Tube rolling question - matching tubes and effects of tube rolling

[Mr. Lin]

Some of you may have noticed that I've happily plunged head first into the hobby of tube rolling. Hardly scratched the surface and I absolutely love it.

But I'm really new to tubes, and I was wondering something tonight. In the not to distant future I'm going to get an integrated tube amp for a second turntable setup. Currently eyeballing the Jolida 202A, it uses the following:
2 matched pairs (4) of 6CA7/EL34 power output; 2 pcs. 12AX7A pre-amplifier, 2 pcs. 12AT7 power drivers.

When rolling tubes on something like this, do they all have to match? In other words, I understand the 12AX7s need to match, but if you roll say Mullards into the amp, does every type of tube need to be a Mullard? I can't imagine this to be the case, as it would make tube rolling prohibitively expensive.

I'm also wondering if changing out particular tubes has a different kind of effect on the sound. For example, will changing out the 12AX7 tubes, which are preamplifier, change the sound more or less than changing the EL34 power output tubes?

Right now I'm just playing with my Pro-Ject Tube Box II, which powers my RM-5 and sometimes my Thorens. It's just two 12AX7 tubes, but it's been very fun so far. Any info on this would be quite helpful.

-Dave

 

[dividebytube]

tube rolling can be circuit dependent. ie, my friend has a 12AX7 based phono preamplifier that uses two 12AX7. The 12AX7s are shared between channels, so he can roll in two different manufacturers to get the type of sound he wants.

In your case of the Jolida, you would want two tubes of the same brand/type/construction. Ie two Mullard 12AX7s... or two RCA 12AT7s... obviously all the tubes (EL34/12AT7/12AX7) don't have to be made by the same company. For example you could roll JJ KT77s for the output tubes, Mullard 12AX7s for the input tubes and RCA 12AT7s for the phase splitter.

Hope that made sense...?

 

[hammr7]

It might be almost impossible to get just one company's tubes on some components. If the component was made by a company that also manufactured tubes (i.e. RCA), then they might have used only RCA tubes. But even RCA relabeled some tubes that were actually produced by other tube manufacturers. And independent companies had the option to pick and choose among the various tube offerings.

While staying with the same tubes for the same application is usually prudent, it takes pretty sophisticated equipment to confirm that tubes actually match performance under a real load. You can certainly tell if tubes are way off from one another, but it isn't an easy call in all applications, especially if the tubes are in a non-critical stage.

 

[analog addict]

I woulodn't sweat it too much....

That's the beauty of tubes....roll 'em in, roll 'em out, and check the bottom line with your ears. Some amps are set up circuit wise to require a closely matched quad of output tubes. Some aren't...The best thing is to know your equipment, and then experiment to your heart's content and your wallets outer limits...

You could even put a new 12AX7 on one channel and a NOS one on the other, and then flip the balance control from one side to the other and see if there's a noticeable difference

Lot different than SS gear, huh?......:thmbsp:

 

[gogofast]

I'm also wondering if changing out particular tubes has a different kind of effect on the sound. For example, will changing out the 12AX7 tubes, which are preamplifier, change the sound more or less than changing the EL34 power output tubes?
-Dave

generally, yes, input tubes make more difference than the output tubes, but i also experienced significant sound difference with output tube rolling. with 7591 and 6v6 tubes - mostly difference in bass and clarity.
tube rolling is all fun, but i believe there's a few things you need to be careful about - like turning the unit off before replacing the tubes, waiting long enough before pulling out output tubes, not powering the unit up right after replacing single tube, and etc.

 

[Bluelobster]

it uses the following:
2 matched pairs (4) of 6CA7/EL34 power output; 2 pcs. 12AX7A pre-amplifier, 2 pcs. 12AT7 power drivers.
The output tubes should at least be matched by pair. I believe this amp is auto bias so to keep current and plate voltages similar they should be matched for at least gain(Gm).
When rolling tubes on something like this, do they all have to match? In other words, I understand the 12AX7s need to match, but if you roll say Mullards into the amp, does every type of tube need to be a Mullard? I can't imagine this to be the case, as it would make tube rolling prohibitively expensive.
The preamp and driver tubes rarely need match by section and almost never tube to tube. You can mix and match, in fact it's a most certain experiment but do the stages similar. i.e. ist stage mullard, 2nd stage amperex etc. Make each side the same throughout the signal chain.
I'm also wondering if changing out particular tubes has a different kind of effect on the sound. For example, will changing out the 12AX7 tubes, which are preamplifier, change the sound more or less than changing the EL34 power output tubes?
The most profound effect you will probably notice is changing the driver tube, the last one before the output. Also in your preamp the first tube in the line stage and phono stage will have the most impact


-Dave[/QUOTE]

 

[Mr. Lin]

Thank you all for the in-depth answers. This is encouraging to hear, sounds like rolling the tubes won't be too hard, except on my bank account. I'm going to look at how expensive tube amps with bias control are, probably out of my range, but seems like that might make tube rolling a little easier.