Noisy 12AY7 in Bassman 5F6-A

[vincenzo]

I open this new tread about a problem with my 5F6A Ceriatone clone. The amp is sounding very well, it has a very nice tone that I like very much but I’m not completely satisfied because of a breath that I think comes from V1, a 12AY7 tube
As a try I’ve put a 12AX7 tube in V1 and the amp was very silent, no noise, no breath so I’ve think that using a new 12AY7 the problem will be solved and I ordered a new selected TAD 12AY7 tube (which price is 3 times the normal price !!!)
When the tube arrived I put it in the amp and …. all was fine, only a very low breath no noise, the amp sounded very better than using the 12ax7 tube (in this amp I didn’t like the 12AX7 as V1)
The day after, when I used my amp, the breath was newly present
If I put on newly the 12AX7 tube I newly haven't breath
The voltage seems to be regular and I’m not able to understand what happen
A friend told me to change the plate resistor of V1 from 100k to 120k and from 820R to 1k, but using the 12AY7 the breath is still there, only a bit mitigated.

[stratele52]

Did the input jacks use their shorting contact to keep noise away ?

[vincenzo]

Did the input jacks use their shorting contact to keep noise away ?

Yes, the imput jacks shorting to ground. But I have not a ground loop or hum. I have a great breath.
With or without the guitar cable I have the hiss.
If I change from 12AY7 to 12AX7 the hiss is lower.

[stratele52]

If your shorting jacks are working , ( sure of that ? ) check your wiring from jacks to V1 grid , need a shield cable ? As a real Ceriatone kit you may not nee it if you do a good wiring job .

Picture of the amp may help .

Do you have heater center tap to ground ?

Do you built the Ceriatone 5F6 A like picture here ? Wiring dress is very important to keep amp noiseless.


http://www.ceriatone.com/productSubPages/AC5F6ABassman/AC5F6ACompleteAmpHead.htm

[vincenzo]

If your shorting jacks are working , ( sure of that ? ) check your wiring from jacks to V1 grid , need a shield cable ? As a real Ceriatone kit you may not nee it if you do a good wiring job .

Picture of the amp may help .

Do you have heater center tap to ground ?

Do you built the Ceriatone 5F6 A like picture here ? Wiring dress is very important to keep amp noiseless.


http://www.ceriatone.com/productSubPages/AC5F6ABassman/AC5F6ACompleteAmpHead.htm

I've a shield cable and the TA have a center tap. I think that the wiring is ok. I repeat that I haven't hum or ground loop but only a hiss that increase as I turn up the vol pot and only with 12ay7 tubes. With 12ax7 tubes tha amp is quieter.

[stratele52]

If your shorting jacks are working , ( sure of that ? ) check your wiring from jacks to V1 grid , need a shield cable ? As a real Ceriatone kit you may not nee it if you do a good wiring job .

Picture of the amp may help .
And pictures ?

 

http://www.ceriatone.com/productSubPages/AC5F6ABassman/AC5F6ACompleteAmpHead.htm

I've a shield cable and the TA have a center tap. I think that the wiring is ok.
Photo will help

I repeat that I haven't hum or ground loop but only a hiss that increase
I know

 as I turn up the vol pot and only with 12ay7 tubes. With 12ax7 tubes tha amp is quieter.

Quieter  or as you write ; " If I change from 12AY7 to 12AX7 the hiss is lower" .?

IMO quieter with 12AX7 mean the 12AY7 is defective but the amp is ok , just need a new tube  . Lower (hiss ) you may have problem in the amp .

[kagliostro]

Vincenzo had this problem with the first 12AY7 he tried

so he ordered a second one and the new tube present the same problem

As far as I can know some octal tubes are prone to have problems

Someone knows if this kind of problem is common to 12AY7 tubes ??

K

[vincenzo]

If your shorting jacks are working , ( sure of that ? ) check your wiring from jacks to V1 grid , need a shield cable ? As a real Ceriatone kit you may not nee it if you do a good wiring job .

Picture of the amp may help .
And pictures ?

 

http://www.ceriatone.com/productSubPages/AC5F6ABassman/AC5F6ACompleteAmpHead.htm

I've a shield cable and the TA have a center tap. I think that the wiring is ok.
Photo will help

I repeat that I haven't hum or ground loop but only a hiss that increase
I know

 as I turn up the vol pot and only with 12ay7 tubes. With 12ax7 tubes tha amp is quieter.

