[L0rdGwyn]

All this amp talk makes the wait so hard until @A2029 finally start working on MY amp!!!
Just couple more parts, and couple more people ahead of me in the queue...........

Good things come to those who wait!

 

[Zachik]

Good things come to those who wait!

GREAT things come to those who wait for a long time!

 

[triod750]

GREAT things come to those who wait for a long time!

So you are hoping for a longer wait then? That's great!

 

[L0rdGwyn]

One cool thing about this amp for tube design nerds - the amp is not designed necessarily to run in class A2, but given the low output impedance of the input stage as well as the interstage transformers, it can make excursions into A2 for additional power output.

Quick review - most single-ended class A tube amplifiers run strictly in class A1 where the grid is biased negatively and remains negative throughout the AC voltage swing. Once that AC wave swings the grid close to 0V, the grid's impedance will rapidly drop and it will begin to draw grid current. Most designs cannot supply this current to drive the grid positive, so the 0V grid line represents a clipping boundary in most single-ended class A designs.

If the design CAN supply that grid current however, the AC wave can swing the grid positive beyond 0V for additional power output. My 801A amplifier is designed to run in class A2 nearly 100% of the time as the grid current is supplied by a cathode follower. In this 45 amplifier, grid current is supplied by the transformer-coupled input stage.

The 45 is typically a 1.5 to 1.75W tube running in class A1.

But here is a 2W sine wave into a 300ohm dummy driving it into class A2 in this design.



And the voltage swing on the grid, it is being driven positive 26V!!!



Obviously these are very distorted waveforms and this is not a kind thing to do to your 45 grids for a prolonged period of time with a signal generator. And, in reality, 2W into a 300ohm headphone is truly a deafening volume (would be roughly 130dB with the ZMF Auteur). So maybe just academic, but if a very power hungry headphone is being used in this amp, the 45 can swing all the way to 0V and slightly beyond without a problem if necessary.

 

[triod750]

"What is he building in there"?

Tom Waits

 

[Zachik]

So you are hoping for a longer wait then? That's great!

Not a matter of hoping, but already is...
Between REALLY long lead-times to everything (especially those Sowter OPTs), and Mischa being a busy guy (with previous commitments) - it just takes time!
My gut is telling me this coming winter break - either I will be busy enjoying the new amp, or Mischa will be busy finishing it up... hopefully, the former

 

[leftside]

GREAT things come to those who wait for a long time!

Agreed.

I wouldn't recommend a custom amp as a first amp - the wait would be too long. You definitely already need a decent amp and something to listen to while you wait. And then patience Yes parts - especially transformers - are also an issue right now.

 

[L0rdGwyn]

Save for a few minor component changes, this 45 amp is done, time to design the box. I have a draft underway thankfully. Very excited people will get to hear this at future CanJam events!

Before I take down the prototype, I'll try a cap-coupled version with active load on the driver tubes for future reference. The interstage transformers in this amp are very high quality, so very expensive.

My DAC chassis is supposed to arrive Friday, maybe if I'm lucky it will get here tomorrow, so looks like the DIY party is going to keep on rolling. Why travel when you're on PTO when you can build tube gear in your basement like a hermit?

 

[whirlwind]

Save for a few minor component changes, this 45 amp is done, time to design the box. I have a draft underway thankfully. Very excited people will get to hear this at future CanJam events!

Before I take down the prototype, I'll try a cap-coupled version with active load on the driver tubes for future reference. The interstage transformers in this amp are very high quality, so very expensive.

Look forward to your impressions of the cap-coupled version.

 

[L0rdGwyn]

Look forward to your impressions of the cap-coupled version.

I was going to try it out today, but I think I will just keep listening I need one of those fancy Herman Miller chairs at my workbench, not the most comfortable place to listen lol.

Speaking of listening...

I haven't talked a whole lot about my Audial S5 DAC. I was told by the designer that it required some burn in. At the time I received it I was also building my PCM56 DAC prototype, so it was a whole lot of DAC to handle at one time. I did a brief A-B listening session in my main two channel system with the S5 and my prototyped PCM56 DAC, at the time I actually preferred my own creation, which surprised me.

Since I broke down my prototype in anticipation of the final build, I have been listening to the S5 exclusively. The other night I was at my desk listening with my 6A5G amp while designing some PCBs, and it sort of dawned on me that the S5 is really an incredible DAC - not sure if it reached burn-in maturation or if it was my ears that burned it, but it has excellent transparency, staging, and dynamics, very musical. That burn in was the real deal, turns out Mr. Rogic knows a thing or two about his own designs!

I also did some brief A-Bing of the capacitor vs. transformer-coupled outputs (which are optional) and pretty quickly concluded that I preferred the transformer-coupled outputs, just a higher degree of realism and a bit more air.

So, the S5 is now even better than I remember it on first listen, so I think my own DAC now has some very stiff competition, one will go in my headphone system, the other in my two-channel system, will be interesting to see how they compare when the PCM56 DAC is in a chassis.

 

[Zachik]

Speaking of listening...

I haven't talked a whole lot about my Audial S5 DAC. I was told by the designer that it required some burn in. At the time I received it I was also building my PCM56 DAC prototype, so it was a whole lot of DAC to handle at one time. I did a brief A-B listening session in my main two channel system with the S5 and my prototyped PCM56 DAC, at the time I actually preferred my own creation, which surprised me.

Since I broke down my prototype in anticipation of the final build, I have been listening to the S5 exclusively. The other night I was at my desk listening with my 6A5G amp while designing some PCBs, and it sort of dawned on me that the S5 is really an incredible DAC - not sure if it reached burn-in maturation or if it was my ears that burned it, but it has excellent transparency, staging, and dynamics, very musical. That burn in was the real deal, turns out Mr. Rogic knows a thing or two about his own designs!

I also did some brief A-Bing of the capacitor vs. transformer-coupled outputs (which are optional) and pretty quickly concluded that I preferred the transformer-coupled outputs, just a higher degree of realism and a bit more air.

So, the S5 is now even better than I remember it on first listen, so I think my own DAC now has some very stiff competition, one will go in my headphone system, the other in my two-channel system, will be interesting to see how they compare when the PCM56 DAC is in a chassis.

Thanks Keenan - very interesting, and I will keep following closely.
As mentioned before, please keep me in mind when you finally feel your DAC is ready for public evaluation

 

[Monsterzero]

The Airmid review is live.

 

[paradoxper]

The Airmid review is live.

Where is the higher output version for something like a Susvara or TC?

 

[Zachik]

The Airmid review is live.

Excellent review!
I knew I would want an Airmid... If only I had room for "just one more amp"

 

[jaboki]

Where is the higher output version for something like a Susvara or TC?

I wonder, could the Airmid be used as a pre-amp to the CFA3?