1V difference? That's quite a bit, but not unexpected. The circuit has the output coupling caps for this very reason.
This is clear but I am not comfortable whit so much dc offset drift....Ok I will try again,
maybe I manage to bias better...
Has anyone tried to lower the source resistors R10 and R11 on MOSFETS for more gain?
maybe I manage to bias better...
Has anyone tried to lower the source resistors R10 and R11 on MOSFETS for more gain?
Something is wrong there i guess, that kind of results could be realistic with bjt input because of base currents but not in this case. Did you tried to measure with opened input and ac (cap) short to ground?
The DC offset is dancing but in 10-20mV over the scale...The JFETS are biased 5.8mA and the P3 is around middle point. The output stage is working very stable! So I powered it on and there is zero hum or noise! Then I connected CD player to it and there is some hum in both channels, so assume a ground loop...Tried to isolate the cable nothing! Has anyone an idea what could be the problem? I have dual mono power supply whit all the grounds returning to a single GND bar which is connected via CL-60 to the chassis...
I guess the problem are the interconnects as they are not shilded...The hum is not very loud on
both channels the same. If I disconect the interconnects the amp is silent. If I dont find anything else I will use an input transformer.
On the other hand, I played a few tracks and this amp is really a step forward!
both channels the same. If I disconect the interconnects the amp is silent. If I dont find anything else I will use an input transformer.
On the other hand, I played a few tracks and this amp is really a step forward!
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damn!
if you made it as dual mono block , then make it all the way
each channel must have own CL60 going from audio gnd to chassis
that way these two audio gnds are isolated for value of two CL60 , and there is no ground loop
I am thinking to use tube front end stage to directly drive the output stage of the burning amplifier or the crippled F4. The BA-3 has a very low output impedance so what would be the max source impedance to effective drive the output stage of the F4? Or do I need a buffer in any case?
if driving it buffer-less , I wouldn't go above 300R of generator output impedance
easy peasy for any proper tube output stage
if cathode follower , go SLCF route
easy peasy for any proper tube output stage
if cathode follower , go SLCF route
So what's the word on delivery of the BA-3 boards to the store? Anticipated date 4/1/2015. On time, delayed, or unknown? I need one more board!🙂
Russellc
Russellc
For those of you wondering, this sounds like good news. received this from the help desk:
APR 08, 2015 | 10:52AM SGT
Customer Care replied:
Hi Cody,
Our apologies for the delay.
We've experienced a minor hiccup at the warehouse which caused us to miss the anticipated ship out date of April 1. But we're working hard on getting the new stocks ready for shipping out asap.
Thanks,
diyAudio Helpdesk
P-BAGSN-1V20/P-BAC-S4V20
I thought I would go town on this one. This is my last amp… I mean it this time. It has been two years in the building as life had other plans.
The power supply is made up of a Sumner 750VA transformer and left over parts from a stillborn Aleph X and all put into the Universal PSU V3. I put in a timer to bypass the CL60s, to placate my audiophile anxieties, but have realized more harm than good will come from this having bypassed the AC filters. There is no change in the sound when they click in.
The P-BAGSN-1V20 Gain boards were populated with Vishay Bulk and “naked” resistors. Mundorf Evo Silver Gold-Oil and Elna Carafine caps were installed as well. The Mundorfs have worked well for me in other Mr. Pass designs.
The P-BAC-S4V20 - Burning Amplifier Complementary Bias and Output Sets were populated using the recommended parts from the build guide. There are 12 devices per channel mounted on ½ inch bar stock with three Mersen 66261-12B heat sinks (obsolete) torqued to the rear. I thought this would be over kill but apparently not. The Amps run at 125F after four hours. “You can never have too much heat sink.”
Reviews are subjective things…but. First the BA3 mono block is loud. “It goes to eleven!” This I did not expect. It goes far beyond what my speakers and spouse can handle. The bass and treble response is excellent. The sound stage wide and deep with the expected air around the instruments. But it’s the vocals that made all this expense worthwhile. They are out front and full of emotion and they sound …well human (?)
I tried a couple of pre-amps and it can down to the venerable P1.7 with a knob on the front as a very good match.
Thanks go to;
Neville : “Replaced my 500r pots with 1K pots and VOILA....... “ I would still be spinning P1 trying to get the voltage up.
h-a Hannes; For his fet matching service. He saved me some time.
The build guides and boards were handy.
And that Nelson guy. You don’t want mess with a guy that has been building heavy Class A amps all his life. ; )
Cheers; Glenn
I thought I would go town on this one. This is my last amp… I mean it this time. It has been two years in the building as life had other plans.
The power supply is made up of a Sumner 750VA transformer and left over parts from a stillborn Aleph X and all put into the Universal PSU V3. I put in a timer to bypass the CL60s, to placate my audiophile anxieties, but have realized more harm than good will come from this having bypassed the AC filters. There is no change in the sound when they click in.
The P-BAGSN-1V20 Gain boards were populated with Vishay Bulk and “naked” resistors. Mundorf Evo Silver Gold-Oil and Elna Carafine caps were installed as well. The Mundorfs have worked well for me in other Mr. Pass designs.
The P-BAC-S4V20 - Burning Amplifier Complementary Bias and Output Sets were populated using the recommended parts from the build guide. There are 12 devices per channel mounted on ½ inch bar stock with three Mersen 66261-12B heat sinks (obsolete) torqued to the rear. I thought this would be over kill but apparently not. The Amps run at 125F after four hours. “You can never have too much heat sink.”
Reviews are subjective things…but. First the BA3 mono block is loud. “It goes to eleven!” This I did not expect. It goes far beyond what my speakers and spouse can handle. The bass and treble response is excellent. The sound stage wide and deep with the expected air around the instruments. But it’s the vocals that made all this expense worthwhile. They are out front and full of emotion and they sound …well human (?)
I tried a couple of pre-amps and it can down to the venerable P1.7 with a knob on the front as a very good match.
Thanks go to;
Neville : “Replaced my 500r pots with 1K pots and VOILA....... “ I would still be spinning P1 trying to get the voltage up.
h-a Hannes; For his fet matching service. He saved me some time.
The build guides and boards were handy.
And that Nelson guy. You don’t want mess with a guy that has been building heavy Class A amps all his life. ; )
Cheers; Glenn
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