Mr. Rollins: Hehehehe, it sounds like you’re getting caught-up on sleep!
While you’re here, I have a few questions about the power supply requirements for the tube front-end:
1: What is the current requirement for the regulated -6.3VDC filament supply?
2: What are the current requirements for the 350VDC and 375VDC supplies?
3: Do either the 350V or 375V supplies need to be regulated, or is a good CLC sufficient.
Also, we didn’t get much technical feedback on the circuit. Can we post it in the Tube section for comment?
Mr. Pass: Are there any other power supply rails you would like to have available – either for an optional solid-state front-end or for the glue (FET biasing, etc.) between the output section and the tube front-end?
-Casey Walsh
While you’re here, I have a few questions about the power supply requirements for the tube front-end:
1: What is the current requirement for the regulated -6.3VDC filament supply?
2: What are the current requirements for the 350VDC and 375VDC supplies?
3: Do either the 350V or 375V supplies need to be regulated, or is a good CLC sufficient.
Also, we didn’t get much technical feedback on the circuit. Can we post it in the Tube section for comment?
Mr. Pass: Are there any other power supply rails you would like to have available – either for an optional solid-state front-end or for the glue (FET biasing, etc.) between the output section and the tube front-end?
-Casey Walsh
Hi Nelson
Rob
Can you tel me the type from Jenson you use.Nelson Pass said:I recommend that you save up your shekels and buy at least one
of Jensen's dual primary/secondary line level transformers. You
can't beat them for passive conversion and/or isolation when
you want to look at something differentially or drive something
differentially. My AP System 1 uses them, and they cost maybe
$40 - well worth it.
Rob
check out www.jensen-transformers.com
for input transformers, something like the JT-11P-1HPC is
a good candidate in price/performance and for output
transformers maybe a JT-112-LCF.
for input transformers, something like the JT-11P-1HPC is
a good candidate in price/performance and for output
transformers maybe a JT-112-LCF.
Nelson Pass said:check out www.jensen-transformers.com
for input transformers, something like the JT-11P-1HPC is
a good candidate in price/performance and for output
transformers maybe a JT-112-LCF.
There is a stalled group buy for a Jensen JT-11P-1 input transformer here:
http://www.diyaudio.com/wiki/index.php?page=Jensen+Input+Transformer+Group+Purchase
are the specs close enough for this one to be used instead?
http://www.jensen-transformers.com/ln_in.html
Stan
Yikes! I missed the Smarmy questions earlier.
Treat this post as a "bump" (which is something I usually rant about--I hope that folks will forgive me) so that this thread bubbles back towards the top. If it's near the top, I'm more likely to remember to answer the questions.
For the nonce: Sure, post the thing in tubes if you want. My predictions as as follows:
One--Poster X will demand that I redo the circuit to use his/her favorite tube, the 6xxx or 12xxx.
Two--Poster Y will demand that I redo the output current source to use a more 'normal' tube current source involving a gas voltage reference tube.
Three--Poster Z will say,"Huh?"
The current requirement questions are entirely valid. I'll pull out the schematic (I've gone on to other things) and try to get a response posted, pronto.
Note, however, that my original goal of sticking to isolation (i.e. 1:1) power transformers got bent a little...unless, of course, you use 240V mains.
Grey
Treat this post as a "bump" (which is something I usually rant about--I hope that folks will forgive me) so that this thread bubbles back towards the top. If it's near the top, I'm more likely to remember to answer the questions.
For the nonce: Sure, post the thing in tubes if you want. My predictions as as follows:
One--Poster X will demand that I redo the circuit to use his/her favorite tube, the 6xxx or 12xxx.
Two--Poster Y will demand that I redo the output current source to use a more 'normal' tube current source involving a gas voltage reference tube.
Three--Poster Z will say,"Huh?"
The current requirement questions are entirely valid. I'll pull out the schematic (I've gone on to other things) and try to get a response posted, pronto.
Note, however, that my original goal of sticking to isolation (i.e. 1:1) power transformers got bent a little...unless, of course, you use 240V mains.
Grey
And links to HiRez versions...
http://photonlogic.com/PicServe/PM/IMG_3187.JPG
http://photonlogic.com/PicServe/PM/IMG_3181.JPG
-Casey Walsh
http://photonlogic.com/PicServe/PM/IMG_3187.JPG
http://photonlogic.com/PicServe/PM/IMG_3181.JPG
-Casey Walsh
moe29: According to my (non-linear) timeline, construction of the tube front-end is still a ways off. This project is a product of Nelson's and Grey's exceedingly generous intellectual philanthropy. The least I can do is build a few prototypes.
jacco (the NUT): I don't want the real estate bubble to pop -- I'd have to give up this hobby!
