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

[Jagner]

CO2,

Try cleaning the potentiometer with a contact cleaner first.  If there's a scratchy sound on your left channel then the problem is on the pot.  If no sound is coming from the left channel, the problem may not be on the potentiometer.

Alps and DACT may be alternatives but may not fit into your amp.  Better check the actual size of your pot.  Some amps require a center tap on the volume control pot.  Better check it else, you may end up buying something you cannot use.

Cheers

[dana]

Hi CO2,

You can also check Eleshop at Ronquillo St. parallel Raon for your volume pot.
They also carry some good brands accdg to friend Owediah (pls check his postings...)
Medyo affordable daw...

[devo]

JAN means "joint army navy" they are military grade tubes and are tighter in specs...

thanks for the clarification........ will tubes having military specifications yield improved sonics compared with commercial ones. also worked once on a semicon but was not able to deal with application, just more on specs comparison between the two. TIA

[CO2]

Thanks guys for your help.

Sir Jag i already removed and inspected the volume pot of the amp and i noticed some deep thinning of the carbon on the input side which maybe the cause of erratic and scratchy sound of the left channel.  I just hope that replacing the pot can remedy the problem.

Sir dana i will try to find time to locate the place as soon as i can.

Nevertheless, here's some pics of the amp. which i think worth restoring:

[JojoD818]

Anyway guys i also want to ask how can i test a busted tube?

TIA

Simpliest way to test a tube is to try it on a known gear, but this will only tell you that it's good or bad. Besides, I will only do this on signal tubes and not power/rectifier tubes. Real tube testers can tell how strong or how weak the tube is.

HTH

[rascal101]

thanks for the clarification........ will tubes having military specifications yield improved sonics compared with commercial ones. also worked once on a semicon but was not able to deal with application, just more on specs comparison between the two. TIA

The JAN specification means that the component or part has been tested about 3 - 4x more than military grade  specification which is already tight. I was surprised myself when I encountered ICs having lot travellers that contain steps repeating the same tests over and over. You can be sure that buying JAN grade is like getting the top 1% of a typical military grade part.

[devo]

The JAN specification means that the component or part has been tested about 3 - 4x more than military grade  specification which is already tight. I was surprised myself when I encountered ICs having lot travellers that contain steps repeating the same tests over and over. You can be sure that buying JAN grade is like getting the top 1% of a typical military grade part.

thanks a lot Rascal for the input................

[ATJr.]

hmmm...i still remember in the early 70's you can buy those JAN tubes (peanut ones) on white cartons for 1peso each, even cheaper than japanese made tubes...the market must have been overflowing then.... :'(

[markmlists]

Just a quick one (or 2) for those who know:

 All things being equal (parts, topologies, maker, tubes) / Theoretically   which should sound better, a) an SS rectified but Tube regulated preamp or b)tube rectified but SS regulated preamp? Why?

Thanks

[JojoD818]

If line regulation, ripple rejection ratio, rms output noise %, delta t/delta v, for your two specimen circuits and provided they supply exactly the same tube circuit.

My answer is the same. But we live in a real world scenario and this circuits can be affected by such so it may also be not the same.

Which one sounds better is subjective and cannot be told by just looking at the parts and mathematical computation. We are scientists, not fortune tellers my friend. 

[ATJr.]

i wish there is an easy answer, but try to consider that designs are more on personal preferences, parts availability and finaly that of costs..meron ding uso-uso dyan, so what is fashionable at the moment is it.

wether-weather din, you see this in many ss designs...

you will see many designs on the web and also the many hypes that accompany such designs...

[markmlists]

If line regulation, ripple rejection ratio, rms output noise %, delta t/delta v, for your two specimen circuits and provided they supply exactly the same tube circuit.

My answer is the same. But we live in a real world scenario and this circuits can be affected by such so it may also be not the same.

Which one sounds better is subjective and cannot be told by just looking at the parts and mathematical computation. We are scientists, not fortune tellers my friend. 

Thanks. I was asking lang sana if may sonic advantage ang tube reg over ss reg since I have access to an od3 kaya I also said na all things being equal. Hoping for something like, "SS should sound better because of this" or "tube reg should sound better because of that." (theoretical) I appreciate your responses though. hehe

Hey, we all can be both and more! Scientist sa umaga, fortune teller sa hapon at dance instructor sa gabi? Thanks Sirs JD and Tony.

[markmlists]

Follow up question..

How does one correctly determine the proper value of a pot to use in a power amp or preamp? Bakit yung iba 50k or 20K or 100K is it also 'subjective'? If not, what is the sense of using a 100K pot with an output impedance (?) of say 500K? Why not use 250K/500k pot din? Sorry for the newbie type questions. I'd appreciate being educated here. Thanks in advance.

[JojoD818]

Thanks. I was asking lang sana if may sonic advantage ang tube reg over ss reg since I have access to an od3 kaya I also said na all things being equal. Hoping for something like, "SS should sound better because of this" or "tube reg should sound better because of that." (theoretical) I appreciate your responses though. hehe

Hey, we all can be both and more! Scientist sa umaga, fortune teller sa hapon at dance instructor sa gabi? Thanks Sirs JD and Tony.

see Tony's post. It is subjective indeed. Built properly, both will achieve what they are designed to do, i.e. regulate.

