I would place greater emphasis on the output impedance, rather than the input sensitivity. Aikido has a fairly low <500 ohm output impedance, so it should have no problems driving the Amity in its various versions. Whether you get enough volume at the speakers will of course depend on the Aikido output voltage, do you know what that is?
I'm not sure either, technically, but I can tell you that an Aikido 6SN7 preamp has a lot of output. My Williamson-style amplifiers like at least 2+ healthy volts to sound good, but I use individual left-right volume controls and a master volume control to knock down the output of my Tubes4HiFi version of the Aikido.
I'll put it on a 'scope this evening and tell you how much undistorted voltage I get out of it.
Since everyone else is sleeping in this morning, I went ahead and checked it. With 1 volt input, I get over 13 volts peak-to-peak at full volume, almost 7 volts RMS. I don't know that much about measuring or calculating this sort of thing (I mostly measure my tube amps) but that would seem like plenty, that you could drive the Amity to full output without a problem.
Hope this helps!
Hope this helps!
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Unless a 6SN7 preamp has a cathode follower output with very low impedance, it will not properly drive the input transformer of the Amity.
Just my opinion, but the note on the Amity schematic says the preamp needs 2k or less output impedance, or you have to use a transformer volume control (and to make the impedance low, that transformer setup will have a voltage loss).
The plate of a 6SN7 is about 7.7k Ohms, far too high of an impedance to drive the Amity.
Just my opinion, but the note on the Amity schematic says the preamp needs 2k or less output impedance, or you have to use a transformer volume control (and to make the impedance low, that transformer setup will have a voltage loss).
The plate of a 6SN7 is about 7.7k Ohms, far too high of an impedance to drive the Amity.
According to John Broskie, the Aikido circuit acts like a cathode follower at the output.
https://tubecad.com/2006/06/blog0071.htm
The Aikido circuit employs a half-mu ('totem pole') input stage driving a cathode follower with active load. So yes, it has a cathode follower output stage, so the output impedance will be nice and low.
13V peak-to-peak is 4.6V RMS.
"1V" of what? Average? RMS? Peak? Peak-to-peak?
I would expect a 6SN7 used this way to give gain near 9. But without correct measurement units I can't make sense of it.
I do think it will work. Will it make ALL the power you paid for? Can't tell.
As I said, these are not calculations I'm familiar with. I generally measure my amplifier projects for frequency response, stability, etc. I used the Picoscope's automatic measurements with 1 volt input from the built-in signal generator. It was a very quick test, I thought it might be helpful to the OP.
The Aikido octal manual has gain calculations at the end. So do the other versions for various types of tubes.
https://www.audiofaidate.org/uploaded/lord_orione/Octal_Aikido_PCB.pdf
OK. Suppose:
The preamp has a low enough output impedance.
The preamp has a high enough output voltage.
The third requirement is that it has enough current to drive the voltage into the low impedance Amity input.
Lots of preamps have low output impedance.
Lots of preamps have lots of volts out into a high impedance load.
Not all preamps can swing lots of volts into a low impedance power amplifier input, because they do not have enough current, or can not do so without distorting.
Your Mileage May Vary.
Try it and see.
The preamp has a low enough output impedance.
The preamp has a high enough output voltage.
The third requirement is that it has enough current to drive the voltage into the low impedance Amity input.
Lots of preamps have low output impedance.
Lots of preamps have lots of volts out into a high impedance load.
Not all preamps can swing lots of volts into a low impedance power amplifier input, because they do not have enough current, or can not do so without distorting.
Your Mileage May Vary.
Try it and see.
Having built the Raven, Amity, and Karna in a few different versions, I can with confidence state the low Aikido output impedance with have no issues driving the input transformer, whether Lundahl, Onetics, Tribute, Jensen, or Cinemag (tried all those, too).
Output voltage is higher than you need, so worst case your volume control might be set fairly low.
My left channel Karna variant attached. Outboard power supply not shown.
The Amity is IMO not the ideal choice, since it is hindered by the interstage transformer. The input transformer is an easy load - by contrast, a 7119 or SN7 driving an IT will be marginal at best. This has been discussed in other threads, with some data to back it up. A fine amp to be sure, just can be improved upon. Point is, don't sweat the Aikido's ability in the application, sweat the IT.
Output voltage is higher than you need, so worst case your volume control might be set fairly low.
My left channel Karna variant attached. Outboard power supply not shown.
The Amity is IMO not the ideal choice, since it is hindered by the interstage transformer. The input transformer is an easy load - by contrast, a 7119 or SN7 driving an IT will be marginal at best. This has been discussed in other threads, with some data to back it up. A fine amp to be sure, just can be improved upon. Point is, don't sweat the Aikido's ability in the application, sweat the IT.
