I consider designing according to the tubes chosen. I'd like to start with those known having lowest noise and microphonics. Of course, the gain factor is also a consideration, for higher gain may compensate for lower noise.
So, actually, my question should be about tubes with best noise to gain ratio.
I use ECC83's in my pre amps.
The valve isnt the only source of noise, great care should be taken with routing of wires and power supply configuration. I always use DC heater supplies too.
I noticed with the valve in a none screened case that it picked up radiated emissions quite badly.
A good earthed metal box does the trick.
The valve isnt the only source of noise, great care should be taken with routing of wires and power supply configuration. I always use DC heater supplies too.
I noticed with the valve in a none screened case that it picked up radiated emissions quite badly.
A good earthed metal box does the trick.
The above goes without saying, or should be obvious. Yet, tubes noise, or noise to amplification ratio, should be considered as well.
We bought a few pairs from LANGREX in UK.You may try also their e-bay shop "Yitry".They cost around 12.50 pounds each.
May I add that they are very reliable sellers.Bought a few times from them.Great.
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Unfortunate that you are restricting yourself to dual triodes as there are a whole crop of high transconductance single triodes and triode connected pentodes that are a great deal quieter, and offer as good or better linearity.
Examples: 5842/417A, D3A, C3G/C3M, 6688, 7788, and so on... These devices all have transconductances an order of magnitude or more greater than an ECC83, an rp 3 - 5% of the typical ECC83, and equivalent internal noise resistances in most cases of less than 100 ohms. Passive components and the cartridge become the dominant noise sources in the system, and in some cases the tubes in question are not very expensive. There are a number of interesting Russian types as well, you'll need to do a bit of research to identify them as I don't remember the type numbers off the top of my head.
For line stage duty the 5687 (a dual triode) is a pretty good choice as well, and may be used in the later stages of a phono pre-amp as well, but mu is relatively low.
Examples: 5842/417A, D3A, C3G/C3M, 6688, 7788, and so on... These devices all have transconductances an order of magnitude or more greater than an ECC83, an rp 3 - 5% of the typical ECC83, and equivalent internal noise resistances in most cases of less than 100 ohms. Passive components and the cartridge become the dominant noise sources in the system, and in some cases the tubes in question are not very expensive. There are a number of interesting Russian types as well, you'll need to do a bit of research to identify them as I don't remember the type numbers off the top of my head.
For line stage duty the 5687 (a dual triode) is a pretty good choice as well, and may be used in the later stages of a phono pre-amp as well, but mu is relatively low.
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Hi Joshua,
Types designed specifically for low noise applications will typical list their equivalent noise resistance - the lower the better.. The best performing devices have equivalent noise resistances of a couple of hundred ohms or less. To get an idea of their noise in nvrtHz use the same equation you would for a resistor.
The D3A is my current choice for a quiet tube. (Available on eBay for < $15 typically, and it will probably outlast you in service..
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The D3A is my current choice for a quiet tube. (Available on eBay for < $15 typically, and it will probably outlast you in service..
Considering my age, that's a fairly safe bet …
Most of the tubes you mentioned are pentodes. Aren't pentodes less linear than triodes?
Again, they were recommending pentodes strapped as triodes. When triode-strapped, pentodes behave like triodes.
Pardon me for raining on your parade, but if you don't know that yet, are you really capable of making designs that exploit these tubes' best chracteristics? Maybe you should be looking to published designs first?
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