[whirlwind]

It sounds phenomenal! The bass is very deep, big soundstage and excellent transparency. Sorry had to finish that nail-biter of a game, pictures aren't my best work either lol. Disappointing loss but great season for the Browns.

It looks fantastic and the glow of those 841 globes
It has all of the bases covered...deep bass, big stage and excellent transparency....enjoy !!

That game, oh my....we had a chance in the 4th quarter...all you can ask.
Was an enjoyable football season, the Browns and music was great in an other wise terrible year.

 

[L0rdGwyn]

Mental gymnastics complete
Here are the windings and impedances for your transformers @leftside
Z/4Z/9Z/16Z
22/88/198/352

Six relays total per transformer (U1-U6 above). For 16Z, no relays are on. For 9Z, relays U1/U2 on, for 4Z relays U1-U4 on, for Z all relays (U1-U6) on.

Awesome, I didn't realize Sowter used the same secondary winding configuration in their custom transformers, my custom OPT from them are single secondary 8ohm. Wiring a switch for four secondaries would be a real headache, great solution using the relays!

It looks fantastic and the glow of those 841 globes
It has all of the bases covered...deep bass, big stage and excellent transparency....enjoy !!

That game, oh my....we had a chance in the 4th quarter...all you can ask.
Was an enjoyable football season, the Browns and music was great in an other wise terrible year.

Thanks! Yeah the door was open in the 4th but they couldn't take advantage, oh well still a great season, I'll take it! No reason they shouldn't be serious contenders next year too.

 

[bcowen]

Thanks! Yeah the door was open in the 4th but they couldn't take advantage, oh well still a great season, I'll take it! No reason they shouldn't be serious contenders next year too.

They had a great year, and honestly I think it's their time. I'm not much of a pro football fanatic, but the effort and determination they showed this year was most impressive.

 

[Ripper2860]

Deleted. Wrong thread.

 

[L0rdGwyn]

Polished up my Auteur today and conditioned the leather, been a while since I tuned it up. I'm back in the headphone saddle, baby! Honestly been a while since I've listened on 'phones, been wrapped up in speaker world for a while.



I decided I did not like the Auricap XO in this amplifier, they have been temporarily swapped back to the Solen Fast-CAP MKP from the prototype. I found they were imparting a harshness/sibilance to the upper midrange and treble. They'll get another chance, I picked up some other caps to try out, going to have a shootout between Obbligato Gold, ClarityCap CSA, Auricap XO, and the Solens when they are all in house.

 

[bcowen]

Polished up my Auteur today and conditioned the leather, been a while since I tuned it up. I'm back in the headphone saddle, baby! Honestly been a while since I've listened on 'phones, been wrapped up in speaker world for a while.



I decided I did not like the Auricap XO in this amplifier, they have been temporarily swapped back to the Solen Fast-CAP MKP from the prototype. I found they were imparting a harshness/sibilance to the upper midrange and treble. They'll get another chance, I picked up some other caps to try out, going to have a shootout between Obbligato Gold, ClarityCap CSA, Auricap XO, and the Solens when they are all in house.

Obviously you need some oil caps. Just make the chassis bigger.

 

[A2029]

Obviously you need some oil caps. Just make the chassis bigger.

@L0rdGwyn should slot in some of these little guys:

95mm D x 220mm L

 

[L0rdGwyn]

Obviously you need some oil caps. Just make the chassis bigger.

@L0rdGwyn should slot in some of these little guys:


95mm D x 220mm L

Even better, I'll just throw together a separate "output capacitor chassis", think those Miflex caps will need one

 

[Xcalibur255]

Are these caps for output coupling? What are the chances you could direct couple instead?

 

[leftside]

@L0rdGwyn should slot in some of these little guys:


95mm D x 220mm L

Are we using these?

 

[bcowen]

@L0rdGwyn should slot in some of these little guys:


95mm D x 220mm L

Let me guess....those are more expensive than my house. Each.

 

[L0rdGwyn]

Are these caps for output coupling? What are the chances you could direct couple instead?

So in this amp, the 841 is direct-coupled to the FET which is cap coupled to the 8665A output transformers. The 8665A were designed to be cap-coupled to a cathode follower (I used a source follower instead), can't direct couple as the OPT cannot take DC on the primary. Since the 841 has an active load and is working into the high input impedance of the source follower, the distortion stays very low. It's like a...filament biased parafeed spud with a FET buffer in the middle. I had all these 841 tubes burning a hole in my pocket, and I picked up the 8665A to do something with, didn't know what, so I just slapped 'em together

 

[A2029]

Let me guess....those are more expensive than my house. Each.

Nowhere near as costly as Duelund caps

Are we using these?

Much much smaller ones of these (0.47uF), haha

 

[CJG888]

I’ve found Obbligatos (Obbligati?) to offer most of the benefits of PIO in a smaller (and more affordable) package.

Seen here as output coupling caps in my NOS DAC (modded Teradak Chameleon):

 

[L0rdGwyn]

So turns out both changes I made between the prototype and the final version of the 841 amplifier were failures

As I mentioned, I was hearing a certain sibilance and "bite" to the upper midrange that became somewhat fatiguing. First I swapped the Auricap XO back to the Solens, which was an improvement, but something was still "off" compared to what I had heard in the prototype. Did I miss this sibilance then? The only other major change I made was swapping the source follower FET from the Alpha & Omega AOTN160 to the fancy SiC Cree C2M1000170D. So what the heck, let's swap it back and see what happens.

Bingo.

The venerable AOTN160 fixed the sibilance, increased the soundstage, and improved the dynamics. So, guess the SiC FET isn't the bee's knees after all. Could be application specific as I did not notice any of these issues when messing around with the Cree chip in my 801A prototype.

So looks like I'll have to roll some different FETs in addition to the output caps, but happy with the AOTN160 for now, the sound kick's ass once again. Maybe I can throw together some sort of modular source follower board to make A-Bing FETs easier

Don't think I ever showed the frequency response of this amplifier.