AIYIMA T20 – Audiophile-Grade Hi-Fi Tube Preamp in Development

[Schlippwhip68]

There could be a difference in electrical requirements from the Denon to allow the T20 to trigger it which the T20 may not provide as the complementary trigger system as it is not always a universal standard as far as I know.

The T20 will be fine and able to trigger another component if that components needs matches what the T20 may provide. From what I have found so far is that although it is a 12v trigger there is something else (?) that needs to match as well which may be the issue with the Denon. The T20 should be fine.

 

[Olmeda]

I wanted to share my experience with the T20 and different power amps regarding background hiss, because after some testing I realized the issue was not caused by the T20 itself, but by gain staging.

My setup uses KEF LS50 Meta, the AIYIMA T20 as the preamp, and the AIYIMA A20 initially in Bypass mode with RCA input. With this configuration, the hiss was clearly audible on the LS50 Meta from about one meter away. At first I assumed the T20 was noisy, but the actual reason was different.

When the A20 is in Bypass mode, the internal volume is fixed at 100%. That means any noise coming from the preamp (in this case the T20, which inherently has a bit of tube noise) gets amplified to the maximum possible level.

To confirm this, I tested with a Fosi V3 as well. The result was identical: zero hiss at normal volume levels, but noticeable hiss as soon as the V3 volume was set to maximum. Once the volume was reduced by roughly 30%, the hiss disappeared completely.

This made the cause very clear: any power amplifier, when operated at full gain, will amplify any upstream noise — even very small amounts. It is not a fault or a defect; it is simply the expected behavior at maximum gain.

After disabling bypass mode on the A20 and using its volume control normally, the hiss disappeared almost entirely. With the A20 set around 60% of the volume range, there is no audible hiss at all, even with the ear close to the LS50 Meta tweeter.

In summary, the hiss was not caused by a problem in the T20, but by running the power amplifier at maximum gain. The configuration that solved it completely was:

– A20 not in bypass mode
– A20 volume around 60%
– Volume control handled by the T20

This fully eliminated the hiss in my system. Hopefully this helps anyone using the LS50 Meta and encountering similar behavior.

 

[SMen]

I wanted to share my experience with the T20 and different power amps regarding background hiss, because after some testing I realized the issue was not caused by the T20 itself, but by gain staging.

My setup uses KEF LS50 Meta, the AIYIMA T20 as the preamp, and the AIYIMA A20 initially in Bypass mode with RCA input. With this configuration, the hiss was clearly audible on the LS50 Meta from about one meter away. At first I assumed the T20 was noisy, but the actual reason was different.

When the A20 is in Bypass mode, the internal volume is fixed at 100%. That means any noise coming from the preamp (in this case the T20, which inherently has a bit of tube noise) gets amplified to the maximum possible level.

To confirm this, I tested with a Fosi V3 as well. The result was identical: zero hiss at normal volume levels, but noticeable hiss as soon as the V3 volume was set to maximum. Once the volume was reduced by roughly 30%, the hiss disappeared completely.

This made the cause very clear: any power amplifier, when operated at full gain, will amplify any upstream noise — even very small amounts. It is not a fault or a defect; it is simply the expected behavior at maximum gain.

After disabling bypass mode on the A20 and using its volume control normally, the hiss disappeared almost entirely. With the A20 set around 60% of the volume range, there is no audible hiss at all, even with the ear close to the LS50 Meta tweeter.

In summary, the hiss was not caused by a problem in the T20, but by running the power amplifier at maximum gain. The configuration that solved it completely was:

– A20 not in bypass mode
– A20 volume around 60%
– Volume control handled by the T20

This fully eliminated the hiss in my system. Hopefully this helps anyone using the LS50 Meta and encountering similar behavior.

OK - I am slightly confused.

A20 should be able to operate in bypass mode with no hiss so long as the T20 is not at full gain surely?

If you are setting the A20 to 60% AND handling volume control with the T20, then there is a problem.

Post edit: I'm using a 3e Audio A5 or A7 - full volume, controlling volume with the T20 no problem (or my hearing is awry ... just asked my 8 and 12 year old if they can hear hiss ... no hiss from two feet from the tweeter though my daughter says she can hear some from 2 inches).

 

[Olmeda]

OK - I am slightly confused.

A20 should be able to operate in bypass mode with no hiss so long as the T20 is not at full gain surely?

If you are setting the A20 to 60% AND handling volume control with the T20, then there is a problem.

