Topic: Newbie and Not-so Noob Thread: Questions (FAQ) on anything Tubes

[s2kov]

use independent bias pots for each tube and you don't need matched quad tubes!

Auto-biasing like the PrimaLuna? No need for matched tubes?

[bumblebee]

use independent bias pots for each tube and you don't need matched quad tubes!

I read Cayin and Duntonic amps have this. Kaso, nasa loob.

[s2kov]

it is the hassle of having the bias pots inside the chassis, you need to open it everytime you adjust the bias!

I read Cayin and Duntonic amps have this. Kaso, nasa loob.

[bumblebee]

Here's something I really like

TYPES OF (FIXED) BIAS CIRCUITS

Many amps which use "fixed" (negative grid) bias have provisions for adjusting the negative grid voltage upward or downward. Making the grids LESS negative will cause MORE current to flow through the tubes. Some amplifiers don't have a bias-adjusting control (pot) but instead use a fixed resistor to set the voltage. If you encounter one with a fixed resistor, the best thing to do is convert it to an adjustable type. Most of the time, the fixed resistor will be in parallel with the bias capacitor; the lower this resistor's value is, the lower the bias voltage will be. If you can locate and identify this resistor, you can replace it with a simple network consisting of a (lower value) resistor in series with a potentiometer. What you'll be shooting for is a range of adjustment that goes from LESS voltage to MORE voltage than is set by the (existing) fixed resistor. Take the value of the fixed resistor and divide by two; pick the closest standard value to your result, and put it in series with a pot which is as close to the original resistor's value as you can find. Example: the existing resistor is 33K; use a 15K resistor in series with a 25K pot to replace it. The original resistor was 33K; you now have the ability to adjust the value from 15K to 40K. This should provide you with sufficient adjustment range to set any plate current you wish. If not, use a different value pot or resistor.

Some amps have a "balance" type bias adjustment, which allows you to vary the negative grid voltage between the two halves of the output stage; this makes a "matched" set of tubes less crucial to good performance, although it can't compensate for tubes that are wildly different. If you encounter this circuit, the easiest way to adjust it is to simply "tune" the control for minimum 120Hz hum on the output. This type can be modded to the *best* type, which is not only variable from side-to-side, but adjustable up-and-down, too. Usually, this circuit will have the "balance" pot's wiper connected to a resistor which is grounded at the other end. You can replace this resistor exactly as outlined above (half the value, add a pot, etc.) and have the best of both worlds.

-LORD VALVE

[Garp]

Hi, just want to note that Auto biasing in Prima Luna is not the same thing as auto-biasing in WS amps or  as is common in many SET amps. Prima Luna is still "fixed biased" in the sense that a negative voltage is applied at the grid (around -40v). The auto bias is there to automatically and dynamically set the bias current as predetermined by Prima Luna. The auto bias in WS amps and common in many class A amps are common cathode bias amps using a bypassed resistor from cathode to ground to make the grid "more negative" with respect to the cathode. Just my 1 cent...

[bumblebee]

Hi, just want to note that Auto biasing in Prima Luna is not the same thing as auto-biasing in WS amps or  as is common in many SET amps. Prima Luna is still "fixed biased" in the sense that a negative voltage is applied at the grid (around -40v). The auto bias is there to automatically and dynamically set the bias current as predetermined by Prima Luna. The auto bias in WS amps and common in many class A amps are common cathode bias amps using a bypassed resistor from cathode to ground to make the grid "more negative" with respect to the cathode. Just my 1 cent...

Sana pati bias setpoint, variable na rin

[eXg]

more on biasing...

how to measure bias (from use of DMM to trimpot adjustment) and how determine correct bias setting for the tubes (in a given circuit)?

[bumblebee]

more on biasing...

how to measure bias (from use of DMM to trimpot adjustment) and how determine correct bias setting for the tubes (in a given circuit)?

Try this link.

[arnoldc]

2ny is correct. The PrimaLuna is a fixed-bias type with circuits to maintain "auto-bias" whereas more traditional ones use a bias potentiometer to adjust the bias voltage manually.

That is different from cathode bias (resistor w/ capacitor bypass) that other amps uses.

[MomonX]

Hello Guru's!

I'm a newbie and have a question for you (maybe a stupid one  ) Using tube amps, Is it ok too hear a slight hum coming out from your speakers? I could only hear it if I stick my ear to it and it's coming only from my right speaker.

