SEWA - Seven Watt Amplifier

[lineup]

Re: New BOZ on the run

Hi Mads and Lineup, my black belt Zen Masters!
----------

I can only recomend to build Mads BOZ with 2SK216!!!!


So, I would like to say thanks to Mads and Lineup
(and donn't forget to Mr. Pass! )
for all the help I got from you!!!


Now I would like to ask Mads:
---------
-Donn't you want to make an integrated design
and PCB for the BOZ-SEWA combo????

That would be
Tyimo

Yes, I would say 2SK216 (to replace original IRF610) is an upgrade of the BOZ preamp.
How much of an upgrade, is hard to say.
Anyway, I judge 2SK216 has some parameters better data for this very preamplifier application.
Among these qualities is LOWER Input Capacitance. Ciss = 90 pF (IRF610 has got 140 pF)
_________________________________________



I agree with Tyimo.
Maybe a new topic for the grand combo called:


BOZEWA


...............................................................................................

... what you say Mad_K ...
... I am trying to push a great new topic into your little head ...

Or why not you Tyimo
you may start The BOZEWA topic here
and share your good working combo with all other potential BOZEWA builders ..

And with assistance of Mad_K and lineup
you may manage BOZEWA thread very well.
Mad_K already has the SEWA thread to be in charge of ...


_________________________________________

Anyway:

I say BOZ is The 100% Perfect Match preamplifier for SEWA.
At least for me, I cant think of anything better.


1 MOSFET Single End Class A pre amp, voltage amplifier, Gain = 8-10
1 MOSFET Single End Class A power amp, current amplifier, with Nominal 7 Watt RMS output


_________________________________________


lineup

 

[qwad]

seems like l'm going to be the smart alec here, with a little parallel thinking l reckon it would be a whole lot simpler and cheaper to use a suitable step-up transformer as they do with some moving coil cartridges and microphones ehhhh? what do you recon mads?, this way you can use yr favourite existing preamps no? cheers TC

 

[Mad_K]

Nice report Tyimo I use Eagle. Integrated is not as interesting, I feel that the voltage and current amp are best kept in separate boxes.

 

[Tyimo]

Hi Mads!

Nice report Tyimo

Thanks!

I use Eagle.

Would you post to me the original Eagle file? I would like to redesign the BOZ PCB for the 2SK216 different pins (GSD) and for a bit biger trimmer pot, if it is possible.

Integrated is not as interesting, I feel that the voltage and current amp are best kept in separate boxes.

Yes, I can understand you, but I thought in that case we could use as less wire connections as possible.

Another question: Should I use Y interconnect cable between CDP and DVDP and the SEWA? I donn't want use input selector, because I can get only bad qualty types here.

Greets:

Tyimo

 

[Tyimo]

Hi Lineup!

... what you say Mad_K ...
... I am trying to push a great new topic into your little head ...

Or why not you Tyimo
you may start The BOZEWA topic here
and share your good working combo with all other potential BOZEWA builders ..

Unfortunately Mads is not interesting to the Integrated version.
Maybe later I will start a new thread, because I still have some upgrade ideas! But first I have to proof it!

And with assistance of Mad_K and lineup you may manage BOZEWA thread very well.

Thanks for your help, I will use it!

Greets:

Tyimo

 

[Tyimo]

Hi Tomcat!

it would be a whole lot simpler and cheaper to use a suitable step-up transformer as they do with some moving coil cartridges and microphones ehhhh?

I am afraid it wouldn't work. It would be too wimpy....

Greets:

Tyimo

 

[Mad_K]

Another question: Should I use Y interconnect cable between CDP and DVDP and the SEWA? I donn't want use input selector, because I can get only bad qualty types here.

Greets:

Tyimo

Bad idea! You'll get all sort of trouble with loading, ground loops etc
You'll have to switch cables, or try to get a 2 pole (or better yet; 4-pole) switch.

 

[Tyimo]

Hi Mads!

I got your mail! O.K.

Bad idea! You'll get all sort of trouble with loading, ground loops etc

Even if only the one source (CDP, DVDP) is on?

Tyimo

 

[Mad_K]

Yes. I strongly suggest you try to find another way. If you get stuck, I'll scrounge my junk box for a input selector for you

 

[Tyimo]

O.K.! Thanks! I will try to get a 2 pole switch

Greets:

Tyimo

 

[dzoli]

Hi Mads,

I received my boards.

Thanks,
Zoltan

 

[lineup]

O.K.! Thanks! I will try to get a 2 pole switch

Tyimo

See my attachment, Tyimo!


I have a couple of these 2-pole, 2-way switches.
These switches I bought has got the switch function: 1-on (off) 2-on
which means in middle position nothing is connected.
And in position 1 or 2, two poles of channel 1 or 2 are connected.

But for this case will be best to try to find switch:
2-poles, 2-way; with function: on - on
which is only two switch positions.


lineup

 

[Tyimo]

Hi Lineup!

