833A (GU-48) Amp

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pre65
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#1111 Re: 833A (GU-48) Amp

Post by pre65 »

Seven months since the last post and nothing has happened since then. :(

The transformer mods are still going to be done, but I really should get on with the 50W SEMOS first.

Just need a shed load of enthusiasm. :lol:
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#1112 Re: 833A (GU-48) Amp

Post by Mike H »

When a project becomes a chore?
 
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#1113 Re: 833A (GU-48) Amp

Post by IslandPink »

So this posting is a false alarm :roll: - I thought you'd started something !
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#1114 Re: 833A (GU-48) Amp

Post by pre65 »

No, not a "chore" as such. Just that my life has expanded a tad and audio amp construction is not the only thing to attract my attention.

I have "stumbling blocks" at the moment, one being the power supply capacitors. My frugalitanariasism is preventing me from purchasing what I think are the ideal caps, and my Ebay searches are not finding the "bargains" that would entice me to part with dosh from my pensioners purse. :(

Normal service WILL be resumed.

I must remind myself to ask Arabian Nick for an up to date copy of his capacitor stock, as I can't find the last one he sent me. :wink:
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#1115 Re: 833A (GU-48) Amp

Post by cressy »

You're not the only one phil, i need to give myself a kick up the arse and get the mike h amp built.
Things got in the way, and I got waylaid by more prosaic matters. I keep staring at it thinking must do this, or that.
Then bottle it and walk away and do something else......
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#1116 Re: 833A (GU-48) Amp

Post by Mike H »

pre65 wrote:I have "stumbling blocks" at the moment, one being the power supply capacitors. My frugalitanariasism is preventing me from purchasing what I think are the ideal caps, and my Ebay searches are not finding the "bargains" that would entice me to part with dosh from my pensioners purse. :(

Normal service WILL be resumed.

I must remind myself to ask Arabian Nick for an up to date copy of his capacitor stock, as I can't find the last one he sent me. :wink:
Frugalitarianism! Must try to remember that :D

Can't you just use "something" for the caps in the interim? Just so it works...
 
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#1117 Re: 833A (GU-48) Amp

Post by pre65 »

Mike H wrote: Frugalitarianism! Must try to remember that :D

Can't you just use "something" for the caps in the interim? Just so it works...
Probably. :wink:
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#1118 Re: 833A (GU-48) Amp

Post by Mike H »

Well there ya go. :D


Know what you mean tho when I'm doing valve amps stuff I'm doing valve amps stuff, when I'm not is cos I'm doing something else.
 
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#1119 Re: 833A (GU-48) Amp

Post by pre65 »

I have seen some 900v (working voltage) 116uf MKP capacitors, which would need to be used in pairs, 1800v rating will be enough.

Series R is listed as 4.6m ohm.

Is there any benefit using MKP over electrolytics in amp power supplies ?
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#1120 Re: 833A (GU-48) Amp

Post by pre65 »

pre65 wrote:I have seen some 900v (working voltage) 116uf MKP capacitors, which would need to be used in pairs, 1800v rating will be enough.

Series R is listed as 4.6m ohm.

Is there any benefit using MKP over electrolytics in amp power supplies ?
Perhaps I should have asked, are their any negative reasons for using MKP capacitors ?
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#1121 Re: 833A (GU-48) Amp

Post by Mike H »

Presumably we're not sure! :D

Benefit I'm guessing better chance of finding high Voltage MKP than high Voltage elec.


Personally if MKP I'd want them to be audio-grade, having had some unfortunate experiences with motor-run caps etc.
 
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#1122 Re: 833A (GU-48) Amp

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pre65 wrote:I have seen some 900v (working voltage) 116uf MKP capacitors, which would need to be used in pairs, 1800v rating will be enough.

Series R is listed as 4.6m ohm.

Is there any benefit using MKP over electrolytics in amp power supplies ?
are you sure you need an amp thta requires 1800v headroom in the power supply caps?
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#1123 Re: 833A (GU-48) Amp

Post by pre65 »

Paul Barker wrote:
pre65 wrote:I have seen some 900v (working voltage) 116uf MKP capacitors, which would need to be used in pairs, 1800v rating will be enough.

Series R is listed as 4.6m ohm.

Is there any benefit using MKP over electrolytics in amp power supplies ?
are you sure you need an amp that it would seem requires 1800v headroom in the power supply caps?

I'm fairly sure that I have NO NEED for such an amp, but as I have most of the parts for the rebuild it would be a shame not to finish them off.

Ht should be about 1300v depending on how it sims up when taking into account the change to cap input, which Nick suggested was a better option.

I need to get all the parameters measured first.
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#1124 Re: 833A (GU-48) Amp

Post by Paul Barker »

You made a very good 833a amp already. But I appreciate more than many the drive you are experiencing.
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#1125 Re: 833A (GU-48) Amp

Post by pre65 »

I found some 1200v (working voltage) 5uf MKP caps on Ebay, so have ordered four (4).

64A max and very low ESR, should be good for the first cap in pairs. :)

Coming from a supplier in Holland so will be a week or so.
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