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F4 & setup options?
F4 & setup options?
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Old 13th June 2011, 10:34 AM   #1
superlian is offline superlian  Norway
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Default F4 & setup options?

Last week i got my second F4 from Reno Hifi ("factory-build")

The F4 is an fantastic amplifier, better than expensive 300B gear and with punch&power. I have used one F4 for 2,5 year now together with a Audio Note M2 Line preamp with high gain and very high output impedance if i understand the specs: http://www.audionote.co.uk/downloads/pre_m2line2007.pdf

I am playing with fullrange and open baffle DIY loudspeakers therefore i bought a second one. I am curious about the posibilities to biamp, paralell, brigde and use it as a power buffer. But i am unsure if the Audio Note match the different configurations of F4.

I am also thinking about active crossover.

I dont understand the consept and consequences with impedance matching and therefore i have a lot of Q:

1) Will my Audio Note match biamping with 2 x F4?

2) Will it match parallell 2 x F4?

3) Is 2 x F4 parallell coupled giving 2 x 25 watt like 1 x F4 but with much more stable power down to 100 watt at 2 ohm?

4) Is it possible to run 2 x 100 watt / 8 ohm brigded with my AN M2 preamp if i use some kind of special cables who convert singel ended to balanced?

5) Since F4 needs a lot of gain, which kind of active crossovers are capable of provide that high gain?

6) In the F4 manual it is one setup with 2 x F4 (4 x 25 watt) with passive crossovers before the amps?? I didnt knew that was possible? Is this passive crossovers the same as the crossovers on the speakers? If yes, what is the advantages with this solution?

7) What is the major sonic differences with my high gain valve preamp compared with a 2A3 or 300B feeding the F4?

8) If the answer on Q4 is no, wich preamp alternatives should i go for?

9) Is it other setup alternatives i have missed?

Last edited by superlian; 4th December 2017 at 08:17 PM.
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Old 13th June 2011, 02:14 PM   #2
Zen Mod is online now Zen Mod  Serbia
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F4 & setup options?
1. yes - if you have enough potent source , voltage vise ( around 2Vpp ) - under condition that gain ( 10x) of M2 is enough for FR or OB spks ; I presume it will be

2. if 1. is yes , then this one is yes , too

3. sort of ; covered in Papa's F4 manual

4. nope ; you need line xformer for balancing duty ; but they made skimpish pre with eeeny weeeny 6SN7 without any sort of buffer , so it isn't ooohmpsie enough to drive xformer , even if pure line one is used - in range of 10K input impedance

5. dunno ; one of solutions is to use additional gain stage between xover and F4

6. yes . virtues are almost nonexistant power in xovers . they're just calculated for entirely different loading impedance - either 47K ( F4 input ) or for some other - in xover net implemented - lower loading impedance

7 . that's your call - to hear difference

8 . plenty of them ; commercial or DIY ?

9. do you have "flea power" tube amp ?
my Papa is smarter than your Nelson !
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Old 13th June 2011, 02:35 PM   #3
buzzforb is offline buzzforb  United States
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What about F3 driving F4. Not enough V swing, correct.
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Old 13th June 2011, 05:43 PM   #4
Itsmee is offline Itsmee  England
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Originally Posted by superlian View Post
8) If the answer on Q4 is no, wich preamp alternatives should i go for?
Don't be shy ZM,

I personally would suggest ZM's own highly regarded Pumpkin preamp, if you don't mind a bit if DIY.
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Old 13th June 2011, 07:46 PM   #5
superlian is offline superlian  Norway
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@ Zen Mod

1a) Audio Note M2 line have a lot of gain: 1 khz = 23 db (or 16 db with feedback on). My experience with F4 and this Audio Note preamp is fantastic My doubt is when i hook up 2 x F4?

1b) I am sorry but I didnt understand your answer. Some folks here In Norway told me that F4 with 47K ohm input impedance and Audio Note M2 Line with 5K ohm output impedance (or 2,5K ohm with feedback on) dont match if i use 2 x F4.

3) Is this setup only for 2ohm loudspeakers?

6a) Please explain it one more time? Is it a better solution to have passive crossovers before F4?

6b) Will it reduce the "bottleneck-effect" ordinary crossovers have on drivers?

6c) How do i calculate theese crossovers?

9) Yes i have, a singel ended tetrode, ca 2x10 watt. Norwegian made.
I understand your hint, i will give it a try

Thank you In advance

Hans Erik
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