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Hi!
Thanks for the valuable info!! The Amity I listened has ECC99 I guess.
Therefore, the 7119 is ideal for Amity. I guess someone out there should have an interstage that is more efficient than the Lundahl, isn't it??
Thanks 🙏🙏
A bifilar Monolith IT would be my recommendation, and the ECC99 should be okay with it. My biggest lesson was 'don't do IT unless bifilar'. A painful learning process.
Given your high output preamp, you may want to richen up the bias conditions of the ECC99 and increase B+; your preamp is driving a lot at the grids.
My conclusions in the many iterations was that a three stage amp was optimal, and never could successfully bridge the gap between sufficient output and low distortion with a two stage - push one stage too far and distortion results. You may have a unique situation in that your preamp essentially represents one of those stages (since its voltage output is so high).
Looking forward to hearing your results - I really like the simplicity yet brute force of these Lynn designs. There is a subjective troll in the back of my mind that says a 'noval anything' will be challenged to drive a 300B, but hoping I am wrong.
Heck, my triode-connected 46 driver just barely stays ahead of the 300B output stage. Interestingly, plate resistance is identical to the ECC99, but I have nearly twice your B+ (more headroom) and twice your plate current (slew into capacitive grid). This might be the overall balancing act you will face with the 9-pin - you can only get so much watt dissipation out of the driver tube, yet on paper you will always be wishing for more volts/amps on that driver tube.
Given your high output preamp, you may want to richen up the bias conditions of the ECC99 and increase B+; your preamp is driving a lot at the grids.
My conclusions in the many iterations was that a three stage amp was optimal, and never could successfully bridge the gap between sufficient output and low distortion with a two stage - push one stage too far and distortion results. You may have a unique situation in that your preamp essentially represents one of those stages (since its voltage output is so high).
Looking forward to hearing your results - I really like the simplicity yet brute force of these Lynn designs. There is a subjective troll in the back of my mind that says a 'noval anything' will be challenged to drive a 300B, but hoping I am wrong.
Heck, my triode-connected 46 driver just barely stays ahead of the 300B output stage. Interestingly, plate resistance is identical to the ECC99, but I have nearly twice your B+ (more headroom) and twice your plate current (slew into capacitive grid). This might be the overall balancing act you will face with the 9-pin - you can only get so much watt dissipation out of the driver tube, yet on paper you will always be wishing for more volts/amps on that driver tube.
Assume Monolith bifilar IT is in used, would it be necessary to raise the B+ voltage on the ECC99?
JB has just confirmed that the Aikido has more than enough juice to drive the Amity.
Referring to Monolith magnetic website,they offer nano core iron. Any comments?
JB has just confirmed that the Aikido has more than enough juice to drive the Amity.
Referring to Monolith magnetic website,they offer nano core iron. Any comments?
The decision regarding first stage B+ is unaffected by bifilar vs layered windings IT. Both the Lundahl and the Monolith are used 1:1, so fundamentally you can treat them the same with regards to how to run your tubes.
My reason for considering an increased bias and/or B+ is that your preamp is capable of driving something around 7V, which will drive positive grid at the ECC99. Not recommended through an input transformer. It's a wonky bias condition you are dealing with.
If you are not familiar with how to do the math on datasheet-to-circuit values, then just keep things as is for now and see how you like it. You will distort the amp at less than 100% preamp output, but so what for the time being.
With a bifilar winding, I am not convinced going nanocrystalline is all that critical. I just went standard, and am more than happy. Personal preference.
My reason for considering an increased bias and/or B+ is that your preamp is capable of driving something around 7V, which will drive positive grid at the ECC99. Not recommended through an input transformer. It's a wonky bias condition you are dealing with.
If you are not familiar with how to do the math on datasheet-to-circuit values, then just keep things as is for now and see how you like it. You will distort the amp at less than 100% preamp output, but so what for the time being.
With a bifilar winding, I am not convinced going nanocrystalline is all that critical. I just went standard, and am more than happy. Personal preference.
If the Aikido capable 10x amplifcation, 2v out with CD should be able to deliver 20v. It is almost 3 times what Amity really needs?
Also, any comments on this output transformer for Amity??
https://sklep.toroidy.pl/en_US/p/TT...6,6kOhm-2xEL34-2x6L6-Push-pull-or-similar/562
The Tribute I tried was specific to the input transformer, whereas the Monolith I used was the interstage. Thus, I cannot comment directly to compare them. They are stellar performers in those respective locations.