Quieter  or as you write ; " If I change from 12AY7 to 12AX7 the hiss is lower" .?

IMO quieter with 12AX7 mean the 12AY7 is defective but the amp is ok , just need a new tube  . Lower (hiss ) you may have problem in the amp .

I think that my english is very bad!!! What is the difference between saying "quieter" and "lower" in english?
Anyway, I think that my 12ay7 is defective. I want to know why the 12ax7 is quieter than 12ay7? Can I find a 12ay7 as quiete as 12ax7? Is there anyone who has had same problems with 12ay7?

[stratele52]

I'm french speaking , that is why I dont know quieter and lower are same 

12AX7 have more gain than 12AY7  .

12AY7 must quieter than 12AX7.  Which brand of tube do you use  ?

Many problem with today's tubes . I have a lot a home to find  the good one.

[vincenzo]

Oh, an Italian and a Canadian who speak English ... I do not think we ever would understand 

Anyway, I used 12AY7 and 12AX7 Electro Harmonics tube at preamp section.
I could think of having guessed one good 12AX7 and one bad 12AY7... but three good AX and three bad AY is a joke 
I swear, my amp sound very great and I like much it... but this hiss 

[stratele52]

Electro H madew good tubes , I don't understand your hiss .

Wainting for some picture wich may help to see where is the issue .

And second question I do not read your answer (my poor english ? )  Did you buitl the amp exactly like on the picture on Ceriatone link ?

[sluckey]

If I change from 12AY7 to 12AX7 the hiss is lower.

So, there's your solution. Still does not answer why. You would think a lower gain tube would produce less hiss. Another tube to try would be a 5751. I've had good luck with those.

One more thing, did you use carbon comp resistors? If so, try changing to metal film, especially for the plate load resistors.

[tubenit]

I have a 12AY7 (or more) in all 3 of my amps.  They consistently have MUCH less hiss/noise than a 12AX7 or 5751.

I also use 12AV7's which I like. And they are not expensive.  However, occasionally one will be microphonic.

My guess is that you have had several problematic 12AY7's and maybe another one would likely be just fine. You could also try a 5751 or the 12AV7.

With respect, Tubenit

[vincenzo]

Electro H madew good tubes , I don't understand your hiss .

Wainting for some picture wich may help to see where is the issue .

And second question I do not read your answer (my poor english ? )  Did you buitl the amp exactly like on the picture on Ceriatone link ?

No, not your poor english, only my few time and carelessness.
I offer my apologies. I will post pics soon.
Anyway, the answer is no, I do not think I have built the amp exactly like Ceriatone, but I sure I make the possible to get a decent build. I have make it three time 

[vincenzo]

If I change from 12AY7 to 12AX7 the hiss is lower.

So, there's your solution. Still does not answer why. You would think a lower gain tube would produce less hiss. Another tube to try would be a 5751. I've had good luck with those.

One more thing, did you use carbon comp resistors? If so, try changing to metal film, especially for the plate load resistors.

I use metal film resistor.

So it is very likely that I have a very bad 12AY7 and good 12AX7.

[vincenzo]

I have a 12AY7 (or more) in all 3 of my amps.  They consistently have MUCH less hiss/noise than a 12AX7 or 5751.

I also use 12AV7's which I like. And they are not expensive.  However, occasionally one will be microphonic.

My guess is that you have had several problematic 12AY7's and maybe another one would likely be just fine. You could also try a 5751 or the 12AV7.

With respect, Tubenit

Where can I find good 12AY7? What brand I buy which is certainly good and low noise, with low hiss?

[vincenzo]

Here are two mp3 files with sample of my amp hiss. Both are registered with my Samsung S4 at 1mt distance from amp.

https://hostr.co/GCPDtztXxqq0

https://hostr.co/VpJurLKkNEQ4

[tubenit]

Where can I find good 12AY7? What brand I buy which is certainly good and low noise, with low hiss?

I have a couple of old stock 12AY7's.  However, I like the EH 12AY7's that Doug sells just as well & they've been fine for me. In fact, I think the only microphonic 12AY7 I've had is old stock.

With respect, Tubenit

[vincenzo]

Where can I find good 12AY7? What brand I buy which is certainly good and low noise, with low hiss?

