up on Joe's Dream Audio System
are Joe's summary and photos of his changes to his impressive audio
system within the last two years:
Time passes and so it is necessary to review the changes the setup went through to give you some inspiration and share my experience.
I swapped the line stage tube from 5687 to a 6H30. The differences
are not substantial, but since I am lazy I decided not to change it
back for the moment.
have changed the subbass amp from differential to push pull and the
last stage of the power supply from 10H + 500µF to 100H and
1µF. This moves the -3dB from 35Hz to 8Hz and tightens the bass
considerably. This is pant leg flapping since the speaker goes down
to 17Hz! Try this with Kraftwerk's Album "Minimum Maximum"
(e.g. Kardiogramm or Mensch-Maschine).
The midbass driver stage was changed from 211 sakuma style to a differential 7N7. It is easier to handle, saved one of my precious 3 phase transformers and added some clarity. A very fine driver stage with lots of headroom! I take a Lundahl LL7903 (1:4) as Phase splitter and a LL 1660AM/PP (4,5:1). This is enough gain, a fine bandwidth and low output impedance.
For my midrange I started with a LL7905 (1:11,2) and a 801. I tried what happens when adding a driver stage to this single stage design. After my very positive experience with high transconductance tubes (EC8020, EC8010, 5842 etc.) I chose the 6C45 which is cheap and common. The topology is pretty standard (Lundahl 7903 1:1, Lundahl 1660AM/35ma, 801 and Tamura F 7004). Without the driver stage the HF cut off started gently at 17kHz, but now it goes up to more than 35kHz, this is an octave! Not bad!
using the 6C45 I had WE437, which is in this set up simply not
necessary. The 6C45 costs a fraction of the WE437 and sounds the
same. It has only two drawbacks, you have to find two similar tubes
(parameters are not as uniform, especially the µ so you have to
buy some more) and it is not sexy. So if you have to impress go for WE437.
6C45 differential amp for the tweeter section
this" David Haigner altered the frequency response of the Altec
515Bs (resonances between 1100 and 1700Hz ) and straightened the
Goto's impedance. A handful of parts but with breathtaking results.
Sometimes you ask yourself why use all this stuff when a simple
change of a single resistor or a little bit different value of a cap
can change the sound so much.
network for Altec 515Bs
to all the DIY guys: it is the crossover not the driver. David shows
this impressively with his Rho-speaker, but you need experience, time
and good equipment ...
these mods have been a nice step forward.
Joe's current system consists of:
Differential phono stage (EC8020, EC8010)
Differential cd amp (PC88)
Differential line stage (6H30)
Midbass: Differential 7N7 - Ultrapath 211 Altec 515B
Midrange-tweeter: 6C45, Ultrapath 801 - TAD 4002z
Super tweeter: differential 6C45, Goto SG 06
All in common are three phase power supplies (except the super tweeter amp), transformers everywhere and lots of iron.
are some more pics...
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