Sir, your repair bench is so neat and clean. What a great setup. I can only dream of having such a nice place to work. That is if I ever get the smarts to repair all of the gear I would like to. I wish I could send you my 3 NAD amps to you for repair. There is a very small chance that I could ever do the quality of repair the you do. 👍👍to you and your expert work!
Very nice! I love Krell gear. I had a bunch of those gnarly brown caps in my KSL too, some of them were crumbling apart. I like this one though, but I think I drink too much for separate left and right level controls, lol.
The Krell KS1-A is the real Krell beast, with two separate mono preamps each with its own chassis and each with its own power supply each having its own chassis.
Thanks Ben for responding. I am rebuilding some Krell KSA 250 and MDA 500 amps. I plan on replacing all those resistors I mentioned before. I will examine the internals on one and let you know what I find.
Excellent job. The Spectrol wire wound volume controls tend to wear out and need to be replaced or rebuilt. I had to replace one in a KBL because when it was turned all the way down it would still allow sound to come through. I was told by Krell it's a pretty common problem.
I thoroughly enjoyed this video. I am a proud owner of Krell PAM-3 that’s missing power supplies 😅.Any chance you can share the schematic for power supplies? Thanks
Not sure how the PAM-3 power supplies compare but I don’t have the schematic for these. The PAM-1 supplies are super simple. It’s just a transformer, bridge rectifier and a capacitor bank for the + and - rail.
If you are referring to the brown resistors in this PAM-1 with the colored stripes I believe those are wire-wound. I have been fooled by them in Audio Research gear from the same era. Some of them when broken in half exposes the metal wire. A carbon comp will just clean snap in half.
Thanks for the tour of the preamp, and sharing some work technique. Kind of crazy output power on that preamp, I can't see where that much is necessary to drive almost any amp, but you cant argue with it's numbers at what would be regular output levels. @ 19:15 It was a good idea to cut the lead instead of leaving them full length, but, I would have also considered getting the board in a vertical position so in heating the pad/lead area, it would transfer heat horizontally to the top / component side of the board a bit better, as I have always gotten better results with a desoldering - vac if I oriented the PCB in a vertical position. The dual external power supplies are crazy overkill IMO, considering the amount of power that preamp actually needs. You could easily negate the dual supply scheme by powering them off of the same AC breaker / line circuit as the large amplifier they are connected to, and the voltage sag from the load of the amp would drag both of them down anyways. Other high end manufactures like Audio Research and Threshold got by just fine with a single internal or external supply.
How do I make sure the top side of the PCB have enough solder when new electrolytic capacitors are in place? The bottom side has no problem because you solder the legs of caps directly.
@NovaluxStereophonic Thank you for your reply! So just one side (the bottom side of PCB) with solder on pad and capacitor 's leg is OK. As such, I doubt why the taking out of old cap need adding extra solder and not just suck all the old solder. Sorry for my dumbness.
@@KSWong-xi8cd The hole is so tight that the solder sucker cannot suck out the solder form the other side on this board. Most other PCBs the method that you suggest works fine.
why didn't hey design it to have two Pots on one knob! You would have thought that would have been a better way! you can even have the volume with a split knob so you can use it for balance. if it was me I would have converted it to that and just had the others as decorative. As I know the Ek caps is the red ones not the maroon ones that are bad! they seem fine I would have kept them in just tested them. it might have been nice to change the bridge rectifier for hire amperage do you know what amperage that is? and a lot of people make mistake and put these UF high frequencies that's not right that just pointless and causes more noise. I would have put a one ferret cap on the end of the power supply would have been nice there's not one on the amplifier? I hate blue LEDs can't stand them order to stuck with green or red or orange or even purple what you can do is rough up the face of the LED with some 600 grit paper it will disperse the light better. You can make the amplifier better by increasing THD to 0.1% in global feedback the designer actually criticise himself in this they were chasing numbers it's a good upgrade increase THD.
@@jamesadvincula477 The issue of quality translation still holds even with royalty free music. It’s like asking if you can call me and have me put you on speakerphone to listen to my system.
Ben, outstanding work!
@@SteveGuttenbergAudiophiliac Thank you Steve!
Great work, your attention to detail is fantastic 👍
Sir, your repair bench is so neat and clean. What a great setup. I can only dream of having such a nice place to work. That is if I ever get the smarts to repair all of the gear I would like to.
I wish I could send you my 3 NAD amps to you for repair. There is a very small chance that I could ever do the quality of repair the you do. 👍👍to you and your expert work!
Very nice! I love Krell gear. I had a bunch of those gnarly brown caps in my KSL too, some of them were crumbling apart. I like this one though, but I think I drink too much for separate left and right level controls, lol.
The Krell KS1-A is the real Krell beast, with two separate mono preamps each with its own chassis and each with its own power supply each having its own chassis.
