help! my HRM overdrive sounds harsh

[yeahyeah]

you have a PM,

and good luck

you have a scope right?

[heisthl]

you have a scope right?

and a listerine and probably a lavoris. diagnosis halitosis,

[heisthl]

Sometimes pain and suffering gives you the blues - other times it gives you a great amp to play blues with. I can't wait for the owner to post some clips of this amp now. It had a few problems but let me start off with this disclaimer: "This amp was really a clean nicely done build, definitely a lot of care was taken on the assembly". The main problem was a defective Volume pot (P3 did not make contact with the wafer)This really made for some interesting micophonics and squeals as well as a nasty hum if you had relays engaged with the volume on 0. The second main problem was the tube socket at V1 - much improvement after replacement. The rest of what I did to the amp was putting good coax on some of the runs, putting the owners troubleshooting tweak values back to stock HRM values.Then I put a 10uf bypass on CL2, added a 100R to the HRM tail, added a few tooth washers here and there for better grounding. It is dead quiet now and sings like a bird - I would say Grail tone w/6L6s. Loads of overtones. Curiously the OD is so good in this one you really don't need boost on. Oh one other thing I had to add a connection point to wire the standby correctly. One word of advice to the D'lite builders out there - wire the standby switch so the first filter is charged all the time. The switch goes between the filter and the OT and choke(or RF Mod resistor) entry points.

[dogears]

Good work HH! Do you find some reason why the 100 ohm on the tail is a good idea?? Just curious...

Sometimes pain and suffering gives you the blues - other times it gives you a great amp to play blues with. I can't wait for the owner to post some clips of this amp now. It had a few problems but let me start off with this disclaimer: "This amp was really a clean nicely done build, definitely a lot of care was taken on the assembly". The main problem was a defective Volume pot (P3 did not make contact with the wafer)This really made for some interesting micophonics and squeals as well as a nasty hum if you had relays engaged with the volume on 0. The second main problem was the tube socket at V1 - much improvement after replacement. The rest of what I did to the amp was putting good coax on some of the runs, putting the owners troubleshooting tweak values back to stock HRM values.Then I put a 10uf bypass on CL2, added a 100R to the HRM tail, added a few tooth washers here and there for better grounding. It is dead quiet now and sings like a bird - I would say Grail tone w/6L6s. Loads of overtones. Curiously the OD is so good in this one you really don't need boost on. Oh one other thing I had to add a connection point to wire the standby correctly. One word of advice to the D'lite builders out there - wire the standby switch so the first filter is charged all the time. The switch goes between the filter and the OT and choke(or RF Mod resistor) entry points.

[heisthl]

Good work HH! Do you find some reason why the 100 ohm on the tail is a good idea?? Just curious...

None whatsoever, I just did it 'cause I've been noticing it in a few HRM pictures I've seen and it makes for one less lead wire when you use it to connect the 2 boards. Based on the way this one sounds I'll be adding it from now on just for the "Mojo" factor.

[benoit]

What does it mean when a resistor value is given as 100r or 470r or whatever? Is it just ohms, or is there more to it?

[mlp-mx6]

Just ohms.

[yeahyeah]

Heisthl is the man!

I talked with him on the phone yesterday and he really went above and beyond.

I'll be anxiously awaiting the amp's arival like a 5 year old kid waiting for christmas. I'll report back when it arrives and I'll see if I can get my buddy with a mac to help me record some clips.

[skyboltone]

One word of advice to the D'lite builders out there - wire the standby switch so the first filter is charged all the time. The switch goes between the filter and the OT and choke(or RF Mod resistor) entry points.

Doesn't that put plate voltage on cold PA tubes? I'd always heard that that's a no no.

Dan

[heisthl]

Cold tubes? why the heaters are running (the whole point of standby is to allow the heaters to get the tubes up to temp). Maybe you misunderstood the connections - the first filter gets voltage but not the choke or OT.

[skyboltone]

Cold tubes? why the heaters are running (the whole point of standby is to allow the heaters to get the tubes up to temp). Maybe you misunderstood the connections - the first filter gets voltage but not the choke or OT.

Yes I did. In my tiny little mine I saw the OT connected to the + side of the first filter cap and the standby switch before it. It don't have to be that way though. Doh!!

Sorry
Dan

[Tonegeek]

One word of advice to the D'lite builders out there - wire the standby switch so the first filter is charged all the time. The switch goes between the filter and the OT and choke(or RF Mod resistor) entry points.

Mine is wired between the diodes and first cap but this way seems like a better idea. Is this just to keep from having such a large inrush when flipping the standby? I would think it is a bit easier on the diodes, fuse, etc.

[heisthl]

Mine is wired between the diodes and first cap but this way seems like a better idea. Is this just to keep from having such a large inrush when flipping the standby? I would think it is a bit easier on the diodes, fuse, etc.

That plus it keeps any high voltage spikes away from the later nodes that probably have lower voltage caps. The addition of a .02 1KV disc cap across the Standby switch is another good thing to add.

[JimiB]

whats your thought on using a MOV here instead?

[novosibir]

The addition of a .02 1KV disc cap across the Standby switch is another good thing to add.

When you have the first filter caps on the hot side of the standby switch, then I'd recommend the .02/1kV cap from the cold side of the switch to ground.

Larry