The Saints have a home tie against the Scarlets to look forward to next month after wingers Noah Cato and Jamie Elliott both scored twice in this emphatic 57-10 victory.
The Welsh side's trip to Franklin's Gardens will be Northampton's third semi-final appearance in four years, and Mallinder was delighted with his team's display after last weekend's 46-14 defeat at Bath.
Saints director of rugby Mallinder said: "It was a good overall performance - we let ourselves down last week and we worked really hard on putting that right this week.
"We defended well and we attacked with a good intensity. We looked after the ball well and worked hard and scored some very good tries.
"We didn't know what the other results were going to be so we set out to make sure it came down to how many tries we scored.
"We said that we wanted to play with a high tempo and score as many tries as we can and that's what we did.
"I'm delighted to hear Sale have done a job for us against the Scarlets as it means we have a home semi."
Northampton had the result wrapped up before half-time as tries by Andy Long, James Craig and Elliott gave them a 22-3 lead before a penalty try secured them the bonus point.
Cato ran in his first before Elliott scored again and, after Joe Simpson's consolation, Alex Waller and Cato added some extra gloss.
Wasps forwards coach Trevor Woodman said: "We had to field players to have a good look at them - Victor (Gresev) and Vladislav (Korshunov) only arrived this week.
"We lose Victor again next week so we wanted to see him for 80 minutes but it's hard to find any other positives after that result.
"After a performance like that, you can draw your own conclusions to how the players performed individually.
"I think if you see the team today and the team next week against Saracens, they're going to be a lot different so the players coming back will have no hangover from this.
"We'll be going back to the team that faced Bordeaux and played well against them a few weeks ago so we'll move on."
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