I'm afraid I have experienced this from 2 of my tube amps (AMX & Dared) at home and I'm using a power line filter on it....  Should I return the amp and have it fixed? or is there something wrong with my system.. or with me??  Thanks!

[RU9]

I'm a newbie and have a question for you (maybe a stupid one  ) Using tube amps, Is it ok too hear a slight hum coming out from your speakers? I could only hear it if I stick my ear to it and it's coming only from my right speaker.

Hi!

From what i read, that  is normal.

My AMX EL84 also slightly hums.

Louie

[ATJr.]

if you have to stick your ear up close to hear the hum, then i guess it's okey. even ss amps that have poor grounding layout are prone to this.

[MomonX]

Thanks! I thought I had problems... 

[bumblebee]

If NOS sounds so good, bakit hindi na lang gayahin yung design ng mga current manufacturers tapos ibenta sa mas mababang halaga tulad ng mga new production tubes?

[odyopayl]

If NOS sounds so good, bakit hindi na lang gayahin yung design ng mga current manufacturers tapos ibenta sa mas mababang halaga tulad ng mga new production tubes?

I'm wondering, inspite of technology  with new & better materials today, why NOS tubes expensive and most of them sounds better than new production? Parang wine kailangan ba ng "aging"? to make it sound better? hehehe or maybe because of new production now a days are made in China?

[KEN]

Mga sir I'm contemplating on getting a tube buffer (MF X10v3) for sometime now but concern on the following...  I'm just a casual listener.

1) Frequent switching on/off (eg. 2x/day), Does it affect the life span of the tube ?

2) Room Temp. - manufacturer  recommends keeping the unit always on, would it be ok even when airconditioning unit is off ? sayang kasi electrc. bill

3) Tube replacement - manufacturer claims tubes used are limited (milspec milusage mu-vista (6112) tube), Does any one knows of any replacement tubes for these ?

Sorry mga bosing I'm newbie on tubes...

TIA

[KEN]

thx sir 2ty, the site has more info than MF site itself with regards to the tubes.
your reply as well as the new info i got, moves me a step  closer on getting it   the only hitch I see is that I cannot test it with my gear since I have to order pa but I guest I'll be ok with it since I already got the xpsu and xdacv3 to compliment it and judging from most reviews available on the net I feel it would be ok for me...

thanks again sir...


 

[JojoD818]

KEN,

when I built my tube buffer last May, it has been on 24/7 for the past 4-5 months, power failures are the only interruptions though. the 6922 tubes are said to have many hours of service especially with such designs wherein the tubes are operated at lower voltages. i think it will take years before you need to replace it's tubes.

hope this helps...

[MomonX]

Hello Ken, Where are you going buy the X-10 tube buffer??? I'm looking all over to get one this.. 

I also saw a review that if you get the MF X-DAC together with this it'll give you an even greater improvement.. I guess a regular cheap DVD player can sound on par/ better than a good (branded) CDP.

Let me know the outcome! 

Thanks!

[KEN]

Thanks sir JojoD818 for the rply, just want to know if  you keep your aircondtng unit on or room temp will do ? I'm worried sayang kasi electric bill specially pag nasa trabaho.

KEN,

when I built my tube buffer last May, it has been on 24/7 for the past 4-5 months, power failures are the only interruptions though. the 6922 tubes are said to have many hours of service especially with such designs wherein the tubes are operated at lower voltages. i think it will take years before you need to replace it's tubes.

hope this helps...

[KEN]

Hi MomonX,

Dito kasi ako based sa Jeddah(Saudi) but the local dealer is based pa sa Riyadh (1.1K Kilo), kaya very hard for me to audition it with my system. Pinoy din kasi yung dealer kaya na informed ako last 2 weeks pa na kadadating lang ng mga stocks nila I already got the XPSU and XDAC v3 to compliment it. The XPSU/XDACv3 alone makes a big difference compare noong CDP(RCD02) lang gamit ko.
 

Hello Ken, Where are you going buy the X-10 tube buffer??? I'm looking all over to get one this.. 

I also saw a review that if you get the MF X-DAC together with this it'll give you an even greater improvement.. I guess a regular cheap DVD player can sound on par/ better than a good (branded) CDP.

Let me know the outcome! 

Thanks!

[markmlists]

Hi.

There is a thread about tube vs ss rectified tube pre-amp but Im not sure if my question qualifies there since I interpreted it as tubes + rectifier on a single plate.. So, here goes:

1. Would a WS Tono Pre Amp or an AMX Pre Amp be considered an upgrade for my Nad 320? I want this 'sweet' coloration in sound (i have been reading about) but im not willing to spend on a tube integrated just yet.