Oh, and leave his mother out of it! 
-Casey Walsh
jacco (the NUT): I don't want the real estate bubble to pop -- I'd have to give up this hobby!
Oh, and leave his mother out of it! -Casey Walsh
I have 2 more months to go and then i will be playing catch up as fast as i can!
I got good news also! The 7mm lump they found in my lung x-ray didnt show up on the CAT scan!!!! WHEEEWWWW!!!! No Cancer! Just a big medical bill!!!
I just sent Casey 120lbs worth of heatsinks. i am hoping he can use them! Should be enough for 6 channels.
Zc
I got good news also! The 7mm lump they found in my lung x-ray didnt show up on the CAT scan!!!! WHEEEWWWW!!!! No Cancer! Just a big medical bill!!!
I just sent Casey 120lbs worth of heatsinks. i am hoping he can use them! Should be enough for 6 channels.
Zc
monster amp
I am new to this thread but you guys have given me some ideas.
I built two mono hybrid amps about 15years ago using a 12AX7 in parallel as a voltage amp connected to a mu follower made up of two power pentodes (the ones used in the futterman amps-I think they 6jt6's-can't remember) wired as triodes. These I ac connected to the gates of 4pairs of hitachi mosfets (npn-pnp). I used a passive bias arrangement and protected the gates with zeners. I also used a speaker saver dc relay which would not connect the speakers until the tubes had warmed up and no dc was present on the outputs.
The output stage was run at +/-85v regulated and the front end was a regulated 400watts. I used those amps for many years and then gave them away. They put out 250watts class AB with a bias of 10watts or so class A. They were single ended. There were many articles in Glass Audio on hybrids. I have built the Pass Aleph 1.2's and the Pass/thargard A-75 which I am using today. I was thinking of designing a front end like yours using the 6sn7 in a differential mode and using a white cathode follower made up of 417A's or 5842's--(now hard to find). The 6h30 perhaps can be considered. This would have low output impedance and the 417A's are listed at 25ma output driven hard.
I would then directly drive maybe 12 pairs of ouputs biased class A using the standard transistor bias. I would imagine I would AC couple to the gates and use zeners to keep the gate voltage within SK's requirements. Inputs would be balanced and I would put a volume control on the front end. Erno Borbely at www.borbelyaudio.com has a balanced line driver which he claims can be used with a solid state output stage. I built this for use as a pre-amp as its gain is too low for a power amp.
My question to you is the following? Is there a magic number for driver current per mosfet? Your monster looks like 48 output devices. With only half that number, could the driver current requirements be lessened?
I am new to this thread but you guys have given me some ideas.
I built two mono hybrid amps about 15years ago using a 12AX7 in parallel as a voltage amp connected to a mu follower made up of two power pentodes (the ones used in the futterman amps-I think they 6jt6's-can't remember) wired as triodes. These I ac connected to the gates of 4pairs of hitachi mosfets (npn-pnp). I used a passive bias arrangement and protected the gates with zeners. I also used a speaker saver dc relay which would not connect the speakers until the tubes had warmed up and no dc was present on the outputs.
The output stage was run at +/-85v regulated and the front end was a regulated 400watts. I used those amps for many years and then gave them away. They put out 250watts class AB with a bias of 10watts or so class A. They were single ended. There were many articles in Glass Audio on hybrids. I have built the Pass Aleph 1.2's and the Pass/thargard A-75 which I am using today. I was thinking of designing a front end like yours using the 6sn7 in a differential mode and using a white cathode follower made up of 417A's or 5842's--(now hard to find). The 6h30 perhaps can be considered. This would have low output impedance and the 417A's are listed at 25ma output driven hard.
I would then directly drive maybe 12 pairs of ouputs biased class A using the standard transistor bias. I would imagine I would AC couple to the gates and use zeners to keep the gate voltage within SK's requirements. Inputs would be balanced and I would put a volume control on the front end. Erno Borbely at www.borbelyaudio.com has a balanced line driver which he claims can be used with a solid state output stage. I built this for use as a pre-amp as its gain is too low for a power amp.
My question to you is the following? Is there a magic number for driver current per mosfet? Your monster looks like 48 output devices. With only half that number, could the driver current requirements be lessened?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.