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SAS Audio Labs TM

50 Watt Ultra Linear Amplifiers
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25 Watt Pushpull Triode Monoblocks

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50WPU KT88/6550 PushPull Ultra Linear/Triode Amplifier:

The KT-88/6550, 50WPU monoblock ultra-linear/triode amplifier reproduces pure, natural, live music. The 50WPU incorporates two total stages with separate power supplies for each stage to eliminate frequency dependent musical feedback that occurs through one common power supply. The 50WPU has a tonal balance switch ( in the power supply), 4, 8 ohm speaker switching, and a unique 60hz hum cancelling control for your convenience. The hum control is not your typical filament balance control but a proprietary designed control to cancel idle hum problems caused by internal and outside 60hz loops.

One other huge plus is that the total harmonic distortion (HD) produced by the first stage (driver/phase splitter) is less than .05% at 50 watts maximum amplifier output. Even at maximum power, let alone that first critical watt out, the distortion is virtually zero. This means the sound is exceptionally clean with all the inner details present. More technically, it means that higher order harmonics created by combining the distortions of each stage are eliminated.

For example, let us say we have a typical amplifier with the driver tube and output tube, say each producing only 2nd and 3rd harmonic distortion. Both tube's HD will combine to produce 4th, 6th, and 9th order harmonics. If we have 4th order, then we also have 8th, 12th, and 16th harmonics. By eliminating the input stage's distortion, those higher harmonics are absolutely minimized/eliminated. Tubes with higher negative grid voltages, higher drive requirements have higher distortion products produced from its driver, thus higher order harmonics created. And Intermodulation distortion products are very generally 3 times higher in amplitude than harmonic distoriton products.

6550/KT-88s require approximately one half the bias of a 300b, 813, 833-A, one third or fourth that for 845, and one fourth that of a 211 etc.

"Push Pull 50WPU" 6550/KT-88 Tube Amplifier Specifications, Price, Ordering:

Number of Chassis:	                  2 (Dual Mono Design)
Frequency Response:                       5-75khz  -1db/-3db respectively 
Power Output:                             50 watts RMS 4,8 ohms 
Sensitivity:                              2 vrms. in for rated output power
Biasing Output Tubes:                     Self Biasing
Input Impedance:                          100k ohms
Global Feedback:			  0
Total Weight ea.:                         27 lbs. (Shipping Wt. 30 lbs)
No. of Stages/Channel:                    2
Driver Tube:                              JJ 6922  (approx 1/8 the distortion of NOS 6sn7)
Output Tubes:                             6550 or KT-88 (Ultra Linear Operation, optional wired triode 25 watts) 
Total Harmonic Distortion at 1 watt:      0.05% or less
Total Harmonic Distortion:                1.3% at 50 watts output typical (Clipping typ. 52 watts) 
Power Requirements:			  120vac 60hz (2 amp slo-blo fuse)

Dimensions per Chassis:                   Width: 19" front (17" chassis, 43.5cm) 
                                          Depth: 14" (25.5cm) 
                                          Height: 8 1/2" (30.5cm)

Monoblock Only:
Wholesale Price ea. 50WPU:               $2395.00 Each 

Continental USA shipping included. Outside USA, check on shipping charges.

Tubes must be installed upon delivery. Plug output tubes in either socket. E88cc into its own socket.


30 day money back guarantee, excluding shipping. Warranty, 5 years labor and parts from date of purchase, and 1 year on small signal tubes. 90 days on output tubes.

Guarantee, Return Policy:

To Purchase

Simply use a Paypal account or Credit card thru Paypal. Use as the email address. Or send a Personal Check, Cashiers Check or Postal Money Order (US dollars) payable to SAS Audio Labs. Please allow sufficient time for such to clear. No refund will be issued if the bottom plate seals are disturbed, scratches or alterations. The audio amplifiers must be returned in double boxes/materials and must be fully insured for the purchase value when shipped via FedEx (not UPS). Prices subject to change without notice.

Danger! Vacuum tubes get very hot during operation and thus precautions should be taken so that children do not come in contact with the tube amplifier.

Design and parts subject to change without notice.

SAS Audio Labs

503 W Jefferson St. Suite #2
Morton, Illinois USA 61550
Tel: (309) 263-0736
12:00 PM - 5:00 PM CST Monday - Friday

Specifications, Prices subject to change without notice.

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copyright©: 01-03-2010. Updated: 5-31-2015. SAS Audio Labs and all contents of this page article, including graphics (except Svetlana Tubes), components, component layouts, "lead to lead wiring" are copyrighted by Steven A Sammet.
All rights reserved. No portion of this article may be reproduced without the written permission from
Steven A Sammet at SAS Audio Labs. SAS Audio Labs is registered with the state of Illilnois.