Two threads merged 13:12 UCT Feb 23 2022I am considering purchasing a Dared MP-5BT on Amazon and the listing noted that the tubes used are 6N1 and 6N2 side by side. Since these tubes are a little hard to obtain currently I was wondering if there are equivalent tubes for both? I was also wondering if the sockets are wired to accept 6N1 equivalents in both or only 6N1 and 6N2 side by side? Thank you!
I saw on some forums where people used the same tubes in both sockets but I wasn't sure if that was for an older model of the MP-5 or something.
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Both the 6N1 and 6N2 have their pin 9 connected to a screen between the two triode sections. That screen should be connected to ground, so I assume that in the Dared MP-5BT pins 9 are connected to ground.
Because of this arrangement, tubes like the ECC81/12AT7, ECC82/12AU7, and ECC83/12AX7 can't be used in the Dared MP-5BT (unless you would use adapters) because in these tube types pin 9 is connected to the centre-tap of the heater.
Tube types with 6.3 V for the heater and with identical pinout as the 6N1 (amplification factor = μ = 33) and the 6N2 (μ = 100) are ECC85/6AQ8 (μ = 57), ECC88/6DJ8/6922 (μ = 33), 6BQ7 (μ = 39), and 6CC41 (μ= 100).
But all this is only about pinout and heater voltage. I don't know the schematic for the Dared MP-5BT so I can't be sure what to expect when replacing the 6N1 and/or 6N2 by the tube types I mentioned.
So if you can find the schematic for the Dared MP-5BT and post it here, forum members can be more specific.
Because of this arrangement, tubes like the ECC81/12AT7, ECC82/12AU7, and ECC83/12AX7 can't be used in the Dared MP-5BT (unless you would use adapters) because in these tube types pin 9 is connected to the centre-tap of the heater.
Tube types with 6.3 V for the heater and with identical pinout as the 6N1 (amplification factor = μ = 33) and the 6N2 (μ = 100) are ECC85/6AQ8 (μ = 57), ECC88/6DJ8/6922 (μ = 33), 6BQ7 (μ = 39), and 6CC41 (μ= 100).
But all this is only about pinout and heater voltage. I don't know the schematic for the Dared MP-5BT so I can't be sure what to expect when replacing the 6N1 and/or 6N2 by the tube types I mentioned.
So if you can find the schematic for the Dared MP-5BT and post it here, forum members can be more specific.
Thank you for the information. Unfortunately I've been looking but haven't been able to find a schematic for this specific amp.
Reading your explanation, is it the case that as long as the voltage of the replacement tube is the same it's not a safety issue to use them? More a sound issue?
I was reading that most side by side tubes are usually the same model so I'm trying to understand placing 6n1 next to 6n2 instead of just two 6n1s. What would happen if I replaced the 6n2 with a 6n1, just sound changes?
Reading your explanation, is it the case that as long as the voltage of the replacement tube is the same it's not a safety issue to use them? More a sound issue?
I was reading that most side by side tubes are usually the same model so I'm trying to understand placing 6n1 next to 6n2 instead of just two 6n1s. What would happen if I replaced the 6n2 with a 6n1, just sound changes?
There could well be a safety issue. If there's dc-coupling between stages going on in the Dared MP-5BT, than just changing tube types without knowing the schematic is a bad idea.
Besides that, the differences between 6N1 and 6N2 are pretty large. In a normal voltage gain stage, the gain of a 6N1 is in the range of 15 to 25 x, while the gain of a 6N2 is in the range of 40 to 75 x. The way the tubes normaly get biased also differs. In a normal voltage gain stage a 6N1 is likely to draw more current than a 6N2, the cathode bias resistor for a 6N1 will likely have a lower value than that of a 6N2. So just dropping in a 6N1 on the spot of a 6N2 (and viceverca) is a bad idea anyway.
Using an ECC88 or a 6BQ7 in place of a 6N1, or using a 6CC41 in place of a 6N2 is more likely to work. But as long as there's no schematic, I can't be sure.
Besides that, the differences between 6N1 and 6N2 are pretty large. In a normal voltage gain stage, the gain of a 6N1 is in the range of 15 to 25 x, while the gain of a 6N2 is in the range of 40 to 75 x. The way the tubes normaly get biased also differs. In a normal voltage gain stage a 6N1 is likely to draw more current than a 6N2, the cathode bias resistor for a 6N1 will likely have a lower value than that of a 6N2. So just dropping in a 6N1 on the spot of a 6N2 (and viceverca) is a bad idea anyway.
Using an ECC88 or a 6BQ7 in place of a 6N1, or using a 6CC41 in place of a 6N2 is more likely to work. But as long as there's no schematic, I can't be sure.
You might try and find another preamp model that uses tubes like 12AX7, 12AU7, 12AT7, 12BH7, 5751, etc.
Most of those tube types have many other to very close to equivalent tubes.
Note: All of the above are individually different in their characteristics: gain (u), transconductance Gm, and plate resistance, rp.
That might give you more kinds of tubes to try for tube rolling.
Normally, you want to use close substitutes for tube rolling.
Otherwise, you should redesign the circuit values to use tubes that do not have the same u, Gm, and rp.
(not to mention the different filament current requirements).
Most of those tube types have many other to very close to equivalent tubes.
Note: All of the above are individually different in their characteristics: gain (u), transconductance Gm, and plate resistance, rp.
That might give you more kinds of tubes to try for tube rolling.
Normally, you want to use close substitutes for tube rolling.