Thanks! I konw these switches and I have some too. Maybe I will use them.

I See you attachment and the background is very smart!! It is the Elektor hybrids output stage.....

Greets:

Tyimo

 

[lineup]

Thanks! I konw these switches and I have some too. Maybe I will use them.

I See you attachment and the background is very smart!! It is the Elektor hybrids output stage.....

Either you would have to use 2 such switches ( 2-pole, 2-ways )
or use one switch ( 4-pole, 2-ways ), like I think Mad_K mentioned.

For me it would be okay, to use two switches,
one for left channel input and one for right channel.
It is more flexible.
Besides, to find a good quality 4-pole switch is not always easy.
------------

Yes,
it is the ElektorHybrid MOSFET follower Current Amplifier.
Using Complementary Lateral MOSFET: 2SK176 / 2SJ56.
To put after the Triode Tube Voltage amplifier.

P1 is for set the idle current to 100 mA in MOSFET.
P2 is for adjust for Zero DC-Offset at output.
There is also a relay, at input, maybe for some delay after power switch on.


lineup

 

[Tyimo]

Thanks Lineup!

One more question:

Do you know the specs of the Elektor Hybrid's tube stage?
I mean would it be good for SEWA preamp? How many gain and output voltage has it? I think it could be good....

Tyimo

 

[lineup]

Thanks Lineup!

One more question:

Do you know the specs of the Elektor Hybrid's tube stage?
I mean would it be good for SEWA preamp?
How many gain and output voltage has it?
I think it could be good....

Tyimo

The PCC88 with voltage supply 138V ( should be within 130-140V )
and in SRPP configuration
and with those components as show in attachement here below
has got following performance.
(It should be noticed, that this is with a very light load.
I think the input stage of MOSFET current amplifier, in schematic in post above is very high:
Possibly 200k or more. Notice input coupling caps are 1.5uF only )

PCC88 SRPP.
Tube Input impedance: 100k
Voltage Gain: +25dB ( x 17.8 )
Input 0.900V RMS gives 16V RMS out ( 65W into 4 Ohm )
Frequency: 10 (0dB) - 100 kHz (-1.7dB)
Damping factor: 3.2
Supply Current at 138V: Less than 5mA, maybe this is <2.5mA per Channel

The Tube Input does not need any Input Capacitor, normally.
=======================


I want to ask, Tyimo.
What is the trafo you use to get ~62 VDC for the BOZ preamp.
You use 1 trafo for both channels?
And what is the data for this transformer?

Is it toroid?
What is AC voltage and VA?


lineup - a tube amateur, does not know much

 

[Tyimo]

Thaaaanks Lineup!

I would like try this SRPP circuit, but with E88CC tubes. I know the heather voltage is different, but the tubes are very similar, it isn't it?

To answer you question here are the data's of my BOZ trafo:
Toroid
220Vac primer
2x30Vac secunder
50VA total
I use one for both channels. It gives 62Vdc under load.

Tyimo

 

[lineup]

Toroid
220Vac primer
2x30Vac secunder
50VA total
I use one for both channels. It gives 62Vdc under load.

How can 60VAC give 62 VDC?

Maybe you are not using a bridge rectifier? ( = 4 diode bridge )

You maybe use half wave rectification?

If I would use 'normal' bridge rectification of 60VAC
I would expect theoretically:
60 x 1.414 = 84 VDC, across the Main Electrolytic Filter Caps.

Especially since the load is not much for a 50VA trafo.
2Channels x 62V x 0.040A = 5 Watt, something.

 

[lineup]

About SRPP
and use E88CC in same way as PCC88
you have to ask those that know better.
But I am sure it could be used in basically same circuit
with a few resistor changes.

How much gain E88CC would give, compared to +25dB, I have no idea.

Anyway it has been said, that SEWA needs at least +20dB, = x10.
So I think PCC88 ( x17.8 ) would qualify, even with a bit more load, say 50-100kOhm load.


You better post that PCC88 SRPP circuit in my Tube Topic.
And ask the valve maffiosos!

Tube Pre Amplifier for SEWA 7 Watt ClassA MOSFET

I think tube guys would easily modify that SRPP schematic to fit E88CC.

 

[Tyimo]

Hi Lineup!

How can 60VAC give 62 VDC?
Maybe you are not using a bridge rectifier? ( = 4 diode bridge )
You maybe use half wave rectification?

I don't know.
I use the BOZ PSU designed by Mads. Maybe may trafo has a bit higher secondary voltage, or my 9.1V Zeners are not so correct, or the new BOZ PSU with the IRF630 give a bit higher regulated voltage. I will measure for you in this evening in different points the voltage values.

O.K. I will post the SRPP there.

What is your favorite record and song? I would like to ask mads too! We could send our best and favorite testing number to each other?!? What do you think?

Greets:

Tyimo