Atma-Sphere Class D Mono blocks

[D.Duttilleux]

Another thing I detest: tube rolling

I remember scoring early Mullard, Philips and Telefunken E88CCs for (almost) nothing... and chuckle at the crazy amounts they sell for today.

 

[Nuforce]

I’ll say this, it is only viable by and large to offer a product with currently available perishables. Call VTS Andy (or equivalent, if there is such a thing) he will set you up putting some Sylvania tubes in those MA-1s and you will be floored by the difference. I promise. Thank me later. As good as these amps are, the Chinese 6SN7GTB are (sorry) but, audio junk. No comparison. They electrically function, but that’s not saying much. My last set last just over 10 years, so is it worth the sound investment? Please, do yourself this favor. It will be like Christmas!
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You are referring to the power tubes or the 6SN7 positions?

I use Shuguang black Treasure CV181 and in the most critical position I use linlai e-6sn7 which are the best octal I've ever heard. Don Sachs recommends them.

I'm interested to try RCA in the power tube section over my Chinese power tubes.

 

[DetroitVinylRob]

You are referring to the power tubes or the 6SN7 positions?

I use Shuguang black Treasure CV181 and in the most critical position I use linlai e-6sn7 which are the best octal I've ever heard. Don Sachs recommends them.

I'm interested to try RCA in the power tube section over my Chinese power tubes.

I have both Chinese brands you mentioned. But only in pairs for sampling on a headphone amp. I imagine if they sounded real good there I might consider looking into a full load for the MA-1s.

The signal tubes, 6SN7GT(A/B) was what I was referring to. Power tube wise I have a lot of Svetlana 1965-68 =C= 6H13C Russian Cold War stock.

 

[D.Duttilleux]

I have a lot of Svetlana 1965-68 =C= 6H13C Russian Cold War stock.

How a cold war can leave a warm glow.

 

[DetroitVinylRob]

How a cold war can leave a warm glow.

They make Love not War (now)

 

[Atmasphere]

You are referring to the power tubes or the 6SN7 positions?

I use Shuguang black Treasure CV181 and in the most critical position I use linlai e-6sn7 which are the best octal I've ever heard. Don Sachs recommends them.

I'm interested to try RCA in the power tube section over my Chinese power tubes.

If you try the RCAs and they are NOS, place them in the amps and let them sit in standby (amber lamp only) for at least 4 days and 4 nights. By preconditioning the power tubes in this manner their lives can be as much as doubled and you will reduce arcing by about 80% within the first 2 weeks of service. The RCAs are more prone to arcing failure as they are not designed for fixed bias service like used in the MA-1. The Russian power tubes (6H13C) hold up the best as a result. But the RCAs allow the amp to make more power and reduce the output impedance a bit so all the feedback says they sound better.

If you don't precondition them their lives will be considerably shorter according to customer feedback we have as well as our own testing. BTW preconditioning works to increase the life of any indirectly heated power tube.

Regarding the difference between the class D and the MA-1, what we hear here is they are very similar in the mids and highs with the class D being a bit more transparent. The bass is different because the class D can act as a voltage source which is what most speakers are designed for. The MA-1 is more of a power source (meaning it tries to put out constant power with respect to load rather than constant voltage). The bass region is where you hear this the most since box speakers have a resonance that is described by an impedance peak. Or the box speaker might employ dual woofers and so have a lower impedance than the rest of the speaker. So the bass is where the biggest difference shows up and is very speaker dependent: the flatter the impedance of the speaker the less difference you hear. Customer feedback and our own experience suggests that the bass of the class D is the last thing to show up during break-in, which seems to take 450-500 hours. So you have to be a bit more patient with them.

We were really interested in getting a good 1st Watt out of the class D. That is where I do most of my listening at home since my speakers are 98dB. At very low power levels its hard to get a handle on the actual distortion because noise dominates the readings. The noise is quite low though, lower than any tube amp, great for horns.

 

[D.Duttilleux]

We were really interested in getting a good 1st Watt out of the class D.

Reminds me of...

 

[Kingrex]

@Atmasphere
Hey Ralph. Would preconditioning of a power tube like a KT88 in PP be similar to just running rhe heaters for 4 days?

 

[Atmasphere]

@Atmasphere
Hey Ralph. Would preconditioning of a power tube like a KT88 in PP be similar to just running rhe heaters for 4 days?

Of course! Preconditioning applies to all indirectly heated power tubes. Just keep in mind that as soon as you apply B+ the preconditioning process has ended.

 

[Kingrex]

Of course! Preconditioning applies to all indirectly heated power tubes. Just keep in mind that as soon as you apply B+ the preconditioning process has ended.

Pretty much all new KT88 have been driven at the factory for 24 hours, then matched. Does this mean there is no way to precondition the tube?

 

[Atmasphere]

Pretty much all new KT88 have been driven at the factory for 24 hours, then matched. Does this mean there is no way to precondition the tube?

If you mean at the tube factory, I would ignore anything marketing you read about that. If from an amp manufacturer then 'yes'.