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Independent review by Bob Macc - one of the first-movers of G21:

http://bobmaccsblog.wordpress.com/2014/ ... um-review/

Jakob E.

The full SOS review is now public:

http://www.soundonsound.com/sos/sep13/a ... af-g21.htm

Jakob E.

Thanks Leigh, Actually, Hannes Bieger of SOS magazine managed to figure most of this out by himself - but asked us for confirmation before publishing. I really respect that sort of in-depth work from a reviewer, when it comes to describe complex stuff like this. And btw you're right - this type of c...

The first user comments are starting coming out:

http://www.gearslutz.com/board/high-end ... bulum.html

Jakob E.

[quote="supafuzz"] Just be careful when you build those. There was transformer in and an input circuit that was redundant among other things. [/quote] Yes, there are several options available on the same PCB. You need to know what you want and what you're doing. If in doubt, refer to groupdiy.org - ...

The GroupDIY forum is probably the best place to start on studio-related DIY electronics:

http://www.prodigy-pro.com/forum/index.php

Jakob E.

Hi Tom,

That's a pretty good offer indeed!

If you have them in "electronic" form, i.e. scanned, it would be very nice to have a copy emailed to groupdiy@ gmail.com

(that's where we currently keep backups of good-to-have schematics - read the meta-meta at groupdiy.org for access info)

Jakob E.

yes. Look up the application notes on e.g. the NE5534 - usually has a simple high-grade RIAA described in detail..

Jakob e.

We've had a serious server array breakdown :? - but everything should be online again..

All the best,

Jakob Erland
Gyraf Audio

No problem, higher voltage ratings are always a good thing.

Unless, of course, for stuff like Zener diodes..

:-)

Jakob E.

[quote="brianroth"] I notice that the Gyraf circuit uses the same "common" bias resistor for all four opamps, as I described. 10 Megs seems high me, however. 1 Meg is more typical for the input of a guitar amp. Bri [/quote] Yup - I agree that it looks strange, but real-life tests showed that many - ...

..that is, gyraf.dk - not gyraf.de..

Jakob E.

RDH4, Chapters 1,2 (Introduction to the radio valve) and 5 (Transformers):

http://www.gyraf.dk/schematics/schematics.html

Jakob E.

Gyraf G9/diy - Dual "real" tube micpre with all whistles and bells:

http://www.gyraf.dk/gy_pd/g9/g9pd.htm

Jakob E.

The page says quite clearly: "DO NOT ATTEMPT THIS PROJECT!" And the resulting oscilloscope will be a very poor tool, as a magnetic-deflected tube like a television tube will lack anything resembling linearity at all but the intended working frequencies (50-60Hz Vert, 15-16000Hz Horiz.) Oh, and you'l...