• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

pma

Major Contributor
Joined
Feb 23, 2019
Messages
4,591
Likes
10,727
Location
Prague
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

Member
Joined
Apr 24, 2018
Messages
75
Likes
116
Location
Texas
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

Major Contributor
Joined
Sep 21, 2019
Messages
1,083
Likes
1,556
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

Major Contributor
Forum Donor
Joined
Mar 16, 2016
Messages
3,440
Likes
9,100
Location
Suffolk UK
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
 
OP
pma

pma

Major Contributor
Joined
Feb 23, 2019
Messages
4,591
Likes
10,727
Location
Prague
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

Major Contributor
Joined
Sep 21, 2019
Messages
1,083
Likes
1,556
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

Grand Contributor
Technical Expert
Joined
Apr 6, 2018
Messages
10,383
Likes
24,749
Location
Alfred, NY
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.
 
OP
pma

pma

Major Contributor
Joined
Feb 23, 2019
Messages
4,591
Likes
10,727
Location
Prague
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

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
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

Major Contributor
Joined
Jul 4, 2018
Messages
2,274
Likes
2,449
Location
Brookfield, CT
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

Grand Contributor
Joined
Mar 1, 2018
Messages
12,579
Likes
38,277
Location
Gold Coast, Queensland, Australia
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

Grand Contributor
Joined
Mar 1, 2018
Messages
12,579
Likes
38,277
Location
Gold Coast, Queensland, Australia
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

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,198
Likes
16,981
Location
Riverview FL
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
 
Last edited:

Doodski

Grand Contributor
Forum Donor
Joined
Dec 9, 2019
Messages
20,745
Likes
20,757
Location
Canada
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 ;)
 
Top Bottom