[Zachik]

Already seems to be a good conversation starter

As if you need incentives for starting conversations...

 

[L0rdGwyn]

I'm fine with a huge chassis if that's what the design calls for ahhahah!

RCA on front panel fine with me if it makes the sonics optimized! Already seems to be a good conversation starter

Lol I'm going to make it as compact as possible! Right now I am targeting 16.5" L x 13" W x 4.25" H, so it will be longer than it is wide with all of the noisy AC in the rear of the chassis.

Here is the current draft of the top plate, no ventilation or anything yet and it will undoubtedly change, colored boxes are internal components.



I think I mentioned it, but my 801A amplifier has RCAs on the front panel. I like these Silver Pulse interconnects from DH Labs, nice and flexible, look pretty good too!

 

[L0rdGwyn]

Also, I freaking love this 45 amplifier...this is going to be a problem.

 

[johnjen]

Ah I see that the magic of the 45 has snared yet another victim.
Bhhhhahahahahahahahahahahahahahaha

JJ

 

[L0rdGwyn]

Ah I see that the magic of the 45 has snared yet another victim.
Bhhhhahahahahahahahahahahahahahaha

JJ

Yup, snared me for the second time in fact lol two 45 amps in this household right now. Edit: oh right, Zach is the victim here, I knew that

Made some real good progress on the chassis today, going to shelve it for the night, then build my PCM56 DAC tomorrow!

 

[zach915m]

Lol I'm going to make it as compact as possible! Right now I am targeting 16.5" L x 13" W x 4.25" H, so it will be longer than it is wide with all of the noisy AC in the rear of the chassis.

Here is the current draft of the top plate, no ventilation or anything yet and it will undoubtedly change, colored boxes are internal components.



I think I mentioned it, but my 801A amplifier has RCAs on the front panel. I like these Silver Pulse interconnects from DH Labs, nice and flexible, look pretty good too!

Ah I see that the magic of the 45 has snared yet another victim.
Bhhhhahahahahahahahahahahahahahaha

JJ

The bigger the better!

The RCA cables on the front will be a good chance for us to show off those blingy cables.

I've actually never heard a 45 amp before so it's very exciting. And having an excuse to look for tubes to buy is always fun.

 

[L0rdGwyn]

I've actually never heard a 45 amp before so it's very exciting. And having an excuse to look for tubes to buy is always fun.

I'm excited for you to hear it! I think I should have it to you by the end of November at the latest. I have been listening to it for the past 4-5 hours, really pleased with this circuit.

 

[Xcalibur255]

Just a thought Keenan, you might want to consider keeping the meters on the same surface in close proximity to the trim pots. I think it's easier to both adjust and watch the bias at the same time this way. If the meters are on the front it's more awkward to keep an eye while adjusting the set screw.

 

[L0rdGwyn]

Just a thought Keenan, you might want to consider keeping the meters on the same surface in close proximity to the trim pots. I think it's easier to both adjust and watch the bias at the same time this way. If the meters are on the front it's more awkward to keep an eye while adjusting the set screw.

Thanks for the input T, I'll keep that in mind. BTW - do you have your finger on the pulse of the NOS 45 market? I feel like prices went up since last I checked, which was probably almost a year ago. Seems like $150 for a pair of NOS ST shaped is pretty commonplace, I was getting much better prices last year.

 

[Xcalibur255]

They're up quite a bit in the last year, yes. I'm seeing globes that test poorly and don't match well going for the same prices that good NOS testing pairs went for just a couple of years ago. Since the T/J factory that made the Fullmusic tubes in China doesn't seem to be operating anymore the only semi-reasonably priced new production 45 is also going up in price and getting hard to find.

It does make me wonder how much longer we have before they start to become genuinely hard to find like a 10 or 50 is now. For the globes at least, I have no doubt the ST tubes will be readily attainable on eBay for quite some time still.

