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View Full Version : Andrew from Australia. Fullrange and Concrete, DIY Tubes, Garrard 401



FR Drew
21-06-2015, 10:48
Howdy all, I'm Andrew from Canberra Australia.

While I've been playing around with HiFi since 1992, for much of that time my income has been restricted and other finance needs have come first. I've got a modest system, but in ways I would say it's quite advanced.

Speakers:
Audiosphere Model II's. These are a concrete ball with a single Coral Flat 5 fullrange unit reflex loaded. Not much output below 70Hz, power handling is limited, but around 92 or 93dB/w so I'm told. Blisteringly fast, quite flat response, but take no prisoners. If there are nasties, you will hear it.

My amp is a DIY affair which is the result of following a particular philosophy:

Better an amp that doesn't commit an errror in the first place than one that tries to correct it with feedback
As few stages as possible while still being usable
Avoid features that affect the time domain (like cathode bypass caps)
Run all stages in triode
Run all stages at the most linear place on the curve you can find

The result is quite a large amplifier for its power output, with 6CG7 triodes for input gain stage and concertina phase splitter (both biassed with LED's). PP output stage is EL84's in triode mode run with fixed bias. Zero local or loop feedback, no cathode bypass caps anywhere, coupling caps are Jantzen Superior Z film caps, one between the input stage and the phase splitter, and one for each arm of the phase splitter output to the EL84's. The result has about 6 watts of class A and instant recovery from overload. Volume control is with one of the now long discontinued ALPS Black switched attenuators.

Source:
Garrard 401 with upgraded main bearing on a Corian and Brushbox plinth, "The Wand" unipivot tonearm and an Ortofon Rondo Blue, feeding a Musical Fidelity VLPS/VPSU phono stage.

Cables:
Audio Magic XStream interconnect
Silicone insulated stranded copper generic for speaker cables (4m run)

My musical diet is pretty broad. A big chunk of 80's pop, old school Metal (Early Sabbath, Led Zep, ACDC, Deep Purple, the first 4 Metallica albums), Blues (Albert King), Female vocal (Joan Baez, Laurie Anderson, Michelle Shocked, Tracy Chapman, Sally Oldfield), World (Mike Olfield, Peter Gabriel, Inti Illumani, Deep Forest), Dance (Yello, Kraftwerk, The Orb), Jazz (Ellington, Oscar Peterson, Miles, Trane), Pink Floyd, ZZ Top As I said, broad...

Still on my journey to finish off the system. Speaker cabling needs sorting out and my feeling is that the phono stage is a weak link. Otherwise, I have to say I'm pretty happy. Just wish that I had more time to chill out and enjoy it.

Macca
21-06-2015, 11:05
Hi Andrew

Welcome to AoS. What a great intro post. Usually we ask if we can see some pictures of the set-up but in this case it is mandatory! ;)

struth
21-06-2015, 11:10
Welcome to AoS Andrew. thats a fine intro. if you have any pics then open a gallery thread as we love ty see good stuff..especially diy a!d new to us stuff.
Albert is one of my favs and i have most of his output, or a good chunk anyways... one of the greatest ever.
nice to have you onboard we have few from down under on the forum.

Ali Tait
21-06-2015, 11:25
Hi, sounds interesting, what is the bearing in your 401?

FR Drew
21-06-2015, 11:49
The bearing upgrade was a sintered brass cylinder with a conical top which replaced the original unit with the flat wear plate... Can't seem to find it on the web...

I'm presently away from home travelling with work, so pics of the system will have to take a while.

Eagle owl
21-06-2015, 15:44
Hello and welcome Andrew.

Geoff. :wave:

Barry
21-06-2015, 23:07
Great introduction Andrew.

We have several valve/tube amp designers/DIY'ers here who would be most interested in your design. :)

Again as has been mentioned some photos would be great if you can manage it.

Welcome to AoS

Regards
Barry

walpurgis
21-06-2015, 23:18
Hi Andrew. Welcome to AOS.

That's definitely one of the more comprehensive intros we've had. Top marks mate :thumbsup:.

So you're using Coral speakers. They are wonderful. I had the 'holy grail' Coral Beta 10s and made the proper full size horn cabinets for them. Wish I'd kept 'em.

Your whole system sounds very interesting. Some photos posted in our Gallery section would be most welcome.


Enjoy the forum,
Geoff.

FR Drew
22-06-2015, 03:52
There are times when I feel I took the soft option by building a triode class A PP amp, and that I should have gone triode SE if I were really serious. After all, this beastie still only gives me 6 or so watts to play with. I could have got that from any number of SET designs out there...

Still, re-tubing an output stage with 4 EL84's won't send me broke, even if I chase fairly special NOS ones. NOS 300B's on the other hand... Now *there's* a money pit...

FR Drew
24-06-2015, 06:41
Pics loaded:

http://theartofsound.net/forum/showthread.php?39208-FR-Drew-s-Garrard-401-DIY-PP-EL84-and-Audiosphere-system&p=659720#post659720

FR Drew
30-06-2015, 23:37
Pleased to report the arrival of some teflon coated silver plated solid core (18ga) OFC speaker cable from Audio Principe in Australia.

Only heard a couple of tracks thus far, but it sounds like there's a significant boost in clarity over the silicone insulated stranded speaker cable that I had previously.