In fact I just ordered a couple channels of F-5 components from Jack a few weeks ago. He is a great resource, and has never let me down.. .
Mark
Mark
more mosfets
I originally built with 3 pairs of MOSFETs, about 450 mA bias. I added two more pairs and was delighted with the result, finding much better bass (to my taste obviously). I hadn't changed the bias so I had more class-A current available, higher device temperatures as well as more devices.
I did some configuration testing and judged them listening to the album 'xx', it's pop but contains some really deep bass passages and a lot of minimally accompanied singing.
3 pairs, 450 mA per pair: good, for me not quite as good as my KT88 push-pull
3 pairs, 700 mA per pair: better, more detailed I thought
5 pairs, 410 mA per pair: my favourite, really impressive bass, I think this is better than my KT88s, and a lot safer to build
So, in summary, I think the amount of current and how hot the devices are is important, but just having more devices will have a impact also. If you've gone to the trouble of building one of these babies, you might want to go the extra yard and check if more devices improves it for you too.
Also, the heatsinks are throwing off heat now
(dQ/dt)>>0!
I originally built with 3 pairs of MOSFETs, about 450 mA bias. I added two more pairs and was delighted with the result, finding much better bass (to my taste obviously). I hadn't changed the bias so I had more class-A current available, higher device temperatures as well as more devices.
I did some configuration testing and judged them listening to the album 'xx', it's pop but contains some really deep bass passages and a lot of minimally accompanied singing.
3 pairs, 450 mA per pair: good, for me not quite as good as my KT88 push-pull
3 pairs, 700 mA per pair: better, more detailed I thought
5 pairs, 410 mA per pair: my favourite, really impressive bass, I think this is better than my KT88s, and a lot safer to build
So, in summary, I think the amount of current and how hot the devices are is important, but just having more devices will have a impact also. If you've gone to the trouble of building one of these babies, you might want to go the extra yard and check if more devices improves it for you too.
Also, the heatsinks are throwing off heat now
(dQ/dt)>>0!
Attachments
Has anyone used a voltage regulator for the front end of the BA-2? What differences might one hear if one was used?
Still enjoying these amps so much. I seem to have a different music collection all of a sudden.
Best wishes,
Chris
Was that a Typo, Zen?
Anyone happen to have a figure for the current draw of the BA-2 front end?
If one was to use a voltage regulator, let's say for the sake of argument a 78XX type three pin arrangement. Would one need two such devices, one for each of the +25V, -25V rails?
Best wishes,
Chris
Anyone happen to have a figure for the current draw of the BA-2 front end?
If one was to use a voltage regulator, let's say for the sake of argument a 78XX type three pin arrangement. Would one need two such devices, one for each of the +25V, -25V rails?
Best wishes,
Chris
wasn't a typo ; answering your question - so see posts #764 & #765
if going to 3-legged regs , use at least LM317 ( even for low side - it's better than 337 counterpart)
Looking at the original article, resistors R210 and R211 should have 1.2 V drops across them, they're 47.5 ohms, so 25 mA per rail per side.
Are you thinking of using the same transformer for the front-end and the output stage? If you use a new, separate transformer for the front-end you can choose higher voltage secondaries. Then, you have freedom to choose regulators where you must sacrifice a lot of voltage in return for the regulation.
OK! 25mA it is. If one was to take the output from the current power supply for the front end then we would have to shave off a few volts for the regulator. What is the lowest voltage that the front end will work at?
Another question: If one used two LM317 per channel for the front end and due to variations in component values each voltage regulator gave a slightly different votage output would this make any difference?
I have used the LM337 in the past with diodes instead of resistors to adjust the voltage output. I preferred the diodes but it does seem the LM317 is the one most discerning listeners turn to.
Best wishes,
Chris
There's an awful lot right now on the Salas shunt reg. The PCBs seem to come up for group buy every few months, they include space for buffer components too, but you wouldn't use this piece of the PCB.
What about this Teddy Reg?
the teddyreg!
It looks doable without a PCB and cheaper than the Salas Simplistic Shunt reg
What about this Teddy Reg?
the teddyreg!
It looks doable without a PCB and cheaper than the Salas Simplistic Shunt reg
Thanks Highfield.
I'm not sure about the wiring of the split rail supply. Would I need for the sake of argument an LM317 for the +rail and an LM137 for the negative? Would I connect both grounds of the two chip circuits to the common ground of the split rail power supply rectifier/caps circuit?
Best wishes,
Chris
I'm not sure about the wiring of the split rail supply. Would I need for the sake of argument an LM317 for the +rail and an LM137 for the negative? Would I connect both grounds of the two chip circuits to the common ground of the split rail power supply rectifier/caps circuit?
Best wishes,
Chris