I have just bought a Fosi BT20A Pro T-amp that is much hyped at the moment. It is based on the TI TPA3255 chip, the big brother to the TI TPA3116 chip
that I have in 3 other amps. Those 3 are Breeze Audio amps, and I actually like them a lot. They are quite cheap but perform very well.
All four amps are upgraded with LM4562 op-amps in the input stage, which are my preferred chip op-amps. I like Sparkos SS3602 discrete op-amps better,
but that is not the subject here.
And the subject is also not if 5532 is the world’s best op-amp. It was 50 years ago, but it is not now. It does not sound good, and it does not measure good,
so let us totally forget about that.
The Fosi BT20A Pro is well rounded, a little mellow almost like an old tube amp, and it does not have the slight boost in the higher midrange that the TPA3116
amps have, but compared to them it does sound a little less immediate. It has 2 replaceable 5532 op-amps, and 2 SMD mounted 5532 op-amps. I am afraid
the SMD chips is a design flaw.
The Fosi has a bass and a treble control and a separate pre out, that the others don´t have. I am not sure what the SMD chips are used for, but I am afraid that
they are for the tone controls, and therefore ruin some of the immediate sound of the amp, because you cannot dial out a tone control, even if the controls are
in the middle. They are still in series with the signal.
Does anyone know what the 2 SMD op-amps are used for, and did anyone make a mod, to get rid of them?
I am sure that there is more quality hidden in this amp, and I don´t care if I lose the tone controls.
Thanks in advance
Arthur.
that I have in 3 other amps. Those 3 are Breeze Audio amps, and I actually like them a lot. They are quite cheap but perform very well.
All four amps are upgraded with LM4562 op-amps in the input stage, which are my preferred chip op-amps. I like Sparkos SS3602 discrete op-amps better,
but that is not the subject here.
And the subject is also not if 5532 is the world’s best op-amp. It was 50 years ago, but it is not now. It does not sound good, and it does not measure good,
so let us totally forget about that.
The Fosi BT20A Pro is well rounded, a little mellow almost like an old tube amp, and it does not have the slight boost in the higher midrange that the TPA3116
amps have, but compared to them it does sound a little less immediate. It has 2 replaceable 5532 op-amps, and 2 SMD mounted 5532 op-amps. I am afraid
the SMD chips is a design flaw.
The Fosi has a bass and a treble control and a separate pre out, that the others don´t have. I am not sure what the SMD chips are used for, but I am afraid that
they are for the tone controls, and therefore ruin some of the immediate sound of the amp, because you cannot dial out a tone control, even if the controls are
in the middle. They are still in series with the signal.
Does anyone know what the 2 SMD op-amps are used for, and did anyone make a mod, to get rid of them?
I am sure that there is more quality hidden in this amp, and I don´t care if I lose the tone controls.
Thanks in advance
Arthur.
I might have found the problem myself. The TPA3255 expects to see a balanced signal coming in on both channels. That could probably be done either by generating a balanced signal from the unbalanced signal, or just by using + and put - to ground. Fosi seems to have chosen the first solution, so all sound has to go through those small sound-destroyers, and it is easy to hear.
There could be 2 solutions to this: Either to un-solder the two 5532 and to connect the unbalanced signal + to +, and ground the negative pin on the TPA3255, or to exchange the 5532 to some better ones, be it OPA1612 or OPA1656. I am just not very good at working with SMD components.
There could be 2 solutions to this: Either to un-solder the two 5532 and to connect the unbalanced signal + to +, and ground the negative pin on the TPA3255, or to exchange the 5532 to some better ones, be it OPA1612 or OPA1656. I am just not very good at working with SMD components.
Arthur,
Reading through a lot of TPA3255-related on the forum, it seems that aside from replacing the stock op-amps, bypassing capacitors are also often recommended as an easy, relatively harmless SQ upgrade. You can use a small ceramic capacitor and place it under the the power caps, 4th and 8th pin of the op-amps sockets (supposedly it cleans up the op-amp power supply), replace the opamp input caps, etc...
Digital Amplifier Circuit: A Study on Sound Quality | Various diaries of moto (office-mos.com)
This is a Japanese modder who dabbles quite a bit with the Aiyima A07, which uses the same chip as the Fosi. He goes into detail here with what could be done to improve TPA amps.
