spritzer

He probably can't solder it though. He's still weighing his options about which end of the soldering iron he should hold...

I think sand just refers to the silicone substrate of solid state devices. In tubes the glass is just the packaging around the active parts. My namesake (

I think Kevin was referring to the F1 which is very picky indeed.

People who like distortion and SET amps? While some of them are good, some are truly horrible designs. The same crap recycled over and over again...

I've been running it with purely my testing components (Pioneer DV-525 DVD player, Noble 10k pot as a passive preamp and Tannoy R2 speakers) but it is very good indeed. Far better than my Gainclone but the true test will be firing up the new Lundahl transformer boxes. I'm with Marc though, lack of distortion is so often misunderstood.

If there were extra boards then sure, you can do something like that but it would be a lot of work. The modushop boxes are also very poor compared to the custom made unit. Since there aren't any extra boards this is a moot point really...

I just spoke to Stuart and he gave me the green light to do what ever I wanted to. This amp does indeed have the custom transformer with white tape around it. Having no markings at all made me more than a little worried when rewiring for 230V... So the plan now is rewiring the tubes for AC and add a small transformer to power them, install a resistor instead of the filaments, change all the rectifier diodes, replace the rest of the caps and try to separate signal and power the best I can by cutting traces. Perhaps a choke in the PSU would be a good idea as well?

Time to close this case once and for all, here is the finished article sitting on its new rubber feet: The back panel is pretty nasty and somebody really should have told the original builder about the magic of masking tape when doing chassis work. Still, it's not like anybody can see it or the truly horrific bottom panel.

Thanks for that Ari. The ECC82 was the alternative I was looking into but since I didn't have any at hand I dismissed the idea. This one has an access panel in the bottom so when I turn it off now I'll take a look if there are any wires underneath the PCB. It's a bit odd though that there are two wires going to the PCB from the pot, per channel. Both go underneath the board so I don't know where they go exactly. I for one have had no issues with AC heaters in the past so that is an option. Not sure what voltage the transformer outputs as this might be a custom model. Not a single marking anywhere except for numbered terminals. One odd thing, the channels were reversed inside the amp. Might have been part of the original tweaks...

While weighing my options (and asking Stuart how far he wants me to take this amp) I figured I should just fix what was really broken. I removed the DACT stepper and stripped it down completely, polished the metal contacts with Auto-sol and then bathed them in De-oxit and Pro-Gold. While I was at it I added a voltage divider directly to the CT2. I didn't have the exact values but it is close to 10dB. Now that it is back in the amp the stepped is working 100% again and the lower volume level is a welcome change.

I've been adjusting the bias for the last few hours and at just over 1A it is around 70

Sorry about that... The filament wiring is just too funny, with traces running all over the board. That should also solve some of the noise issues. The plan is to remove the filaments from the main circuit so that is a non issue really. I think the mods here were just better parts and some very expensive tubes (125$ each) with no care taken to just how messed up the PCB is.

Stuart did say you looked this one over. Thanks for the link, I was doing this the hard way by inserting a pot at the input, adjusting it for the range I liked and then measuring it. I'm not really looking into any major mods for it but does anybody have the schematic? Using the filaments is just a terrible idea...

Nope.

One of these rare amps stopped by for a visit: This one belongs to Stuart but I'm taking a look at it for him to sort out the unbelievably noisy CT2 stepper and do something about the very high gain. I was thinking about a simple voltage divider on the input instead of messing with the circuit. I might also change out the PSU caps as some do appear to be stock. Any further ideas about this beast? I did read Doug's thread on the SHA-1 but I doubt I'll do something as extreme. It very noisy though and quite frankly, doesn't sound very good with RS-2's and Mullard E88CC tubes. Very edgy and with crappy bass. There also appears to be a small channel imbalance.

That would work but the chassis is pretty small. There is also the issue of all PC coolers being pretty small (since the processors are so small) so it would have to be modified. There is also the noise of the fan and pump to think about.

Yeah you are right but I'm still going to try and add some internal sinks just in case. There is really no such thing as too much metal... I could always just store it outside. It's pretty warm now at 7

That would work but the issue isn't really about using a larger chassis. I'm going to build a second F5 with all the trimmings and my usual level of insanity so I just want to convert this one into something useful. You can see the heatsinks I'm going to use in the upper left corner of the above picture. That plus solid aluminum panels all around should be more than enough.

I just love the fact that somebody stopped and took a picture instead of helping the cat.

Ahh that would mean it would power the RS-2's sitting on my desk now or the K1000 that is 5 minutes away? Nate is right though, no way around this except increase cooling capacity or dialing back the 120W of heat this thing gives off. I'm going to see if there are any cheap sinks available locally that I could just bolt onto the inside to add surface area and if that doesn't do it, look figure out how low I need to go. There was somebody in DIYA working on a mini amp but his posts are a bit of a mess.

Time for an update. I'm going to try and finish this amp once and for all but the stupidity of the original builder is still haunting me. Here is how the amp looks now: It works just fine even after I made it go arcy-sparky last summer. The short was violent enough to melt the probes I was using so the lesson here is "don't work on amps after being awake for 23 hours". Still, no parts were blown. Now the issue with the amp is heat, a lot of it in fact. The original builder thought he'd save some money and bought the 3U/300mm Dissipante chassis which is just too small. According to the specs Modushop posts these sinks are 0.45W/C and with each sink dissipating 60W it gets to 90+

It really depends on what the difference is to you ears. My biggest issue with the Exstata is just how bloody unlinear it is, the bass is wooly and undefined and the top end is edgy even with the SR-007. Even the most basic Stax amp can't be accused of doing that nor the transformers. Now before somebody claims the Exstata can't drive the SR-007, that is just not correct and I use all of my amps with the Omegas. The SRM-300 or SRM-Xs can drive them just fine but not the Exstata? Sure it isn't up to the BH levels but a SRM-1 Mk2 works just fine.

Yeah, the ET1000 is what Beyer could have been. Anybody claiming the T1 is something special really has to try the granddad...

Woot!!!!

Indeed that is the question and it isn't simple to answer. I was just reading the measurements for the Pass INT30 and with something that well designed we could find the sweet spot but amps such as these are all too rare...