In bypass mode the A20 sets its internal gain to the maximum, exactly like running a power amp with no attenuator. That means the A20 will amplify whatever noise floor is present at its input by the maximum amount. The T20, being a tube-based preamp, has a slightly higher inherent noise floor than a purely solid-state unit, even if it measures reasonably well.

So the key point is: even if the T20 is not at full volume, the A20 in bypass is still running at full gain, so it is amplifying the T20's intrinsic tube hiss to its maximum level. This is why hiss became audible with bypass enabled.

When bypass is disabled, the A20’s internal volume control acts as a passive attenuator before the gain stage. Setting it somewhere around 60% simply reduces system gain so that the T20's noise floor is not amplified excessively. The T20 then becomes the main volume control.

 

[SMen]

In bypass mode the A20 sets its internal gain to the maximum, exactly like running a power amp with no attenuator. That means the A20 will amplify whatever noise floor is present at its input by the maximum amount. The T20, being a tube-based preamp, has a slightly higher inherent noise floor than a purely solid-state unit, even if it measures reasonably well.

So the key point is: even if the T20 is not at full volume, the A20 in bypass is still running at full gain, so it is amplifying the T20's intrinsic tube hiss to its maximum level. This is why hiss became audible with bypass enabled.

When bypass is disabled, the A20’s internal volume control acts as a passive attenuator before the gain stage. Setting it somewhere around 60% simply reduces system gain so that the T20's noise floor is not amplified excessively. The T20 then becomes the main volume control.

OK - so replicating this with the 3e audio A7 (just now) does not result in hiss. 3e full volume, Aiyima T20 controlling volume.

Post edit: running in balanced mode.

 

[Olmeda]

OK - so replicating this with the 3e audio A7 (just now) does not result in hiss. 3e full volume, Aiyima T20 controlling volume.

Post edit: running in balanced mode.

Different power amplifiers have very different input sensitivities, internal gain structures, and noise floors.
So two amps at “full volume” do not behave the same when driven by the T20.

Here’s the key technical point:

The A20 has significantly higher gain than the 3e Audio A7.
That means that, at 100% volume / bypass, the A20 amplifies the T20’s tube noise floor much more aggressively than the A7 does. Even a 6–12 dB difference in gain is enough to change audible hiss from “clearly noticeable” to “completely inaudible.”

I still need to test the T20 in balanced mode, although my current RCA connection is a good-quality one.

I just tested it in balanced mode and the result is the same as with the RCA cable. The hiss is slightly lower, but it’s still there.

 

[SMen]

Different power amplifiers have very different input sensitivities, internal gain structures, and noise floors.
So two amps at “full volume” do not behave the same when driven by the T20.

Here’s the key technical point:

The A20 has significantly higher gain than the 3e Audio A7.
That means that, at 100% volume / bypass, the A20 amplifies the T20’s tube noise floor much more aggressively than the A7 does. Even a 6–12 dB difference in gain is enough to change audible hiss from “clearly noticeable” to “completely inaudible.”

I still need to test the T20 in balanced mode, although my current RCA connection is a good-quality one.

I just tested it in balanced mode and the result is the same as with the RCA cable. The hiss is slightly lower, but it’s still there.

OK I understand. I think Aiyima should have set the A20 gain a bit lower - especially for use with their T20!
I don't mind a bit of hiss. Takes me back to preferring tape recordings without Dolby noise reduction!

 

[Olmeda]

OK I understand. I think Aiyima should have set the A20 gain a bit lower - especially for use with their T20!
I don't mind a bit of hiss. Takes me back to preferring tape recordings without Dolby noise reduction!

Yes, exactly. In my case the hiss wasn't just a faint noise — it was clearly audible from about one meter away, which felt excessive. It’s possible that different tubes with a lower noise floor could reduce it somewhat, and even swapping the tubes left-to-right already helped a little in my unit. But the main factor really seems to be the power amplifier running at maximum gain.

Once I disabled bypass on the A20 and set its volume to about halfway, the hiss disappeared completely. With that configuration the system is silent at the speakers, even with my ear close to the LS50 Meta tweeter.

So in my setup, managing gain on the A20 solved it entirely

I should also add that I use this setup as a secondary system for background listening, not for playing at very high volumes.

 

[OldManMatt]

One would think that if Aiyima is selling these 2 components as "matching" then they would have done a better job matching the gain between them.