50w Single-Ended BAF2015 Schade Enabled

[Soundhappy]

Soundhappy,
what is the size of your heatsink? My input transformer is no brand, It is 600:600. Last time I used it in a DAC sounded really good.

I have yet to hook up the amp for an audition, probably I will this weekend.

Thanks Dmy!
I do to get luck and try Jensen and Cinemag in the future.

One heat sink dimensions in inches :
width= 11.81
high= 12.99
deep= 5.11

Interesting CCS construction tip is not use one 0.2 R but 0.1R+ 0.1R two resistors.
With installed switch who connect 10 000uF to C or D tap points show on Mr Pass 2SK77B schematic.
In C position is 2H second harmonic character dominate and in D position is 3H third harmonic with less distortion.
With C tap connection B1XFRMR preamp can be nice I guess !
On D tap connection Korg B1Triode preamp can sound fantastic.
Please Dmy write about music reproduction quality from Schade 50W after first time prototype audition

 

[dmy]

Thank you Soundhappy for the heatsink size. I may start to hunt for more heatsink. I guess I should wait until I hear the amp first before spending more money. hehe......

Certainly I will report back my impression of the amp after I listen to it.
Last time I measured, with input grounded there was about 4+mv/AC on the output which I assume can be noise/hum. My speaker is not efficient (86db) this probably noticeable?

I have serveral tube preamps, I will see which one team up with this Schade amp well.

 

[Soundhappy]

I have serveral tube preamps, I will see which one team up with this Schade amp well.

Maybe You can find huge heat sinks from metals recyclers in the town ?
Cheap quick solution is car style mono blocks
Example photo show stereo amp but for 50 watt´s class A two mono's is better.
Then close them in beauty square boxes or not ?
Oh tube preamp that reason for 9V1 zener diode who protect IXYS mosfet.
Preamp with low output impedance ~ 25 Ohm is the best or use jfet's buffer with tube pre.
Have fun

 

[dmy]

Finally hooked up the amp. My speaker is a pair of bookshelf Kairos. Preamp is tube using Russian 4P1L, not ideal for the Schade 50w as its output Z is in the Ks range. I have been using this pre all this time in my system it is close by and easy to connect to so I used it. At this point I just want to find out if my prototype can paly music anyway.

Yeap, I heard music from the speakers but the highs were rolled off, badly. The bass was loose and muddy. Obviously the preamp was not capable driving the Schade. I do not have low output Z preamps all other pres are in the 1k - 1.5k range. I did not bother to try them I am afraid the result would be similar. I need a capable preamp.....

What preamp do you use to drive the Schade?

 

[Zen Mod]

have you CD with headphone output ?

or any other decent source , headphone out with volume ?

 

[dmy]

I might be able to borrow a CDP with variable output

 

[dmy]

have you guys experienced this, a loud popping sound when turning off the amp?

 

[Soundhappy]

No popping if turning off my Schade 50W

It's probably because big filtering capacitors.
Do You try make PSU with TH = CL-60 thermistors ?
....and with no polarised capacitor 0.0033 ( 3.3nF )rated ~150V or more.
See positions in the ciruit on Papa psu schematic example.

 

[dmy]

I did not use thermistor. I installed a 30 seconds soft start circuit to cut down the in-rush
current. I will replace the on/off power switch see if this would make a difference.

 

[analog_sa]

I will replace the on/off power switch see if this would make a difference.

Do you have a capacitor in parallel to the switch?

 

[dmy]

Do you have a capacitor in parallel to the switch?

No I did not put a cap there. I should try that. Thanks

 

[Soundhappy]

....I do not have low output Z preamps all other pres are in the 1k - 1.5k range.
I did not bother to try them I am afraid the result would be similar.
I need a capable preamp.....

What preamp do you use to drive the Schade?

@ Dmy

Life is easy if between tube preamp and Schade 50W You install jfet's impedance buffer.
Every preamp output ~ 1.5K with the buffer together become 25 Ohm and give excellent frequency response from DC to ~ 200KHz.
It's single-ended 50 watt's and 20 dB of gain from IXYS mosfet
so no need for lot of more gain from preamp if good quality audio source
DAC or CD player ( no gadget : tablet's , smartphone etc. ).
Input transformers sound performance of Jensen and Cinemag is highly recommended or similar ( better ?)
Worse input transormers roll off low and high frequency and bring more distorsion to the music.
Do Your input transformers specyfications datasheet are garantie OK for an audio power amplifier ??
Schematic source : First Watt
Best regards

 

[dmy]

I used this input transformer in a DAC before, it is not the transformer that roll off the freq.

The circuit you provided below, can the DC be kept at 0v all the time? It does not employ cap to block DC any DC at the output will saturate the input transformer though.

 

[Soundhappy]

Matched 2SK170 | 2SJ74 pairs with Ids ~ 8.2 mA is ideal
but trimmer do the job if not perfect match and you get 0V DC all the time, +- 12V buffer PSU is regulated, stabilized

 

[Soundhappy]

More informations about impedance buffer | passive preamlifier is in Papa article :

http://www.firstwatt.com/pdf/prod_b1_man.pdf

B1 Rev.1 output impedance = 50 Ohm so Schade amp can go -3 dB 100 kHz at high frequency.

This version is build with 4 pcs. of 2SK170 BL grade and have 10 uF electochemical capacitors at the output.

 

[dmy]

Thank you, Soundhappy. I will keep this in mind. The DIY audio store is currently out of the transistors

 

[Soundhappy]

This is verified genuine Toshiba seller , write him message about jfet's Idss=8.2 mA matched pairs.
Genuine Toshiba 2SK170BL/2SJ74BL high transconductance JFET complimentary pair | eBay

Perfect for the buffer no worry if little mismatch after all trimmer help to get 0V DC.

or this one Punkydawgs shop with tighty matched pairs but at higher price
Toshiba 2SJ74 + 2SK170 LAB MATCHED QUAD to 0.03mA AND 4mV (7ma range) | eBay

Greetings

 

[dmy]

Will look into building the buffer. Thanks.

 

[kacernator]

Sound quality

So, have someone finally compared Schade 50W to another amps?
Is it worth building this class A space heater?

 

[Soundhappy]

@ Kacernator

Simple answer : the excellent fidelity music reproduction is an complex art.

We can't separate amplifier from the audio source, preamplifier and the speakers interactions, sound coloration , psu quality etc.etc..

Schade 50 with C and D switch on the CCS can play more H2 or H3.
Your choice

50 watts from single transistor triode connected and with 20 dB of gain how many other amplifiers actually can do this ?

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