spritzer

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...

You are always so cranky... A SS amp with 2+% distortion is just facepalm material. The problem we have is that we are stuck with 1960's mentality and transformers optimized for that age. Most amps you can use today can easily driver a 1:15 to 1:20 transformer so why use a higher ratio?

Shitload of Kiwame/Koa resistors.

That's about what Stax said back in the day. Compared to the Exstata then it isn't anything to complain about.

There isn't a whole lot of distortion in the SRD-7 but it will naturally only add to what the amp is doing. The 1:25 ratio isn't that bad but I do prefer lower ratio's as unlike 1971 when the SRD-7 was introduced, we have power to spare. Higher ratio can only mean more distortion. Transformers do have merit and I'm getting good results from the massive Lundahl irons. Not cheap by any means and about 5 times larger then the SRD-7 trafo's but this is team overkill after all. Even the small LL1630 was very nice upgrade over the WEE at CanJam even if it was struggling a bit with the lower ratio. Add a small diecast box, one of my bias boards and it's also cheaper than the WEE, at least for people who don't have to pay silly import fees. I did one WEE owner claim that it was as good as it gets which just shows how clueless people really are. The 717 was indeed changed but whetther they did it to save money or just that the neutral sound of the KGSS wasn't their cup of tea. Neutral it isn't and the 727 (after mods) is a better amp just because of that.

Happy Birthday John!!!

Nope.

I would never go back to the Mk1 pads but I haven't bought a set in a while so no idea on prices...

There is nothing to secure the driver with in a Sigma chassis. The older Lambda drivers are glued together and then attached to the baffle but here it is all loose. One could glue it together but it is far from easy to do...

Go to thread tools above the first post of the page and click on "download thread". That should do it.