June 2005

4 manufacturers SE output transformers have been tested with Hasling 300B SE tube power amp, each inserted and working under exactly the same conditions, current, B+ , drive a.s.o. The way the schemes are set up, it is very easy and fast to compare technical performance. The first spectral analysis sheets can be downloaded for closer examination. Please notice the huge dynamic 24 bit range of Spectra PRO and Lynx L22 prof. Audiocard (146 dB), unveiling harmonic products all the way down to the noise floor at –146 dB ! On James 1000Hz 1,0 w spectral sheet I have drawn a red line at –96 dB. This line level indicates the dynamic range of 16 bit analyzers, here is the noise floor, and older 16 bit analyzers are still used by the many audio manufacturers. So pay attention to this in comparison with SpectraPRO.

With 16 bit analyzers you will only see what is over this line (looking good, less spectral harmonic), so is Spectra from this point of view, but everything that Spectra detects under this line, would be buried in the 16 bit systems, as if they did not exist. But they are there.

They just have a much lower dynamic range, and higher noise floor. The Spectra 24 bit analyzer is a tough working tool, and thank you Spectra, for that. THD of the Spectra/Lynxcombination is as low as 0,00023 %. The scope shows a 1 KHz square wave 200uS horisontal/division, at the output (8,0 Ohm res. Load) with the James OPT, showing the high bandwidth of the amp/OPT combination, and the quality of the James OPT. Fall and rise times are fast, just one very fast ring period, high above the audio band. Additional scope pictures will be shown for the other transformers as well. Type numbers for the transformers will be published after the listening tests.
To be continued……

Graphs and tables

February 2005

Static transformer tests (spectral analysis) of two different brands (very well known, and widely used) are taking place for the moment, and a potted pair of far east transformers, being a high end product, according to the maker, is on their way to me for testing too. So it will be interesting to see and hear what these transformers do and what they sound like against each other.
The two brands show very big differences in distortion, both in the midband and bottom/high end, at 1,0w/8 Ohm, but also the frequency response, especially the low end at higher levels, e.g. 8,0 w/8 Ohm output/30 Hz. The distortion is very different throughout the band between the 2 products, and differs more than 10 times at some places in the band !
The listening tests for all 3 brands are expected to be finished during March/April

January 2005

I have just finished an interesting test match between 300B / SV6550 C, operating in my SE class A amp, under the exact same conditions, adjustable fixed bias, 90 mA transformer primary current (2,75 K Ohm), voltage, transformer, 8 Ohm load.
The 6550 pentode is operated in triode connection, that is screen 2 connected directly to the anode. 4 pcs. of the Svetlana winged C are tested.
Rp is app. 700 Ohm according to both tubes data.
I wanted to check if the 6550 is an alternative to 300B tubes, as the 6550 has anode dissipation data almost identical to the 300B, around 40 w, but the 6550 has very reasonable prices, compared to the 300B´s, but what about the quality in a single ended class A amp ?
Analyzer is Spectra PRO, / Lynx L22 Studiocard.
Spectral content for both 300B and SV 6550 C is almost identical, test frequency 1000 Hz, the second harmonic (2,0 KHz) is dominating, third harmonic (3,0 KHz) lower, fourth harmonic (4,0 KHz) is lower than third harmonic, fifth harmonic (5,0 KHz) is lower than fourth, etc. Just where we want them to be.
But, the 6550 second harmonic is just 37 dB down below 1000 Hz level, the 300B second harmonic starts at incredible 67 dB down, and the 3,4,5 harm. way under....... (1,0 w ref.). So, the pattern is the same, the 6550 is just 30 dB higher all over in the spectral content. The 6550 result is average of 4 tested tubes.
Here are the results :

1,0 w output in 8 Ohm : 300B ref : 0,04 % THD 2,0 w output in 8 Ohm : 300B ref : 0,07 % THD 4,0 w output in 8 Ohm : 300B ref : 0,11 % THD 6,0 w output in 8 Ohm : 300B ref : 0,28 % THD

6550 : 1,38 % THD 6550 : 2,11 % THD 6550 : 3,40 % THD 6550 : 4,81 % THD

The 300B ref tubes used are from an european manufacturer, and are the lowest distortion type out of 3 different brands, and is not from Svetlana.
At 8 w output the 300B THD is still below 1 %.
The 6550 tube has app. 30 times higher distortion than the 300B ref. up to app. 4 w output 1000 Hz. So this tube is out of my considerations as alternative
output tube here. The 300B ref. with its extremely good linearity is high above the quality of the SV 6550 C, but have also another price.
You cannot say that the 6550 tube is a bad tube, as this level of distortion is quite common for many SE class A amps. Used in push-pull amplifiers with negative feed-back, these distortion figures can be well hidden.
The input / driver section in the Hasling SE 300B amp has really low distortion and low output impedance, as well as shunt reg supplies in the design, thereby being able to focus on the qualities of the output tube section.

