845 vs 805: Choosing High-Power Triodes

For audiophiles seeking the ultimate in SET amplifier performance, the 845 and 805 tubes represent the pinnacle of high-power directly heated triodes. Both are capable of exceptional sound quality, but they have distinct characteristics that make them suitable for different applications.

Power and Performance

845 Specifications

Power output: 20-30 watts in SET configuration
Plate voltage: 1,000-1,500V
Plate dissipation: 100W
Filament: 10V @ 3.25A

805 Specifications

Power output: 30-50 watts in SET configuration
Plate voltage: 1,250-2,000V
Plate dissipation: 125W
Filament: 10V @ 5A

The 805 offers more power but requires more robust power supply and cooling.

Sound Characteristics

845 Sound Profile

Powerful and dynamic presentation
Extended bass response with authority
Clear and detailed highs without harshness
Excellent for large-scale orchestral music
Good balance between power and refinement

805 Sound Profile

Authoritative and commanding presentation
Deep, controlled bass with excellent extension
Refined midrange with natural tonality
Effortless dynamics even at high levels
Ultimate power and control

System Requirements

845 Amplifier Requirements

High-voltage power supply (1,000-1,500V)
Robust output transformers
Adequate cooling and ventilation
Speakers: 88-92 dB sensitivity
Professional installation recommended

805 Amplifier Requirements

Very high-voltage power supply (1,250-2,000V)
Heavy-duty output transformers
Excellent cooling system essential
Speakers: 85-90 dB sensitivity
Professional installation strongly recommended

Safety Considerations

Both tubes operate at dangerous voltages and require:

Proper electrical knowledge for installation
Adequate safety measures
Regular maintenance
Professional service when needed

WARNING: These are not beginner-friendly tubes. Improper installation or operation can be dangerous.

Cost and Availability

Initial Investment

845 tubes: Generally more affordable
805 tubes: Premium pricing
Both require matched pairs

Operating Costs

Higher power consumption than lower-power tubes
Shorter lifespan due to high operating stress
More expensive replacement costs

Making Your Choice

Choose 845 if:

You want high power without extreme requirements
Your speakers have 88-92 dB sensitivity
You prefer a balance of power and refinement
You have a medium to large listening room
You want slightly lower operating costs

Choose 805 if:

You need maximum power from SET design
Your speakers have 85-90 dB sensitivity
You want ultimate authority and control
You have a large listening room
Cost is not a primary concern

Amplifier Design Considerations

Power Supply

845: Requires robust but manageable supply
805: Demands exceptional power supply design

Output Transformers

Both require high-quality transformers
805 needs transformers rated for higher power
Proper impedance matching is critical

Cooling

845: Good ventilation required
805: Excellent cooling essential
Both generate significant heat

Tube Life and Maintenance

Expected Lifespan

845: 2,000-3,000 hours typical
805: 2,000-3,000 hours typical
Both depend heavily on operating conditions

Maintenance

Regular bias checks
Visual inspection for damage
Cleaning of tube sockets
Professional service recommended

Our Premium Offerings

PSVANE ACME 845

Precision matched pairs
Tested at full power
Comprehensive test report
Secure packaging
Product page: PSVANE ACME 845

PSVANE ACME 805

Carefully matched pairs
Extensive burn-in and testing
Detailed matching data
Handling instructions included
Product page: PSVANE ACME 805

PSVANE ACME 211

Some high-voltage triode amplifiers are designed around 211 rather than 845 or 805. If the manual specifies 211, use the PSVANE ACME 211 and do not substitute 845 or 805 unless the amplifier maker explicitly supports it.

For all ACME high-voltage triodes, compare the lineup on the PSVANE ACME Series collection.

Conclusion

Both 845 and 805 tubes are capable of extraordinary performance in properly designed amplifiers. The choice depends on your power requirements, speaker sensitivity, and system goals.

For most audiophiles, the 845 offers an excellent balance of power and practicality. The 805 is for those seeking absolute maximum performance from SET design.

Expert Consultation

Given the complexity and cost of these tubes and their amplifiers, we strongly recommend consulting with experienced tube amplifier designers or technicians before making your decision.