You certainly are persistent.JojoD818 said:If I change all of the transistors to higher voltage ratings, do you think it is possible to use higher voltage rails? Say +/-63V?
Jojo
You may have some trouble finding them. I think at least one of the transistors would end up needing a voltage rating of 100+ volts.
Best is to ask Rod. He's usually pretty good about answering questions if you buy his PCBs.
He has a discussion group at his site now, why not post this question there?
jean-paul said:
yeh, unfortanly its also 25E more then i can afford. im on a rapidly running out student budjet, and ive got a drum kit to support. although if i like the sound of the amp, i will consider buying a pcb when i make a hi version if i like the sound, but for high power from a drum kit i dont see the need
Hi!
Correctamundo! I get my parts from a multiple places. First I try the cheapest mailorder in Germany (Reichelt), then I get the Panasonic FC electrolytes I always use from Farnell, sometimes also Welwyn RC55 resistors from Farnell, those small cases and a good shielded mains cable fromrolleyes: ) Conrad, for semiconductors not found at either Reichelt or Farnell I take a look at RS Components, and BHC SlitFoil caps, O- and R-core transformators from LCAudio and some even more special parts from Thel...
Sadly the variety of semiconductors available is not that great at all of those sites compared to DigiKey et al.
I am lucky that I bought DoZ, DoZ-pre and later the P3A boards from ESP while I still had a credit crad - credit cards are a lot harder to get in Germany than in America, and since the one I had is no longer available, so far four banks (including my "home" bank) have refused me a new card because of myself being a student with no "official" income... but I am persistent... still wnat to try the ESP 300W subwoofer amp later this year, and I want to use premade boards...
Bye,
Arndt
JojoD818 said:
Correctamundo! I get my parts from a multiple places. First I try the cheapest mailorder in Germany (Reichelt), then I get the Panasonic FC electrolytes I always use from Farnell, sometimes also Welwyn RC55 resistors from Farnell, those small cases and a good shielded mains cable from
rolleyes: ) Conrad, for semiconductors not found at either Reichelt or Farnell I take a look at RS Components, and BHC SlitFoil caps, O- and R-core transformators from LCAudio and some even more special parts from Thel...Sadly the variety of semiconductors available is not that great at all of those sites compared to DigiKey et al.
I am lucky that I bought DoZ, DoZ-pre and later the P3A boards from ESP while I still had a credit crad - credit cards are a lot harder to get in Germany than in America, and since the one I had is no longer available, so far four banks (including my "home" bank) have refused me a new card because of myself being a student with no "official" income... but I am persistent... still wnat to try the ESP 300W subwoofer amp later this year, and I want to use premade boards...
Bye,
Arndt
Raising the voltage that much (you are talking about a 50% voltage increase) will probably change the working point of the circuit's elements, so you need at least to re-arrange them a bit.
Output devices can be paralleled but in a different way, look at the 300W subwoofer project at ESP.
The final result is that your project won't be a P3A at all...
If your transformer gives +/- 63V and 80-100W are enough you can lower the rails either regulating the supply or using something like a lamp in series with the primary of the trafo.
If you need considerably more power go for a different project, like Holton's symmetrical amp, or the Leach amp, or whatever you like.
Cheers
Andrea
Output devices can be paralleled but in a different way, look at the 300W subwoofer project at ESP.
The final result is that your project won't be a P3A at all...
If your transformer gives +/- 63V and 80-100W are enough you can lower the rails either regulating the supply or using something like a lamp in series with the primary of the trafo.
If you need considerably more power go for a different project, like Holton's symmetrical amp, or the Leach amp, or whatever you like.
Cheers
Andrea
Andrea,
The only reason why I thought it may work is because I compared it to the 300w esp amp and it has very similar values for the resistors, etc. But it uses a +/-56V supply rail. However Rod said to be careful with the output devices so I will use lots of my stock toshiba devices.
If the mod works fine, if it blows
I'll just stick to the P3A setup.
Jojo
The only reason why I thought it may work is because I compared it to the 300w esp amp and it has very similar values for the resistors, etc. But it uses a +/-56V supply rail. However Rod said to be careful with the output devices so I will use lots of my stock toshiba devices.
If the mod works fine, if it blows
I'll just stick to the P3A setup.Jojo
Those are feedback components. They determine the gain and frequency response of the amp.JojoD818 said:
At DC, or very low frequencies, the capacitor acts like an open circuit and R4 and C3 are effectively out of the circuit. There is 100% feedback, so gain at DC is 1. At higher frequencies, C3 becomes more like a short circuit so gain increases to R5/R4 = 22 = 27dB.
C1 also affects low-frequency response. It forms a filter in conjunction with R2.
Just want to tell..
I have just built a modified esp3a amplifier, running at +/-52V, 4 ohms load. Works and sounds good!!!
Powersupply/channel:
One 500VA toroid transformer
Two 47000uF 63V RIFA capacitors.
Amplifier:
Q1, Q2, Q3, Q9 = 2N5550
Q4 = MJE 350
Q5, Q6 = MJE1503x
I use two pairs of Sanken 2SA1216/2SC299 transistors each with a 0R1 5W emitter resistor.
R9, R10 = 3k3
Q4, Q5 and Q6 need to have small heatsinks.
I also placed Q9 (Vbe multiplier) at the top of Q5 to have a very stable bias current.
Otherwise I haven't done more modifications yet, but I'm thinking of increasing the current through the input stage and VAS stage and add degeneration resistors, and a balanced input.
/Freddie
I have just built a modified esp3a amplifier, running at +/-52V, 4 ohms load. Works and sounds good!!!
Powersupply/channel:
One 500VA toroid transformer
Two 47000uF 63V RIFA capacitors.
Amplifier:
Q1, Q2, Q3, Q9 = 2N5550
Q4 = MJE 350
Q5, Q6 = MJE1503x
I use two pairs of Sanken 2SA1216/2SC299 transistors each with a 0R1 5W emitter resistor.
R9, R10 = 3k3
Q4, Q5 and Q6 need to have small heatsinks.
I also placed Q9 (Vbe multiplier) at the top of Q5 to have a very stable bias current.
Otherwise I haven't done more modifications yet, but I'm thinking of increasing the current through the input stage and VAS stage and add degeneration resistors, and a balanced input.
/Freddie
Freddie,
I wish you can update me to any other mods you do so that I can also mod my P3A. Mine is running at +/-63V right now (happily).
Transistors used were:
2N5551
2SD669
2SB649
2SC2344
2SA1011
2SC5200 X2
2SA1943 X2
BTW, I attached (using mica insulators) Q9 to tha main heatsink not knowing if it's really necessary. Any suggestions?
I wish you can update me to any other mods you do so that I can also mod my P3A. Mine is running at +/-63V right now (happily).
Transistors used were:
2N5551
2SD669
2SB649
2SC2344
2SA1011
2SC5200 X2
2SA1943 X2
BTW, I attached (using mica insulators) Q9 to tha main heatsink not knowing if it's really necessary. Any suggestions?
Yup, you're right. An off-by-one error.Freddie said:
Actually (if I'm not mistaken
/Freddie
"If I increase or decrease the value of C3, what happens? Does the bass response vary with C3?"
As I mentioned, there are two low-frequency cutoffs. The first has a cutoff (-3dB) frequency of 1 / (2*pi*R4*C3).
The second is 1 / (2*pi*C1*R2).
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