Otherwise, you should redesign the circuit values to use tubes that do not have the same u, Gm, and rp.
(not to mention the different filament current requirements).
Initially I would say no, but before I answered to your question I made a simulation that show that 6N1P actually work very well.
Gain of the circuit is about halved.
My test circuit was: Ra = 100k, Rk = 1k, +Ub = 250 V.
Gain of the circuit is about halved.
My test circuit was: Ra = 100k, Rk = 1k, +Ub = 250 V.
Oh thank you. So besides the volume being a little lower there's no ill effects from using the 6n1 in a 6n2?
Unfortunately not, I tried to find one but none was available. The name of the amp is Dared MP-5BT. Initially I think the older model of the amp did use two 6n1s but the most recent model changed one of the tubes to 6n2.
I've done it with 6SL7 vs 6SN7, and 12AX7 vs 17AU7 or 12AT7.
Try it and see - nothing will blow up.
Try it and see - nothing will blow up.
You can't just swap two (very) different tubes and expect "hifi" without judging and measuring what part values must be modified . That is the noobs way of working with tubes 
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If you can, remove the bottom off of the amp and create your own schematic (and it might have a PCB which makes drawing a schematic more difficult than point to point wiring).
If not . . .
Then . .
Look up the pin-out of the 6N2. Plate pins, cathode pins.
Take an ohmmeter and measure:
Plate to Plate, divide by 2, that is the value of the individual plate load resistors.
Cathode 1 to Cathode 2. If that is 0 Ohms, they connected the cathodes to each other, and are using a single common cathode bias resistor. If they connected the cathodes together, measure from either cathode to ground; that is the common cathode resistor.
If they did not connect the cathodes together, then measure Cathode 1 to ground; Cathode 2 to ground; those are the individual cathode resistors.
Now you have a partial schematic, including the cathode resistor(s), and the plate load resistors. That tells us quite a bit about the circuit.
Perhaps we will have a little better idea of how the circuit will perform when changing from a 6N2 to a 6N1 (6n1P?).
"All tubes are equal, but some tubes are more equal than others"
That is just a restatement of a line in George Orwell's novel "Animal Farm".
Your Mileage May Vary
If not . . .
Then . .
Look up the pin-out of the 6N2. Plate pins, cathode pins.
Take an ohmmeter and measure:
Plate to Plate, divide by 2, that is the value of the individual plate load resistors.
Cathode 1 to Cathode 2. If that is 0 Ohms, they connected the cathodes to each other, and are using a single common cathode bias resistor. If they connected the cathodes together, measure from either cathode to ground; that is the common cathode resistor.
If they did not connect the cathodes together, then measure Cathode 1 to ground; Cathode 2 to ground; those are the individual cathode resistors.
Now you have a partial schematic, including the cathode resistor(s), and the plate load resistors. That tells us quite a bit about the circuit.
Perhaps we will have a little better idea of how the circuit will perform when changing from a 6N2 to a 6N1 (6n1P?).
"All tubes are equal, but some tubes are more equal than others"
That is just a restatement of a line in George Orwell's novel "Animal Farm".
Your Mileage May Vary
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In the thread you started last Saturday, you wrote that you were considering purchasing a Dared MP-5BT on Amazon. This amplifier comes complete with tubes, so with a 6N1, a 6N2 and a 6E2. The price is$ 398.00.
So what is this thread really about? Are you even sure that you can't buy 6N1 and/or 6N2 in packs of one?
So what is this thread really about? Are you even sure that you can't buy 6N1 and/or 6N2 in packs of one?
Thank you. So there's no harm to the amp or the tubes to give it a try?
Thank you. What does that mean practically speaking?
This was meant as a general caution after previous responder wrote you could use a 6N1 in place of a 6N2 with no harm. It means that you need to know what heater current your power transformers can supply. If the transformer was designed for supplying “just enough” current to heat the 6N2 (340 ma), it might overheat if you plug in a 6N1 in that socket that will draw 600 ma. It may not be a problem to try out for a short time, but not good practice in the long run.
Could you explain what you want to accomplish and exactly want you think of doing? It sounds to me if you may have some misunderstanding. This Dared MP-5BT appears to require one 6N1 and one 6N2 plus a tube rectifier to drive a 2x25 watt solid state amplifier section. Each tube envelope has two triodes inside. The amp was likely designed to have a high gain 6N2 tube VA (voltage amplifier) followed by a 6N1 phase splitter. What do you want to switch and why? Both tube types are very common and will likely remain easily obtainable, despite the current supply situation.
Bottom line: I agree with a responder above that wrote: ‘You can't just swap two (very) different tubes and expect "hifi"’
Could you explain what you want to accomplish and exactly want you think of doing? It sounds to me if you may have some misunderstanding. This Dared MP-5BT appears to require one 6N1 and one 6N2 plus a tube rectifier to drive a 2x25 watt solid state amplifier section. Each tube envelope has two triodes inside. The amp was likely designed to have a high gain 6N2 tube VA (voltage amplifier) followed by a 6N1 phase splitter. What do you want to switch and why? Both tube types are very common and will likely remain easily obtainable, despite the current supply situation.
Bottom line: I agree with a responder above that wrote: ‘You can't just swap two (very) different tubes and expect "hifi"’
I personally haven't seen such a crap design that an extra 2 Watts of draw would damage the heater supply (that doesn't mean they don't exist though), and going by #8, it will work well if the typical 250V B+ voltage and 100k/1k resistors are in the circuit.
The only thing this will accomplish of course is lower gain.
The only thing this will accomplish of course is lower gain.