sangram said:
The Panasonic resistors were only available in ammo rolls of a few thousand last I checked (and I haven't checked recently).
I get performance numbers very similar to NP's using the Vishay CMF55/RN55 resistors.
If you're not using one of the boards, make sure that the gate-stopper for the MOSFET is immediately adjacent to the MOSFET gate.
Thanks for that hint Jack.
I did see D-K willing to offer smaller quantities (IIRC) but I was worried about the tolerances. anyway that's old hat now. I look forward to getting my parts soon. I assumed the Dale/Mills resistors would give slightly improved performance everything else constant, but obviously NPs got some tricks hiding in that very pretty PCB.
I will be using a perfboard, and will try to keep all connections as physically short as possible, and use the thickest possible connection for the ground planes. Since I don't yet have an oscilloscope, I shall be offering my dummy loads as sacrificial offerings for the amp.
I am hoping to take a few liberties with the connection for TH1 and TH2, as I will probably mount them on the FET itself, is this advisable, or is a little more distance the way to go? I assumed that thermal drift would be best corrected by a very close thermal coupling to the output transistor.
Apart from that, I'll do a bunch of trial layouts to keep the connections short, so that when the parts arrive I'll be ready to go.
Last Q, how much capacitance in the power supply are we talking about for a *mono* amp? Is about 60,000uF good, or should it be 80-100,000uF? The manual points to a power supply for (I assume) a stereo amp, as the review pics seem to show 8 Panasonic TS capacitors shared between two stereo channels. My version will be built as monoblocks, but I'm not sure that just halving the capacitance is a great idea. I don't have any difficult loads, and am aiming for 5A supplies per channel.
I did see D-K willing to offer smaller quantities (IIRC) but I was worried about the tolerances. anyway that's old hat now. I look forward to getting my parts soon. I assumed the Dale/Mills resistors would give slightly improved performance everything else constant, but obviously NPs got some tricks hiding in that very pretty PCB.
I will be using a perfboard, and will try to keep all connections as physically short as possible, and use the thickest possible connection for the ground planes. Since I don't yet have an oscilloscope, I shall be offering my dummy loads as sacrificial offerings for the amp.
I am hoping to take a few liberties with the connection for TH1 and TH2, as I will probably mount them on the FET itself, is this advisable, or is a little more distance the way to go? I assumed that thermal drift would be best corrected by a very close thermal coupling to the output transistor.
Apart from that, I'll do a bunch of trial layouts to keep the connections short, so that when the parts arrive I'll be ready to go.
Last Q, how much capacitance in the power supply are we talking about for a *mono* amp? Is about 60,000uF good, or should it be 80-100,000uF? The manual points to a power supply for (I assume) a stereo amp, as the review pics seem to show 8 Panasonic TS capacitors shared between two stereo channels. My version will be built as monoblocks, but I'm not sure that just halving the capacitance is a great idea. I don't have any difficult loads, and am aiming for 5A supplies per channel.
sangram said:
You can mount the thermistors right on the MOSFET's --
One thing you (or anyone else) might want to do at the outset is to put a current limiter on the Vcc Vee rails -- my Tektronix power supply already limits itself to 400mA -- but you can use an LM317 and LM337 with a resistor from output to adjust where I(limit) is 0.5A -- you can get the amp cooking and thermally stable at this level -- then remove the current limiter and get the bias up to the recommended 1.3A.
Once I have the amp stable at 400mA I use a non-current limited power supply -- and run the Vcc and Vee through a pair of Tektronix DM511 meters -- these are fused at 2 amps.
All this TEK stuff was bought on the cheap in the last recession -- that was a technology recession, not a housing/banking recession. Bankers don't use DM511's.
Thanks for that too - but is there any downside to not stabilising the amp at a lower current? I could use a bunch of lower-rated transformers (I already have some 18V/1A transformers lying around somewhere) and use those instead temporarily.
Since this is pretty much my first discrete build, is this a routine adjustment? And do you always run with a current-limited supply? I thought the ZTX450/550 would limit current automatically.
Speaking of which, can I decrease the 150 ohm resistors to achieve the lower current limit, and swap them back in once I'm done? It should not be too much trouble to swap a few parts around. Maybe provision for a socket of some kind to easily set the amp's current limits?
I was anyway probably going to back off the bias to 1A for long-term running from the recommended 1.3 as we're cooking ourselves in the Indian heat. Maybe push it back up to full bias in winter.
Edit: doh, I see why this is necessary. I'll figure out something.
Since this is pretty much my first discrete build, is this a routine adjustment? And do you always run with a current-limited supply? I thought the ZTX450/550 would limit current automatically.
Speaking of which, can I decrease the 150 ohm resistors to achieve the lower current limit, and swap them back in once I'm done? It should not be too much trouble to swap a few parts around. Maybe provision for a socket of some kind to easily set the amp's current limits?
I was anyway probably going to back off the bias to 1A for long-term running from the recommended 1.3 as we're cooking ourselves in the Indian heat. Maybe push it back up to full bias in winter.
Edit: doh, I see why this is necessary. I'll figure out something.
Looks really nice
Your a nice friend to build this beauty
Im a bit surprised that theres no hum issues from placing trafos close to backplate and signal connectors
I suppose theres good ventilation in top lid/plate
I hate saying such, but I would have liked to see a row of ventilation holes in the case bottom along both heatsinks
What are those ugly monster tubeamps in the picture?
Your a nice friend to build this beauty
Im a bit surprised that theres no hum issues from placing trafos close to backplate and signal connectors
I suppose theres good ventilation in top lid/plate
I hate saying such, but I would have liked to see a row of ventilation holes in the case bottom along both heatsinks
What are those ugly monster tubeamps in the picture?
Re: hum F5
for test - try disconnecting gnd (shield) on ONE channel of CD -AMP cable ;
you probably have ground loop ; if that helps , write again
vitalica said:Hi,
My F5 is very stable.
But I have a problem: when you connect the CD player cable the hum is a very big ... I've tried several cables, but it's just the same ... Without cables, the F5 is very quiet. Can somebody help me with an advice?
Thancks!
Vitalie
for test - try disconnecting gnd (shield) on ONE channel of CD -AMP cable ;
you probably have ground loop ; if that helps , write again
Re: hum F5
Make sure BOTH are plugged into the SAME outlet. If you can't do that, then use a quality power strip to supply power to both pieces of equipment. Most CD players are NOT grounded, so this may or may not be the problem.
Ron
vitalica said:Hi,
My F5 is very stable.
But I have a problem: when you connect the CD player cable the hum is a very big ... I've tried several cables, but it's just the same ... Without cables, the F5 is very quiet. Can somebody help me with an advice?
Thancks!
Vitalie
Make sure BOTH are plugged into the SAME outlet. If you can't do that, then use a quality power strip to supply power to both pieces of equipment. Most CD players are NOT grounded, so this may or may not be the problem.
Ron
