Tube sets vs mix and match - worth it?

Jowes_84

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The amp was gifted to me and I want to preserve what is original. That includes the original tubes, which I don’t want to wear out. If I start playing them 3-6 hours a week I am sure at some point they will give up.
I’ll go through my stash and see what I have or buy a matched quad of tubes.
 

Jowes_84

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I know that sounds odd, but in the world of electronics, current sharing works that way. The current will simply flow past the weaker devices to the load. Let's look at transistors for a moment.
In a power amp you have drivers and outputs. The drivers share a small portion of the actual load through a medium resistance, say 100 Ω or so. They also feed the outputs, which are larger, handle more current, and are coupled to the load with very low ohm resistors. The lower the value of the emitter or emitter/collector resistors say .2 Ω, the tighter the tolerance in Vbe output matching has to be in order for the audio current to be shared equally. The higher the value of resistors, say .68Ω, the wider the spread can be and current will flow evenly across the devices. The trade off though, is performance. Many parameters like damping factor, will be much worse, the higher the value these resistors are. Generally, for .47Ω resistors, I have never seen a problem as long as the outputs have a 10% spread in Vbe (That's the Base to Emitter voltage that the transistors just turn on at).. If the resistors are .2Ω, that won't work. The devices with the lowest labeled Vbe will turn on and conduct, and the others that are more than 5% higher than that either won't turn on, or won't deliver any AC current (audio current) to the load. The same holds true for tubes. Because of the impedance's and other parameters involved, there is no need for separate cathode resistors in a power tube circuit. Still, in order for power sharing to be equal, they have to be within 10% of each other. Otherwise, it will be like Brutus and Olive Oil on the same tug of war team. The current will flow right past the weaker tube....
Hope this helps....
Ok
I like the analogies. But in the end, Ohm’s law applies. And whether a tube is doing what it should can only be determined through a scope. Bias at 50% PD vs 85% PD does not tell me anything about how strong the tube is and it’s contributing output into the load (reflected impedance at OT primary)
I would need a scope to judge.
 

Dacious

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I'd measure the current draw of the existing tubes. Then sub one at a time of your stash in. Watch out for horrible sounds and idle red plate.

Providing neither happens measure current draw and select 4 within say 4-5ma of each other. They do need to be 6L6GCs but brand is almost irrelevant. I'd match them to sides - so if you have a 42,42, 45 and 47 ma draw put one 42 with one of the higher draw on each side.

I'd consider more than 5ma to be too big a difference personally. Especially at those volts.
 

Jowes_84

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I'd measure the current draw of the existing tubes. Then sub one at a time of your stash in. Watch out for horrible sounds and idle red plate.

Providing neither happens measure current draw and select 4 within say 4-5ma of each other. They do need to be 6L6GCs but brand is almost irrelevant. I'd match them to sides - so if you have a 42,42, 45 and 47 ma draw put one 42 with one of the higher draw on each side.

I'd consider more than 5ma to be too big a difference personally. Especially at those volts.

Thx Dacious
I set the voltage selector to 260V input and B+ is still around 540VDC at idle… I will be cautious.

Initially however, I was asking for experience with offered (example TAD) matched sets of tubes, particularly output tubes, new production. I know there were thousands of threads on here so apologies if I should just go to the search engine first.
If anybody has actually bought complete sets and is happy with them, please let me know.
Thanks all!
 

El Marin

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Experiment with preamp tubes to your heart’s content. However, I’d replace the power tubes with a matched set. You’ll also have to bias the amp with the new set.

T(...)
I’ll go through my stash and see what I have or buy a matched quad of tubes.

Yeah, this... I would first check and then if not, go for a comercial set. I like TAD for power valves. Then for preamp I have some local sellers that test them an sell some NOS or uised in good shape
 

Jowes_84

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Just found these bad boys…
But I read the Russian NOS tubes don’t like high plate voltages… which I have in this amp.
So out goes the order for a new set of Tung Sol Reissues or JJs unless someone has a better idea.
image.jpg
 

radiocaster

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Just found these bad boys…
But I read the Russian NOS tubes don’t like high plate voltages… which I have in this amp.
So out goes the order for a new set of Tung Sol Reissues or JJs unless someone has a better idea.
View attachment 924056
6P3SE are fine with high plate voltage. Not so with regular 6P3S. The box may not indicate what's inside.