I have a couple of old stock 12AY7's.  However, I like the EH 12AY7's that Doug sells just as well & they've been fine for me. In fact, I think the only microphonic 12AY7 I've had is old stock.

With respect, Tubenit

You'll refer Doug's NOS tubes or current production? Do you sell your 12AY7?

[stratele52]

Anyway, the answer is no, I do not think I have built the amp exactly like Ceriatone, but I sure I make the possible to get a decent build. I have make it three time 

You built 3  amps like this one ? Or you rebilt same amp 3 times ?

The way you built the amp could be an answer to your noise ; photo please

[vincenzo]

Some pictures

[stratele52]

Thank's vincenzo , I wish to see more pictures like  the complete circuit too . Need to see all chassis ground , volume  wiring .....

To trouble shouting your amp we need all the information

[sluckey]

I don't think you need to be troubleshooting this amp. I think you just need to find a tube that has less noise.

[stratele52]

I don't think you need to be troubleshooting this amp. I think you just need to find a tube that has less noise.

I think you don't understand what I write , if all tubes you put in the amp are noisy , maybe it is not the tubes ? Could be something else ?

[tubenit]

I think you don't understand what I write , if all tubes you put in the amp are noisy , maybe it is not the tubes ?

However, he stated several times that NOT all of the tubes are noisy. Just the 12AY7's. In light of that, I am like Sluckey thinking that trying another 12AY7 would be the next step.

only a hiss that increase as I turn up the vol pot and only with 12ay7 tubes. With 12ax7 tubes tha amp is quieter.

With respect, Tubenit

[sluckey]

I think you don't understand what I write , if all tubes you put in the amp are noisy , maybe it is not the tubes ? Could be something else ?

I do understand what you write. But I don't think you are listening to Vincenzo.

[vincenzo]

    I read that lower the input grid resistor from 68k to 33k or 10k reduce considerably the hiss. What do you think? I do not want to spend a lot of money on research of perfect tube.

[sluckey]

    I read that lower the input grid resistor from 68k to 33k or 10k reduce considerably the hiss. What do you think? I do not want to spend a lot of money on research of perfect tube.

I've never heard that. Why are you opposed to using a 12AX7?

[vincenzo]

    I read that lower the input grid resistor from 68k to 33k or 10k reduce considerably the hiss. What do you think? I do not want to spend a lot of money on research of perfect tube.

I've never heard that. Why are you opposed to using a 12AX7?

Because with the 12AX7 the amp is more gain. I love the sound of original Bassman 5F6A and i play blues.

some link:
http://ax84.com/bbs/dm.php?thread=466363
http://ax84.com/bbs/dm.php?thread=460755
http://ax84.com/bbs/dm.php?thread=470031

Anyway, if you search Google "hiss reduction grid resistor" you'll find a lot of information

[HotBluePlates]

    I read that lower the input grid resistor from 68k to 33k or 10k reduce considerably the hiss.

Anyway, if you search Google "hiss reduction grid resistor" you'll find a lot of information

People write a lot of things on the internet. People also repeat a lot of bad info, because it is what they heard and they don't understand how it works (or doesn't work).

I agree with Sluckey that this is unlikely to reduce your hiss, but try it for yourself. Unsolder the wire from the jack to the 68kΩ resistor, and resolder it directly to the 12AY7 grid. That's zero series resistance. I think you'll find it doesn't solve the hiss.

Think for a moment: the 12AX7 has more gain from grid to plate than the 12AY7. If the source of the hiss was outside the tube and in the grid circuit (like the 68kΩ resistor), the 12AX7 would have louder hiss than the 12AY7.

Without an oscilloscope or a listening amp to determine where the hiss is happening (if it even is outside the tube), I don't know what to tell you. The only clues indicate the tube itself is the source of the noise, as the higher gain tube had less hiss.

[sluckey]

You KNOW that the 12AY7s you have are noisy and that's unfortunate. You proved it by using a higher gain 12AX7 that produced less hiss. I think you are chasing band aid solutions when you clearly understand what the real problem is. I think you will get no satisfaction.

[vincenzo]

So, what do you advise me to do? I'm sure that if I buy a lot of 12AY7 the only sure thing that will happen is to empty my pockets.
So, if there is a way for lower the gain of 12AX7 perhaps it is the best solution. Otherwise I am forced to hold the noisy 12AY7.
What would you do?

