Sonic Frontiers SFP-1

[Jempie]

HI

If got an Sonic Frontiers SFP-1 can I change the 12at7 for 12au7
I miss gain.

Thx
Jempie

 

[MINUX75]

YOU cannot. The bias is very different. the cut off is -2V for the ECC81/12AT7 and -8V for the ECC82/12AU7. The plate current is 10 mA both for the ECC81 and ECC82

 

[rayma]

If got an Sonic Frontiers SFP-1 can I change the 12at7 for 12au7
I miss gain.

It's unlikely that you can substitute the tube directly without other circuit changes.
Why do you need more gain, for phono or line level?
The 12AU7 is a low gain tube with a mu of 20. The 12AT7 has a mu of 60.

 

[directdriver]

SFP-1 schematics MC & MM stages

 

[Jempie]

Hi need more gain line level

 

[Jempie]

I need more gain I thought that the ecc81/82/83 can be change without damage anything.

I have try now an step up on MM but still not enough gain.
Many to try the change the fet.

 

[directdriver]

First you said you don't get enough gain at line level but the SFP-1 is a phono preamp. And now you said you need a "step up on MM". I am really confused. What is it that you're trying to achieve? Can you tell us more about your system or what's in the signal path, what kind of cartridge you're using?

 

[rdf]

View attachment 576418

View attachment 576419

Wherever you got these, thanks!

 

[Jempie]

Need more gain if I try an simple phonomena phono stage I have more gain. Now 58 phonomena 65
So if I need more gain on the line of phono I don't know

 

[directdriver]

Here you can find the specs and downloadable user manual. I wouldn't change the tubes and should leave them as intended. 12AU7 will give you LESS gain. Assuming you are using a low output MC cartridge, you can try to add a step-up transformer of moderate gain and make sure the MC stage's input impedance stays at 47K. Or you can using a high gain step-up transformer into the MM stage. Or you can use a line preamp with higher gain. Or.... use a different phono preamp!

Specifications
Frequency response: 20 to 20,000Hz
Total harmonic distortion: 0.05% at 1.0V input
Gain: 37dB (MM), 57dB (MC)
Output impedance: 47k ohms (adjusted internally)
Channel separation: >40dB
Tube complement: Sovtek/Mullard 6922, 12AT7A
Dimensions: 480 x 280 x 100mm
Weight: 10kg

 

[Jempie]

I have try an stepup t5 with MM, but when connecting the t5 less gain.
What does go wrong. It should have more gain.

 

[Jempie]

use the phono stage in MM 37dB with T5 26dB total 63 dB
connecting the T5 but the gain is lower instead of higher
strange....

 

[kevinkr]

There is no SUT I am aware of that is compatible with an MM (moving magnet) cartridge. Connecting an MM to a typical MC SUT will present the MM cartridge with something looking a lot like a short to its relatively high source impedance, the transformer gain will not compensate for that.

 

[Jempie]

So there is no way too increase the gain for mc
Then I need to sell this preamp

 

[Jempie]

how about the `jasmine LP2.5DU phono stage?

 

[Bare]

So there is no way too increase the gain for mc
Then I need to sell this preamp

Agreed Sonic Frontiers was wayyy More advertising Hype than actual performance.

 

[Jempie]

Ok thx

 

[DF96]

The circuit looks 'interesting'. I am unable to see exactly how they do RIAA, but I suspect that the curve will depend on valve gain rather more than is wise from an engineering point of view. Scope for tube rolling, though! Some may regard this as a good feature.

 

[Jempie]

DF96, can you help me with this I need more gain.
Thx

 

[DF96]

Sorry. To change the gain would need a redesign. To do a redesign would require a careful reverse engineering of an 'interesting' circuit - which may or may not contain basic flaws. You can't simply swap valves and get more gain.