K.
Reading through a lot of TPA3255-related on the forum, it seems that aside from replacing the stock op-amps, bypassing capacitors are also often recommended as an easy, relatively harmless SQ upgrade. You can use a small ceramic capacitor and place it under the the power caps, 4th and 8th pin of the op-amps sockets (supposedly it cleans up the op-amp power supply), replace the opamp input caps, etc...
Digital Amplifier Circuit: A Study on Sound Quality | Various diaries of moto (office-mos.com)
This is a Japanese modder who dabbles quite a bit with the Aiyima A07, which uses the same chip as the Fosi. He goes into detail here with what could be done to improve TPA amps.
K.
Hi Karlson,
thanks for chiming in. I will try to cut my teeth with Google translate 🙂
The Fosi is so mellow sounding that i can´t live with it as it is. They have made 2 design flaws in my opinion: Implementing a tone control and using LM5532s for
balancing the signal to the TPA chip.
thanks for chiming in. I will try to cut my teeth with Google translate 🙂
The Fosi is so mellow sounding that i can´t live with it as it is. They have made 2 design flaws in my opinion: Implementing a tone control and using LM5532s for
balancing the signal to the TPA chip.
Arthur,
If I am understanding correctly, "mellow" means the amp is too laid back, too soft for your taste? Swapping out the stock opamps with LM4562s might have worsened it I fear.
LM4562 - LM49720 and the op-amps along the same lines are known to be neutral and don't impart much of a sound signature (information gathered from the TPA3251 modding thread). And obviously, different folks for different strokes 😉 Some may find the neutrality unbearable, in which case OPA 1612/1656 would be a better option (closer to "tube sound", more warmth).
Even though I have a love-hate relationship with op-amps (It's nice to be able to change them out, and curse in 50 languages when you can't), I believe you should start with getting the 2 aforementioned OPAs, see if that helps. They are pretty cheap and doesn't require any soldering (unless you buy the chips and DIY a pair).
Also do a basic check of your entire system, from source to speaker. You'd want to make sure it's not only the amp acting up. If it's indeed a lack of synergy caused by the amp, no need to waste time and move onto a more worthwhile one 🙂
K.
If I am understanding correctly, "mellow" means the amp is too laid back, too soft for your taste? Swapping out the stock opamps with LM4562s might have worsened it I fear.
LM4562 - LM49720 and the op-amps along the same lines are known to be neutral and don't impart much of a sound signature (information gathered from the TPA3251 modding thread). And obviously, different folks for different strokes 😉 Some may find the neutrality unbearable, in which case OPA 1612/1656 would be a better option (closer to "tube sound", more warmth).
Even though I have a love-hate relationship with op-amps (It's nice to be able to change them out, and curse in 50 languages when you can't), I believe you should start with getting the 2 aforementioned OPAs, see if that helps. They are pretty cheap and doesn't require any soldering (unless you buy the chips and DIY a pair).
Also do a basic check of your entire system, from source to speaker. You'd want to make sure it's not only the amp acting up. If it's indeed a lack of synergy caused by the amp, no need to waste time and move onto a more worthwhile one 🙂
K.
Yes all the details have disappeared. Normally I run an AKM4497 DAC with output transformers, into a Pass BA-3 Jfet preamp, into a Pass F-5 class A amp, into DIY OBL speakers with AMT-1 tweeters, and an active 15" sub with passive radiator. But recently I made myself a little project: "See what you can get for few money", but that does not include the speakers and the cables.
This new system is: PC with isolated USB -> Topping D20 DAC -> TPA amp -> DIY speakers based on SB Textreme 7,5" and SB Satori with textile cones, and silver cables. I have used this system extensively for a few months, and I only exchange one item at a time.
I have actually had good experience with a small TPA 3116 based Breezer amp, upgraded with LM4562, but that is a little on the bright side, probably because a slight ringing from the output filters. The concept is the same as the TPA3255, but the last should be a little bit more well behaving with a higher switching frequency. So I am quite sure that there is a lot of good sound possible from this chip. But I am afraid this Fosi is a bad implementation. AiYima A07 seems to be a better implementation, very close to the Breezer. And the 3e Audio seems to be a more HiFi like implementation too.
