Hagerman Technology LLC: Cymbal Vacuum Tube Push/Pull Power Amplifier 6H30 6W DIY Kit

"Cymbal" 8W Amplifier (discontinued)

The Cymbal monoblock power amplifier is a unique and modern push-pull design using ultra-linear 6H30 triodes in a zero-feedback circuit. The uncommon circuit is optimized for sonics rather than raw power. Perfect for efficient drivers and horns, its eight watts of output power are extremely well-controlled by virtue of an astoundingly low 1.6 ohm output impedance (8 ohm tap). Overdrive into clipping is soft with a clean recovery. The input stage is fully differential and has a ground-lift switch to eliminate pesky ground loops.

The monoblocks are built in mirror image pairs. A second input offers capacitive coupling and can be designed to a set high-pass frequency to match systems requiring a subwoofer. Plenty of high quality iron is used in this design, including a fully choke-regulated B+ supply.

The Cymbal is not an "el-cheapo" amplifier, rather a fully tricked out and substantial product. The half-kit DIY version will cost you approximately $550 in raw parts each.

Is the Cymbal right for you? Yes, if you have efficient speakers with a reasonable impedance curve. If an SET works for you, then a Cymbal will be perfect. An example of an easy speaker to drive is the BK-16 from Madisound. Or the remarkable Horns at The Horn Shoppe.

Completed Cymbals

Completed Circuit Board

Features

All vacuum tube topology
Pure Class A amplifier stages
No feedback
No hum
Differential input stage
Low output impedance
Vacuum tube B+ rectification
Choke regulated B+

Specifications

Power	8W into 8 ohms
Input Sensitivity	1.5Vrms (15dB gain)
Input Impedance	47k ohm
Bandwidth (-3dB)	10Hz to 95kHz
Distortion	0.18% @1kHz @1W
SNR	95dB A-weighted
Damping Factor	5
Size	7.25" x 11.65" (PCB)
Weight	14 lbs
Input Voltage	100V, 110V, 120V, 200V, 220V, 240V
Tubes	6H30 x 5, 5AR4 x 1

Reviewer Excerpts

"The Cymbal sounded quick and agile. It had good bass extension and control with the JBLs. The highs were extended and fairly smooth. Midrange coloration was minimal. I would place this amplifier in the resolution-over-romanticism category, although it sounded quite smooth and pleasing - somewhat reminiscent of a good SE amplifier in the same power range. It is a neutral, truthful, balanced sounding amplifier that will allow the user to listen relatively deeply into the music with appropriate loudspeakers. The Cymbal's low overall distortion and lack of compression (until it ran out of steam) belied its power rating, and will play convincingly loud with any speaker of reasonable efficiency." - Kevin Kennedy

Read the entire article at Positive Feedback Online.

Measurements

The Cymbal amplifier has low distortion despite using no feedback. This is due to the superior linearity of true triodes and remarkable circuit design. Distortion is mainly 3rd order, just 0.18% at 1W.

1kHz sinewave and residual distortion

1kHz distortion versus output power

The 10kHz squarewave response is near perfect. Very wide bandwidth for a tube amp.

10kHz Squarewave response

Frequency response at 1W

Downloads

Customer Testimonials

I'm running the cymbals with a solid state balanced FET preamp the Coda 02b and Klipsch LaScala's 1994 vintage. They are dead quiet, not buzz, no hum, and the music is crystal clear, lifelike and with a black bottomless noise floor. I also own a Morrison ELAD preamp which is well known for its extremely low noise floor, beyond human hearing. When run with my Bryston 3BST, speakers are dead quiet too. The cymbals noise floor is every bit a match in depth, and with low distortion, yet you use triodes and no negative feedback (of course there's some in the tubes), quite an engineering feat. Perhaps the best testamonial of the cymbal comes from my mom, who said, its sounds like "you're there" and from my dog. While playing the DVD "Assasins" with Sly Stallone and Antonio Bandaras, a cat "meows" in a warehouse. My dog freaked out and started barking like crazy and stormed around the house looking for the "cat". You fooled the keen ear of a dog with lifelike low distortion. In the phony audiophile world of pseudo EE science, super duper silver solder and magic cables, your products are a fresh perspective.