You might have a listen after 50 hour burn in time and see what happens.

 

[c1ferrari]

What was/were your source/s, Amir?

Rather curious...
Hope it will be resolved

 

[tony ky ma]

Oh boy. I used to have nice memories of tubes but they are almost erased with two recent lousy experiences.

First it was the tube in the Nova DAC. When I turn them on, it just added gritty distortion -- something I don't usually associate with tubes.

Recently we got an audiophile tube power amp. Boy, did it sound bad. It had the same gritty character and no bass to boot. I mean almost zero bass response! You had to squint to hear any.

Didn't think it was so easy to make a bad tube stage/amp. But I guess it is.

Others have similar experiences?

I need to go visit Steve to remind myself of good tube sound again .

Hi Amir
I have to turn all 55 tubes on in my system for listening, tubes are OK to me. you know tubes can easy to replace not like SS but even same number of tube still have a very big different in quality, depend on who and when in production, of cause they all have life time limit but depend on how the design of using, bias stabilization always the main issue , lot of commercial circuit design are not as good as what we expected, they burn tubes, every two years have to replace all the power tubes ( KT88 or 6550 ) in my case I use military and industrial grade NOS tube (805 810 838 ) so far almost 10 years without problem , tube in DAC must be a small one like 12AT7 or 6DJ8 or whatever, should last pretty long time, try a same number NOS tube to see any change of it ? still no good then something wrong in circuit
tony ma

 

[amirm]

Brand new out of the box? You might have a listen after 50 hour burn in time and see what happens.

The unit was a loaner from the designer. And it had been running for a week or two in the showroom before I got to it. So it certainly had some mileage on it.

 

[amirm]

Rather curious...
Hope it will be resolved

The source was our standard: PC driving an Audiophilleo USB to S/PDIF which in turned fed the Berkeley DAC. Then direct to the power amp.

We are returning the unit so not sure we will be able to resolve the issue other than the designer accepting that it has weak bass.

 

[amirm]

Hi Amir
I have to turn all 55 tubes on in my system for listening, tubes are OK to me. you know tubes can easy to replace not like SS but even same number of tube still have a very big different in quality, depend on who and when in production, of cause they all have life time limit but depend on how the design of using, bias stabilization always the main issue , lot of commercial circuit design are not as good as what we expected, they burn tubes, every two years have to replace all the power tubes ( KT88 or 6550 ) in my case I use military and industrial grade NOS tube (805 810 838 ) so far almost 10 years without problem , tube in DAC must be a small one like 12AT7 or 6DJ8 or whatever, should last pretty long time, try a same number NOS tube to see any change of it ? still no good then something wrong in circuit
tony ma

Hi Tony .

As I noted, in this case the designer and manufacturer brought the unit in for us to evaluate. So I assume it was in the state he wanted it. This is a very small company so probably one person's design and not representative. I was just referencing my old memories of my brother designing a simple tube amp which while lacking strong bass, had very nice sound otherwise.

 

[tony ky ma]

Hi Tony .

As I noted, in this case the designer and manufacturer brought the unit in for us to evaluate. So I assume it was in the state he wanted it. This is a very small company so probably one person's design and not representative. I was just referencing my old memories of my brother designing a simple tube amp which while lacking strong bass, had very nice sound otherwise.

Hi Amir
Lacking strong bass, otherwise nice sound, that will be your personal favor, I guess you like SS sound better with punch !, tube amp's transformer needs speaker matching, direct drive to sound coil usually will doing good for tube amp, like full range speaker or in multi amps system, for those speaker with passive network will depend on the design, so some can sound good with tube amp but some don't, for me bass is going to how deep , not stronger, I rather care about the end tail sound of double bass how clean and detail and feeling gentle shake to body of organ's bass better than those heavy punch hit to my face, all this are belong to personal favor nothing to be argue good or bad
tony ma

 

[microstrip]

Oh boy. I used to have nice memories of tubes but they are almost erased with two recent lousy experiences.

First it was the tube in the Nova DAC. When I turn them on, it just added gritty distortion -- something I don't usually associate with tubes.

Recently we got an audiophile tube power amp. Boy, did it sound bad. It had the same gritty character and no bass to boot. I mean almost zero bass response! You had to squint to hear any.

Didn't think it was so easy to make a bad tube stage/amp. But I guess it is.

Others have similar experiences?

I need to go visit Steve to remind myself of good tube sound again .

Amir,

I think your post mostly shows that before loosing your valuable time listening to bad tube designs next time you should do some previous research or consult trusty people ...