I have quite a lot experience with op-amp rolling, and have settled for LM4562 for chips, Sparkos SS3602 for normal discrete and Sparkos SS2590 for Pro op-amps. I have a device with OPA1612, but haven´t had the opportunity to try out OPA1656.
This new system is: PC with isolated USB -> Topping D20 DAC -> TPA amp -> DIY speakers based on SB Textreme 7,5" and SB Satori with textile cones, and silver cables. I have used this system extensively for a few months, and I only exchange one item at a time.
I have actually had good experience with a small TPA 3116 based Breezer amp, upgraded with LM4562, but that is a little on the bright side, probably because a slight ringing from the output filters. The concept is the same as the TPA3255, but the last should be a little bit more well behaving with a higher switching frequency. So I am quite sure that there is a lot of good sound possible from this chip. But I am afraid this Fosi is a bad implementation. AiYima A07 seems to be a better implementation, very close to the Breezer. And the 3e Audio seems to be a more HiFi like implementation too.
I have quite a lot experience with op-amp rolling, and have settled for LM4562 for chips, Sparkos SS3602 for normal discrete and Sparkos SS2590 for Pro op-amps. I have a device with OPA1612, but haven´t had the opportunity to try out OPA1656.
Sweet mother of mercy 😳 I feel humbled after reading just the first sentence. For reference, let's just say my entire setup I'm using cost less than a single SB Extreme 😵
Anyway, now that I have barely survived a heart attack, lots of A07 owners reported a great deal of improvements going from NE5532 to OPA1656, giving more detail, better soundstage, less muddy bass, etc... I can attest to this too, as I also own an A07 with 2x 1656, though with nowhere near as impressive a setup like yours.
You're the first I have seen so far to dislike the Fosi. It basically dethroned the A07 as the go-to mini desktop amp a few months ago, and generally got glowing reviews. Even though it's got a nice case, tone controls and all that flair, I have always liked the Aiyima's simplicity. But it needs a ton of improvements too.
I think in order to obtain a real difference, you need to step up to jlesterp or 3e Audio's products. They stick to the TI's recommendations and do it better. Most Chinese implementations, while giving impressive perf for the price and are good time killers, are nowhere near as good, with the occasional fake/underperforming parts thrown in.
Anyway, now that I have barely survived a heart attack, lots of A07 owners reported a great deal of improvements going from NE5532 to OPA1656, giving more detail, better soundstage, less muddy bass, etc... I can attest to this too, as I also own an A07 with 2x 1656, though with nowhere near as impressive a setup like yours.
You're the first I have seen so far to dislike the Fosi. It basically dethroned the A07 as the go-to mini desktop amp a few months ago, and generally got glowing reviews. Even though it's got a nice case, tone controls and all that flair, I have always liked the Aiyima's simplicity. But it needs a ton of improvements too.
I think in order to obtain a real difference, you need to step up to jlesterp or 3e Audio's products. They stick to the TI's recommendations and do it better. Most Chinese implementations, while giving impressive perf for the price and are good time killers, are nowhere near as good, with the occasional fake/underperforming parts thrown in.
I have just reconnected the small Breezer TPA3116 based amp, and it sound MUCH better. I have just put the Fosi on our local sales list, and I am almost
sorry to sell it to somebody else - but I did write in my add that it lacks detail. It is by far the worst amp I have had on my small system. People who use 5532 in HiFi systems should be put to jail immediately 🙂 I remember when it came out about 50 years ago, it was a far better op-amp than LM741 and its dual siblings, but that is many years ago, and a lot happened since.
sorry to sell it to somebody else - but I did write in my add that it lacks detail. It is by far the worst amp I have had on my small system. People who use 5532 in HiFi systems should be put to jail immediately 🙂 I remember when it came out about 50 years ago, it was a far better op-amp than LM741 and its dual siblings, but that is many years ago, and a lot happened since.
Thanks for sharing your experience with the Fosi BT20A Pro. I literally had my finger on the button to order this amp, when I came across this thread. I'm 68 and have collected and enjoyed many mid to high end systems over the years, but lately I have been drawn by the (new to me) mini amps and the ability to roll chips like tubes. I've enjoyed everyone's input , but I am curious to know exactly which "Breeze" amps you may be referring to.
Many Thanks........Russ A.