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Old 12th June 2013, 06:16 PM   #21
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...From the schematics it is easy to see why his rectifiers had short life. They were expensive and didn't sound good at all to me...
Rectifiers did not sound good ?
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Old 12th June 2013, 08:40 PM   #22
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I had a pair of the Quicksilver KT88 amps back in the 1980s. I had to buy a quad of 5AR4s at a time and ended up with stacks of them by keeping a quad or two in my stock. I sold the amp but kept the 5AR4s and they are now worth more than the amp....

I asked Mike Sanders for a schematic and he told me to draw it out myself; so I did.
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Old 12th June 2013, 09:06 PM   #23
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Rectifiers did not sound good ?
I think he means the amps.

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I had to buy a quad of 5AR4s at a time and ended up with stacks of them by keeping a quad or two in my stock. I sold the amp but kept the 5AR4s and they are now worth more than the amp....
Sad considering running 2 per amp, they should have lasted quite some time with a properly designed PS.

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Old 12th June 2013, 10:16 PM   #24
john65b is offline john65b  United States
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From the schematics it is easy to see why his rectifiers had short life. They were expensive and didn't sound good at all to me.
I think the Rectifier issue has been beaten to death by now. Everyone knows that first cap was almost 10x too big and gave those rectifiers a real short life. The couplling caps at 400v were not spec'ed high enough. Yes, got it.

Short of the reliability corrections, is this amp worth building? I think so. I like how simple it is. Williamson may sound better (maybe?) but too difficult to get dialed in correctly. This is why I initially asked if there were any real improvements with the tubes I have...but I think I will stay with the original design, and a KT88.
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Old 12th June 2013, 10:23 PM   #25
john65b is offline john65b  United States
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Palustris, that is not an 8417, but the KT88 schematic....is the transformer impedance 4200 ohm? What is the tube compliment? Sorry, not familiar with that amp...
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Old 12th June 2013, 10:47 PM   #26
45 is offline 45  Italy
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Rectifiers did not sound good ?
The amp didn't sound good, rectifiers just died after few hundred hours.
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Old 12th June 2013, 10:53 PM   #27
llwhtt is offline llwhtt  United States
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The input/driver tubes in that latest schematic are 12FQ7s.

Craig
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Old 12th June 2013, 10:57 PM   #28
john65b is offline john65b  United States
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45 - your schematic shows the KT88 with SS rectifier...how did your friend have to replace all those the 5AR4 rectifers if they were SS?? Or is that not a QS Amp schematic?
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Old 12th June 2013, 11:04 PM   #29
45 is offline 45  Italy
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Originally Posted by john65b View Post
I think the Rectifier issue has been beaten to death by now. Everyone knows that first cap was almost 10x too big and gave those rectifiers a real short life. The couplling caps at 400v were not spec'ed high enough. Yes, got it.

Short of the reliability corrections, is this amp worth building? I think so. I like how simple it is. Williamson may sound better (maybe?) but too difficult to get dialed in correctly. This is why I initially asked if there were any real improvements with the tubes I have...but I think I will stay with the original design, and a KT88.
You can modify the power supply but will not be enough. That simplicity is the main limitation for its performance. I didn't like it. I would rather build an amp from a classic Acrosound schematics. Like this below. The TO 340 was 5K plate-to-plate.
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Old 12th June 2013, 11:05 PM   #30
llwhtt is offline llwhtt  United States
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The schematic that 45 posted is an old Michaelson and Austin TVA-???, NOT a Quicksilver.

Craig
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