Hello all, Just wanted to bounce an idea off of those of you with more experience than I...
I have some small outputs from a sony reel-to-reel which are single ended and were originally used with 6AQ5's. They are 5K to 8ohm with a 600ohm secondary also.
As a simple breadboard excercise ( and because the breadboard is already configured) I would like to try a 6CG7 with both sections in parallel loaded by the opt. to drive a 45 with.
The paralled sections of the 6CG7 should have an Rp of ~ 3700 ohms, which I realize is a tad high to be optimum.
I could try cap coupling to the grid of the 45 but I would also like to try the 600 ohm secondary as well. That would be a 1:3 stepdown ratio correct?
My question concerns the gain and voltage to the grid of the 45. The loading by the transformer should allow me to swing more volts than resistive loading
but will it be enough if I use the 600 ohm secondary?
I am also curious if putting the 8 ohm output in the cathode of the paralled 6CG7 would be a worthwhile improvement. My understanding of cathode feedback is limited but it should A. lower output impedance of the stage and B. lower the gain somewhat as well.
My maths are a bit lacking unfortunately.
Any body tried this before?
I have some small outputs from a sony reel-to-reel which are single ended and were originally used with 6AQ5's. They are 5K to 8ohm with a 600ohm secondary also.
As a simple breadboard excercise ( and because the breadboard is already configured) I would like to try a 6CG7 with both sections in parallel loaded by the opt. to drive a 45 with.
The paralled sections of the 6CG7 should have an Rp of ~ 3700 ohms, which I realize is a tad high to be optimum.
I could try cap coupling to the grid of the 45 but I would also like to try the 600 ohm secondary as well. That would be a 1:3 stepdown ratio correct?
My question concerns the gain and voltage to the grid of the 45. The loading by the transformer should allow me to swing more volts than resistive loading
but will it be enough if I use the 600 ohm secondary?
I am also curious if putting the 8 ohm output in the cathode of the paralled 6CG7 would be a worthwhile improvement. My understanding of cathode feedback is limited but it should A. lower output impedance of the stage and B. lower the gain somewhat as well.
My maths are a bit lacking unfortunately.
Any body tried this before?
Unfortunately the only way it might work at all would be as a straight choke. Have a good look at the drive requirements of the 45 and understand that you need as much as 90V peak to peak to drive it full output, with straight choke loading a 6CG7 has sufficient mu to get the job done, but rp even paralleled is high. A 5842 might be a good fit with that transformer configured as a choke.
I've designed and built a number of amps with choke or IT coupling.
A nice little integrated with volume, and source selection is realizable with 5842 choke loaded into a 45.
A nice little integrated with volume, and source selection is realizable with 5842 choke loaded into a 45.
Thanks for the reply. I have around 15 5842's I can play around with since I have a couple of Tubelab SE's running in the house.
Just thought I would give the 6CG7 a try because I have about ten times as many of those...
This is my first time dipping my toes in the transformer coupling/choke loading waters. I usually use a 10M45S alone or as a cascode for a plate load.
I am planning a build with an interstage transformer driving a 307A and just wanted to mess about with the breadboard and some parts I have on hand to see if that direction is right for me before I drop the cash on some real iron.
Thanks for the advice, any suggestions for an interstage for this purpose that doesnt cost two arms and legs?
Just thought I would give the 6CG7 a try because I have about ten times as many of those...
This is my first time dipping my toes in the transformer coupling/choke loading waters. I usually use a 10M45S alone or as a cascode for a plate load.
I am planning a build with an interstage transformer driving a 307A and just wanted to mess about with the breadboard and some parts I have on hand to see if that direction is right for me before I drop the cash on some real iron.
Thanks for the advice, any suggestions for an interstage for this purpose that doesnt cost two arms and legs?
When p2p wiring with the 5842 would it be better to put a grid stopper on each pin "cone" style or just use one pin for the connection? Plate and cathode stoppers as well?
I do not have my scope anymore and cannot check for oscillation so I tend to go brute force at the moment.
I do not have my scope anymore and cannot check for oscillation so I tend to go brute force at the moment.
Since you do not have the scope definitely go brute force as you describe.
The transformer used as a choke may make a pretty decent load for the 5842, LF extension probably will not be the ultimate due to limited inductance but seems viable.
Lundahl would be my go to for either chokes or IT for this amp.
The transformer used as a choke may make a pretty decent load for the 5842, LF extension probably will not be the ultimate due to limited inductance but seems viable.
Lundahl would be my go to for either chokes or IT for this amp.
Since you have the 6CG7, which is a nice, low distortion triode, I suppose you could use it as a common-cathode stage, then DC or AC couple that to a 5842 cathode follower. Use the transformer/choke as the cathode load for the cathode follower (maybe?).
I mean, if you really want to hear what the 6CG7 sounds like and you really want to use that transformer that way...
Or maybe not.
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I mean, if you really want to hear what the 6CG7 sounds like and you really want to use that transformer that way...
Or maybe not.
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