Thanks for these, unfortunately my printer looks like it goofed it up printing to true scale. Are the C205,C206 caps still supposed to be 1000uf? They look smaller compared to the C1 on the Bias board. My guess is the C205,206 are 10-12mm caps. I only say this as a put a panasonic resistor up to the power resistors on the front end board and they did not fit.
I have a chassis from BA 2008 with four pairs of complementary
IRFP230's per side which would seem natural for a BA-2. It came
with what is either a 300 or 330 VA power transformer which, per
the BA-2 article, would seem to be enough for only one channel
(I can wire it up for 20V+20VAC). For this reason, I'm looking at
possibly getting 2 300VA transformers or one 600-800VA piece.
In this box, space becomes an issue. There has been some
discussion of putting the front end and bias boards in an externally
attached box. I thinking it might be easier for my fat fingers if
I put the power supply outboard and the additional signal circuitry
inside, perhaps with a final set of PS caps inside as well. Pluses
and minuses?
thanks,
Skip
IRFP230's per side which would seem natural for a BA-2. It came
with what is either a 300 or 330 VA power transformer which, per
the BA-2 article, would seem to be enough for only one channel
(I can wire it up for 20V+20VAC). For this reason, I'm looking at
possibly getting 2 300VA transformers or one 600-800VA piece.
In this box, space becomes an issue. There has been some
discussion of putting the front end and bias boards in an externally
attached box. I thinking it might be easier for my fat fingers if
I put the power supply outboard and the additional signal circuitry
inside, perhaps with a final set of PS caps inside as well. Pluses
and minuses?
thanks,
Skip
If your speakers are not too hard to drive, it might work ok with your 300Va trafo
F5 also works with about half of what is suggested in manual
I dont think that trafo would have been there if not
My speakers are fairly sensitive 16 ohm coaxes (Altec 605Bs), so the
load will be minimal. I guess I can bias the outputs until the either
the heatsinks are too hot or the provided transformer sings and just
back it off.
thanks,
Skip
" ... Thermistors TH1 through TH3 are high power types such as Keystone CL60. TH1 and TH2 are used to suppress inrush surges on turn-on, and also are useful at reducing mechanical noise in the transformers in conditions of high line noise. ..." - From the Burning Amp-2 Manual by Nelson Pass.
I wanted to be specific here, because the (single) original THx Thermistor in BA-Fest2 chassis number 26 finally gave up the ghost = smoked. I bypassed it as a make do until a replacement(s) arrives.
Now, without the Thermistor(s) as per the pdf manual file above, my transformer does have some "mechanical noise" and electrical noise ... Don't let this happen to you = do install the TH1 through TH3 as per the power supply diagram in the manual. Thermistors do work and they do reduce transformer mechanical and electrical noise, no kidding. I intend to install two on the primary side just like the diagram, toot sweet.
I wanted to be specific here, because the (single) original THx Thermistor in BA-Fest2 chassis number 26 finally gave up the ghost = smoked. I bypassed it as a make do until a replacement(s) arrives.
Now, without the Thermistor(s) as per the pdf manual file above, my transformer does have some "mechanical noise" and electrical noise
... Don't let this happen to you = do install the TH1 through TH3 as per the power supply diagram in the manual. Thermistors do work and they do reduce transformer mechanical and electrical noise, no kidding. I intend to install two on the primary side just like the diagram, toot sweet.
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Found 'em at the local surplus house (HSC Electronics) ... "3934", ~ 5 to 6 ohms (cold), 5 Amp rated, @ US$0.65 each ... so I got eight for this and other projects (doubling up in parallel for higher wattage amps). HSC has hundreds (!)
My intention is to use two on the primary side ... and one in the ground link from the common, "star" analog ground point back to chassis ground (as per the PS diagram in the manual).
If anyone else needs some, I'll go fetch and pass them back to Variac or Nelson P.
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So if I understand this right, ( correct me if Im wrong), the best way (sound quality-wise and more future -proof) to build a BA-2 would be:
- one chassis with the bias and output stages, and the big power supply
- second chassis with the gain stage ( and separate regulated power supply ?)
- 3-pin connection between the two chassis( GND, D, OUT)
- one chassis with the bias and output stages, and the big power supply
- second chassis with the gain stage ( and separate regulated power supply ?)
- 3-pin connection between the two chassis( GND, D, OUT)
Yes. Nelson recently wrote and mentioned that getting the gain stage away fro mthe power supply is better than he had expected, or I think thats what he said. And yes, there will be various Gain Stages, that will work with both the BA-1 and BA-2.
Whether anewer one is better for your system, that depends- newer isn't always better. For example, the BA-2 isn't an improvement on the BA-1, it is just different. Complementary vs. single-ended.
But by having various Gain Stages you can try them and find out!!
As far as the separate power supply for the gain stage, I had assumed so, but can't speak for Papa Pass.
Whether anewer one is better for your system, that depends- newer isn't always better. For example, the BA-2 isn't an improvement on the BA-1, it is just different. Complementary vs. single-ended.
But by having various Gain Stages you can try them and find out!!
As far as the separate power supply for the gain stage, I had assumed so, but can't speak for Papa Pass.
Well, yeah... And that is exactly how we designed the gain boards- in the large chassis given away at the show they vertical at the rear so they can be right next to the inputs, but they end up right above t he AC fuse holder and reasonably close to the second set of caps in the pi filter. Neither should be a real problem, just not perfect. The smaller chassis might be a problem, they are mighty small inside. Changing from the big computer grade caps to more modern, more compact caps might be helpful.
Also, even in the big chassis they might be a bit hard to access to adjust the pots. Anyway it isn't essential to have them separate, just convenient to adjust, less noise and easy to swap out the gainstage for any new ones..
Also, even in the big chassis they might be a bit hard to access to adjust the pots. Anyway it isn't essential to have them separate, just convenient to adjust, less noise and easy to swap out the gainstage for any new ones..
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Maybe the essential thing with this is having the special bias curcuit close to outputs
As I understand it, doing it that way makes it possible to use almost any preamp with gain, as gainstage, maybe even a tube preamp
I suppose thats what a power buffer is
Im not sure, but I seem to remember that BA-2 would be prepared for higher voltage, and the BA-1 prepared fore higher bias mostly, not sure tho
But I decided to focus on BA-2 because it seemed to offer wider range of options, more power, if thats the right word
As fore highest sound quality, maybe BA-1 might be the better one, hard to say
Or was there something about the BA-1 would work only with the gain stage, not sure
But my uncertainty tells me I have to go back and study it again
As I understand it, doing it that way makes it possible to use almost any preamp with gain, as gainstage, maybe even a tube preamp
I suppose thats what a power buffer is
Im not sure, but I seem to remember that BA-2 would be prepared for higher voltage, and the BA-1 prepared fore higher bias mostly, not sure tho
But I decided to focus on BA-2 because it seemed to offer wider range of options, more power, if thats the right word
As fore highest sound quality, maybe BA-1 might be the better one, hard to say
Or was there something about the BA-1 would work only with the gain stage, not sure
But my uncertainty tells me I have to go back and study it again
I was planning on having separate PSU from main boards and outputs... Has anyone got a BA2 up and running yet ?