There is excellent and horrible tube equipment - perhaps I will never listen to some of the best sounding, but reliability and long term maintenance are key aspects for any tube electronics I consider for my purchases. OK, I would make an exception if my neighbor was selling a pair of Futterman OTLs cheap. They sound so good with ESL63 .

 

[MylesBAstor]

Oh boy. I used to have nice memories of tubes but they are almost erased with two recent lousy experiences.

First it was the tube in the Nova DAC. When I turn them on, it just added gritty distortion -- something I don't usually associate with tubes.

Recently we got an audiophile tube power amp. Boy, did it sound bad. It had the same gritty character and no bass to boot. I mean almost zero bass response! You had to squint to hear any.

Didn't think it was so easy to make a bad tube stage/amp. But I guess it is.

Others have similar experiences?

I need to go visit Steve to remind myself of good tube sound again .

Amir:

1. Sounds like Peachtree doesn't select their tubes and put crappy ones in. The better tube companies routinely reject 2/3rds of the tubes they get in

2. Vis a vis the tube amp: while it's clear a tube amp could have crappy bass, that the bass is totally MIA sounds to me like a mismatch somewhere eg. cables, impedance between line stage and amp (though usually it's a tube preamp with ss amp), speakers, etc. What cables and speakers were you using with this amp and did the amplifier have enough power for the speakers? Was wondering if the amplifier also sounded dynamically restricted too?

 

[mep]

I think (and I could certainly be wrong) that JA did the measurements on the PeachTree and found the tube circuit added a bunch of distortion.

 

[flez007]

Oh boy. I used to have nice memories of tubes but they are almost erased with two recent lousy experiences.

First it was the tube in the Nova DAC. When I turn them on, it just added gritty distortion -- something I don't usually associate with tubes.

Recently we got an audiophile tube power amp. Boy, did it sound bad. It had the same gritty character and no bass to boot. I mean almost zero bass response! You had to squint to hear any.

Didn't think it was so easy to make a bad tube stage/amp. But I guess it is.

Others have similar experiences?

I need to go visit Steve to remind myself of good tube sound again .

... Too much time listening those JBL Arrays 1400 Amir ...

 

[Tom B.]

Amir,

Myles nailed it in post #16. Without an overview of the circuit topology or seeing the schematic for either of those units, I would guess either a poor choice of operating point for the individual tubes or loading mismatch in the input/output side.

The first suggestion in #16 is correct; it could just be a case of bad tubes. Not all tubes have proper characteristics for a given circuit, despite being either new or having identical part numbers. Manufacturers (or sometimes other end-users) will often give you baseline examples of what particular tubes offer good performance in their units. Rolling a few different tubes into the unit(s) would have been a good data point, but you probably only had on hand what was shipped inside.

It's awfully easy to make a 'gritty' tube circuit....harmonica players do it to their portable amplifiers all of the time. Feed a tube a signal so large that the output tries to swing beyond the limits of the power supply rails, and you get that nasty, gritty sound. Or change a cathode resistor just a bit to push the operating point to an area of non-linearity. Either way you get the idea. Again, without seeing the particular circuit on paper I am guessing here.

The signal we are feeding a (tube) gain stage can be greatly affected by loading on the input side, with cables sometimes being a big factor. All tubes have some inherent internal capacitance (Miller effect) which is additive to the capacitance of the cables in use and coupling capacitor, if any. Now we take into account the presence of a grid resistor....most tube gain stages have them....and we have created a filter. This filter by design will pass signals of certain frequencies and reject others. The circuit designer has to assume a certain amount of input capacitance and allow for this in his design. Ask anyone with a low-output cartridge and tube phono stage how big of a factor cables can be......

On the output side, a tube gain stage is designed to work into a certain load, and if the load changes, so does the operating point. That's why many tube amplifiers have output transformers with multiple taps.....for proper performance we have to present the amplifier with a load for which it was designed to run into. This basic idea applies to all tube gain stages.

You mentioned....... Didn't think it was so easy to make a bad tube stage/amp. But I guess it is.

Not only is it easy to make a bad tube circuit, it's also easy to take a good one and for various reasons, get poor performance out of it. Much of what hits the market today is pretty good, though, and it will be interesting to see if you get any feedback on those units.

Hope this helps,
Tom B.

 

[amirm]

Guys, this was a lighthearted thread. It was not an attack on tubes. I thought I made that clear . I was just observing that despite my excitement for trying out tubes, the last two opportunities which presented themselves by chance, were opposite. I guess I must have been fortunate to have only run into good tube experiences.

Tom, thanks for the detailed explanation. Yes, it helps.