Interested in the following entry level, affordable Tube Amps

Decided to purchase a TubeCube 7 which is the same thing as the Miniwatt N3 to tide me over for a while. Price was right and it is a full tube amp and not a hybrid.

Initial impressions are good. Mellow sound. Hearing a more 3D like soundstage than I have with all solid state amps with the exception of my old Yamaha A500 with the new KnuKonceptz Kord Kable 14 Gauge Copper Speaker Wire I just added a week or so ago. Incredible sound from this speaker wire and it doesn't cost much at all. Will have to try it with the TubeCube once I get Banana's on the wire. Using AQ Type 4 with the TubeCube right now and it sounds excellent. Good instrument separation and the midrange is very mellow. Bass is a bit weak. High end is mellow despite the stock Sino pre amp tube apparently having a "bright" rating from the Tube Depot website guide for tubes.

I want to swap out the pre amp tube. 12ax7 pre amp tube. What would improve the bass a bit but still keep it tight? I've read the Tung Sol and Genelex get good reviews from people using them for this same amp. Wondering about Mullard, Sovtek and any other manufacturer of pre amp tubes as well.

Budget is somewhat limited. Don't want to spend more than around $25 for the pre amp tube right now. Since a bright tube with this amp isn't the same as having a bright high end on a solid state, that is a non issue at this time. I can tame that with the cables if required. Right now the Sino tube is fine except the bass is just too weak.
From my guitar days, the 12au7 is a good substitue for the 12ax7. Lower gain and less bright.
 
Don't you have to change the bias of the amp if you change the tube from a 12ax7? Not sure how to do that. Perhaps staying with a 12ax7 is best but finding a better tube than the Sino is best in this case.

Not for little signal tubes, just power tubes
 
Looking at Tube Depot comparisons of the 12AX7 tubes. Which is more important for a amp like the Tube Cube? Signal gain or sensitivity? Can't seem to find one that is strong on both. I will be getting a pre amp to use and would that make a difference in regard to which is more important?
 
You just never know till you give them a try. This would also be affected by your source + speaker sensitivity.
 
Don't you have to change the bias of the amp if you change the tube from a 12ax7? Not sure how to do that. Perhaps staying with a 12ax7 is best but finding a better tube than the Sino is best in this case.

Not for little signal tubes, just power tubes

The response above is a bit misleading or, at least, incomplete and oversimplified.

There are several tubes that have the same pinout (the same pin goes to the same element in the tube: plate, grid, cathode in a triode tube) as the 12AX7 and use the same heater voltage.

Yes, you can interchange them without doing any harm. However, that does not mean that they are designed to use the same value resistors and other parts in the circuit. A circuit that is optimized for a 12AX7 and one that it optimized for, say, a 12AU7 are different. If you want to optimize the circuit for a different tube you do need to change the operating points including the bias (cathode resistor), the plate load (plate resistor), grid leak resistor, cathode bypass capacitor and maybe even the supply voltage and the negative feedback circuit.

The amplification factors of these tubes are much different. For 12AX7 it is 100. For 12AU7 it is only 20. The 12AT7 is 60. Another popular sub is the 5751, which is 70. They can all be used and they will alter the sound but they will not be operating as designed unless circuit changes are made.

I will be getting a pre amp to use and would that make a difference in regard to which is more important?

There are different types of preamps. Some provide gain (signal boost) and some not. Many times you don't really need any more gain but a preamp might be convenient if it has multiple inputs to connect multiple sources or even remote controls. If you use a turntable you will need a phono preamp.

Back in the old days preamps, or the preamp sections of integrated amps, had these knobs called tone controls. Very handy. If you wanted a bit more Bass you just turned the knob a little bit. Too bright? A slight turn of the a knob called Treble and it's fixed. No need buy several new tubes in the hopes that one of them would solve your problem. :rolleyes:
 
Decided upon a Mullard 12AX7. For the most part, it gets good reviews for Hi Fi applications.

Yes, I am going to get a preamp in the near future. I have a CD player, cassette deck and tuner to use. Eventually will add a turntable when I can afford to buy one.
 
Decided upon a Mullard 12AX7. For the most part, it gets good reviews for Hi Fi applications.

Yes, I am going to get a preamp in the near future. I have a CD player, cassette deck and tuner to use. Eventually will add a turntable when I can afford to buy one.

NOS I hope. The new production ones aren't the same animal, being made by a totally different company (New Sensor). They're just not as good
 
New production for now. Don't have the time or money to spend on a NOS tube at this time. Will have to wait until a later time. I have too many other things that I have to buy and spend money on for the next few months.
 
Howdy folks,
I have Jadis and Antique Sound Lab equipment I've had for over 20 years. Have done some "preventative" cap upgrades for the fun of it and of course regular tube rolls with various NOS and current production tubes. Just ordered an OldChen EL34 wired for SEP. I passionately hate Chinese stuff as a matter of principle, but for economic and DIY reasons, I've ordered this amp for my workshop system. We'll see how it goes. Not expecting Jadis-level performance or build, but I hope to upgrade and mod the amp as required once I can inspect it. I'll report back on the verdict...
 
Yeah, some Russian and Eastern European companies bought the rights to brand their tubes with some of the famous names of the past - Mullard, Tung Sol, Genelex Gold Lion, and probably others. Some of them might be decent tubes (I've never used any myself) but they are not the same as their vintage namesakes. Having the famous name on the tube just allows the manufacturer to charge more $$$ than they would have been able to otherwise.

If they've gotten good reviews from users who are familiar with the real things, try some. I'd suggest you try some vintage tubes too, for comparison. NOS vintage examples of 12AX7s tend to be pricey but there is nothing wrong with strong testing used tubes, which can be found at more reasonable prices - probably cheaper than the current production rebrands.

