SET amp owners thread

[bonzo75]

My recently completed SET project amp. The B+ and filament power supplies are in two separate rack-mounted chassis which are connected to this main amplifier via umbilical cables. My speakers are Altec Lansing A7-500 which are using active crossovers at 500Hz - this SET is driving the high frequencies and a McIntosh MC240 is powering the low frequencies.

There is a thread here with the details of the build.


View attachment 113594

hi, what are the drivers in the A7? And is the crossover standard or something you have changed?

 

[Ampexed]

hi, what are the drivers in the A7? And is the crossover standard or something you have changed?

I use 802D and I also have a pair of Frankenstein drivers I made while I worked at Altec in Anaheim which are 902 with the Tangerine phase plug removed and replaced with the regular 802 phase plug. The woofers are 416-8-B.

The crossovers are all active line level - there are no passive crossovers in the system. The diaphragms for the HF drivers are custom ones I made while at Altec which are 4 ohm instead of 8 or 16 ohm. I've modified a number of existing 8 ohm diaphragms for 4 ohms but it is trickier than building them from scratch. This 4 ohm modification reduces mass considerably and allows for better high frequency extension. The link below leads to a page which goes into detail.

 

[adamaley]

Any reason why you prefer the regular phase plug over the tangerine version?

 

[Ampexed]

Any reason why you prefer the regular phase plug over the tangerine version?

The Tangerine sounds very harsh to my ears. I tried to like it, I really did, but it just doesn't cut it for me.

 

[Norway]

Her are my new AirTight 211. Rey happy!

 

[acousticsguru]

Her are my new AirTight 211. Rey happy! View attachment 114210View attachment 114211View attachment 114212

Nice! I realize this may seem irrelevant, but I've always thought 211 to be one of the prettiest, if not the prettiest tube to look at. Enjoy!

Greetings from Switzerland, David.

 

[adamaley]

Her are my new AirTight 211. Rey happy! View attachment 114210View attachment 114211View attachment 114212

We'll be waiting patiently for your impressions.

 

[Norway]

We'll be waiting patiently for your impressions.

First impressions are WOW! Om my VOTT the SQ is just on another level compared to the SS amps. The room is huge and the separation of the instruments/voices is simply fantastic. The only issues is the transformer hum that is clearly auditable as the 817 are extremely sensitive… but I guess that’s the nature of zero FB design!?

 

[Ampexed]

First impressions are WOW! Om my VOTT the SQ is just on another level compared to the SS amps. The room is huge and the separation of the instruments/voices is simply fantastic. The only issues is the transformer hum that is clearly auditable as the 817 are extremely sensitive… but I guess that’s the nature of zero FB design!?

Are the filaments of the 211 tubes being run on AC or DC?

 

[adamaley]

First impressions are WOW! Om my VOTT the SQ is just on another level compared to the SS amps. The room is huge and the separation of the instruments/voices is simply fantastic. The only issues is the transformer hum that is clearly auditable as the 817 are extremely sensitive… but I guess that’s the nature of zero FB design!?

That sucks regarding the hum. Are there no hum adjustments dials?

 

[Norway]

Are the filaments of the 211 tubes being run on AC or DC?

I have no idea. The amps are not modified or mangled with.

 

[Norway]

That sucks regarding the hum. Are there no hum adjustments dials?

No other adjustments than bias.

 

[Argonaut]

but I guess that’s the nature of zero FB design!?

Not universally no … however what matters most, and more importantly, is your delight in how you are connecting to your music in such a revelatory way , enjoy your evening

 

[bonzo75]

The airtight 211 hum is mentioned here

Air Tight ATM-211 tube monoblock power amplifier Measurements

Sidebar 3: Measurements With the bright glow of its directly heated output tube lighting up the room, the Air Tight ATM-211 amplifier was very different from the products that usually pass through my measurement lab. I also had problems getting it to behave at first. When its AC supply lead was...

www.stereophile.com

 

[Norway]

Apart from the hum both amps are totally noice free, no hiss from the 288/1505 or UHT. The level of hum is not affected by the attenuator (gain/volume adjust) on the ATM-211

 

[Norway]

The airtight 211 hum is mentioned here

Air Tight ATM-211 tube monoblock power amplifier Measurements

Sidebar 3: Measurements With the bright glow of its directly heated output tube lighting up the room, the Air Tight ATM-211 amplifier was very different from the products that usually pass through my measurement lab. I also had problems getting it to behave at first. When its AC supply lead was...

www.stereophile.com

Yes! I was aware of this issue. And frankly I don’t really care as the SQ more than compensate for this minor issue.

 

[DasguteOhr]

That sucks regarding the hum. Are there no hum adjustments dials?

For Hum here be careful lethal voltage close there.

 

[Argonaut]

For Hum hereView attachment 114213

Yup …A good Ol In circuit ‘Hum Bucker’ altho there are several very good ‘plug In’ products on the market these days

 

[DasguteOhr]

Yup …A good Ol In circuit ‘Hum Bucker’ altho there are several very good ‘plug In’ products on the market these days

Balancing the heating voltage does not always help with direct heating tubes. but usually the hum afterwards so low that is tolerable.

 

[Norway]

Are the filaments of the 211 tubes being run on AC or DC?

DC! According to the manual “to eliminate hum”