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What is on your workbench right now?

pma

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I am curious what what is on your workbench right now. I am testing a "small" power amplifier module :).

amp_test.JPG
 

House de Kris

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Just yesterday I opened up an E-mu ESI-32 to replace the 20x4 LCD display. I've given up on trying to guess at what it says.
 

Cahudson42

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A 'new' (for me) Yamaha RX-596. Everything works! Including the input selector. Cost $18 from our US on-line 'Goodwill' thrift store . (Sorry not accessible from CZ Pavel:)

Only minor mod planned. Going to replace the idle current 'clipped resistor' adjustment - the 1k fixed replaced by a series pair of about 500-700ohm fixed, and a 500ohm multiturn pot. Need to be ordered..
 

sergeauckland

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Currently an original 1970 something Cambridge Audio P50 amplifier. I've had it for years, decided to measure it and check whether it still meets spec. (It's cold outside, and I was bored)

Distortion is fine, as is frequency response, but noise a bit over spec, but then I don't know how it was measured. I expected the noise increase to be hum, but it isn't, just a bit more hiss than I would have expected. Equal in both channels, so probably more to do with specs than a fault or components failing.

S
 
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pma

pma

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Interesting layout - tell us about it? A KA-5010 type? Or? Looks like about a 5kg heatsink:)
Hi, thanks for asking, it is not a KA-5010 topology. It is an amp with complementary differential JFET input, MOSFET cascode, MOSFET VAS and 4 pairs of 15A BJT power transistors. Brief schematics attached.

amp_pma.png
 

Cahudson42

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Brief schematics attached.
Neat! Maybe perfect for Magnepans. Or for a redo of the 'Back to the Future' speaker-blowing-up scene..

Will you be detailing it more on your website?
 

SIY

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Many things at once. Jan and I built a dummy load last night for power amp testing, he’s been working on a new all-pass filter, we’re in the throes of collaborating on a hybrid mic preamp design, and a low distortion oscillator with matching twin T notch filter.
 
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pma

pma

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Neat! Maybe perfect for Magnepans. Or for a redo of the 'Back to the Future' speaker-blowing-up scene..

Will you be detailing it more on your website?

There is an info on my web, the project is not new
http://pmacura.cz/pa2.htm
however it is a new implementation now, maybe higher supply voltage, maybe a bridge, we shall see :).
 

March Audio

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Many things at once. Jan and I built a dummy load last night for power amp testing, he’s been working on a new all-pass filter, we’re in the throes of collaborating on a hybrid mic preamp design, and a low distortion oscillator with matching twin T notch filter.


Just waiting for the parts to arrive to build this myself. Time is always an issue. Is Jan going to make the design available?
 

JP

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Many things at once. Jan and I built a dummy load last night for power amp testing, he’s been working on a new all-pass filter, we’re in the throes of collaborating on a hybrid mic preamp design, and a low distortion oscillator with matching twin T notch filter.

Was hoping you’d say Puffin :)
 

restorer-john

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John's been going through one of his storage sheds. Rang Dad to ask if he still wanted some turntable feet (he had an HK TT with rotten feet) and took him a few tables as parts only. "Do you think you can restore it and make it go, as I like these HK turntables?", he said after cleaning one all afternoon.

So, drilling out broken epoxied arm rests for replacement, replacing RCA/power cables, cleaning switches, bearings, repairing the FG board etc. All for a TT I nearly put in the skip...

My tip of the day for working on turntables: 3 toilet rolls. They are just the right height, soft but strong and can be placed over bearings, slid around to support the deck upside down, whatever.
hktt (1).jpeg


hktt (2).jpeg
 

restorer-john

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Just yesterday I opened up an E-mu ESI-32 to replace the 20x4 LCD display. I've given up on trying to guess at what it says.

A hot air rework unit can sometimes resurrect the ribbon-to-glass contacts and give you a working LCD. I've had a decent success over the years.
 

RayDunzl

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Mount for 75" TV...

Two four foot vertical angle iron (red lines) bolted to the back of the rack , with a fancy tilt/extend/swivel wall mount bolted to them.

Ok, so the cables aren't "dressed". Maybe after I finalize where the permanent things will go.

I had enough of that working Telecom. Don't worry about it. No hum, no buzz, no foul, and not really visible from the front.

Dust? Yeah, there's some. Working on it.

1580447112574.png1580462425579.png
 
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Doodski

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John's been going through one of his storage sheds. Rang Dad to ask if he still wanted some turntable feet (he had an HK TT with rotten feet) and took him a few tables as parts only. "Do you think you can restore it and make it go, as I like these HK turntables?", he said after cleaning one all afternoon.

So, drilling out broken epoxied arm rests for replacement, replacing RCA/power cables, cleaning switches, bearings, repairing the FG board etc. All for a TT I nearly put in the skip...

My tip of the day for working on turntables: 3 toilet rolls. They are just the right height, soft but strong and can be placed over bearings, slid around to support the deck upside down, whatever.
View attachment 48020

View attachment 48021
Nice setup for working on a, "hobby" @restorer-john ;)
 
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