That's another reason why I advocate buying vintage console amps as an introduction to tubes. They usually come with American or European vintage tubes and the small signal tubes like the 12AX7s usually still test quite strong. Even the output tubes usually have life left in them.
 
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Having the famous name on the tube just allows the manufacturer to charge more $$$ than they would have been able to otherwise.
The Amperex bugle boy come to mind. Would there be much difference between a Amperex 12AX7 with bugle playing vacuum tube character printed on it, compared to just a orange globe labeled Amperex 12AX7?
 
The Amperex bugle boy come to mind. Would there be much difference between a Amperex 12AX7 with bugle playing vacuum tube character printed on it, compared to just a orange globe labeled Amperex 12AX7?

I don't know if anyone has bought the rights to the Amperex name. If so, and one of those is a new production "Amperex", then yes, they are certainly charging more because of the name and the only thing in common is the printing on the tube and box.

I know there are vintage Amperex tubes labelled as "Bugle Boy" and with the orange globe. I'm not an expert but I was under the impression that the orange globe design was produced a bit later and that the Bugle Boys are earlier production. You'd have to check with some of the serious tube nerds to see if the construction or sound was different or if they were produced in different manufacturing plants.

Some brands used manufacturing codes that will tell you when and where a tube was made. And by whom. It was common practice to manufacture tubes and brand them with other companies' names on them. Sometimes companies that sold amps but didn't make tubes wanted their name on the tubes. There were also companies that were resellers. They bought tubes from a variety of manufacturers and had their own private label printed on them. Some of the tubes sold to these resellers were batches that were rejected by the quality control department of the manufacturer. Other times they were just excess inventory but normal quality. Sometimes one tube company bought tubes from another tube company and put their name on it. This usually happened when the company needed some of that type of tube but didn't have a production line set up to make them at the moment. It was cheaper to buy from a competitor and relabel them than to set up a production line for a relatively small run. All the big manufacturers did this from time to time.

OK, here's a link that might explain some of it as far as Amperex goes: http://www.33audio.com/enter/amperexbox.html
 
I know there are vintage Amperex tubes labelled as "Bugle Boy" and with the orange globe. I'm not an expert but I was under the impression that the orange globe design was produced a bit later and that the Bugle Boys are earlier production.

The link mentions orange globe labeled tubes are newer.
 
Looking at Tube Depot comparisons of the 12AX7 tubes. Which is more important for a amp like the Tube Cube? Signal gain or sensitivity? Can't seem to find one that is strong on both. I will be getting a pre amp to use and would that make a difference in regard to which is more important?

Just to clarify my earlier comments . . . tube rolling is fun and all but trying to use tubes as tone controls is a total crapshoot. Various parts and tube changes will affect the sound of an amp but they are relatively subtle and completely unpredictable. You will spend way more than you need to and the results will likely not be exactly what you are looking for.

I would suggest looking for a used, decent quality, graphic EQ, a tool that is not only made to accomplish what you're trying to do but it can also be adjusted to optimize the tone of different recordings. For someone who is on a budget, I think that's a better choice. I'm not saying that the new production Mullard won't be an improvement on the tube that comes with the amp - it probably will be better - since even the most diehard fans of Chinese amps seem to agree that the tubes that come in them suck. I'm just saying that it or any other tube is not an effective, predictable and adjustable method of adjusting tone.

Decided upon a Mullard 12AX7. For the most part, it gets good reviews for Hi Fi applications. Yes, I am going to get a preamp in the near future. I have a CD player, cassette deck and tuner to use. Eventually will add a turntable when I can afford to buy one.

Modern gear is optimized for line level inputs such as your CD player, cassette deck and tuner. They put out a signal that is plenty hot enough. If the amp has a volume control, that's all you really need. A volume control is used to attenuate (reduce) the signal going into the amp. Turning it all the way up gives you the full signal coming from the source. In most cases that full signal is actually already too hot and the amp will exhibit higher, and often obviously nasty, distortion. So a preamp that provides gain (boosts the signal even more) is not really necessary unless the signal coming in to the amp is too low with the volume on the amp turned up all the way. If you add a graphic EQ to deal with your tone issue, those usually have an output level on them too so you can use it with an amp that has no volume control too.

Some tube preamps, known as tube buffers, do not provide gain. They are often used to add a tubey sound quality to solid state power amps. If they have multiple inputs and allow you to switch between sources that might be a better choice and may be less expensive. Unfortunately, some preamps (often Chinese) are mostly for looks. They have a tube that glows but they operate the tubes under operating conditions that are extremely different (very low voltages and currents) from how the tube is meant to be operated. Functionally, they are mostly eye candy and have little effect on the sound compared to a properly designed circuit. So do your homework!
 
I would suggest looking for a used, decent quality, graphic EQ, a tool that is not only made to accomplish what you're trying to do but it can also be adjusted to optimize the tone of different recordings. For someone who is on a budget, I think that's a better choice. I'm not saying that the new production Mullard won't be an improvement on the tube that comes with the amp - it probably will be better - since even the most diehard fans of Chinese amps seem to agree that the tubes that come in them suck. I'm just saying that it or any other tube is not an effective, predictable and adjustable method of adjusting tone.

With an entry level Chinese tube amplifier, a graphic equalizer would help without burning money on NOS tubes that may or may not give one the tonality they are searching for...which is probably more bass. There are also PC related programs/Apps/phone Apps or whatever for equalization on the line end of things, which might be a better option than a budget graphic equalizer.
 
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