To hopefully clarify things, the Transcendence "Grounded Grid" preamp DOES NOT USE a classic grounded grid stage ANYWHERE. Others have correctly described the circuit. The name is a FAKE!
Real grounded grid circuits have been used in audio, but very seldom. The ultra low input impedance of a GG stage seems attractive as a moving coil input stage, but it has many disadvantages. To bias the tube correctly and to isolate your fragile megabuck cartridge from potential disaster if a tube fails, normally one would need a coupling cap in there, and at such low impedances it would have to be a BIG cap, and hence very likely to be sonically ugly.
The only commercail usage I have ever seen of a real GG stage was the MC phono input of the VTL "Ultimate" preamp of the late 80s. An incomplete schematic is shown in the VTL "book" - they place a big electrolyic cap right in the millivolt signal path...
Regards, Allen
Real grounded grid circuits have been used in audio, but very seldom. The ultra low input impedance of a GG stage seems attractive as a moving coil input stage, but it has many disadvantages. To bias the tube correctly and to isolate your fragile megabuck cartridge from potential disaster if a tube fails, normally one would need a coupling cap in there, and at such low impedances it would have to be a BIG cap, and hence very likely to be sonically ugly.
The only commercail usage I have ever seen of a real GG stage was the MC phono input of the VTL "Ultimate" preamp of the late 80s. An incomplete schematic is shown in the VTL "book" - they place a big electrolyic cap right in the millivolt signal path...
Regards, Allen
Hi Allen,
As far as the impedance stuff goes, the input impedance of the line stage is 50K to 100K depending on which pot you use. The output impedance is like 200 or 300 Ohms.
As far as its name goes, i won't debate you whether it is a true grounded Grid or not. That is something you and Bruce ought to be discussing. However the name is a grounded Grid Preamp, so, GGP it is.
Thanks for your information on your kits. Interesting idea to have them in modules.
Ray Bronk
As far as the impedance stuff goes, the input impedance of the line stage is 50K to 100K depending on which pot you use. The output impedance is like 200 or 300 Ohms.
As far as its name goes, i won't debate you whether it is a true grounded Grid or not. That is something you and Bruce ought to be discussing. However the name is a grounded Grid Preamp, so, GGP it is.
Thanks for your information on your kits. Interesting idea to have them in modules.
Ray Bronk
So as far as Ray Bronk is concerned, if Bruce Rozenblit calls a circuit "grounded grid", then it is a grounded grid circuit even if it isn't. Has he been reading too much "Alice in Wonderland" recently? Seriously, the grouded grid circuit has been around and known as such in radio electronics textbooks for decades , probably before Rozenblit was born. In a grounded grid circuit the input is to the cathode and the grid is grounded (doh!) : it's for impedance matching purposes ; it's not of much use in audio, by itself. Rozenblit should be made to print correction slips for his book.
Look Guys,
Let's make one thing clear here. If it isn't a Grounded Grid line preamplifier, then that to me is no problem. my point is everyone the world over knows of this preamp as Bruce's Grounded Grid Preamplifier, even if it ain't so ma or in maybe your case Mum. I am not here to debate it, or discuss that. Like I said in a couple of messages ago, you guys need to be up on his messagbe board and debate with him whether it is a true grounded grid or not. All I am trying to do is to borrow one and see if I like it or not. It's either a preamp that people either love or hate. There is nothing in between. I'm just the poor smuck in the middle of this. I do appreciate the education. and thanks.
By the way, other than the book, I thought the Alice and wonderland movie was boring.
Ray Bronk
Ray Bronk
Let's make one thing clear here. If it isn't a Grounded Grid line preamplifier, then that to me is no problem. my point is everyone the world over knows of this preamp as Bruce's Grounded Grid Preamplifier, even if it ain't so ma or in maybe your case Mum. I am not here to debate it, or discuss that. Like I said in a couple of messages ago, you guys need to be up on his messagbe board and debate with him whether it is a true grounded grid or not. All I am trying to do is to borrow one and see if I like it or not. It's either a preamp that people either love or hate. There is nothing in between. I'm just the poor smuck in the middle of this. I do appreciate the education. and thanks.
By the way, other than the book, I thought the Alice and wonderland movie was boring.
Ray Bronk
Ray Bronk
Mr. Jduffy,
I would challenge you to go up to the Transcendentsound message board and ask Bruce why this is a Grounded Grid Preamp. I will be monitoring the board to see your question. As a matter of fact, he even mentions that as a fact that it was used in RF circuits You might go up to his site and read the stuff he says on it. Then go to the message board and post your question.
As a matter of fact, I would heartily suggest that all of you techy types go up there and ask him the same question, and give your reasons why you don't think it is a Grounded Grid Preamplifier.
Again, I am putting out the call, if someone has one of these sitting in a closet, because you found something better, then maybe I can work out something to borrow it from you for a week or so. Thanks, again for the education.
Ray Bronk
I would challenge you to go up to the Transcendentsound message board and ask Bruce why this is a Grounded Grid Preamp. I will be monitoring the board to see your question. As a matter of fact, he even mentions that as a fact that it was used in RF circuits You might go up to his site and read the stuff he says on it. Then go to the message board and post your question.
As a matter of fact, I would heartily suggest that all of you techy types go up there and ask him the same question, and give your reasons why you don't think it is a Grounded Grid Preamplifier.
Again, I am putting out the call, if someone has one of these sitting in a closet, because you found something better, then maybe I can work out something to borrow it from you for a week or so. Thanks, again for the education.
Ray Bronk
Hi Jduffy,
Actually, my apologies. I should have looked closer at the tags. I really ment to have this go to Barretter and others. They were both saying how this isn't a true grounded Grid. All I was doing was to say, hey go up to Bruce's board and challenge him on it, not here, where he can't even defend his position. I hope all goes well for you. Again, my apologies. Looking back, didn't mean to attack you at all.
Ray Bronk
Actually, my apologies. I should have looked closer at the tags. I really ment to have this go to Barretter and others. They were both saying how this isn't a true grounded Grid. All I was doing was to say, hey go up to Bruce's board and challenge him on it, not here, where he can't even defend his position. I hope all goes well for you. Again, my apologies. Looking back, didn't mean to attack you at all.
Ray Bronk
This borrows from the FVP5 but the passive feedback network is different, values scaled from Walt Jung's passive RIAA preamp. It sims to about +/- 0.3dB but I've found that the values always need more tweaking once solder has hit the copper.
I keep poking my head in from planting the dahlias.
I keep poking my head in from planting the dahlias.
An externally hosted image should be here but it was not working when we last tested it.
What are you trying to achieve? The circuit is quite old, the concepts involved are not overly complicated, and whether or not this deserves the name grounded grid has been discussed at nauseam. I presume there have been a dozen or so posts on the same subject over the years. Just accept that he is selling it under the name "grounded grid preamplifier".
DC- coupled ...
Hi,
look at the attachments here:
http://forum.frihu.com/read.php?8,5359,page=2
Kind regards
Darius
Hi,
look at the attachments here:
http://forum.frihu.com/read.php?8,5359,page=2
Kind regards
Darius
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