But it's too much of a pain to figure out which tubes are good in general if you don't have a tester. Maybe if you have something simple with only 2 tubes you can.
 

cherryburst1

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Ok
I like the analogies. But in the end, Ohm’s law applies. And whether a tube is doing what it should can only be determined through a scope. Bias at 50% PD vs 85% PD does not tell me anything about how strong the tube is and it’s contributing output into the load (reflected impedance at OT primary)
I would need a scope to judge.
Easier than that. in a quartet, put in a matched set. Disconnect both cathodes from ground on either the pull side or push side. Put a AC ammeter--not DC, in series with each cathode to ground, 10-100mA scale. Both meters need to match each other and checked for calibration.
Play a 1kHz sinewave thru the amp at a high but non-clipped level and observe AC current thru each tube. Power down, cool down and replace one of those tubes with a different tube with a lower bias point--at least 15% lower. Repeat test and observe. You will see the original tube producing AC current, the different tube very little if at all. This is why we match tubes within 10% of each other. This characteristic has been known for decades. Nothing new under the sun...All things that have conductance and share a load works this way. Some technologies/topologies are more critical than others regarding tolerances, but it is generally accepted that 10% spread is acceptable for VT power amps. It does seem odd and illogical, but you will see that's how it works.:cool:
 
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Dacious

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Thx Dacious
I set the voltage selector to 260V input and B+ is still around 540VDC at idle… I will be cautious.

Initially however, I was asking for experience with offered (example TAD) matched sets of tubes, particularly output tubes, new production. I know there were thousands of threads on here so apologies if I should just go to the search engine first.
If anybody has actually bought complete sets and is happy with them, please let me know.
Thanks all!


Ok, I thought you were asking about used mismatched tubes. Yes the matched sets I've had where something like an AVO tester has been employed have worked fine. Even used ones.

I just put some used 70s EL84s in a newish AC15C1 and apart from a little blue glow in one which indicates imperfect vacuum they're great. Quiet, sparkly and plenty of life.
 

Jowes_84

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Thanks for all your replies.

It took until today to get back to the amp - it also had some other minor things to address besides output tubes.
I just put in a quad of russian 6P3S-E s ... I had 6 tubes in my stash.

It turned out pretty well, 2 well-matched pairs on either side. No need for new, expensive tubes... unless the soundcheck (next Thursday) goes wrong, but I don't think so.

Biased at 69% left pair / 71% right pair for now.

As I don't have a tester, I pretended the amp was only running a pair of tubes and started with only two tubes inserted, one left (brown OT wire), one right (blue OT wire).
This way, I could isolate pairs with very little deviation in plate current at a certain fixed bias voltage and put the other two back in my stash.

This worked well enough, just takes a bit of time.
I won't be doing this often if the Russian NOS tubes last as long as I hope they will.
 

Vibroluxer

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Just my opinion. I'd use the original tubes and then only change one if you ever need too. I have sold a few amps with wicked good nos tubes but at the end of the day no one cared about them. As long as the amp works, well, that should satisfy nearly everyone.

Lastly, and in your case most importantly, you really like how the amp sounds with the current tubes.

So there ya have it, my reasons for keeping it as is and playing it with the current configuration.

Keep us posted and enjoy that new amp!
 

Jowes_84

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Amp sounds great now. The 6P3S-Es seem to hold up pretty well despite the >500V on the plates and around 20W plate dissipation per tube.
No red-plating
No unpleasant sound
Very pleasant overdrive actually and tight bass.
Would NOS 6L6GCs sound better? Maybe. Maybe not. But the difference would surely not be heard in the mix.
Happy. On to the next project;)
 

schmee

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You want the power tubes fairly well matched. If you can find that in your stash..... that will work.
But if the ones you have are good, just use them unless they are something high value / coveted!

If the preamp tubes are good and not noisy ....use them! They seem to last forever.

