• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Bad sounding Grant G100 AMS KT88 Amp

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#42
Oh, I didn't even think about that. Yes, the tubes are going to greatly affect the sound. I think the new Genelex 12AX7 is a good-sounding tube. And the Gold Lion KT88 is probably the best new version of that tube. Especially if you are trying to squeeze 100 watts out of a pair! I find the Russian-made tubes generally sound much better than the Chinese.
 
#46
grovergardner said:
Typically, a Williamson amplifier will have low sensitivity and require a healthy drive voltage. My original Williamson-style monoblocks do. There's also good bit of Miller capacitance at the input. I could also be that the amps are very revealing. ;-) They were certainly well-regarded back in the day.

I use an Aikido-style 6SN7 preamp with mine and it's a wonderful match--lots of voltage output and a very linear, low-distortion signal. Using my DAC as a source isn't nearly as satisfactory.

IMO any decent 6SN7 preamp, like an Icon or Cary, would be a good match for a Williamson. Also good would be a triode 6V6 preamp. You definitely want active gain. I personally have a preference for octal preamps.
Click to expand...
I have in stash oscillating Audio Research SP-9 MKll, what do you think about this preamp? Is it worth to repair or trash it? 6922 I have replaced, but it changed nothing, so I think it one or several FETs.
petertub said:
If the amp sounds bad i would start with some measurments to find out what shortcomings there is. Speculation
without data is just speculation
Click to expand...
If you read the thread, you found out why amp was sounding bad. After measurements (not all of them is here), repair and adjustments amp sounds quite good.

And finally all caps are arrived, this might help to improve the sound too.
 
#47
I have not read the full thread but was amazed by all advices that seemed to be pure rubbish.
An amp that sounds bad has faults that decent measurment will catch, and with them as base fault
diagnosing and correction ought to be a straight forward thing.
I understand that you have measured and corrected the amp, which i obviously missed in my fast reading, sorry and congrats to a successful repair.
 
#48
petertub said:
I have not read the full thread but was amazed by all advices that seemed to be pure rubbish.
Click to expand...
I was too, thought here I can find someone, who have had this amps and knows something about them.
petertub said:
An amp that sounds bad has faults that decent measurment will catch, and with them as base fault
diagnosing and correction ought to be a straight forward thing.
Click to expand...
I know this, but earlier have not much time to properly diagnose the amps. And then thought they are ok, but sounding rubbish.
petertub said:
I understand that you have measured and corrected the amp, which i obviously missed in my fast reading, sorry and congrats to a successful repair.
Click to expand...
Thank you very much!
 
#49
Masa1897 said:
I have in stash oscillating Audio Research SP-9 MKll, what do you think about this preamp? Is it worth to repair or trash it? 6922 I have replaced, but it changed nothing, so I think it one or several FETs.

If you read the thread, you found out why amp was sounding bad. After measurements (not all of them is here), repair and adjustments amp sounds quite good.

And finally all caps are arrived, this might help to improve the sound too.
Click to expand...

It's been eons since I heard ARC equipment but the SP-9 is highly regarded and would probably serve very well here. I personally would be lost in repairing a preamp with SS components. ;-) If you can find a way to do it it would be worth it, I'm sure.

Have you ever DIY'd your own components?
 
#50
grovergardner said:
It's been eons since I heard ARC equipment but the SP-9 is highly regarded and would probably serve very well here. I personally would be lost in repairing a preamp with SS components. ;-) If you can find a way to do it it would be worth it, I'm sure.
Click to expand...
Thanks, need to find time and figure out wich FETs are bad. The problem with FETs is that, they're only marked with color not the type.
grovergardner said:
Have you ever DIY'd your own components?
Click to expand...
Many of them. But now I have not much time to design something from scratch.
 
#53
Sure.

Sadface

Thread 'Home Brewed Aikido Preamp'

G'day Guys,

I've been working through this one for a while now and I have nailed down enough of the design details to do a board layout.

Firstly a bit of background as this is not my first rodeo with the Aikido.
My first was a Tubes4hifi.com SP14 kit which I have absolutely loved the sound of since it first fired up something like a decade ago.
http://www.tubes4hifi.com/SP14.htm

I've also built one using Broskie's 12vac Aikido pcb.
New Aikido 12Vac PCB and part kits
I built the 18vac version using 12AU7 tubes. This is testing in my system. It's an amazingly elegant solution...

Be sure you use the final version. They work nicely, no ground loops!
 
#54
Here is the thread for the Aikido boards by @Sadface . Gerbers and documentation in post #20.
Sadface

Thread 'Home Brewed Aikido Preamp'

G'day Guys,

I've been working through this one for a while now and I have nailed down enough of the design details to do a board layout.

Firstly a bit of background as this is not my first rodeo with the Aikido.
My first was a Tubes4hifi.com SP14 kit which I have absolutely loved the sound of since it first fired up something like a decade ago.
http://www.tubes4hifi.com/SP14.htm

I've also built one using Broskie's 12vac Aikido pcb.
New Aikido 12Vac PCB and part kits
I built the 18vac version using 12AU7 tubes. This is testing in my system. It's an amazingly elegant solution...
 
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