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Old 10th April 2013, 01:16 PM   #31
Pano is offline Pano  United States
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Old 18th June 2013, 06:01 AM   #32
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Quote:
Originally Posted by Piersma View Post
Hi all,

Is anybody interested in almost all components and PCB boards for the ULTI-AMP as mentioned above.
It is available for anyone who is seriously interested in building his own audio power amp.

Best regards
Piersma
Dear sir, if you have the article about this amp, please post it to forum or send it to me at nkanil.klm@gmail.com or at least the pcb layouts.
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Old 18th June 2013, 12:55 PM   #33
Piersma is offline Piersma  Netherlands
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Default Lay-out

hi,

I have to disappoint you, i don't have any digital copy of the article nor the lay-out. It was done by Elektor 15 years ago.

best regards,
Piersma
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Old 22nd July 2013, 12:33 PM   #34
JackV is offline JackV  Netherlands
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Default UltiAmp

Hi Piersma,

Looks like the ultiamp was very popular in the Netherlands!
I build 2 Monoblocks for 10 Years ago.
Audio Quality is very fine compared to more expensive commercial Amplifiers.

From the beginning I have some issues which I couldnīt solve and now I learned to live with:

1. The Heatsinks (where the 4 Sanken Transistors are mounted) gets extremely hot. I now use heatsinks twice the size and still need to use forced cooling so the Protection doesn't shut down every half an hour in summer.

2. The 6.3A fuses are destroyed approximately once every two months.

All voltages and currents seem to be in the appropriate range. Although the idle current in the Sanken Transistors is slowly fluctuating between min 165mA and max 200mA.

Do you have any suggestions/Ideas/Experience with these issues.

Thanks in advance,
JackV
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Old 24th July 2013, 09:42 AM   #35
Piersma is offline Piersma  Netherlands
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hi Jack,

Over more than 10 years i have had a lot of (private)questions concerning this so called Ulti-Amp. All the builder ran into (serious) troubles, most of them are mentioned in this thread.

Temperature of the heatsink should be around 55 degrees (C)
What is your supply voltage and idle current?

When are the fuses blown? Powerup? It could be that the protection triacs are fired undeliberately. For a short time you might try it without.
I have had other Ulti Amps showing the same behaviour.

regards,
Piersma
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Old 25th July 2013, 07:38 AM   #36
JackV is offline JackV  Netherlands
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Hi Piersma,

Thanx for your reply!

I was also starting to blame the Triac's. How could one solve this, are they necessary when you can shut down the Optocouplers?

Railvoltage is +/- 42V, idle current in Powerstage 165-200mA.
I was thinking about ocsillation but I can't see anything with a Scope.

How did you solve these issues?

My Ultiamp is build original, that means no upgrades (2N..., BFX... are installed) I had to adapt the feedback circuit (Both 1M resistors) to get the offset to 0V.
Maybe this could be the issue.

Regards,
JackV
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Old 27th July 2013, 08:46 PM   #37
Piersma is offline Piersma  Netherlands
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Default Fuses blown

hi Jack,

You should check the output offset without the OP-77 DC servo, it should be in the range of serveral hundreds of millivolts or less. Extend the time to open de opto-couplers. This solved the problems in 2 Ulti Amp's which were brought in years ago.

regards,
Piersma
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Old 27th July 2013, 09:29 PM   #38
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Quote:
Originally Posted by JackV View Post
Hi Piersma,

Looks like the ultiamp was very popular in the Netherlands!
I build 2 Monoblocks for 10 Years ago.
Audio Quality is very fine compared to more expensive commercial Amplifiers.

From the beginning I have some issues which I couldnīt solve and now I learned to live with:

1. The Heatsinks (where the 4 Sanken Transistors are mounted) gets extremely hot. I now use heatsinks twice the size and still need to use forced cooling so the Protection doesn't shut down every half an hour in summer.

2. The 6.3A fuses are destroyed approximately once every two months.

All voltages and currents seem to be in the appropriate range. Although the idle current in the Sanken Transistors is slowly fluctuating between min 165mA and max 200mA.

Do you have any suggestions/Ideas/Experience with these issues.

Thanks in advance,
JackV
I found with class ab amps I didn't need very much bias current.
I got away with around 10mA and got no crossover distortion.
Sounded good too.
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Old 29th July 2013, 07:53 AM   #39
JackV is offline JackV  Netherlands
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Default Measuring Session

Hi Piersma,

I will perform a measurement session to get some values including your suggestion of a decoupled OP77 (and also I think the LM337).
The only drawback here is finding time...

By extending the optocoupler time you mean increasing the delay at which the optocouplers switch on during power-up (C3 / R4)?

I will post some results when I've performed the measurements.
I will also try to find out if the Triacs are activated shortly during Power-up. Maybe I will disable the Triacs completely (protection through optocouplers and Fuses).

@nigelwright7557: I believe the Ultiamp was originally designed with 200mA idle current through the SA/SC combination Class Ab

Regards,
JackV
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Old 19th August 2013, 08:38 AM   #40
JackV is offline JackV  Netherlands
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Default Measurements

It looks like the DC-setting is not correct.
The used LED's have a voltage of 1,7V, not all equal, therefor all currents in the Voltage amplifiers are too high. I will need to find LED's with specified 1,55V or change the resistors (R13, R14, R27).
Correction of DC offset is needed (already changed R74, R55) to succeed.
Also I found out that the currentsensing (Protection circuit 'A') is very sensitive. Measuring with a Multimeter resulted in two blown fuses (6,3A). For now i disconnected the Triacs.
maybe I could live without them!

Any suggestions?

Thanks!
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