SMPS powered tube amp

siliconray · 22nd February 2012, 07:22 AM

Today I received the SMPS power modules and SMPS powered tube amp. Tubes are 6N3+6P1. It could be used as headphone amplifier as well as 3W small power amplifier. The first impression it's light weight. Don't have time to listen to it. Pics first. I will post more testing result later.

malibujeff · 22nd February 2012, 02:19 PM

Looks nice.

DJNUBZ · 23rd February 2012, 04:37 AM

I'm really curious to hear your review. Shame you don't have a copy with a linear power supply to compare it to.

siliconray · 1st March 2012, 01:58 PM

Sorry for delay so long. Finished most of testing today, all I can say is awesome. It the best tube amp below 5Wx2 I've ever seen. I will compare with transformer powered amp tomorrow. Results will be posted soon

siliconray · 2nd March 2012, 04:41 AM

Sorry for so late. It's a time cost work to measure and adjust and measure and adjust. Now we are sure the R2 is in it's best condition. We are also sure it's the best status for a low cost 6P1 tube.

This design has no feedback from the output of the transformer. So the quality of transformer is important for the bandwidth. See the following result:
Instrument: HP3563A
Load: 8 Ohm
Signal Level: about 3V RMS
Sweep Freq: 10Hz to 100KHz

According to the curve, the amp has a very flat freq response between 40Hz to 20KHz, swing less than 1dB. 3dB bandwidth is 25Hz to 35KHz.

siliconray · 11:43 AM

The distortion is tested at 1KHz, 8Ohm, 0.5W, 1W, 2W and 3W output power. THD is kept less than 1.8% when the output power is less than 3W. It goes high rapidly when the power is above 3W.

1.275% @ 0.5W

1.45% @ 1W

1.34% @ 2W

1.95% @ 3W

siliconray · 2nd March 2012, 11:47 AM

siliconray · 2nd March 2012, 11:51 AM

I had thought the SNR would be high due to the switching mode power supply. To my surprise, the figure is even better than transformer powered amp, about 88dB!

siliconray · 2nd March 2012, 11:58 AM

tested with a pair of full range with 91dB sensitivity. I don't know how to describ the listen due to my poor English. Just want to say it's the best small (<3W) tube amp I have ever heard. Human voice is very sweet, treble is clear, bass is soft. I believe it could be better if replace 6P1 with better tubes.

siliconray · 2nd March 2012, 12:18 PM

We did a compare testing between SMPS and transformer.

Freq response: almost the same. slight higher (about 0.1dB) better than transformer.

Hum: Transformer has audiable hum at 20cm away from the speaker. SMPS may also has audiable hum, but I can't hear it even when my ear touched the speaker. Maybe a bat can hear it.

Distortion: SMPS has lower distortion, especially when the output power is close to 3W. SMPS is 1.85% while transformer is 3% when @3W 1KHz

SNR: 88dB vs 78dB, SMPS win

Sound quality: Similar in midrange and treble. But SMPS wins in Bass.

Weight: 4.2kg VS 2.5kg

23rd February 2012, 04:37 AM	#3
DJNUBZ diyAudio Member Join Date: May 2003 Location: Chicago	I'm really curious to hear your review. Shame you don't have a copy with a linear power supply to compare it to. __________________ My 3d printing startup, need something printed? Car Audio Connoisseur

1st March 2012, 01:58 PM	#4
siliconray diyAudio Member Join Date: Sep 2011	Sorry for delay so long. Finished most of testing today, all I can say is awesome. It the best tube amp below 5Wx2 I've ever seen. I will compare with transformer powered amp tomorrow. Results will be posted soon __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

2nd March 2012, 04:41 AM	#5
siliconray diyAudio Member Join Date: Sep 2011	Frequency Response Sorry for so late. It's a time cost work to measure and adjust and measure and adjust. Now we are sure the R2 is in it's best condition. We are also sure it's the best status for a low cost 6P1 tube. This design has no feedback from the output of the transformer. So the quality of transformer is important for the bandwidth. See the following result: Instrument: HP3563A Load: 8 Ohm Signal Level: about 3V RMS Sweep Freq: 10Hz to 100KHz According to the curve, the amp has a very flat freq response between 40Hz to 20KHz, swing less than 1dB. 3dB bandwidth is 25Hz to 35KHz. __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

2nd March 2012, 11:39 AM	#6
siliconray diyAudio Member Join Date: Sep 2011	Distortion The distortion is tested at 1KHz, 8Ohm, 0.5W, 1W, 2W and 3W output power. THD is kept less than 1.8% when the output power is less than 3W. It goes high rapidly when the power is above 3W. 1.275% @ 0.5W 1.45% @ 1W 1.34% @ 2W 1.95% @ 3W __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me Last edited by siliconray; 2nd March 2012 at 11:43 AM.

2nd March 2012, 11:47 AM	#7
siliconray diyAudio Member Join Date: Sep 2011	Waveforms __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

22nd February 2012, 02:19 PM	#2
malibujeff diyAudio Member Join Date: Mar 2010 Location: Georgia	Looks nice.

2nd March 2012, 11:51 AM	#8
siliconray diyAudio Member Join Date: Sep 2011	SNR I had thought the SNR would be high due to the switching mode power supply. To my surprise, the figure is even better than transformer powered amp, about 88dB! __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

2nd March 2012, 11:58 AM	#9
siliconray diyAudio Member Join Date: Sep 2011	Listening tested with a pair of full range with 91dB sensitivity. I don't know how to describ the listen due to my poor English. Just want to say it's the best small (<3W) tube amp I have ever heard. Human voice is very sweet, treble is clear, bass is soft. I believe it could be better if replace 6P1 with better tubes. __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

2nd March 2012, 12:18 PM	#10
siliconray diyAudio Member Join Date: Sep 2011	Comparing with transformer We did a compare testing between SMPS and transformer. Freq response: almost the same. slight higher (about 0.1dB) better than transformer. Hum: Transformer has audiable hum at 20cm away from the speaker. SMPS may also has audiable hum, but I can't hear it even when my ear touched the speaker. Maybe a bat can hear it. Distortion: SMPS has lower distortion, especially when the output power is close to 3W. SMPS is 1.85% while transformer is 3% when @3W 1KHz SNR: 88dB vs 78dB, SMPS win Sound quality: Similar in midrange and treble. But SMPS wins in Bass. Weight: 4.2kg VS 2.5kg __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Battery Powered Tube Amp	Alexrmc92	Tubes / Valves	11	13th September 2011 06:00 PM
Using a powered sub with my tube amp	Guytute	Tubes / Valves	11	29th December 2008 10:54 PM
High Powered 3cx300a1 Tube Amp	BlackUnikorn	Tubes / Valves	22	21st June 2006 12:17 AM
Line-powered SMPS for Power Amp?	marcus66	Class D	47	8th October 2004 12:49 PM
Battery powered tube headphone amp	mig-ru	Headphone Systems	1	3rd February 2004 10:59 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read