Hi,
I built the Pass F6 a few years ago, and love it. I have the channels biased at 1.6vdc each, rails are +/- 24vdc, and it sounds very 3D, warm, and class A. I would love to have a little more power for my 5 ohm, Infinity sattelites. I am biamping from 140hz down into a pair of Rythmic subwoofers. I am looking over the F5 Turbo article by Pass, and see where he says that simply increasing the rail voltages from +/-24vdc to +/-32 vdc, on the F5, will give you double the peak power. I have most of the parts ,less chassis, to build an F5, but I am wondering if I can simply swap out my power transformer on my F6 to one with dual 24vac secondarys similar to the F5 , and increase the power. Anyone know what kind of wattage increase I can get by doing this for my 5 ohm speakers?
Thanks in advance,
mg16
I built the Pass F6 a few years ago, and love it. I have the channels biased at 1.6vdc each, rails are +/- 24vdc, and it sounds very 3D, warm, and class A. I would love to have a little more power for my 5 ohm, Infinity sattelites. I am biamping from 140hz down into a pair of Rythmic subwoofers. I am looking over the F5 Turbo article by Pass, and see where he says that simply increasing the rail voltages from +/-24vdc to +/-32 vdc, on the F5, will give you double the peak power. I have most of the parts ,less chassis, to build an F5, but I am wondering if I can simply swap out my power transformer on my F6 to one with dual 24vac secondarys similar to the F5 , and increase the power. Anyone know what kind of wattage increase I can get by doing this for my 5 ohm speakers?
Thanks in advance,
mg16
That would increase the power supply voltage by 33%, and increase the power output by (4/3)^2 or about x1.8 what you have now.
This assumes the front end will work on the higher DC voltage. Of course you will need a higher VA transformer and suitable heat sinks.
This assumes the front end will work on the higher DC voltage. Of course you will need a higher VA transformer and suitable heat sinks.
With a demanding 4 or 5 ohm speaker load, you'll have to take into account the current that the output stage is able to supply. NP's "F5 Turbo V1 for 4 ohm load" adds another set of outputs and doubles the bias current, for example.
Yes, thank you.
That would definitely be the way to go, but....
I do not feel technically competent, in correctly adding the extra circuitry and parts , to the DIY store, F6 boards I have mounted to my heatsinks.
The simplicity of swapping the xformer appeals to me.
I already have 50vdc rated caps in the power supply, and my heatsinks at 1.6 A bias get barely warm.
I think they can handle the extra dissapation of heat.
mg16
That would definitely be the way to go, but....
I do not feel technically competent, in correctly adding the extra circuitry and parts , to the DIY store, F6 boards I have mounted to my heatsinks.
The simplicity of swapping the xformer appeals to me.
I already have 50vdc rated caps in the power supply, and my heatsinks at 1.6 A bias get barely warm.
I think they can handle the extra dissapation of heat.
mg16
Also be careful with the jfets. They're basically running at rail voltage and Idss. The 2sj74 will be running at higher voltage than its spec'ed value and unless the Idss of the jfets are low, you could be pushing against their thermal dissipation limits as well. At the minimum I suggest some TO-92 heatsinks for them
The JFet front end will be the limiting factor for the rail voltage. I would take a more conservative approach by changing the power transformer to one with 22VAC secondaries. Consider using TO-92 heatsinks on the JFets.
The output Mosfets can then be replaced with IXTQ75N10P. Boost the bias current to 1.8A, checking the temperature of the heatsinks. (This is a good operating point for those Mosfets.) See if that gets the sound you want from your system.
The output Mosfets can then be replaced with IXTQ75N10P. Boost the bias current to 1.8A, checking the temperature of the heatsinks. (This is a good operating point for those Mosfets.) See if that gets the sound you want from your system.
Do you have enough gain in the preamp? Maybe you need some passive line level high pass filtering before the F6 so the speakers don't suck up so much power?
I am using an Audio Research LS25 MKII. It has switchable gain settings for 0, 6, or 12 db. I typically use the middle,(6db) gain setting.
I need the volume set at 3 O'clock to get a nice, satisfying, sound in my listening room. It is right on the edge. Any louder and I have to run for the volume control due to the little 5" mid/woofers on the sattelites being overdriven. The Infinity Modulus,(original 1990's model), are rated at 125 watts with minimum suggested at 25 watts. I estimate I have maybe 40 watts at 5 ohms of clean power from the F6. Not much headroom for my classic rock LP's, although biampling helps.
I need the volume set at 3 O'clock to get a nice, satisfying, sound in my listening room. It is right on the edge. Any louder and I have to run for the volume control due to the little 5" mid/woofers on the sattelites being overdriven. The Infinity Modulus,(original 1990's model), are rated at 125 watts with minimum suggested at 25 watts. I estimate I have maybe 40 watts at 5 ohms of clean power from the F6. Not much headroom for my classic rock LP's, although biampling helps.
Just build a Stasis, problems solved
https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/
https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/
crude way of saving little drivers from flopping around too much
Attachments
I am using the Marchand, 4th order, passive, high pass filters on my satellites.
https://www.marchandelec.com/xm46-pllxo.html
mg16
https://www.marchandelec.com/xm46-pllxo.html
mg16
Thanks for all your responses. I am going with TungstenAudio's suggestions.
TO-92 heatsinks on the jfets, Dual 22vac secondary transformer, and 1.8A bias.
Change Mosfets to IXTQ75N10P.
TO-92 heatsinks on the jfets, Dual 22vac secondary transformer, and 1.8A bias.
Change Mosfets to IXTQ75N10P.