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Old 14th October 2005, 11:20 AM   #21
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My contribution to this is: If it ain't broken don't fix it.

If the amp works good, don't do anything. There are always a risk messing things up and impossible to repair later. Replace parts only if you have to.

A thirty years old cap might have many years left if it has not been put out for high temperatures.
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Old 14th October 2005, 11:40 AM   #22
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Very sage advice Peranders having been there done that, I wholeheartedly agree (though I did get it back to working properly in the end )

Tony.
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Old 14th October 2005, 12:09 PM   #23
beppe61 is offline beppe61  Italy
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Dear Mr. Peranders,

thank you so much for your kind and very valuable reply.
Let me please ask you further opinions between the lines.

Quote:
Originally posted by peranders
> My contribution to this is: If it ain't broken don't fix it.
If the amp works good, don't do anything.

The fact at Odyssey Audio, a well considered audio company, offers caps increase made me think about the possibility.
And it seems indeed that a lot of their customers pay for it.
Without having their amps broken anyway.

> There are always a risk messing things up and impossible to repair later.

that is indeed a risk and a point.
But it is a sort of experiment. and what if the outcome would be remarkable?
It costs about 20 USD of surplus Sprague, Mallory ...

> Replace parts only if you have to.

I read that just replacing an electrolytic caps in series with the signal with a film one has a nice improvement in the sound.

> A thirty years old cap might have many years left if it has not been put out for high temperatures.
Nice to hear this. Sprague make great caps indeed.
My amp should be of the 1978 and they seem to work just fine.
But i don't know about their ESR now.

Thank you so much.
Kind regards,

beppe61
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Old 14th October 2005, 12:26 PM   #24
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Quote:
Originally posted by beppe61
But i don't know about their ESR now.
Hi beppe61,

This may not be an issue. I tested (measured) with speaker workshop some 16 yo caps I took out of my amplifier.

Now I'm not sure if the resistance that speaker workshop reports is ESR ( I'm assuming it is) but the 16 YO generic brand caps actually had lower resistance than brand new panasonic FC caps of the same value and voltage!!! (I can't remember the exact figures but I think it was something like 6 ohms for the panasonic, 3 ohms for the old ones, and 1.5 ohms for rubycon ZA) All were 10uf 16V from memory. I wondered whether it had been wise to replace them!! having said that I only checked two, and the amp did sound better ( the bass improved) after changing the caps out (note these weren't the power supply caps).... It is of course possible that I only thought I could hear a difference, but that is a whole other kettle of fish

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Old 14th October 2005, 12:27 PM   #25
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Beppe already made up his mind, i think.

Bartolomeo Aloia is the Nelson Pass of Italy.
I believe STEG is mainly in the car audio business nowadays.
If the amplifier you have is virtually the same as the one on Ebay it is a very fine looking amplifier, 30 years ago it must have been a luxury amplifier.

Even so, every commercial audio designer needs to monitor costs, the likes of Krell also.
Every dollar spent on parts raises the price tag by 5 to 6 dollars of the end product for high grade equipment.
The multiplication factor for consumer electronics is likely to be in the order of 10.
For an integrated amplifier choosing between a 7200uF or 15.000 uF capacitor will also be cost driven.
imo, replacing capacitors that were produced in the 52th week of 1975 is not a bad option.

Replacing them by bigger ones could be an improvement, but you'd have to check the rest of the powersupply, and see what the output stage is like.
But the looks, the choice of capacitors, and the name of the designer this must be a high quality design.
There is no point comparing an integrated class AB amplifier with a US high bias class A amplifier.
Putting 160.000uF in a vintage integrated amplifier is a waste of money and asking for problems.
Turning a classic Lancia Fulvia into a thoroughbred Ford Mustang is bad taste.
Maybe such a goodlooking Aloia design should be kept original.
No doubt there is room for upgrading, i have had very good results replacing and adding parts in amplifiers, such as; capacitors, resistors, transistors,opamps and different wiring.
Do you have the possibility of making/showing us a picture of the interior, Beppe ?
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Old 14th October 2005, 12:43 PM   #26
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by wintermute


Hi beppe61,
This may not be an issue.
I tested (measured) with speaker workshop some 16 yo caps I took out of my amplifier.
Now I'm not sure if the resistance that speaker workshop reports is ESR ( I'm assuming it is) but the 16 YO generic brand caps actually had lower resistance than brand new panasonic FC caps of the same value and voltage!!! (I can't remember the exact figures but I think it was something like 6 ohms for the panasonic, 3 ohms for the old ones, and 1.5 ohms for rubycon ZA) All were 10uf 16V from memory. I wondered whether it had been wise to replace them!! having said that I only checked two, and the amp did sound better ( the bass improved) after changing the caps out (note these weren't the power supply caps).... It is of course possible that I only thought I could hear a difference, but that is a whole other kettle of fish
Tony.
Hello Tony,

very interesting experience of yours.
I am already sold on the idea of replacing them.
Now I have only to find 2 nice 15 or 20.000 uF.

Thank you very much again.
kind regards,

beppe61
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Old 14th October 2005, 01:08 PM   #27
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The Krell is a class A amp, such amps demand very large capacitances in the power supply to reduce ripple as they are always drawing heavy continuous curents. Id probably replace the 30 year old caps with somewhat larger ones too. Dramatically increasing thier size may lead to problems with inrush currents and stress the rectifiers and transformer.
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Old 14th October 2005, 01:22 PM   #28
beppe61 is offline beppe61  Italy
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Hello Jacco,

nice to hear that Aloia is also known in The Netherlands.