2. Is there merit in using any of these 2 (amx/tono) with NAD 320?

3. Also, since some of the tube threads were started a couple of years ago-when semi restored vintage tube gears are priced more competitively than the 2 brands I mentioned, Im not sure if one is still available. Meron pa bang affordable vintage ngayon? Or WS / AMX na ang most affordable ticket to tubes ngayon?

4. Can I use a Pre-amp with my other SS Intergrated without a pre-amp provision? Via Tape 1/2 input kaya puede?

Unfortunately, I do not have time to audition on weekends so please lend me your ears instead. (thanks)

Opinions and subjective views are most welcome.

Thanks.

[odyopayl]

Hi.

There is a thread about tube vs ss rectified tube pre-amp but Im not sure if my question qualifies there since I interpreted it as tubes + rectifier on a single plate.. So, here goes:

1. Would a WS Tono Pre Amp or an AMX Pre Amp be considered an upgrade for my Nad 320? I want this 'sweet' coloration in sound (i have been reading about) but im not willing to spend on a tube integrated just yet.

- For me definitely not an upgrade for your NAD 320, but it might improved the sound of your system. In this kind of hobby it is much better to hear it for yourself.

2. Is there merit in using any of these 2 (amx/tono) with NAD 320?
In my experience (tono) there is. Again better to hear it yourself

3. Also, since some of the tube threads were started a couple of years ago-when semi restored vintage tube gears are priced more competitively than the 2 brands I mentioned, Im not sure if one is still available. Meron pa bang affordable vintage ngayon? Or WS / AMX na ang most affordable ticket to tubes ngayon?
Pre-owned, DIY projects and  AMX as well as WS (Tono) products are affordable.

4. Can I use a Pre-amp with my other SS Intergrated without a pre-amp provision? Via Tape 1/2 input kaya puede?
In case of Tono pre-amp you can integrate it with your SS and believe same thing with the AMX

Unfortunately, I do not have time to audition on weekends so please lend me your ears instead. (thanks)
Find time/ways  to audition anything before buying, you need your ears.

Opinions and subjective views are most welcome.
Hi markm just my opinion

Thanks.

[JojoD818]

Thanks sir JojoD818 for the rply, just want to know if  you keep your aircondtng unit on or room temp will do ? I'm worried sayang kasi electric bill specially pag nasa trabaho.

Hi KEN,

Nope, no air conditioning here sir (no electric fans too). Besides, I'm sure that even frequent (several times a day) on and off won't damage the unit. I even modified mine to have a slow turn-on for the heaters to even lengthen their already long life. 

Turning audio or any electrical equipment when no one is around is a healthy habit, aside from other reasons, you are also promoting green earth.

[ATJr.]

@KEN,
looking at the casing for that buffer and at 14watts power consumption, i reckon not even a 30*C temp rise! so heat is not an issue imho! but wether you will like the sound from it is!

[KEN]

thanks sir JojoD818...ur info is a big help, tamang tama yung XPSU may  on/off switch.

Hi KEN,

Nope, no air conditioning here sir (no electric fans too). Besides, I'm sure that even frequent (several times a day) on and off won't damage the unit. I even modified mine to have a slow turn-on for the heaters to even lengthen their already long life. 

I agree 100% sir...

Turning audio or any electrical equipment when no one is around is a healthy habit, aside from other reasons, you are also promoting green earth.

[KEN]

Thx sir 2ny with ur rply...i'm relieve of my worries...

@KEN,
looking at the casing for that buffer and at 14watts power consumption, i reckon not even a 30*C temp rise! so heat is not an issue imho!

basing on my  XPSU/XDACv3 combi experience, I feel(hope) I would like the effect of the x10v3 on my system.

but wether you will like the sound from it is!

Galing talaga dito PinoyDVD... thanks gain mga sir sa mga replies nyo...

[bumblebee]

Sirs,

What's the difference between driver and preamp tubes? Which affects sound more?

TIA.

[ATJr.]

Sirs,

What's the difference between driver and preamp tubes? Which affects sound more?

TIA.

a driver tube by its name drives the output tubes, provides the nescessary voltage swing at the grids, and can be as high as 200volts peak to peak, a  preamp drives the power amp. power amps may requires a few volts rms to drive it to full power output!

both however can use the same type tubes.

as to which affects the sound more, there is no easy answer!

[bumblebee]

Thanks for that, Sir 2ny.