I'm now selling my heavily modified Little Dot MK6. The amp performs light years better after the mods than stock! There's no comparison. There's too many mods to list and go through in a classified but key mods are: 5998/421A mod: There's a switch to place the amp in 5998/421A mode. This bias the 5998 correctly and makes it sound much better. CCS tail: There's a SS constant current source (CCS) tail on the driver stage cathodes which limit tube rolling somewhat, but increases performance (balance). I can remove it if you wish and replace with a resistor. Driver tubes that are compatible with the amp using the CCS are ECC35, 6SL7 and 6H9C. Also 6C8G if using a adapter like you see in the pic below. Coupling caps: Jupiter copper foil paper and wax and Mundorf Silver/Gold/Oil in key signal positions makes a huge difference in sound. There's also a switch to change the anode resistor values to maximize performance of the WCF output stage to a given load. The formula is in the Cavalli WCF paper. I have it configured to match 20 ohm and 110 ohm headphones using both 6AS7 and 421A's. I can remove this switch or customize it to your needs. The RCA input jacks are disconnected. Only the XLR jacks are connected. But I can redo that if you wish. SE output jack is completely removed (noisy anyway!) and replaced with the anode resistor switch. I'm sure I've forgotten something, feel free to ask questions! Price is including a quad set of russian 6N5S (6AS7G) and a pair of Sylvania 6SL7! I also have a NOS/NIB matched quad set of WE421A's (exactly like the ones pictured below, I had eight but sold four), NOS matched quad of 5998's and a used quad of GEC A1834's. Also have several pairs of ECC35's I could sell with the amp. Make offer on the tubes! I can ship anywhere but you're paying for it! Price is not including paypal fees! Ad 5% if you don't want to use "paypal friend" Here's how the insides look now: All caps, except driver stage psu electrolytic, have been replaced. Also added caps on key positions to increase speed and performance. You can read up on the mods here: https://www.head-fi.org/threads/lit...s-all-verified-mods-are-on-first-page.782183/ All power resistors are replaced with Mills wirewound 5W and 12W. There're also some naked Z-foils in there! Cost for only the boutique caps are over £700, total cost for mods are well over £1000! The amp is also quite heavily modded on the outside!