December 2004

Back again from European Triode Festival 2004, 3 - 5 December, in Langenarken at Bodensee, in the Southern part of Germany, with many new impressions from triodefreaks from all over the world. Most faraway countries this year was USA, Japan and Greece, but of course many wellknown faces from Europe. Many exiting systems, but unfortunately none in the top world class.
The large system with the 8 pc. Altec 16 inch woofers on big baffels had both coloration and distortion masking the finer details, and the french horn system had low distortion with Jean-Michel Le Cléac´h´s tube amp, but the horn had some resonances in female singers frequency range. But the most disapointing thing was, that the music was not involving. We danes who were there, had been looking forward to hear the system with passive filters, and I am sure that the digital filters were a lot to blame for the disappointing sound.
Lynn Olsons lecture on amplifier loops, Manfred Huber about bias workshop, and the legend Jean Hiraga about stereo recordings during the second world war in 1944, was really interesting. The recording were played on site, and the sound quality was amazing, when you take into consideration the recording was 60 years old.

hasling 300B SE tube amplifier.
My 300B amp development has almost finished. There will be some examinations left around output transformers, among which a James transformer, compared to the one I am using at the moment. There will also be further testing of the 300B tubes from different manufacturers.
At the moment 3 different brands have been tested, and there is a big difference in distortion. I am going to test 3 - 4 brands further.
The input/driver stage is a new design, never seen before. It is super linear as bigswing driver, with wide frequency responce, low impedance, and DC coupled untill the grid of the 300B tube. THD untill now at 1000 Hz in 8 Ohm and 2 w output is 0,07%, at 4 w output 0,11%, and without negative feed-back, with the second harmonic dominating. Input amplifier tube is 6SN7GT.

November 2004

From Sound Technology, USA, we have now received the latest version of their Spectra PRO software, being presented at the AES 2004 meeting in San Francisco now in November. I think they expect an award, like they got for their previous softwares.
This software, together with the Lynx L22 studiocard, being among the leaders in the world, related to low noise level and dynamics (app. - 146 dB analogue), give us the possibility to print-out spectral data curves from distortion products of a single frequency and its harmonics, plus intermodulation products of two tones and their mixed and harmonic products in the audio band and extended to app. 100 KHz.
These pages will be available for every product, with distortion printed out in percentage.

In the lab the hasling super shunt regulator has ended the development, and will be inserted in the new tube products, after the listening test in the protopypes has finished. The super shunt is extremely stable on the voltage output, versus varying current load (we are talking micro volt here), and has extremely low noise too.

Products being developed

SE (single ended) tube power amplifier class A, 300B / SV 6550 C
Expected sales : 2005 1. quarter

Push / pull tube power amplifier class A, SV 6550 C
Expected sales: 2005 2. quarter

New generation moving coil (head amp. Mk3 bat) prepreamplifier
Sales: 2004 4. quarter

New generation Moving Coil (head amp mk.3 bat) prepreamplifier.
After app. 20 years with previous versions of hasling head amp it was time to develope an even better version.

The new hasling head amp mk.3 bat differs from earlier versions by being disconnected from the mains power supply,
and the bipolar design changed to field effect transistors (FET´s), having data similar to tubes.
The battery supplies are sealed back-up batteries with low output impedance and extremely low
noise, and charger with 2 charging levels for the batteries.

The condition of the batteries are controlled with a pushbutton, and 3 light emitting diodes (LED´s)
indicates high, mid and low battery voltage levels, with high precision.
With the charger disconnected, and batteries fully charged, playing time is app. 3 weeks
around the clock, and recharging takes 8 – 10 hours (overnight).
Diode light indications for Charge and Power On, and switch for Charge ON / OFF.
Gain is 32 dB (40 times), and inputs can be loaded by resistor switches to match most quality pick-ups on the market correctly.

The amplifier has extremely low noise, and its sonic qualities exceed the previous hasling head
amps with great distance.

Intermodulation distortion scemes will soon be available.
Datasheet and price: please see HeadAmp.