Nothing about class a, but forgive me, here my story continues:
I compared the "overcaped" NIGC with the buffered and regulated version (class a/b for the opa627) tonight.
The regulated version shows in fact more "musicality" than the overcaped version. More details, good soundstage.
But my favourite tonight (at the left):
Two times 2 Watt valve amp, single end, class A.
May be in future I will use chipamps just for subwoofers...
Franz
I compared the "overcaped" NIGC with the buffered and regulated version (class a/b for the opa627) tonight.
The regulated version shows in fact more "musicality" than the overcaped version. More details, good soundstage.
But my favourite tonight (at the left):
An externally hosted image should be here but it was not working when we last tested it.
Two times 2 Watt valve amp, single end, class A.
May be in future I will use chipamps just for subwoofers...
Franz
Franz, your 'overcaped' version is not the correct way to use these chips, as I said.
Anyway, with your speakers your 2w valve amp may please more to you.
Even then, it's a question of taste, and I don't discuss that.
But if you had "normal" speakers instead of your full-range horns you couldn't even bare to listen to that valve amp.
You seam to have a good match between amp and speakers, and for your musical tastes, so no need to fiddle.
Don't discard chipamps just because you have a better choice on your system.
I've heard lots of things, lots of them I have no money to buy, and believe me, these chips are very good, I have lots of pleasure listening to music.
BTW, I made my sub amp with chips.
2 // OPA549s.
Anyway, with your speakers your 2w valve amp may please more to you.
Even then, it's a question of taste, and I don't discuss that.
But if you had "normal" speakers instead of your full-range horns you couldn't even bare to listen to that valve amp.
You seam to have a good match between amp and speakers, and for your musical tastes, so no need to fiddle.
Don't discard chipamps just because you have a better choice on your system.
I've heard lots of things, lots of them I have no money to buy, and believe me, these chips are very good, I have lots of pleasure listening to music.
BTW, I made my sub amp with chips.
2 // OPA549s.
Franz G said:
I agree with carlosfm. For a 1W output, even the 10k uF seems to be an overkill, and would just tend to give you more potential problem. Removing those 10k uF will save you amp cost and space.
But I agree with you, that on a 1W, what you did might really sound better.
I wonder if anyone did experiment the AN1192 for LM3886, using the capacitors:
- 2x 1200uF in the PSU board
- 2x 10k uF, 2x 470uF, 2x 0.1uF near the power pins
These are multiple bypassing which FranzG nearly implemented, but would give out more power (of course with buffer circuit).
Thanks for posting your observations.
Hi Carlos, here she is: -
DOB April 23 1923
Are you still interested to go naughty with her today?
By the way, after listening for the whole night (I just can't stop), I can say the amp is having more punch at the low and more details at the high. The vocal is especially good. So good that I'm wondering does Class A biasing introduced some MSG?
When I compare to the change of sound stage by changing the caps to BG, BG caps are shifting the spectrum to the high while biasing to Class A is expanding the spectrum. I think my PCB has to go through another surgery to solder these resistors on it permanently.
Sunny
DOB April 23 1923
An externally hosted image should be here but it was not working when we last tested it.
Are you still interested to go naughty with her today?
By the way, after listening for the whole night (I just can't stop), I can say the amp is having more punch at the low and more details at the high. The vocal is especially good. So good that I'm wondering does Class A biasing introduced some MSG?
When I compare to the change of sound stage by changing the caps to BG, BG caps are shifting the spectrum to the high while biasing to Class A is expanding the spectrum. I think my PCB has to go through another surgery to solder these resistors on it permanently.
Sunny
Franz G said:
All the tests I make are without the sub.
And I know my speakers very well without the sub.
There's no lack of bass with 33uf caps on the chip.
Maby there is on your implementation, with your PCB.
You recognized that the PCB traces may be a little thin.
Don't concentrate just on a frequency band, listen to the music as a whole.
I don't like the result of having big caps near the chip, with regulated PSU.
Pay attention to bass quality and tightness, midband, treble, detail, "air", speed.
When I mean big, I'm saing more than around 100uf.
From 33 to 100uf gave the best results when I tested it.
soundNERD said:
It is good for small signal amplifying applications only. Very limited power.
Audio electronics is where specialization is very much used. It's less problematic to have several stages, each doing a specific task, instead of one doing it all.
Even so, inside a small signal chip (e.g.: OPA627) or a large signal chip (e.g.: LM3886) there are sub-stages that also different tasks.
But as a rule, small signal chips specialize in doing low-noise amplification or fast signal handling, having limited power capability to drive it.
That's why in this forum the combination OPA627/BUF634 became quite popular, each chip doing a specific task.
Carlos E. Martinez
I am on the way to try this:
... drive the EL84 SE tubes with an OPA627, instead of the ECC82.
Franz
An externally hosted image should be here but it was not working when we last tested it.
... drive the EL84 SE tubes with an OPA627, instead of the ECC82.
Franz
Franz G said:I mean by "marketing calculation": just add all capacitance in an amp and write about the sum in the flyer
Here is the PSU schematics:
An externally hosted image should be here but it was not working when we last tested it.
The testamp looks like this:
An externally hosted image should be here but it was not working when we last tested it.
It is important to say: this amp sounds different than the buffered version. I am sure, bass is better.
But I can not tell you up to now, wich amp I prefer. Give me one or two weeks of comparing them.
Carlos: please dont forget we use different speakers: I drive fullrange speakers in backloaded horns. I NEVER use more than 1W output!
Franz G,
May I suggest something, if you haven't tried it yet?
How about decreasing the gain to around 11-15 instead of 27-30. LM’s have very good frequency response, so a bit more NFB may be a good thing in your case. This way you'll have much lower distortions and you won't have to attenuate the input signal that much (you said you use only 1W). I'm sure the sound will be different and hopefully better. I remember experimenting with the gain and I liked gain of 22 better than gain of 30. It was smoother but not lacking detail.
I'm very curious to hear what you'd find. I'm looking into building full range speakers with about 94dB/m sensitivity and driving them with GC (no buffers at all).
/Greg
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