This amp you are building deserves to have a nice pair of globes in it, especially with those interstages I'm sure it'll be crazy transparent.

 

[L0rdGwyn]

They're up quite a bit in the last year, yes. I'm seeing globes that test poorly and don't match well going for the same prices that good NOS testing pairs went for just a couple of years ago. Since the T/J factory that made the Fullmusic tubes in China doesn't seem to be operating anymore the only semi-reasonably priced new production 45 is also going up in price and getting hard to find.

It does make me wonder how much longer we have before they start to become genuinely hard to find like a 10 or 50 is now. For the globes at least, I have no doubt the ST tubes will be readily attainable on eBay for quite some time still.

This amp you are building deserves to have a nice pair of globes in it, especially with those interstages I'm sure it'll be crazy transparent.

Okay, so I'm not crazy! I wonder the same, every so often I have a mini panic about the availability of my favorite NOS tubes and have to hold back from buying whatever is available. The transparency and 3D-ism with the globes in this amp might be the best I have ever heard, hopefully Zach can find a good pair of globes for a decent price. Cooling off the bias in this amp doesn't cause a significant drop off in sound quality, so running at 28-30mA or so and a pair of globes should last a very long time.

 

[Xcalibur255]

For sure, a genuinely solid pair of globes will last darn near forever at 250V/30mA bias. My beloved KenRads see 275/34 and they're not showing any significant signs of weakening after 7 years of intermittent use. As long as something unlucky doesn't happen I would say one good pair will take care of it. 45s generally aren't prone to becoming noisy over time but it does happen.

I can keep my eyes peeled. Or I'm possibly being presumptous there. Maybe Zach is old hat at tube hunting.

 

[Zachik]

BTW - do you have your finger on the pulse of the NOS 45 market? I feel like prices went up since last I checked, which was probably almost a year ago. Seems like $150 for a pair of NOS ST shaped is pretty commonplace, I was getting much better prices last year.

Yup - good 45 ST pairs seem to go for $150-200, and globes for twice as much!

 

[jgwtriode]

I got a chance to have the "Airmid" in house for a week or so - and I without a doubt can highly recommend it for ZMF's. I know @L0rdGwyn told me that it can change a bit in impedance output with different tubes, but the two sets I tried in it (6080 Amperex and the stock tubes) both sounded fantastic.

The one thing that that Airmid does right that stands it in front of the pack - is that is has a holographic, dimensional and forward mid range, that is coupled with resolution and low end weight. All of this works together in harmony to produce a cohesive and exciting sound, and I didn't have to work hard at tube rolls to find it. None of these strengths gets in the way of each other - which is also rare! While you can get to that spot with other amps many times, it can be after spending a lot on tubes and/or find the right headphone combo. The Airmid did this throughout the ZMF line-up really well, and quickly was a shop favorite among our other audiophile staff members.

We had the amp lined up with the Euforia and Glenn OTL. And while I definitely can never get into comparisons that say "one is better than the other" I can without a doubt recommend the Airmid among those amps, and I think out of the three, it's the easiest one to achieve a "ceiling" of sound that performs on the highest level of OTL amps.

So anyways - @L0rdGwyn is already building me a 45 based amp that I'm super excited for that he has mentioned here, if he wasn't, I'd already have put an order in for one of these as it's just that good! I really couldn't get over the "segmenting" of sounds that adds to the "3-d-ish-ness" of our headphones. It just makes you want to keep listening.

Good for you Zach! 45's are absolutely gorgeous to listen to. Had VAIC cobalt meshplates with magnequest cobalt transformers(bottlehead paraglows) for a couple of years. Never heard a more musical engaging amplifier. Will be hoot to hear further about the results.

Happy listening,

jgwtriode

 

[johnjen]

And just as a teaser…

Ya know what tube is a lot like the 45 in just about every way, except has ≈ 1/2 the power?




wait for it…





the 71A…
buuhhhahahahahahahahahahahahahahaha…

JJ