[pravous]

L0rdGwyn makes quiet tube amps. Even his OTL amp doesn't hum.

With certain tubes I will get hum on the Airmid. In pretty much every case those tubes will hum on my BHC which leads me to believe that it has more to do with the tube itself rather than the amp or OTL topology. I have not had problems with power tubes (other than being obviously dead) but I have had some 6j5, 6c5, 76 and 37 that never stopped humming despite hours of burn in. One random thing I have noticed about many of my noisy tubes is that despite testing on spec for gm, current and resistance, the filament current draw will bounce around and never settle down.

 

[Marutks]

With certain tubes I will get hum on the Airmid.

MonsterZero said his Airmid is dead quiet. And Aegis too.

 

[pravous]

Monsterzero has a higher end chain upstream of his Airmid. Could be my less than refined dac/streamer that is causing some of my noise issues. Doesn’t change the fact that it is very tube specific. Certain rolls are dead quiet with the volume pots pegged, others have a background hum when no music is playing. I am also more of the Bcowen school of tube rolling. If it fits it sits

 

[Marutks]

Monsterzero has a higher end chain upstream of his Airmid.

He is using DACs with tubes in them (Lampizator).

 

[xtr4]

He is using DACs with tubes in them (Lampizator).

The tube noises cancel each other out lol

 

[JazzVinyl]

 

[Xcalibur255]

Yup that about sums the hobby up. Although I have to point out that the "logic bypass" switch appears to be in the wrong position at present.

 

[raindownthunda]

Posting some measurements @A2029 shared for Blue Halo+ in various modes / tube configurations for those interested in these sorts of things:

BH Mode: 6N6P driver (no power tubes) @ 0.06 Vrms:

BH Mode: 6N6P driver (no power tubes) @ 0.35 Vrms

BH Mode: EL34 driver (no power tubes) @ 0.06 Vrms

BH Mode: EL34 driver (no power tubes) @ 0.35 Vrms

BH+ / RES mode: EL34 driver + 4 power tubes @ 0.06 Vrms:

BH+ / RES mode: EL34 driver + 4 power tubes @ 0.35 Vrms:

BH+ / CCS mode: EL34 driver + 4 power tubes @ 0.06 Vrms:

BH+ / CCS mode: EL34 driver + 4 power tubes @ 0.35 Vrms

 

[mordy]

Can you just briefly summarize what the charts show because I do not understand how to read or interpret the data?

 

[triod750]

Peak performance?

 

[raindownthunda]

Can you just briefly summarize what the charts show because I do not understand how to read or interpret the data?

• BH mode with quiet tubes (6N6P) has 1/4 of the distortion as running bigger tubes (EL34).
• BH+ mode has twice as much 2nd harmonic distortion as BH mode.

I'll let @A2029 chime in if there's anything else to add

Back to the subjective...

I've been trying Resistor mode (No CCS) with BH+ and it's a totally different amp. Much more relaxed listen with emphasized thumpy bass. This sounds a lot more "tubey" and lush while still having a solid technical foundation. Really enjoyable listen with slower songs. Vocals and acoustic guitar sound especially magical, sweet and creamy. Not so good with complex / faster tracks i.e. metal as too much detail is lost. I can see myself listening to this for a more calming/relaxing session where I'm trying to shut off the analytical brain at the end of the day. Immediately reminded me more of the Bottlehead Crack w/o Speedball, but that's not really a fair comparison as this is on a completely different level. If I had to pick only one, I definitely prefer CCS for everyday listening.

 

[leftside]

• BH mode with quiet tubes (6N6P) has 1/4 of the distortion as running bigger tubes (EL34).
• BH+ mode has twice as much 2nd harmonic distortion as BH mode.

I'll let @A2029 chime in if there's anything else to add

Back to the subjective...

