I have a 2SK1530/2SJ201 class A/AB (adjustable) amplifier, that has unity voltage gain and no negative feedback.
I have attached the circuit for one mono side, power supply included.
What should I drive it with? I would like a discrete voltage gain stage, with as little feedback as possible.
Thanks!
I have attached the circuit for one mono side, power supply included.
What should I drive it with? I would like a discrete voltage gain stage, with as little feedback as possible.
Thanks!
Attachments
How 'bout one with no feedback, highly linear, ultra low noise, outstanding common-mode rejection, can accept balanced and unbalanced sources, and has infinite PSRR?
An externally hosted image should be here but it was not working when we last tested it.
se
@ Steve: I don't know if you're joking, can I seriously use a transformer as a voltage gain stage?
Do I know you?
I do have a BOZ that I could use. I just wasn't sure if it was the right type of thing
Could I do the same thing with a 6N6P or 6N2P?
Do I know you?
I do have a BOZ that I could use. I just wasn't sure if it was the right type of thing
Could I do the same thing with a 6N6P or 6N2P?
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In theory I would suppose yes, however I've not used those tubes in practice. If I remember correctly the 6N6 is much like the 6H30 but for lower power duties. The main factors to consider are gain, internal resistance (R plate) and (perhaps the most important) the linearity. Check out the anode curves. The 6h30 is very good - notice how parallel the lines are. This leads to good open-loop performance which I guess you are searching for. When it is constant current source loaded the output impedance is roughly equal to the internal plate resistance, which is about 1350-ish Ohms for the 6H30. As long as your power buffer has reasonable input capacitance then they should match up fine. You will get a gain of about 14 from it as a single tube stage.
Oh absolutely.
Of course you can't take just any step-up trannie and drop it into any circuit or any situation. But as long as you provide it with proper loading, drive it from a source which doesn't overload it or have too high an output impedance, absolutely you can use a transformer as a voltage gain stage. And a very nice one at that.
se
Mr. Eddy was NOT jesting. While a trafo can't yield power gain, it most certainly can step a voltage up. Steve has put a considerable amount of resources into making trafo based voltage gain blocks work well.
Gripacer, what is the magnitude of the I/P signal and how much voltage gain do you need? If you are starting with the CDP "standard" of 2 VRMS, your best bet (IMO) is a vacuum triode. Why? Fact, vacuum triodes are the most linear amplifying devices ever made. If the gain structure works out, a 6SN7 section will require (sic) zero NFB.
Cool! My source is the (+) outputs of a CS4397 DAC chip. It puts out 1.4vpp (avg) according to the data sheet, but I think it puts out a full 2v, as it gets as loud as a regular CD player output, and doesn't require a preamplifier. RL=1k min, CL=100pf max.
What do you think is a suitable transformer under $50 ea?
Yes, I think that's a great idea too. After reading Lukasz Fikus' pages, I have been quite impressed by the triode as a voltage gain stage.
I'm not actually sure how much voltage I need...
- I am starting with around 2v
- The MOSFET stage is rated at 10w class A, 35w class AB.
- The supply voltage will be 18-0-18VAC
How much would be suitable?
I have 6N6P and 6N2P triodes on hand. Should I follow the Lampizator SRPP design (two triodes, self biasing)?
Hi Gripracer,
The trafo idea seems better than the JFET BOZ. I might try that one too sometime.
The JFET BOZ can be found here:
http://www.diyaudio.com/forums/pass-labs/103050-jfet-boz.html
Some of the posts are quite hilarious!
The trafo idea seems better than the JFET BOZ. I might try that one too sometime.
The JFET BOZ can be found here:
http://www.diyaudio.com/forums/pass-labs/103050-jfet-boz.html
Some of the posts are quite hilarious!
I'm really not sure, perhaps you could suggest a gain factor for these parameters?
- The MOSFET amp is rated at 10wpc/Class A, and 35wpc/Class AB.
- My source puts out 2v
- Speakers are ~90db sensitive
I do like the idea of a transformer voltage stage the more I think about it
Here is the BOZ that I built. I used a PCB from jims_audio on eBay. The JFETs and rectifier are not installed in that picture.
An externally hosted image should be here but it was not working when we last tested it.
I'm really not sure, perhaps you could suggest a gain factor for these parameters?
- The MOSFET amp is rated at 10wpc/Class A, and 35wpc/Class AB.
- My source puts out 2v
- Speakers are ~90db sensitive
I do like the idea of a transformer voltage stage the more I think about it
Well, it'd put you pretty much right at the edge of what I'd recommend, but consider the CineMag CMLI-10C.
What's the input impedance of your MOSFET amp? Should be ok if it's 1Meg or more.
se
And that depends largely on the proper care and feeding of the transformer. If that's done right, it can work spectacularly well.
An externally hosted image should be here but it was not working when we last tested it.
se
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That's a matter of perspective. A large percentage of music lives below 2 kHz, just where your plot starts to fall apart. Very fine at high frequency, yet the the deterioration of performance with decreasing frequency is very poor.
I've always figured that a constant level of distortion against frequency contributes to good overall sound quality of a system, however I may be wrong.
(Perhaps somone should invent a transformer with built in negative feedback
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