That´about what I got with the bigger transformer.
I decided to to go Parafeed with LL1674.
An externally hosted image should be here but it was not working when we last tested it.
Just waiting for some (Green)capacistor.
This is the Schema I am going to use.
An externally hosted image should be here but it was not working when we last tested it.
I put another 1 ohm´s resistor in paraleell with the others,and got 2,75 A trough the amp,it gets a "little"hotter.
An externally hosted image should be here but it was not working when we last tested it.
Hi Lineup!
It is not magic!
In the Nishiki hybrid thread a dutch member "Culture" posted the place where I found the complet article. I made a little "tuning" on the pics for the parts values.
http://www.elektuur.nl/Default.aspx...61390&Free=True
Greets:
Tyimo
It is not magic!
In the Nishiki hybrid thread a dutch member "Culture" posted the place where I found the complet article. I made a little "tuning" on the pics for the parts values.
http://www.elektuur.nl/Default.aspx...61390&Free=True
Greets:
Tyimo
PCC88 Hybrid MOSFET
yes
now
I found also the Free PDF with article in dutch language
for free download.
I put here a working link to this PCC88 Triode + 2SK176/SJ56 MOSFET Follower.
Elektor1997 High-End Tube-MOSFET Hybrid - full article in PDF
yes
now
I found also the Free PDF with article in dutch language
for free download.
I put here a working link to this PCC88 Triode + 2SK176/SJ56 MOSFET Follower.
Elektor1997 High-End Tube-MOSFET Hybrid - full article in PDF
I try to answer instead.
Yes, you may have seen in the other PCC88 topic
that what they say, they are similar in data.
E88CC and PCC88.
Aside from the heater is difference.
Regarding the voltage gain ( ~18 ) and driving SEWA's 100 kOhm input
( if removing first 100kOhm resistor in SEWA circuit, the one to ground )
I cant see any problems using that simple SRPP circuit for SEWA.
-----------
Yes, it is much, much better to put the volume pot, 100 kohm, at the tube circuit input.
As you say, instead of that 100 kohm resistor.
-----------
The output from tube circuit need ONLY ONE cap to couple to SEWA.
As SEWA has got as high as 100 kohm input impedance,
470nF - 1.0 uF can be used. This is MORE THAN GOOD!
Of course you need no potentiometer at SEWA input.
Only that capacitor from tube output to SEWA input.
------------------
I am starting to wanting such a sound system, myself.
With the Single End SEWA Class A as power amp!
What will sound better:
The BOZ with 2SK216 as preamp
or the E88CC basic SRPP tube preamp.
I might start looking for and ordering some MOSFETs.
I will go for 2SK216 Bride Of Zen, if I can find this very good TO-220 transistor here.
Maybe I can use 2SK1058 Lateral MOSFET for SEWA.
I am sure this wouldn't be very bad.
lineup
Yes, you may have seen in the other PCC88 topic
that what they say, they are similar in data.
E88CC and PCC88.
Aside from the heater is difference.
Regarding the voltage gain ( ~18 ) and driving SEWA's 100 kOhm input
( if removing first 100kOhm resistor in SEWA circuit, the one to ground )
I cant see any problems using that simple SRPP circuit for SEWA.
-----------
Yes, it is much, much better to put the volume pot, 100 kohm, at the tube circuit input.
As you say, instead of that 100 kohm resistor.
-----------
The output from tube circuit need ONLY ONE cap to couple to SEWA.
As SEWA has got as high as 100 kohm input impedance,
470nF - 1.0 uF can be used. This is MORE THAN GOOD!
Of course you need no potentiometer at SEWA input.
Only that capacitor from tube output to SEWA input.
------------------
I am starting to wanting such a sound system, myself.
With the Single End SEWA Class A as power amp!
What will sound better:
The BOZ with 2SK216 as preamp or the E88CC basic SRPP tube preamp.I might start looking for and ordering some MOSFETs.
I will go for 2SK216 Bride Of Zen, if I can find this very good TO-220 transistor here.
Maybe I can use 2SK1058 Lateral MOSFET for SEWA.
I am sure this wouldn't be very bad.
lineup
I am currently using PCC88's in place of ECC88's in all of my preamp circuits. I run them at 6.2V without any issues, and I anticipate 10yrs of service because of the lean heater.
