F4 amplifier
Hello,
In mono balanced operation, you can achieve up to 100 watts output into an 8 ohm load if the amplifier is driven by a balanced source with balanced XLR connector.
100 W RMS into 8 ohms => 28,28 V RMS to 8 ohms.
The F4 have not voltage gain then It is necessary to have about 30V RMS to balanced input.
The balanced output capability of the preamplifier must be 30V RMS with 24 to 30 db voltage gain.
Do you know preamplifiers that agree?
Darry
Hello,
In mono balanced operation, you can achieve up to 100 watts output into an 8 ohm load if the amplifier is driven by a balanced source with balanced XLR connector.
100 W RMS into 8 ohms => 28,28 V RMS to 8 ohms.
The F4 have not voltage gain then It is necessary to have about 30V RMS to balanced input.
The balanced output capability of the preamplifier must be 30V RMS with 24 to 30 db voltage gain.
Do you know preamplifiers that agree?
Darry
Preamplifiers...
I asked Mr Pass earlier in the thread to provide a list of the commercial preamplifiers that could drive an F4 well and he didn't answer. This was after I had a lot of time going through the measurements at Stereophile for various preamps. I eventually called Mark at FirstWatt and according to him, all 3 of the Pass Labs preamps have enough gain to drive the F4 to clipping even though the max stated gain from said preamplifiers is 14db. I would love to hear some comments on this and am just reporting what I was told.
Thanks,
C
I asked Mr Pass earlier in the thread to provide a list of the commercial preamplifiers that could drive an F4 well and he didn't answer. This was after I had a lot of time going through the measurements at Stereophile for various preamps. I eventually called Mark at FirstWatt and according to him, all 3 of the Pass Labs preamps have enough gain to drive the F4 to clipping even though the max stated gain from said preamplifiers is 14db. I would love to hear some comments on this and am just reporting what I was told.
Thanks,
C
I would suggest that you go to the same place I did, which is the
Stereophile.com reviews section on preamplifiers. Under the
measurements of each product, you will find the gain and
maximum output figures for each reviewed product. My experience
is that gain of 14+ dB and voltage output to 13 volts is adequate
to drive an F4, assuming a loudspeaker of 90+ dB sensitivity.
Stereophile.com reviews section on preamplifiers. Under the
measurements of each product, you will find the gain and
maximum output figures for each reviewed product. My experience
is that gain of 14+ dB and voltage output to 13 volts is adequate
to drive an F4, assuming a loudspeaker of 90+ dB sensitivity.
less 
Sorry Jocco, not to get too morbid, you can get my Snap-On roller chest but, that chassis is reserved as the urn for my ashes
I machined it out of $2/lb aluminum from the local metal recycler. The PS board is a supersized cvillers 'simple CRC'. The F4 Board layout, with a few modifications, is Veteran's. Thanks and thank you... Mr Pass. On power up , I had the same bias issues as lykkedk with voltage variations across the source resistors. All the same, It still sounds wonderful. Compared to a 69JLH (bi-amped to 120hz) The F4 really grabs my ls35a's by the scruff. On the high end, where the JLH is a little tubey and forgiving, the F4 has extended, detailed highs.The F4 also has a tighter, much less laid back midrange. I'll shut up now and sort out the output bias.
Attachments
My power supplies and chassis are about done,,,
but I got my order from Digikey today. The mica insulators for the output devices are a tiny bit SMALLER than the metal on the back of the MOSFETS. It seems to me that the spacing should be enough, with the low voltage.. but if not the consequences would be very unpleasant.. What do you think?
but I got my order from Digikey today. The mica insulators for the output devices are a tiny bit SMALLER than the metal on the back of the MOSFETS. It seems to me that the spacing should be enough, with the low voltage.. but if not the consequences would be very unpleasant.. What do you think?
Thank you Mr. Pass!!!
while I have you here....
For D1 and D2 I ordered this:
1N4736A-TP
Zener Diode 1w 6.8V DO41
as listed here:
http://61.222.192.61/mccsemi/up_pdf/1N4728-1N4764(DO-41G).PDF
Does this seem to be OK? Apparently the 2N4736..... was a typo?
Is the particular 1N4736 I got ?
while I have you here....
For D1 and D2 I ordered this:
1N4736A-TP
Zener Diode 1w 6.8V DO41
as listed here:
http://61.222.192.61/mccsemi/up_pdf/1N4728-1N4764(DO-41G).PDF
Does this seem to be OK? Apparently the 2N4736..... was a typo?
Is the particular 1N4736 I got
?
Some interest was expressed on the Burning Amp thread as to how I am coming along. I'm going for a bit of a classic look..
Here is the power supply for one stereo F4 which I will be using as a single balanced channel. There is another of these for the other amp.
On the first floor: 1000VA toroid run at 220 configuration on our 120 lines to get correct output.
Second floor: Pi filter with 30,000uF caps, the creamy choke filling of two toroidal chokes, then two more caps....
Missing is bizarre heatsink tower with actual amp boards..
You can see the whole thing(s) at the show!
Variac..
Here is the power supply for one stereo F4 which I will be using as a single balanced channel. There is another of these for the other amp.
On the first floor: 1000VA toroid run at 220 configuration on our 120 lines to get correct output.
Second floor: Pi filter with 30,000uF caps, the creamy choke
filling of two toroidal chokes, then two more caps.... Missing is bizarre heatsink tower with actual amp boards..
You can see the whole thing(s) at the show!
Variac..
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