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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Wed Nov 02, 2011 8:57 am
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stratele52 wrote:
I won't change the 20 MFD capacitor for a 100 MFd , this will change the tone. Originals value or very closer are the best.
The amp have also two 70 MFD , 350 volts capacitors in series. This make a 35 MFD capacitor at 700 volts. High voltage capacitor is a must here.

Put only a good name brand capacitor; Sprague Atom or F&T, not import cap.

Replace also the bias circuit capacitor. It is a 80 MFD at 70 volts. You can put a 100 MFD at least 70 volts, 100 volts is better. This cap is very very important for keep your tube well biased if not red plating.

I'm very surprise if your friend is a tech and specialized on guitar amp and can't find specs anywhere ; Those available on web easely.
Here the schematics;

http://www.el34world.com/charts/Schemat ... _ii_83.pdf


+1

I'd question any amp tech who made such a recommendation for cap values when the original specs are so easily available. "Passion" is no substitute for competence.

JMOOC

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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Wed Nov 02, 2011 1:23 pm
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+1000 Retroverbial


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Wed Nov 02, 2011 5:34 pm
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Well, the reason he suggested is because it would give the amp a cleaner sound at louder volumes. I did have a small talk and said i wanted the amp to "break" after a certain point. So we decided on putting .47uf at 500V capacitors instead. And the stock speakers are not in good conditions so I'm switching them out for WGS Vet 10" speakers. They sound really vintage and warm.

heres a link to how they sound.

http://www.youtube.com/watch?v=H34FYYL3-Kg


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Wed Nov 02, 2011 6:41 pm
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What speakers are currently in the amp?

Arjay

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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Wed Nov 02, 2011 7:02 pm
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2 original speakers, but one is broken. And the other 2 have the original magnets but the cone has been replaced by a very genereic, very bassy one.


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Wed Nov 02, 2011 8:05 pm
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That tells me precisely nothing.

Can you post some pics?

Arjay

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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 1:24 am
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Dar5544,
I think you do a good move with other speaker. I'm pretty sure originals speakers are not as good like old ones in Blackface. Because CBS area.......

II,m curious about this cap 0.047uf , but wich one is it ? where it goes ?


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 8:02 am
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The capacitors are the 5 axial ones that go on the outside of the chasis and are covered by a metal plate. The original ones had leaked sometime and when i opened it the liquid was as hard as a rock. These were 20uf at 500v capacitors. I'm switchin them out for 47uf because i dont want the amp to break too early at higher levels, more headroom. But its not high enough to shape the tone waaayy too much,


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 8:37 am
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Those electrolytics under the doghouse are the filter caps for the power supply -- they have absolutely nothing to do with the tone of the amp.

Arjay

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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 9:29 am
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Retroverbial wrote:
Those electrolytics under the doghouse are the filter caps for the power supply -- they have absolutely nothing to do with the tone of the amp.

Arjay

Correct as usual,and I've been wondering why they think it controls breakup...somebody is misinformed,or uneducated on the function of tube amp components.


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 9:50 am
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Retroverbial wrote:
Those electrolytics under the doghouse are the filter caps for the power supply -- they have absolutely nothing to do with the tone of the amp.

Arjay


Yes It seems they affect the Tone


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 9:54 am
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Dar5544 wrote:
So we decided on putting .47uf at 500V capacitors instead.



Ok 47uf not .47 uf, really not the same.


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 10:38 am
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stratele52 wrote:
Retroverbial wrote:
Those electrolytics under the doghouse are the filter caps for the power supply -- they have absolutely nothing to do with the tone of the amp.

Arjay


Yes It seems they affect the Tone


:?: :?: :?:

The sole purpose of a filter-cap array is to provide ripple-free DC to the amp.

WTFO?

Arjay

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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 11:49 am
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I'm sure you'll write to me Retroverbial,

I must admit I read that somewhere in one of my (Weber ? ) book. I'll try to find where. Maybe it is a subtil tone change.

I will come back with this information as soon as possible.


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Post subject: Re: Suggestion on Silverface SR tube change.
Posted: Thu Nov 03, 2011 12:00 pm
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To weigh in... about the only thing I could think of... if more capacitance in the main power filter supply "IN GENERAL" can contribute to punchier, bit more responsive bass. But, really should be done keeping time-constants of your PS in mind. Not just abitrarily boosting the mfd.

Esp in tube rectified amps. Increasing mfd, too much can easily lead to rectifier failure.

Best way to do this is to add A BIG CHOKE in-between the first two sections of the PS filter circuit. We're talking a 1-2 Hy choke that can handle 100-200mA range (so we'll talking the size of a good 30 watt OPT).

This choke can effectively drop humming to zero. And is much better for the ripple effect on the rectifier and PT. But, you'll get a much tighter, cleaner tone. LOUD all the time. If that's what you want.

Check this Cita2 schemo:


http://www.drtube.com/schematics/harmankardon/cit2.gif


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