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Yes, the OTL kit is a very good introduction to the breed as well.
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Well... It seems like the ol' grounded grid topic has raised its head again recently, with Anthony's AoS design, and Hamish's valve amp 'epiphany', since this topic was last contributed to ;)
Marco.
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OK, could I ask a question or two inspired from personal interest and not to interrogate anyone, or to upset anyone please??
Firstly, whatever happened to the Bill Beard designs, or even the man himself?
And lastly, does anyone with technical knowledge know the audio configuration of a "grounded grid" amplifier please, and what are it's virtues and characteristics please??
Regards
Dave
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I thought you knew about GG from a previous post elsewhere Dave? Off the top of my head GG where used in audio Freq applications and have high bandwidth, a very low noise floor and are very linear in operation.
They also have low o/p impedance but because the signal is modulating the cathode and not the grid the i/p impedance is also very low so a wide bandwidth buffer stage (like a cathode follower) is needed before the GG stage. Input overload margins are also very good.
As to sound I found they are very neutral, detailed and fast - nothing warm and cuddly about the presentation, in fact a good design like the BR one has little or no 'character' IMHO. The respond well to component tweaks IME.
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Hi Neal
Sorry no, and still no reply to my question "And lastly, does anyone with technical knowledge know the audio configuration of a "grounded grid" amplifier please, and what are it's virtues and characteristics please??"
So do you use a cathode follower into a grounded grid stage? Can't see why they would have a low output impedance though? Or electrically why it would be better than an ordinary grounded cathode stage? (thus saving one valve)
Nearly there I think?
Regards
Dave
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Baffles me too I thought a grounded grid input stage was input to cathode and grid grounded
but it seems you can call a cathode coupled stage anything you like.
See http://www.tubecad.com/2007/05/blog0106.htm
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Hi Dave,
Why the sudden obsession with grounded grid - are you planning on building something? :)
Marco.
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Glenn's doing something along those lines already *I think.* I'll have to dig his emails out, as he told me how differently he treats the line stage these days and Cathode something-or-other was mentioned.
Forgive my amateurishness here..
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OK I've dug out Audio Reality by BR.
He uses a 2 stage 12AU7A configuration. First stage is simple cathode follower, signal fed to grid, 75v plate voltage and cathode tied to negative 200v supply via 51K resistor. (Used for the reasons I stated above)
The signal is derived accross the 51K res and the CF o/p is direct coupled to the cathode of the next stage, the GG. The GG Grid(!) is tied to ground via a resistor and it uses an active plate load in the shape of another 12AU7A. The active load is coupled to the plate of the GG via a resistor and the output is taken from the cathode of the active load....so low o/p impedance.
If you have a look on the BR web site you can download Audio Reality as a PDF for $18, the cct is in the back with full description.
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A bit of a thread Resurrection from someone who has not posted on here for 12 years.....
I was chatting with a friend last night about old hifi shops I used to frequent, stuff I'd bought and how things used to be back then, and Subjective Audio came up.
A quick search reminded me about this place, and then I saw mention of Beard gear. I've just searched my old posts and this is from a reply I posted in 2009, about one of my experiences with Howard, must have been back in 1985..
I was a builder, driving a mini van (street cred - I had it in bucket-loads) and a scraggy scruffy mess too (me, and the van)
I went to Howard first to buy a cassette machine,and he opened the shop especially for me on a sunday, which really impressed. It was my first ever hifi shop experience.
A few weeks later, he called me to say he had something that I might be interested in.
So, off I trotted in my van late Saturday afternoon.
I was shown the beard amps and maggies, and told I could take them home for the weekend - now remember that this guy had no address for me, just my Mums address, as I was renting. I went to get my van from where I had parked it, and he got the gear outside the back of the shop. I pulled up, and once he knew I was there, he shot off, as he had a date of some sort. So, I was packing this gear into the back of the van when a copper came round the corner to see a scruffy geezer cramming big expensive boxes into a tatty van. 'Ello' ello' ello, he said, whats all this then. I explained that I had been lent the gear for the weekend, so had no paperwork to prove I hadn't nicked it, and Howard was out of reach (no mobiles back then).
I spent the next few hours at the station until my Mother was contacted and could vouch for me etc, then I was allowed to go.
Now, the maggies came ina big box - it was too long for me to close the doors, so I drove across London with the back doors open, a piece of string holding the gear that was worth 6 months income. Guess what - I got stopped by the police again, and it was only after my tale was verified that I was allowed to go home, finally.
Needless to say, I wasn't about to take the stuff back after all that, so kept it all, and thus began my life with a hifi. Still got the beard, though lent it to a friend many years back, so doubt I'll ever see it again, and the maggies are waiting in Mums attic for when I can bring them down here.
Back to today - The amp is still in use - I gave it to a friend to look after when I was in hospital for a prolonged time following a motorbike smash. My Linn LP12 (which didn't come from Howard) I left with my mum who threw it out as it was not playing at the right speed. The Maggies I gave to someone else a year or so ago as they had lived in my mums attic (if only the LP12 had been put up there) and anyway, I don't have the space for them.
Does anyone know what happened to Mark who worked at Subjective Audio ?
The friend who now has the Beard also knows Howard, but we didn't get round to discussing how.
Sorry for repeating my tale on an already old thread, but hopefully some might find it of some interest..