I've been trying Resistor mode (No CCS) with BH+ and it's a totally different amp. Much more relaxed listen with emphasized thumpy bass. This sounds a lot more "tubey" and lush while still having a solid technical foundation. Really enjoyable listen with slower songs. Vocals and acoustic guitar sound especially magical, sweet and creamy. Not so good with complex / faster tracks i.e. metal as too much detail is lost. I can see myself listening to this for a more calming/relaxing session where I'm trying to shut off the analytical brain at the end of the day. Immediately reminded me more of the Bottlehead Crack w/o Speedball, but that's not really a fair comparison as this is on a completely different level. If I had to pick only one, I definitely prefer CCS for everyday listening.

Looks like you're running some early 50's Mullards up front there.

 

[A2029]

Posting some measurements @A2029 shared for Blue Halo+ in various modes / tube configurations for those interested in these sorts of things:

BH Mode: 6N6P driver (no power tubes) @ 0.06 Vrms:

BH Mode: 6N6P driver (no power tubes) @ 0.35 Vrms

BH Mode: EL34 driver (no power tubes) @ 0.06 Vrms

BH Mode: EL34 driver (no power tubes) @ 0.35 Vrms

BH+ / RES mode: EL34 driver + 4 power tubes @ 0.06 Vrms:

BH+ / RES mode: EL34 driver + 4 power tubes @ 0.35 Vrms:

BH+ / CCS mode: EL34 driver + 4 power tubes @ 0.06 Vrms:

BH+ / CCS mode: EL34 driver + 4 power tubes @ 0.35 Vrms

Can you just briefly summarize what the charts show because I do not understand how to read or interpret the data?

• BH mode with quiet tubes (6N6P) has 1/4 of the distortion as running bigger tubes (EL34).
• BH+ mode has twice as much 2nd harmonic distortion as BH mode.

I'll let @A2029 chime in if there's anything else to add

When you look at the charts, the cursor is pointing to the peak of the frequency that is being tested/measured. In this case it was a 1000Hz test tone run at either 0.06V or 0.35V; voltages that correspond to medium listening volume and loud listening volumes into a pair of HD650 headphones. The 1000Hz test tone is numbered as "1", and each of the harmonics has the number listed ("2" for 2nd harmonic, "3" for 3rd harmonic, etc.). On the top left of the graph is a legend showing the distortion from each of the harmonics of the 1000Hz test tone.

Using BH mode alone, I've seen 2nd distortion as low as 0.003% for some tubes at 0.06V - pretty dang low for a tube amp. When you start using power tubes, it usually has a multiplicative effect on the distortion out from the amp, where the distortion will approximately double (BH+ mode with CCS bias). Depending on the tube combination, using power tubes with RES bias on the BH+ can further increase the distortion out by up to 2-10X. In all cases, the distortion profile follows the typical profile for tube amps; 2nd harmonic highest, 3rd less than 2nd, 4th less than 3rd, etc.

 

[LobalWarming]

Monotonicity FTW!

 

[mordy]

• BH mode with quiet tubes (6N6P) has 1/4 of the distortion as running bigger tubes (EL34).
• BH+ mode has twice as much 2nd harmonic distortion as BH mode.

I'll let @A2029 chime in if there's anything else to add

Back to the subjective...

I've been trying Resistor mode (No CCS) with BH+ and it's a totally different amp. Much more relaxed listen with emphasized thumpy bass. This sounds a lot more "tubey" and lush while still having a solid technical foundation. Really enjoyable listen with slower songs. Vocals and acoustic guitar sound especially magical, sweet and creamy. Not so good with complex / faster tracks i.e. metal as too much detail is lost. I can see myself listening to this for a more calming/relaxing session where I'm trying to shut off the analytical brain at the end of the day. Immediately reminded me more of the Bottlehead Crack w/o Speedball, but that's not really a fair comparison as this is on a completely different level. If I had to pick only one, I definitely prefer CCS for everyday listening.

"Back to the subjective"

To me how it sounds is the objective lol.
Do the charts tell you anything about how it sounds? Are there desirable distortion levels or is ultra-low distortion the goal? My guess is that the lower the distortion, the clearer the presentation, but I am not clear on the function of harmonic distortion.