Want a better way to know? Build both and listen.   

[JojoD818]

Follow up question..

How does one correctly determine the proper value of a pot to use in a power amp or preamp? Bakit yung iba 50k or 20K or 100K is it also 'subjective'? If not, what is the sense of using a 100K pot with an output impedance (?) of say 500K? Why not use 250K/500k pot din? Sorry for the newbie type questions. I'd appreciate being educated here. Thanks in advance.

I think that during the haydays of tubes (matagal na yun siguro), only high value pots are available since most tube gears have high output impedances (they use high value pots to prevent loading the preceeding stage), while they started to manufactur lower value of pots to accomodate ss applications.

[ATJr.]

Follow up question..

How does one correctly determine the proper value of a pot to use in a power amp or preamp? Bakit yung iba 50k or 20K or 100K is it also 'subjective'? If not, what is the sense of using a 100K pot with an output impedance (?) of say 500K? Why not use 250K/500k pot din? Sorry for the newbie type questions. I'd appreciate being educated here. Thanks in advance.

depende yan sa output resistance ng preceding stage, low values of ouput resistance say 1K, 20k or so is desireable for low noise. 500k is used if the preceding stage has an output resistance greater than 50K...

there is such a rule as rule of ten(10) in electronics, i am sure many knows this, that is if a resistor is in series or in parallel with another resistor, then as long as it is 10x or more in value, then for pratical purposes, this resistor is is taken as if it was not there.

the reverse of that rule is applied in the case of output resistance loaded or shunted by volume pots.

[markmlists]

Fully appreciated both responses...

[rascal101]

sirs,
pwede paki-explika - tube buffers

what is decware's zsla-1? nakalagay sa descprition - single ended triode - stereo line stage, pero sa schematic diagram heading - tube attenuator / buffer.
http://www.decware.com/linestage/zp1.htm
click- "specs" on the left side of the display, schematic will appear at the bottom of next display

sa link na ito - http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1154211013&read&3&4& 
may nagtanong tungkol sa tube buffers, at may sumagot to the effect na di lagi kailangan o advisable na gumamit ng tube buffer, depended sa gamit na gears.

eto po setup na balak ko insert tube buffer*--->   dvdplayer -*- tubepreamp (12au7) - t.amps

worry ko baka "over"/"redundant" instead of improving the sound eh makagulo pa?
 
maraming salamat po

Sir Oweidah,

Iyung TDS202 niyo di ba puwedeng after DVD player niyo

dvd player -> TDS202 -> pre-amp -> power amp

My take on this tube buffer ...

Ang buffer stage kasi di ba unity gain siya so ano iyung sense na maglagay ng tube buffer. Naiintindihan ko kung gusto mo ng current gain which is typical for SS. Kung hindi siya unity gain, bakit hindi na lang tawagin na tube amp stage kasi after sa DAC ng CDP o DVD player may gain stage ka naman dun eh. Kailangan mo talaga siya dahil di naman kaya nung DAC na i-drive iyung output signal niya patungo sa pre-amp without significant attenuation.

[ATJr.]

you are correct, the only reason to use a tube buffer is so that your system will have that tube sound which is in nowadays...try it and you may even like it.

[s2kov]

The buffered circuit has good drive capability and a low O/P impedance. The power amp want´s as low load as possible to draw the signal.

[rascal101]

you are correct, the only reason to use a tube buffer is so that your system will have that tube sound which is in nowadays...try it and you may even like it.

Kung hindi na babasagin ang tubo ... 

Seriously, if the intent is to get that "tube" sound I think it is best to use a tube pre-amp or power-amp. To me (at least) a differential amp stage (via diff amp IC or discrete) after the DAC IC would make more sense.

[ATJr.]

even the "foreplay" preamp has a gain of about 2 very close to unity right? a preamp is also a buffer, while a buffer is also a preamp, you put them before the power amp, that is why they are called preamps...

[JojoD818]

geez, I crack myself up! LOL!

[ATJr.]

LOL!!!

[s2kov]

is it that foreplay has 10dB gain?

[ATJr.]

from my caculations of the foreplay's  gain of x2 is 6db, while a gain of 10db is x3.16,  so you see my calculations are quite good.



 

[s2kov]

so, 2 is a voltage gain which is different to what i thought?

ayuz!

from my caculations of the foreplay's  gain of x2 is 6db, while a gain of 10db is x3.16,  so you see my calculations are quite good.



 

[rascal101]

even the "foreplay" preamp has a gain of about 2 very close to unity right? a preamp is also a buffer, while a buffer is also a preamp, you put them before the power amp, that is why they are called preamps...

Kaya nga huwag mo nang gagalawin pa CDP mo at maglagay ng tube buffer ek ek. Mag tube pre-amp ka na lang o di kaya power-amp. 

Ang 2 hindi malapit sa unity. Malayong malayo pa iyun. Kung ang tangkad ko eh doble sa iyo sasabihin mo ba sa akin malapit na at mag sing tangkad na tayo. 

[ATJr.]

no problemo, you are free to think and speak as you like!

[JojoD818]

no problemo, you are free to think and speak as you like!

and also free to do as you please. 

rascal,

yun ek ek sa iyo na hindi mo nadidinig pwedeng nadidinig ng iba. your ears are not theirs, as theirs are not yours.