Most over kill preamp I have seen so far. Krell never fails to amaze me. 🤑
I'm glad you went back to the original LED colors. I'm so tired of blue.
Thanks Ben for responding. I am rebuilding some Krell KSA 250 and MDA 500 amps. I plan on replacing all those resistors I mentioned before. I will examine the internals on one and let you know what I find.
Excellent job. The Spectrol wire wound volume controls tend to wear out and need to be replaced or rebuilt. I had to replace one in a KBL because when it was turned all the way down it would still allow sound to come through. I was told by Krell it's a pretty common problem.
You should recap your car every year! 😵
Neat
I thoroughly enjoyed this video. I am a proud owner of Krell PAM-3 that’s missing power supplies 😅.Any chance you can share the schematic for power supplies? Thanks
Not sure how the PAM-3 power supplies compare but I don’t have the schematic for these. The PAM-1 supplies are super simple. It’s just a transformer, bridge rectifier and a capacitor bank for the + and - rail.
cheers
Well done on the Krell Preamp repair! Have you found any issue with the carbon composition resistors used in some Krell designs?
If you are referring to the brown resistors in this PAM-1 with the colored stripes I believe those are wire-wound. I have been fooled by them in Audio Research gear from the same era. Some of them when broken in half exposes the metal wire. A carbon comp will just clean snap in half.
Nice quality film caps used throughout the signal stages but I'm surprised to see residual flox from Krell's manufacturing.
Thanks for the tour of the preamp, and sharing some work technique. Kind of crazy output power on that preamp, I can't see where that much is necessary to drive almost any amp, but you cant argue with it's numbers at what would be regular output levels. @ 19:15 It was a good idea to cut the lead instead of leaving them full length, but, I would have also considered getting the board in a vertical position so in heating the pad/lead area, it would transfer heat horizontally to the top / component side of the board a bit better, as I have always gotten better results with a desoldering - vac if I oriented the PCB in a vertical position. The dual external power supplies are crazy overkill IMO, considering the amount of power that preamp actually needs. You could easily negate the dual supply scheme by powering them off of the same AC breaker / line circuit as the large amplifier they are connected to, and the voltage sag from the load of the amp would drag both of them down anyways. Other high end manufactures like Audio Research and Threshold got by just fine with a single internal or external supply.
How do I make sure the top side of the PCB have enough solder when new electrolytic capacitors are in place? The bottom side has no problem because you solder the legs of caps directly.
@@KSWong-xi8cd The through hole is plated so as long as solder is on the bottom side of the board the connection to the top will be made.
@NovaluxStereophonic Thank you for your reply! So just one side (the bottom side of PCB) with solder on pad and capacitor 's leg is OK. As such, I doubt why the taking out of old cap need adding extra solder and not just suck all the old solder. Sorry for my dumbness.
@@KSWong-xi8cd The hole is so tight that the solder sucker cannot suck out the solder form the other side on this board. Most other PCBs the method that you suggest works fine.
why didn't hey design it to have two Pots on one knob! You would have thought that would have been a better way! you can even have the volume with a split knob so you can use it for balance. if it was me I would have converted it to that and just had the others as decorative.
As I know the Ek caps is the red ones not the maroon ones that are bad! they seem fine I would have kept them in just tested them.
it might have been nice to change the bridge rectifier for hire amperage do you know what amperage that is? and a lot of people make mistake and put these UF high frequencies that's not right that just pointless and causes more noise. I would have put a one ferret cap on the end of the power supply would have been nice there's not one on the amplifier?
I hate blue LEDs can't stand them order to stuck with green or red or orange or even purple what you can do is rough up the face of the LED with some 600 grit paper it will disperse the light better.
You can make the amplifier better by increasing THD to 0.1% in global feedback the designer actually criticise himself in this they were chasing numbers it's a good upgrade increase THD.
Hello sir. If you have schematic of this preamp please send me. Thankyou.
I was not able to locate a schematic for this unit unfortunately :(
the ROE caps are from Roedenstein, they are really bad, most other european caps do a good job.
Frako, also not so good…
@@NovaluxStereophonic some of the old philipses... mwea...
🤑
18:25 That is an excellent technique! Thanks for sharing!
great work, great lab, great technic. I would like to have that Hakko rework station...at least the electric desoldering tool.
bro can you play some song or a actual sound check. so that we can listen how good that kind of amp
@@jamesadvincula477 No, the quality does not translate well over RUclips and copyright infringement prevents monetization.
@@NovaluxStereophonic okay. but i guest there is a lot of free song to use for sound check on youtube. thanks any way
@@jamesadvincula477 The issue of quality translation still holds even with royalty free music. It’s like asking if you can call me and have me put you on speakerphone to listen to my system.