The only issue I would have with the SRPP is that it might not be drawing enough current to drive a mosfet. I would guess that its only drawing about 6mA and I would be happier with something like 10-12mA for such a heavy duty job. Do you know what its spec'd to be drawing.
Shoog
The only issue I would have with the SRPP is that it might not be drawing enough current to drive a mosfet. I would guess that its only drawing about 6mA and I would be happier with something like 10-12mA for such a heavy duty job. Do you know what its spec'd to be drawing.
Shoog
Theres absolutely no reason why you couldn't adjust it to draw more current, simply change the two cathode resistors. Don't have any personal experience with SRPP as i have heard mixed things about them and so avoided them.
The reason they are disliked is exactly the problem you might encounter with a mosfet - ie input capacitance of the load. They like a constant load impedance because the load variations directly feed into the top valve and effect its output. This is because the load is in parallel with the top valves cathode resistor and so dynamically varies the cathode resistors effective value. As you can see this would have a bad effect on linearity. If you can cast iron guarantee that the load load is constant over its total range then they should work very well.
As I have said before I think some rugged anode follower would be a better bet., something like a hot 12B4.
Hope that helps.
Shoog
The reason they are disliked is exactly the problem you might encounter with a mosfet - ie input capacitance of the load. They like a constant load impedance because the load variations directly feed into the top valve and effect its output. This is because the load is in parallel with the top valves cathode resistor and so dynamically varies the cathode resistors effective value. As you can see this would have a bad effect on linearity. If you can cast iron guarantee that the load load is constant over its total range then they should work very well.
As I have said before I think some rugged anode follower would be a better bet., something like a hot 12B4.
Hope that helps.
Shoog
Hi again!
I also decided to build Stefano Perugini's very nice 6N30's SRPP tube pramp too! It will give a lot of mA, so the Mosfet inputcapacitance is not problem. I hope.....
What do you think, what is the value of the Rload resistor, if I use it with the SEWA? 100K?
Tyimo
I also decided to build Stefano Perugini's very nice 6N30's SRPP tube pramp too!
It will give a lot of mA, so the Mosfet inputcapacitance is not problem. I hope..... What do you think, what is the value of the Rload resistor, if I use it with the SEWA? 100K?
Tyimo
Attachments
The 5687 is an excellent sounding valve with plenty of grunt. I have a backup preamp with the 5687 which sounds nearly as good as my main preamp (its CCS loaded). I found it difficult to get hum free without DC heaters - so I would advise to go straight for DC.
Cant find the datasheet, but if memory serves its got a mu of about 16.
Shoog
Cant find the datasheet, but if memory serves its got a mu of about 16.
Shoog
Tyimo said:
Very nice PCB!
Tyimo said:
6N30 / 6H30 / 6H30pi they say is a good Russian tube.
Gives a lot of mA current, good for drive!
------------------------------
See attachment, of SEWA Class A voltage follower.
In schematic, The SEWA input impedance is set by R2 and R9.
They are both 100 kOhm in original.
S, Input impedance is 100k parallel with 100k. And this makes it 50 kOhm.
But we do not need R9, if we couple the input ( R3 ) to a tube output.
( or any other output WITHOUT cap.
In fact WE MUST remove R9, if using an output that is not at 0V = ground level. )
This makes input impedance of SEWA is = R2 = 100 kOhm.
-------------------------------
I think using two 2SK1058 to replace those IRFP240 in SEWA
woul be a considerable improvement. If they can take the heat ..... ?
IRFP240 Ciss, input capacitance = 1300 pF
Hitachi 2SK1058, input capacitance = 600 pF
Big difference! Less than 50 % .....
There is another company that has taken over rights to Hitachi Lateral MOSFET.
---------------------------------------------------------------
Renesas provides lateral construction MOS FET optimum for high fidelity amplifier.
Power MOSFETs for General Amplifier:
Renesas - Lateral MOSFET List
They have made new clean and good DATASHEET for each Device!
*note:
Lateral MOSFET were specially made for use in Audio Amplfiers.
This is why they have lower Vgs, among other qualities.
IRF HEXFET are primary intended for Switching Heavy Loads very fast.
And NOT for low distortion HiFi amplifiers.
lineup
Attachments
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