By Steve Graham
As promised in the preview, a prototype of the EL84 amplifier based on the Tubelab.com circuit board is now built and playing music. It went together with only one hitch. An intermittent resistor was giving me fits…but once diagnosed and replaced, it was all smooth sailing. I gave it at least 100 hours of break in before some serious listening commenced.
The Finalé Audio F-7189 II had been returned, so my Dynaco ST35 clone was used as a reference to quantify the Tubelab’s performance. No, the Tubelab isn’t a Black Friday deal that would smoke the Finalé. At about one fifth the price of the Finalé, that can’t be expected. But the Tubelab is still darn good.
Listening to the Tubelab (TL):
Compared to the ST35 clone, the TL sounds a little fuller in the bass. It doesn’t seem to slow it down though, it still has good pace and drive. The system was the same used in the Finalé F-7189 II review, see link immediately above. In the highs, neither the ST35 nor the TL has the pellucid clarity of the Finalé. But through the midrange, the TL beats the ST35 clone. The TL has a deeper, wider and better-defined sound stage. It unravels Mark Knopfler’s guitar and his vocals with Emmylou Harris in greater detail – yet in a smoother, more engaging manner. Space, depth and the recording venue of naturally-recorded classical music is more clearly presented by the TL.
All in all, both amps are pretty good, considering that their output transformers are at least 50 years old. I suspect that the TL could sound even better with some new “iron” (transformers).
Step up, be our patron, get a great amp:
Update: A patron has been found! Build cost will be about $900 Canadian, roughly $700 US, for that our patron will, once I have detailed the build process for everyone, get themselves an amplifier like the one pictured above: assembled, tested and ready to plug and play. HOWEVER, it will have all new parts, including tubes, a chassis like the one pictured above, and especially, Hammond transformers. Shindo, the Japanese builder of exotic amplifiers, considers the Hammonds sufficiently decent to use in their Montille line.
All the money a patron pays goes into parts to build the amp. My labour to machine the chassis, assemble and test the finished amplifier is free. The final parts selection isn’t cast in stone. A volume control like the prototype is possible (if desired), as well as multiple (line level) inputs. Transformer selection is open for discussion too.
Oh, yeah. I goofed a bit on my parts order. The finished amp will have dress-up rings in the top plate like my N-F-P phono project from earlier this year.
Late breaking news:
The prototype amp was exhibiting a very low-level hum. As may DIY’ers know, getting rid of the last bit of hum can be a chore. The amount of hum was so slight, I had to put my ear practically right on the woofer of a medium-efficiency speaker to hear it. I had a $15 Hammond power supply choke kicking around, and once installed, the residual hum was gone! It was just an educated guess but it worked. Sometimes it’s better to be lucky than good-looking.
Editor’s Note: I just want to thank Steve for continuing to offer these great projects to interested readers. As the song goes, get it while you can…