This just an edgewise fit-in between looney JBL Eon bookends. Just preserving my insanity, you understand.
The IT 70 has an output stage that I prefer not to think too much about. This attitude, I’m afraid, is the price of being an old git. Don’t do it, it’s bad for you. Anyway, as usual, your first question is likely to accompanied by the bemused scratching of the head and the “What’s he on about?” I have problems with a power amp that is as big as an adolescent black clock. Especially as they used to take up half of your front room.
“What is he on about?” Well, screwed to the heatsink INSIDE the amp (quite an interesting feat for the heat; it probably gets out up a ladder) is a device with a lot of legs (even more than a black clock) and that is your amp. It’s about half the size of a book of matches. And if you’ve ever tried to replace one, you’ll find a number of matters all come together to make life intolerable. It will be a double sided pcb, and the tracks will be rather short of the thickness of the foil they wrap kitkats up in. Which means that if you get a soldering iron anywhere near them, they peel off and wave bye-bye. Now, unfortunately, to desolder anything you have to get it hot. I rest my case.
Now, you all think I’m just after a cheap laugh; but whatever you read in these blogs is, sadly, based on fact. Here’s the proof of the pudding.
This is what the amp looks like on the outside; quite a nice looking thing.
This is it on the inside. Have a good look at that silver ribbed thing in the middle. That’s the heat sink that gets rid of the heat from the power amp.
This is the power amp. You see the little flat black thing on the silver heatsink? That’s the power amp. This is progress.
Just to try to be a bit less bitchy, there is a common fault with these amps that is relatively simple to put right. The overdrive channel radically underdrives to the point of not doing anything at all. If you look at the Heatsink/rat trap thingy, at the very left of the brown pcb is a white block. This is a 5watt wire wound 120 ohm dropper resistor, and its where the anode voltage of your valve comes from. It’s not unusual for it to go open. It’ll cost you fifty pence, the whole thing unscrews on four screws, and you solder a new one in. WITH THE AMP UNPLUGGED!!!!!!!!!!!!
I feel better now. It’s been a bad day. Tea time.