I seen that EH has a 7025 tube out that is supposed to be quieter than their 12AX7.
Anyone here tried them?
I am thinking of giving them a try in my phono stage.
Anyone here tried them?
I am thinking of giving them a try in my phono stage.
The difference between a 12AX7 and a 7025 lies in the construction of the heater. The 'X7 heater is folded, while the 7025 heater is spiral wound and hum bucking. The stock of either variant needs culling out of "phono grade" specimens. Where a 7025 or equivalent, like the Sovtek 12AX7LPS, always provides a benefit is when the tube is AC heated.
RCA's original passive EQ phono preamp specifies 7025s, as AC heating was allowed for. Back when the design came out, a DC heater supply was truly a royal PITA. It is possible to obtain acceptable residual hum levels in an AC heated phono section, but it is LOTS of work.
RCA's original passive EQ phono preamp specifies 7025s, as AC heating was allowed for. Back when the design came out, a DC heater supply was truly a royal PITA. It is possible to obtain acceptable residual hum levels in an AC heated phono section, but it is LOTS of work.
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If the only difference is the heater it should not be any different (for me) than the EH12AX7. I built my phono stage with dc heater supply. It is basically a Hagerman cornet 2 with some changes.
Exactly! Buy phono grade tubes from a reliable dealer. A good dealer culls the tubes with lowest noise out, to be employed in phono service. My go to guy is Jim McShane. However, he's not the only game in town.
The EH 7025 are definitely quieter than the EH 12AX7 tubes. Plus, I had a better success rate with these 7025 tubes having better triode-triode DC balance as compared to the 12AX7 tubes, even when matched. While some claim these 7025 have less gain, that is not my experience as they measure relatively the same as the 12AX7 on my VTV tube characterizer.
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cyto,
You are in the US.
Go to Eurotubes.com and order the JJ ECC803, ECC83, various versions of your choice.
I personally do not purchase the gold pin versions, but they have that too.
They even have a new Frame Grid version.
They have newer stock, not tubes that sat on the shelf for years.
JJ in Slovakia has greatly improved their tubes over the years, they are first rate now.
These preamp tubes all use spiral filaments.
They all are re-tested for noise, and other characteristics too.
This is very important.
I know the people there, and a couple of designers who made the various testers (some at Eurotubes, and also one of my former co-worker when we worked at a major test and measurement company).
They also have the JJ 5751, a lower u version of the 12AX7/ECC83. It might not have exactly the same plate resistance, etc. to drive your phono RIAA equalizer filter.
I have exclusively been using JJ tubes from Eurotubes.com
I am convinced.
For those of you who are not in the US, they ship to a number of countries.
You are in the US.
Go to Eurotubes.com and order the JJ ECC803, ECC83, various versions of your choice.
I personally do not purchase the gold pin versions, but they have that too.
They even have a new Frame Grid version.
They have newer stock, not tubes that sat on the shelf for years.
JJ in Slovakia has greatly improved their tubes over the years, they are first rate now.
These preamp tubes all use spiral filaments.
They all are re-tested for noise, and other characteristics too.
This is very important.
I know the people there, and a couple of designers who made the various testers (some at Eurotubes, and also one of my former co-worker when we worked at a major test and measurement company).
They also have the JJ 5751, a lower u version of the 12AX7/ECC83. It might not have exactly the same plate resistance, etc. to drive your phono RIAA equalizer filter.
I have exclusively been using JJ tubes from Eurotubes.com
I am convinced.
For those of you who are not in the US, they ship to a number of countries.
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So if I’m following this correctly, a 7025 is a 12AX7 with a spiral wound filament. Which means the Sovtek 12AX7LPS (LPS = Long Plate, Spiral wound filament) is a 7025, or does a 7025 always have a spiral wound filament and a short plate?
One way to say it is that type 7025 is a designation that RCA gave to their own special version of type 12AX7. Today it can mean anything the builder wants it to mean. In American manufacturers parlance, four numerical digit valves were often the "industrial" and "special series" versions of commercial types.
A maybe surprising note: the US military often preferred selected valves from large volume assembly lines over specialized valves from shorter assembly lines. Apparently, reliability was better for typical static equipment.
All good fortune,
Chris
A maybe surprising note: the US military often preferred selected valves from large volume assembly lines over specialized valves from shorter assembly lines. Apparently, reliability was better for typical static equipment.
All good fortune,
Chris
The JJ versions of the ECC803 long plate, ECC82 short plate, and 5751 all have spiral filaments.
And most of the other JJ "preamp" tubes have spiral filaments too.
A few of the JJ "power" tubes have spiral filaments (My JJ 7591 tubes have spiral filaments)
I think the JJ 6V6 has spiral filaments.
Eurotubes.com puts the JJ tubes into two categories: "preamp" and "power" tubes.
Check out their site; they do ship to some overseas locations.
Remember, Eurotubes vigorously re-tests the JJ tubes when they receive them.
I am able to drive over to Eurotubes and pick up what I want there.
Your Mileage May Vary (I never used that quote that way before).
And most of the other JJ "preamp" tubes have spiral filaments too.
A few of the JJ "power" tubes have spiral filaments (My JJ 7591 tubes have spiral filaments)
I think the JJ 6V6 has spiral filaments.
Eurotubes.com puts the JJ tubes into two categories: "preamp" and "power" tubes.
Check out their site; they do ship to some overseas locations.
Remember, Eurotubes vigorously re-tests the JJ tubes when they receive them.
I am able to drive over to Eurotubes and pick up what I want there.
Your Mileage May Vary (I never used that quote that way before).
I’m asking because I am going to build a phono preamp (EAR834 clone) for my wife and it was recommended by prior builders that a 7025 tube be used specifically in the place of the “nominal” 12AX7. I have been using tubes since 2007 and have been happy with the Sovtek 12AX7LPS. Just not sure whether the LPS is comparable to a 7025 in terms of noise and microphony.
The first tube is most critical for noise and hum. Use JJ E83CC ( a framegrid tube build identical to Telefunken and later TESLA )
They do but are currently out of that tube with the current matched triode option. I ordered some ECC99 tubes from them in the past and am fine waiting for them to get restocked.
