Quicksilver

[lpd]

I recently rebuilt my Quicksilver 8417's to KT88 mono blocks. I rebuilt the power supply as per the Triode Electronics suggested via 100mf cap off the rectifier and strapping the 320mf caps together with 100K ohm resistor between them. Also put individual bias taps for each output tube, and a ultralinear/triode switch.

Here's the link to the conversion on the ps. Only difference on my amps is that I added a 100K ohm resistor between them (a friend suggested this).

Conversion

Any thoughts on this?

Also the front end is single triode 12AX7 to 12BH7. Is it recommended to convert this to the 12FQ7 version?

 

[Geek]

Hi,

I say go for a 5751

Cheers!

 

[lpd]

Gregg,
What do you think about the 100K between the caps? I've never seen this practice before although I'm still learning. Is there any negative aspects to this mod ie: power supply?

 

[Geek]

You mean the ones parallel with the caps? They equalize things with series caps. Keeps the dynamic voltages the same across each. Otherwise one may creep up until *poof*

Cheers!

 

[lpd]

The resistors are between the caps. He indicated that they added a little extra "filtering". Thanks for clarifying.

 

[Burnedfingers]

I had one KT88 Quicksilver in the past that had a diode mod in the power supply. Basically the diodes supplied the DC and the tubes slow turn on was the icing on the cake. Never lost a rectifier tube in a Quicksilver after doing the diode mod on the others I have owned.

I can't say that I agree with the Triode Electronics conversion. I have found the amplifier will function fine with or without the conversion. There is enough drive without paralleling up the tube sections to run 6550's or KT88's.

The bias modification is the best thing you can do for this amplifier.

THe 5751 is a fine replacement for the 12AX7 in the front end.

 

[lpd]

Hey,
I found the 12AX7 fine to drive the KT88....what about the power supply conversion? I like the double rectifier as well.

 

[Burnedfingers]

diode mod on my KT88 Quicksilver mono block amplifiers

 

[Burnedfingers]

I sure would like a copy of your KT88 amplifiers schematic.

 

[lpd]

Burned,
I haven't a schematic for you. I have a friend with the 12FQ7 version that I was considering copying but I like the 12AX7 driving the 12BH7 fine. I put a switch on my amp so that I can operate in ultralinear or triode on the KT88's which is nice to have as an option.

KT88's in triode are a very nice sounding tube. I sacrifice a little bass, but in triode it seems to have better detail.

Thanks,

peter

 

[john65b]

Old thread, but a bit confused on that 100k resistor in the beginning of this thread...

if you put that 100K between the positives of the caps (all current would have to run through this resistor), are you not dropping your B+ ? And wouldn't that resistor have to be a monster wattage of 1562.5 watts *(bias is 125ma)?

P=(.125)*(.125)*100,000?

I believe the 100k resistors are paralleled from + to - on the big 320uf caps...