The Midlife Crisis - My 833C Amp Build

Magz · 2013-05-14 2:52 pm

The OPT cores are Metglas AMCC1000. Attached are the specs for this series from Elna Magnetics:

http://www.elnamagnetics.com/wp-content/uploads/catalogs/Metglas/powerlite.pdf

Magz · 2013-05-14 3:56 pm

BTW, OPTs have both 4 ohm and 8 ohm taps. I'll be using the 4 ohm with my hot-rodded Infinity RSIIb speakers.

Unison845 · 2013-05-14 4:31 pm

Hello Matthias,

Did you plot the frequency response of the Hammond 1642SE transformer? Does it have any ringing problem?

Mister Ed said:
Hi,

This is an very intresting thread, because I was starting my own "Midlife Crisis 833C Amp" nearly at the same time (On March 18 I was ordering two of this "Monster-Tubes" to playing around with this ).

So I try to discribe this project in my bad english...

The starting Point was the german "silvercore-project". But in my opinion is 15W out of this Monsters like sex with no touching . For this I don't need to build a new amp, I could use some of my older projects...

The frist step were a lot of simulations with LTSpice...and some tests with the B+
The Picture shows the current and at the voltage near 1kV...
833c Test | 833ctest | hifi-forum.de Bildergalerie

And yes, the Spice-model of the 833A is far away from real 833C!

I was calculating the amp for about 50W sine...makes a B+ of about 1kV and a bias current of 200mA.

The reason were, I want to use normal available parts for all... And 1kV is much more handy like 2.3kV ...Over all it was expensive enough to be an "Midlife Crisis Amp" also.
The first two stages are build from one 12AT7 followed by an SRPP (2 x 6CV7/EL34) in triode mode driving the 833 with up to 100V peak to peak
trough an electolytic capacitor of 47uF (briged by 100nF MKP).
I use a lot of Hammond transformers, including the OTP 1642SE.
Kupfer und Eisen...1642SE | eisen1642se, kupfer | hifi-forum.de Bildergalerie

Ok, the 8ohm outputs of this transformers are useless, but because I have 8ohm speakers only I can use the 16ohm output so I have a Raa of 10kohm and this seems to fit perfectly for the 833C...

Here some photos of one the ready monoblocks...while testing...
833C Endtest | 833c, endtest | hifi-forum.de Bildergalerie
SAM 0226 | sam0226 | hifi-forum.de Bildergalerie
833c | 833c | hifi-forum.de Bildergalerie

And some scope photos...
833C 20Hz | 20hz, 833c | hifi-forum.de Bildergalerie
833C 100Hz | 100hz, 833c | hifi-forum.de Bildergalerie
833c 1KHz | 1khz, 833c | hifi-forum.de Bildergalerie
833C 10 kHz | 10, 833c, khz | hifi-forum.de Bildergalerie
SAM 0234 | sam0234 | hifi-forum.de Bildergalerie
power...About 60V peak to peak are 50W sine...
833C 50W Audio | 50w, 833c, audio | hifi-forum.de Bildergalerie
And some photos at live action...
833C Amp | 833c | hifi-forum.de Bildergalerie
833C | 833c | hifi-forum.de Bildergalerie
833C Amp | 833c | hifi-forum.de Bildergalerie

Matthias.

JLH · 2013-05-14 6:21 pm

Magz said:
BTW, OPTs have both 4 ohm and 8 ohm taps. I'll be using the 4 ohm with my hot-rodded Infinity RSIIb speakers.

Beautiful transformers. I know they were not inexpensive , but would think they will be well worth it. Those are probably the nicest OPTs I've seen used in a 833 amp.

hpeter · 2013-05-14 6:22 pm

Magz said:
BTW, OPTs have both 4 ohm and 8 ohm taps. I'll be using the 4 ohm with my hot-rodded Infinity RSIIb speakers.

i bet it´s bit HEAVY

nhuwar · 2013-05-14 6:24 pm

Magz said:
BTW, OPTs have both 4 ohm and 8 ohm taps. I'll be using the 4 ohm with my hot-rodded Infinity RSIIb speakers.

Is that ruler metric or imperial? If its inches then those thinks are huge.

Nick

CV6045 · 2013-05-14 7:37 pm

Please please tell me where you got that Massive Output Transformer from ???

Magz said:
BTW, OPTs have both 4 ohm and 8 ohm taps. I'll be using the 4 ohm with my hot-rodded Infinity RSIIb speakers.

Funker · 2013-05-14 8:13 pm

Magz said:
I received an update from Monolith on the progress of my OPTs. The amorphous cores have been received and the bobbins have been wound. Performance is a little better than specification:

L=68H (spec>60 H)
-3dB FR = 7Hz - 66kHz (spec 8Hz - >60kHz)
32 Hz saturation frequency at 1400 Vrms input (spec <35 Hz)

Attached is a picture of the core from one OPT with the bobbin in place. Note the teflon dielectric. An metric ruler and an ECC83 are in the picture for size reference.

They are still waiting on the laser-cut enclosures; once those arrive the OPTs will be assembled and on the way to me!

Hi,
wow! What a huge piece of iron & copper.

Respect!!

73
Wolfgang

Magz · 2013-05-14 11:19 pm

nhuwar said:
Is that ruler metric or imperial? If its inches then those thinks are huge.

Nick

Metric.

Magz · 2013-05-14 11:20 pm

CV6045 said:
Please please tell me where you got that Massive Output Transformer from ???

Monolith Magnetics, located in Belgium. BTW, I don't have them yet, that's an in-construction photo from them.

www.monolithmagnetics.com

.

Magz · 2013-05-14 11:25 pm

hpeter said:
i bet it´s bit HEAVY

Each complete core (per channel) weighs 14.2kg. Then add in the wire, steel can, potting epoxy, etc.

MelB · 2013-05-14 11:40 pm

You sure this is going to be cheaper than a Corvette?

lexx21 · 2013-05-14 11:59 pm

Are they going to provide some sort of mounting hardware for the transformers or are you planning to build your own mount?

ethermion · 2013-05-15 12:03 am

So, at the current exchange rate, you are paying around $2500 per OT before shipping?

Props, indeed. Midlife, perhaps. Crisis, it certainly would be in my house.

Hope it works.

daqvin_carter · 2013-05-15 12:12 am

MelB said:
You sure this is going to be cheaper than a Corvette?

I fear I would choose the 883 amplifier over a Corvette.
Though my wife would probably not think so highly of me.

JLH · 2013-05-15 12:34 am

The Monolith Magnetics web site is getting crushed with traffic now - LOL!

N4BBQ · 2013-05-15 12:37 am

I'm loving this build. It gives me hope in humanity.

Magz · 2013-05-15 2:41 am

lexx21 said:
Are they going to provide some sort of mounting hardware for the transformers or are you planning to build your own mount?

They will be potted in a steel can with four mounting holes in the bottom. They will be mounted through the top panel of the Landfall Systems chassis...Landfall assures me the chassis can handle it with no sweat.

Mister Ed · 2013-05-15 3:01 am

Hi Magz,

WOW

....monstertransformer!..

How much are they cost?
I like this... a lot of iron and copper!

Matthias.

Magz · 2013-05-15 3:12 am

Mister Ed said:
Hi Magz,

WOW ....monstertransformer!..
How much are they cost?
I like this... a lot of iron and copper!

Matthias.

Well, you know what they say...the heart of an SET is the output transformer. Why skimp there?

Hell, there are people in this hobby who spend that much on a powercord! I consider this a much more sensible investment.

The Midlife Crisis - My 833C Amp Build

Member

Member

Attachments

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member

Member