>
Quote:
Originally posted by jacco vermeulen
Beppe already made up his mind, i think.
Bartolomeo Aloia is the Nelson Pass of Italy.

He is indeed one of the most famous (maybe the most) of italian audio designers.
This is a quite old (but still nice) design. Low global feedback, few parts, powerful power supply, nice components for its time.
I think they were hand-made and tested one by one.

> I believe STEG is mainly in the car audio business nowadays.
If the amplifier you have is virtually the same as the one on Ebay it is a very fine looking amplifier, 30 years ago it must have been a luxury amplifier.

Yes, same model. May be just a little more used.
It was about the equivalent of about 400 euro in the 1978.

> Even so, every commercial audio designer needs to monitor costs, the likes of Krell also.
Every dollar spent on parts raises the price tag by 5 to 6 dollars of the end product for high grade equipment.
The multiplication factor for consumer electronics is likely to be in the order of 10.
For an integrated amplifier choosing between a 7200uF or 15.000 uF capacitor will also be cost driven.
imo, replacing capacitors that were produced in the 52th week of 1975 is not a bad option.

Thank you jacco. So you approve the idea of the replacement ?
If only I could get a drop more in the bass.
I have compared this amp with a pair of Albarry monos and honestly there is no comparison in favour of the english amps.
Through the red front panel anyway I can see a 500 VA transformer and two huge caps.
Nice amps these Albarry.

> Replacing them by bigger ones could be an improvement,

I really hope so.

> but you'd have to check the rest of the powersupply

600 VA transformer. discrete diodes bridge. all in all nice.

> and see what the output stage is like.

a single pair of BJT in metallic case. I have to read the model.
the amp is specified at 70 W/channel with 8 ohm and about 100 W with 4 ohm loads.

> But the looks, the choice of capacitors, and the name of the designer this must be a high quality design.

I agree completely here. Actually I like its clean and punchy sound.

> There is no point comparing an integrated class AB amplifier with a US high bias class A amplifier.
Putting 160.000uF in a vintage integrated amplifier is a waste of money and asking for problems.

What do you think of 2 nice blue high-grade americans of about 15.000 or 20.000 uF?
Could you suggest any particular brand and model?

> Turning a classic Lancia Fulvia into a thoroughbred Ford Mustang is bad taste.

I cannot agree more. different cars for different tastes.

> Maybe such a goodlooking Aloia design should be kept original.

This amp will be like a test bench. As I said I am trying to get just some bass out of it.

> No doubt there is room for upgrading, i have had very good results replacing and adding parts in amplifiers, such as; capacitors, resistors, transistors,opamps and different wiring.

very interesting. I would like to have time to do the same.
I like very much the idea of restore audio things.

> Do you have the possibility of making/showing us a picture of the interior, Beppe ?
I will try to get a digital camera, that I do not own myself and shot some photos.
The power amp has a nice modular structure. Very interesting and possibility to extract these modules for any purpose.
Dear Jacco, as I understand you have a great experience on audio equipment mods, would you mind if I contact you privately?

Thank you very much again for your kind and very valuable reply.

Kind regards,

beppe61
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Old 14th October 2005, 01:31 PM   #29
beppe61 is offline beppe61  Italy
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Thank you Mr. Tweeker for your kind and precious advice.

Quote:
Originally posted by Tweeker
> The Krell is a class A amp, such amps demand very large capacitances in the power supply to reduce ripple as they are always drawing heavy continuous curents.

Of course, but in AB design there is the need to cope with impulsive high demands of current during musical peaks.
I think that a fast and big capacitance reservoir is always a nice plus.

> Id probably replace the 30 year old caps with somewhat larger ones too. Dramatically increasing thier size may lead to problems with inrush currents and stress the rectifiers and transformer.
Do you think that just doubling the total capacitance could cause some problems like those you mention ?
After all 30 years are always 30 years.
If one reads the lifetime value of caps I think that time has arrived.

Thank you very much again and kind regards,

beppe61
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Old 14th October 2005, 03:31 PM   #30
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Dear Beppe:
I am probably the least indicated to advice you but I value your interest in renewing your amp's life

My (limited) experience comes from building Hypex' UCD180 ClassD amp: an easy and rewarding experience. As these are modules one only has to put together the PS and connections. Believe me the sound is first class and the bass is excellent, not floor shaking but deep, expansive and articulated.

I'm sure you will notice an improvement in sound when you upgrade but first check rectifier's current capacity (they are cheap) and soft start (for your 600VA Tx).
Well, I have tried these caps:
1)BHC ALS40 (RS nş 381-9908 ) which are very good sounding, with excellent bass and a bit dark presentation.
2) Epcos Sikorel(RS nş 190-8955 ): great sounding, more transparent-detailed.
Those caps are NOT cheap! And probably overkill on your project, but in mine they were terrific. Note that this is a very personal opinion of caps that I found at RS components (search the site for better options).
You may consider these RIFA (RS nş189-793 ) wich are said to be very good and cheaper.

You may also consider changing the stock power cord and speaker/RCA connectors and internal wiring.

Appart that, I must say that I think you are a very kind and polite person and that your posts are a delice to read

I hope this helps

Mauricio
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