2. amps-preamps
  3. 157647-13968

Preamp and impedance question

I am asking a custom builder to build an amp using Luxman mq-300 schematic.  I have two questions:

1) the Mq-300 is a power amp.  I don’t have a preamp.  Can I just add a volume pot to a power amp schematic?  I did some research about passive preamp, but it seems even a passive preamp has a circuit and a transformer.  Is it better to buy a separate passive preamp?

2) the transformer is designed for 8 ohm.  If I want it to support 4 ohm, I need to upgrade the transformer.  I know that the speaker impedance curve can dip to 5 ohm at 30Hz.  Is it important to have 4 ohm support?

thanks.
gte357s
georgehifi's avatar
georgehifi
10,312 posts
 
atmasphere
I think its pretty obvious this isn’t about EPDR...

Yes it was, as this is what I answered to below, saying a 4ohm transformer would be a very good idea as that speaker "5ohm is a nominal figure" you can bet it goes down to 4ohm or even lower, and when combined with any -phase angle (epdr) could be even lower again.
gte357s 2) the transformer is designed for 8 ohm. If I want it to support 4 ohm, I need to upgrade the transformer.
The OP needs a 4ohm tap if not 8ohm also end of story!!!!!!!!!
That MQ300 Lux had one, you two are dreaming to think he only needs an 8ohm tap with that amp he’s getting built, and will have better resale value with both taps.
atmasphere's avatar
atmasphere
11,807 posts
 
Yes it was
Ha ha, that's pretty funny.
georgehifi's avatar
georgehifi
10,312 posts
 
So are you sunshine, so are you, in more ways than one.
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