If you buy power tubes, you dont have to buy pre tubes from the same brand.
In 6L6's I kinda like the TAD's I have. JJ's are good, but seem a bit "in your face" in 6L6GC's to me.

I highly recommend getting Mullard RI for new 12AX7 pre tubes. Reliable as heck, quiet, albeit a bit more money than JJ, EH, TAD etc.
 

Masmus

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Somehow, the internet has decided that nobody matched tubes back in the day. These people are mistaken.
It was necessary then, it is still necessary today.
The number one reason for matching tubes in the 60’s were to have your home hi-fi sound balanced. And there were a lot more stereo systems than guitar amps back then. This is the main reason matched tube were readily available.
 
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Papanate

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Hello Tube experts

the original tubes in my recently acquired Fender 4x6L6 from the late 70’s are still Running great. But I want to save them for if and when I plan to either give away or put in storage (not happening soon)
Tube set from TAD will cost me around 300,-
I have a large stash of NOS or hardly used tubes and could possibly mix and match something myself, considering bias balance as well as bias pots being installed.
I am using the amp for bass and guitar frequently-so reliability is a consideration.
I don’t want to wear out the original tubes.
It’s 300,- vs mix and match for free (probably costing me a full day of work though)
Thoughts? Advice?
Thanks all

Play the set that is in there - then sub out your mix and match set. Don't spend the $300.
 

Jowes_84

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Thanks schmee.
You want the power tubes fairly well matched. If you can find that in your stash..... that will work.
But if the ones you have are good, just use them unless they are something high value / coveted!

If the preamp tubes are good and not noisy ....use them! They seem to last forever.

If you buy power tubes, you dont have to buy pre tubes from the same brand.
In 6L6's I kinda like the TAD's I have. JJ's are good, but seem a bit "in your face" in 6L6GC's to me.

I highly recommend getting Mullard RI for new 12AX7 pre tubes. Reliable as heck, quiet, albeit a bit more money than JJ, EH, TAD etc.

It seems everyone needs to find their „standard“ tubes they like. For 6v6s, JJs are great imho
But for 4x6l6 amps I am lacking experience and wanted to try something different. I am sure the TADs would have been ok - but after all, I did not really need them. The Russians will do.
Pre amp tube rolling is both fun and exhausting at the same time.. and buying new tubes might actually be a good option.
 

loopfinding

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I buy cheaper JJ’s or tung sol, or occasionally old radio pulls, and pay the extra money to have them matched closely and tested for microphonics by the supplier (the factory matching on new sets is generally just “good enough” and not up to snuff).

Operating tip top for humless/noiseless recording and without a bias balance is more important than the toanz for me. They’re going to more or less do what you want under heavy load, there’s no need to squeeze that last 5% if it includes crappier operation.
 

schmee

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Thanks schmee.


It seems everyone needs to find their „standard“ tubes they like. For 6v6s, JJs are great imho
But for 4x6l6 amps I am lacking experience and wanted to try something different. I am sure the TADs would have been ok - but after all, I did not really need them. The Russians will do.
Pre amp tube rolling is both fun and exhausting at the same time.. and buying new tubes might actually be a good option.
That's why I went to The Mullard RI. Not for the 'faux' name. For the performance. I kept having to play with swapping hissy, or crackly or etc vintage pre tubes. Drove me crazy!
I tried JJ pre tubes, terrible! I usually dont hear much difference in tubes but they were nasty. I think I must have gotten a couple of defective ones or something. Some people like them.
Then I tried the EH 12AX7 lps and some were noisy, one was bad.
I've used probably 25 Mullard without a single issue.
I sold all my vintage pre tubes last year. Made a ton of $. Good riddance! RCA, Mullard, Bugle Boy, Amperex etc
 

Jowes_84

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JJ pre amp tubes… I also had a new one squealing in my JTM45 kit build and replaced it with a TAD pre which worked fine. Do they sound much different though… no clue.
Then again my TAD 6v6 experience was not all that great, there is an opportunity for things to go wrong with any tube imho.
Maybe go solid state/modelling?
😅
Just kidding.
Thanks all for your education. Looking forward to to becoming more proficient making decisions on all things tube/valve/glowing bottle.
 




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