[eleventeen]

I would try a few more tubes. But I think you have the correct idea: Your 12AY7 is noisy. It is possible to have more than one noisy tube.

I have a very nice pile of noisy 12AX7! I wish they were not! Wishing will not change this.

[HotBluePlates]

Buy from a vendor that tests their tubes and guarantees low noise (which is funny, because the 12AY7 was originally designed to be a low noise tube for the input stage of audio amplifiers).

Make sure whoever you buy from has a return/exchange/money-back policy.

If you buy from a physical store, take your amp and see if you can try the tubes in your amp before buying (so you can select a low-noise tube).

Or use a 12AX7 and turn the volume control a few notches lower... in the end, that will be the same as using a 12AY7.

[sluckey]

So, what do you advise me to do?

If it's really really important to you to use the 12AY7 because that's what the original used or for some perceived tone reason, then you'll have to buy another one. I'd definitely buy from a different vendor and probably buy a different brand.

However, I know I could not hear a difference between the 12AY7 and a 12AX7 in that socket. I suggest you compare the two tubes. Ignore the hiss and try to concentrate on the tone. You'll have to turn the volume down a bit when using the 12AX7. If you don't hear a significant tone difference, then just use the 12AX7 and take your true love out to dinner with the money you saved.   

The AX has a higher gain than the AY, but in this particular circuit that higher gain simply means you'll turn the volume down some. Higher gain in this case does not translate to crunchier or grittier or distorted sound, just a little more clean tone.

[kagliostro]

Steve my proposal is to use the 12ax7 tube with a split load resistor

what do you think about this and my be also lower only a bit the B+ to the plate of V1 ?

Franco

[vincenzo]

If I decide to put a 12AX7, need I to change something in the circuit?
For example, the value of some resistance or capacitor.

[tubenit]

If I decide to put a 12AX7, need I to change something in the circuit?
For example, the value of some resistance or capacitor.

IF ........... I were going to do that ...........  I'd change a 100k plate/1.5k cathode
to 100k plate and 2.2k or 2.7k cathode resistor and use a 5uf instead of a larger cathode cap.

Just an idea since you're considering sticking with the 12AX7.

With respect, Tubenit

[vincenzo]

If I decide to put a 12AX7, need I to change something in the circuit?
For example, the value of some resistance or capacitor.

IF ........... I were going to do that ...........  I'd change a 100k plate/1.5k cathode
to 100k plate and 2.2k or 2.7k cathode resistor and use a 5uf instead of a larger cathode cap.

Just an idea since you're considering sticking with the 12AX7.

With respect, Tubenit

I do not understand!! V1 resistor cathode is 820R not 1.5K. What do you refer?
Anyway, increase the resistor cathode reduce gain, right?
Decrease bypass cap what do?

[tubenit]

V1 resistor cathode is 820R not 1.5K

Is there a chance that the cathode resistor 820R is "shared"? 

IF so, ........... then think 1.5k.   

Yes, increase resistor and lower cathode cap value for less gain.

with respect, Tubenit

[vincenzo]

V1 resistor cathode is 820R not 1.5K

Is there a chance that the cathode resistor 820R is "shared"? 

IF so, ........... then think 1.5k.   

Yes, increase resistor and lower cathode cap value for less gain.

with respect, Tubenit

  So, if I think 1.5k (820*2), also 2.2k or 2.7k is shared? If yes, I will put a 1.1K or 1.35K?

[tubenit]

So, if I think 1.5k (820*2), also 2.2k or 2.7k is shared? If yes, I will put a 1.1K or 1.35K?

Yes, you are thinking of this correctly.  IF shared,  use  1.2k or 1.5k.  

And use a smaller cathode cap such as 5uf, 10uf or 2.2uf.  Experiment by paralleling them with insulated alligator clips. Try a 5uf and then parallel another 5uf or a 10uf .................... etc......    See what you like there.

With respect, Tubenit

[vincenzo]

Tubenit, what is the difference between change the resistor and cap cathode as you suggested and make a split load plate resistor as Kagliostro suggested?

p.s. I'm learning a lot on this forum and I want to thank all those who have written in this topic.
  

[sluckey]

Changing the cathode resistor/cap actually changes the gain of the tube.

Using a split load plate resistor does not change the gain of the tube, but you only use part of the signal due to the voltage divider in the plate load.

Either way produces a smaller signal out of the preamp, just as if you had turned the volume control down a little.