FO SEMELAB output devices is inside engine room 2 parallel connected devices (dual die) so compared to other brands FO is configured with 4x output devices, look page 2 in attached SEMELAB application note.
Yes I know Byrtt.
LC not here
LC is temporarily BANNED. He was too busy on solid state forum, that he fell under the Administrators eye.
We can hope that the ban would lift soon and that we can send him on some anger management class.
By the way why is LC not here?
LC is temporarily BANNED. He was too busy on solid state forum, that he fell under the Administrators eye.

We can hope that the ban would lift soon and that we can send him on some anger management class.

Thank you very much for posting.
It seems the height of the modules is respected. Can you post the dimensions?
Cheers,
M.
I think the height of the L module is the same as M, the difference is the width.
With new hole arrangement the L module should fit in existing silver and black mamba cases.
I know that LC is following the discussion. If/when he sends me dimensions I will post them.
LC is temporarily BANNED. He was too busy on solid state forum, that he fell under the Administrators eye.
We can hope that the ban would lift soon and that we can send him on some anger management class.![]()
So sad 🙁
In my 4 channel amp temperatur on heatsink is 51 Celsius. This is more then I like but it is a hot day as well.
In my 4 channel amp temperatur on heatsink is 51 Celsius. This is more then I like but it is a hot day as well.
Seems to be normal. I measured around 15 degrees more than ambient temperature with one FO per heatsink. With 2 FO's per heatsink it can get pretty hot. 😕
But I still listen with smps1200A180 power supply.
For all waiting to the First One L - 250 W/8 Ohm module, here's preliminary PCB drill plan to enable you to prepare your heatsinks and chassis in advance.
Overall height of the assembled module is 42 mm. 😉
Pcb dimensions are in the post #2984.
Pcb dimensions are in the post #2984.
Yes, thank you.
I found the dimensions of all three version on an old post.
Height (or width? or length?) is 5cm, so, as has been commented, one could use existing heatsink and swap modules. 🙂
Very clever move from LC.
We miss you,

Cheers,
M.
PS: as probably occurred to most F.O.V1.4 owners, a violent urge to improve the source was experimented...I am tweaking my NOS DACs periodically but still feel I will not be able to match the F.O...so I ate my pride and ordered the new Mosaic UV (USB) DAC from -ECdesigns-. For those interested, -EC- just posted a very detailed description of his most clever invention, on his thread. A worthy read...
Why and how was the FO1.4 better? Size or definition of soundstage? Resolution? Oomph, strength? Listener fatigue? Etc.View attachment 556045
View attachment 556046 Thev F5 v3 was no good. First one was so much better. Dac was Buffalo with Lampizator Tubestage and Pre was tubes as well.
Wow,
Today, the first time I listened to the amplifier I built based on the modules "first one amplifier". First impression: WOW !!! The class better than my another amplifier based on the modules UCD400HRX. Cool!!!
Today, the first time I listened to the amplifier I built based on the modules "first one amplifier". First impression: WOW !!! The class better than my another amplifier based on the modules UCD400HRX. Cool!!!
Attachments
Today, the first time I listened to the amplifier I built based on the modules "first one amplifier". First impression: WOW !!! The class better than my another amplifier based on the modules UCD400HRX. Cool!!!
Congratulations.
And it will improve as it burns-in... 🙂
Do you have an extra soft-start unit?
Congratulations.
And it will improve as it burns-in... 🙂
Do you have an extra soft-start unit?
That's right, I use soft starts. Perhaps this excess protection, but it does not hurt.
Today, the first time I listened to the amplifier I built based on the modules "first one amplifier". First impression: WOW !!! The class better than my another amplifier based on the modules UCD400HRX. Cool!!!
Nice build Maciekw.
Will you share the schematic around LL1540 ?
Hi maciekw
well done. I see you use a single hypex. This is fine only if you use differential input. Otherwise the cross talk is too bad, and the damping is very much reduced.
using a LL is a very good idea ! but I see you have a switch on the rear panel with potentially a direct connection for the RCA plug to the FO : just avoid that and put your RCA on the primary winding of the LL, as the XLR !.
if you want to be convinced, just put a single tone sine on one chanel, and mesure the output on the second chanel, you ll be amaized, (I ve got a 40db crosstalk on mine!). The FO is designed for dual supply, if you use only one supply then you must accomodate some tricks to keep this amp to the level it deserves.
also as you have transformer I would suggest to invert one chanel and connect the loudspeker of this chanel with the reverse polarity (which will then restore the correct phase) and then you balance the power consumption on the 2 rails, especially for the lows which usually are mono.
then you will get a wonderfull FO
cheers
well done. I see you use a single hypex. This is fine only if you use differential input. Otherwise the cross talk is too bad, and the damping is very much reduced.
using a LL is a very good idea ! but I see you have a switch on the rear panel with potentially a direct connection for the RCA plug to the FO : just avoid that and put your RCA on the primary winding of the LL, as the XLR !.
if you want to be convinced, just put a single tone sine on one chanel, and mesure the output on the second chanel, you ll be amaized, (I ve got a 40db crosstalk on mine!). The FO is designed for dual supply, if you use only one supply then you must accomodate some tricks to keep this amp to the level it deserves.
also as you have transformer I would suggest to invert one chanel and connect the loudspeker of this chanel with the reverse polarity (which will then restore the correct phase) and then you balance the power consumption on the 2 rails, especially for the lows which usually are mono.
then you will get a wonderfull FO
cheers
Last edited:
According to the Lundahl’s recommendationNice build Maciekw.
Will you share the schematic around LL1540 ?
Attachments
Hi maciekw
well done. I see you use a single hypex. This is fine only if you use differential input. Otherwise the cross talk is too bad, and the damping is very much reduced.
using a LL is a very good idea ! but I see you have a switch on the rear panel with potentially a direct connection for the RCA plug to the FO : just avoid that and put your RCA on the primary winding of the LL, as the XLR !.
if you want to be convinced, just put a single tone sine on one chanel, and mesure the output on the second chanel, you ll be amaized, (I ve got a 40db crosstalk on mine!). The FO is designed for dual supply, if you use only one supply then you must accomodate some tricks to keep this amp to the level it deserves.
also as you have transformer I would suggest to invert one chanel and connect the loudspeker of this chanel with the reverse polarity (which will then restore the correct phase) and then you balance the power consumption on the 2 rails, especially for the lows which usually are mono.
Good idea, thank you.
I forgot to mention that to mesure the crosstalk I was refering to above, you have to put a dumy load (4..8 ohm) on the chanel 1. Because in fact this all about the current going back in the ground wire and then impacting the 0V reference of the second chanel. even if you wire the RCA 0V together, a resistance still exist and exhibit a voltage accross it. Easier to understand with a simulation or a measurement of course 🙂
According to the Lundahl’s recommendation
Thanks Maciekw,
Did you notice any sound degradation when use the LL1540 ?
When it is better with or without the trafo ?
Why and how was the FO1.4 better? Size or definition of soundstage? Resolution? Oomph, strength? Listener fatigue? Etc.
You named it all.
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