I always had you down as more of a Wayne Kerr person 
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Used to use Wayne Kerr frequency response analysers in me first job testing bits of mixing consoles in Salford. Back on '89. I miss those Wayne Kerrs.
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We used to be knee deep in these
(SRS DG535 delay generators, but just known as ‘SRS boxes’) at work. That said, we never had enough and there was always a risk of turning up in the morning to find that the neighbours had filched one of yours that ‘didn’t seem to be doing anything’. Brilliant pieces of kit.
We have just had a bunch of those dropped off for calibration. We don’t do enough to warrant doing it ourselves so ship them off to the US. Repaired a few. Power supplies tend to go pop at the slightest provocation.
Just discovered we have your details from some Stanford stuff you ordered from us in 2007. We do quite a bit of business with STFC.
I don’t recall ever blowing any of ours up. But they were usually used in RF-screened racks with filtered mains supplies so they wouldn’t see much EMP.
Mostly if we destroyed stuff it was the input components in reasonably fast scopes. We used to monitor short pulses of UV light using vacuum photodiodes which ran at 2-3kV. There was a series capacitor which isolated the DC from the scope, but if you powered the diode then plugged it into the scope the full kilovoltage appeared transiently across the scope’s input. Easy to do if you’re a bit bleary first thing in the morning. It usually meant £1k+ down the drain before tea break.
Not sure what I’d have been buying in 2007. Probably DG535s !
Can you “liberate” some 
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I would like to be able to yes.
If I was a sneaky fucker I would replace them on every unit that came back in, and ‘recycle’ the old ones. Now there is a thought…
lol
Just ordered a pair of these, might just get around to building the FirstWatt M2X
Hope they are the correct ones…
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Those look nice quality, but the burning question is, have you sourced JFETs or are you going a different way? Soooo many choices…
Just going to do NP’s original front end first, I have the JFets already (I think) but if not the store sells both the Linear Systems and Toshiba versions.
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I thought the Tosh K170/J74 are like rocking horse shit and that’s why he came up with the M2X
I think NP has relaxed a bit with his stash, they do limit how many you can buy.
NP was/is supplying a bloke on ebay with the real deal as well, think his name was punkydawg or something similar.
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Am now really annoyed.
The phono stage which was working properly prior to swapping out a couple of load resistors for Charcrofts and a PSU capacitor for a Claritycap TC and reworking a few tag boards as a result is now humming. I have swapped all of the power supply components (caps and chokes) in the phono stage, I have remade all of the connections for the grounds on tag boards and yet there is still a 100Hz hum that simply will not go away. Nothing else in the setup has changed and everything that has changed has been remade or components swapped out.
Edit: including the ClarityCap TC, which has been swapped out for an identical one with no difference.
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Was the previous cap an electrolytic ? If so then that would have had some Equivalent Series Resistance (ESR) whereas a polyprop will have essentially none. The effect of the ESR can be to limit the peak charging current and thus to limit any associated 100Hz noise. Whether this can account for your new noise will depend on the circuit details. But when you make a change and observe an effect, even if it’s an undesirable effect, your first suspicion should be that the effect has been caused by the change. The obvious check would be to drop the previous cap back in.
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It was, a Mundorf MLytic. The phono stage has an offboard PSU a bit like a World Designs PSU3, the phono stage box has three power supply caps, one directly from the input and then one in an LC stage which feeds a cascode first gain stage and another in an RC stage for the final cathode follower. The second gain stage which is CCS loaded runs directly from the first cap.
I have tried the TC as both the cap in the LC for the cascode and the first cap with hum in both cases.
Tried phono stage after pub. Hums like a hummy thing. Sounds really quite good.
Know what needs to be done re hum. Will do that in a few days when have a mo.
Feeling good.
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