But it's not close enough to get similar performance. At least Rowland doesn't using so high value resistors, likewise I can't observe any big supply bypassing or decoupling caps near the chips in his Concentra/Concentra II Integrated Amplifier. A 10K gain setting resistor is clearly visible. At the right side there are only perhaps 100nF bypass caps. A feedback resistor connected directly to Ground pin (to minimize trace resistance and inductance, as well as DC offset I guess), so signal ground is omitted. However what is it a strange R29 resistor?
Re: Trim pots
The pot is not connected to the output, it's connected to one of the inputs.
A dc-servo can be applied to either positive or negative input. The pot is a simplified, manual, dc-servo so why shouldn't it work on a non-inverted amplifier?
And what is the resistor connected to pin 10 (R111, R104...) on the LM3886 at the picture of the Model 10 amplifier? Shouldn't it be connected to the pot if it was a inverted design?
I have not seen the schematic for Model 10 so correct me if I'm wrong. To me it looks like a non-inverted design...
Edit: regarding the change to from DRV134 to a transformer; offcourse it must have sounded better, the transformer is made for the job (depending of how you connect it offcourse), the DRV134 isn't. You don't use a balanced line-driver do bridge a amplifier, you use a bridging adaptor to bridge amplifiers!
sendler said:
The pot is not connected to the output, it's connected to one of the inputs.
A dc-servo can be applied to either positive or negative input. The pot is a simplified, manual, dc-servo so why shouldn't it work on a non-inverted amplifier?
And what is the resistor connected to pin 10 (R111, R104...) on the LM3886 at the picture of the Model 10 amplifier? Shouldn't it be connected to the pot if it was a inverted design?
I have not seen the schematic for Model 10 so correct me if I'm wrong. To me it looks like a non-inverted design...
Edit: regarding the change to from DRV134 to a transformer; offcourse it must have sounded better, the transformer is made for the job (depending of how you connect it offcourse), the DRV134 isn't. You don't use a balanced line-driver do bridge a amplifier, you use a bridging adaptor to bridge amplifiers!
Re: Re: Re: Trim pots
Well I might have to back down on this one. I was thinking about a design that works on ordinary OP-amps but now I'm not so sure it works on LM3886. Circuit below, not tested!
DRV134 datasheet says:
The DRV134 (and DRV135 in SO-8 package) converts single-ended, ground-referenced input to a floating differential output with +6dB gain (G = 2).
The BPA300 (and almost every other LM3xxx-based amplifiers) have a unbalanced, single-ended input. To bridge this amplifiers you need to convert one unbalanced signal to one unbalanced, non-inverted and one unbalanced, inverted signal. The signals need to be unbalanced, referenced to ground, and not a floating differential signal.
The DRV134 is not suitable for the job and there can be issues when using it for that. The job can easily been done with a dual OP-amp and some resistors instead.
sendler said:
Well I might have to back down on this one. I was thinking about a design that works on ordinary OP-amps but now I'm not so sure it works on LM3886. Circuit below, not tested!
An externally hosted image should be here but it was not working when we last tested it.
leadbelly said:
DRV134 datasheet says:
The DRV134 (and DRV135 in SO-8 package) converts single-ended, ground-referenced input to a floating differential output with +6dB gain (G = 2).
The BPA300 (and almost every other LM3xxx-based amplifiers) have a unbalanced, single-ended input. To bridge this amplifiers you need to convert one unbalanced signal to one unbalanced, non-inverted and one unbalanced, inverted signal. The signals need to be unbalanced, referenced to ground, and not a floating differential signal.
The DRV134 is not suitable for the job and there can be issues when using it for that. The job can easily been done with a dual OP-amp and some resistors instead.
Re: Re: Re: Re: Trim pots
That could work. Thanks for getting back with that so fast. That would explain the seemingly extra resistor in the photo. I have 8 3875s arriving tomorrow in order to try a bridged/ parallel. I was going to build them inverted to get rid of the de-coupling cap but may try that dc offset circuit with non-inverted instead to keep a reasonable input impedance for use with my passive stepped attenuators.
CJ900RR said:
That could work. Thanks for getting back with that so fast. That would explain the seemingly extra resistor in the photo. I have 8 3875s arriving tomorrow in order to try a bridged/ parallel. I was going to build them inverted to get rid of the de-coupling cap but may try that dc offset circuit with non-inverted instead to keep a reasonable input impedance for use with my passive stepped attenuators.
Re: Re: Re: Re: Re: Trim pots
No problem, but notice that I have not tried this myself! I don't guarantee that it works with LM38xx!
I also thought that the extra resistor was strange and therefore I think that they might use something like this above.
Note, R5 might not be needed and there is a more simplified construction: remove R4 and R5 and connect R3 directly to the center-tap of the pot....
sendler said:
No problem, but notice that I have not tried this myself! I don't guarantee that it works with LM38xx!
I also thought that the extra resistor was strange and therefore I think that they might use something like this above.
Note, R5 might not be needed and there is a more simplified construction: remove R4 and R5 and connect R3 directly to the center-tap of the pot....
Re: Re: Re: Re: Trim pots
1) The signals do not need to be unbalanced, where did you get that from? If anything, being balanced makes a better performing amp.
2) What does the fact that it is floating have to do with anything? If it was a problem, add some resistors to reference it to ground.
CJ900RR said:
1) The signals do not need to be unbalanced, where did you get that from? If anything, being balanced makes a better performing amp.
2) What does the fact that it is floating have to do with anything? If it was a problem, add some resistors to reference it to ground.
Re: Re: Re: Re: Re: Trim pots
1) No it don't need to be balanced, but my statement was regarding the design at Shine7, witch does not have a balanced input. Indeed balanced signal makes better performance, if the design is constructed as balanced! The BPA300 is constructed for single, unbalanced, earth-referenced inputs, not differental, floating inputs!
2) The fact? Don't you want two boards that "see" the same signal, except that one is inverted? Yes you do. There is differences in the signal from the DRV134. Have you measured the frequency-signal on each board bridged with a DRV134, and how does it look? Sure, use resistors to ground but how about the high and undefined offset?
It could work pretty well with AC-coupled amps though...
leadbelly said:
1) No it don't need to be balanced, but my statement was regarding the design at Shine7, witch does not have a balanced input. Indeed balanced signal makes better performance, if the design is constructed as balanced! The BPA300 is constructed for single, unbalanced, earth-referenced inputs, not differental, floating inputs!
2) The fact? Don't you want two boards that "see" the same signal, except that one is inverted? Yes you do. There is differences in the signal from the DRV134. Have you measured the frequency-signal on each board bridged with a DRV134, and how does it look? Sure, use resistors to ground but how about the high and undefined offset?
It could work pretty well with AC-coupled amps though...
DJNUBZ said:
Yeah, that's way more than I would or could ever pay for an amp.
You've got to respect, though, that there is a market out there for amps this expensive.
If the Rowland amps sounds a good as is rumored, I could see some well-heeled listener springing for one despite the fact that the active devices are relatively cheap. Some folks just don't have any desire or time to dally with DIY (a lot of folks couldn't care less if the output devices in their amp cost $5 each or $50 each simply because they would never set out to build an amp themselves; the final arbiter is then sound quality, aesthetics, build quality, cost, etc. If these things meet their expectations for the price, that's all that matters). Usually, a listener contemplating this sort of purchase has the means to indulge any sort of amp he or she wants. This amp is for them.
Luckily for us less monetarily endowed, there IS DIY. We can get great sound out of relatively inexpensive chipamp kits, Class-D kits, or other diy projects like Pass DIY and some cool tube offerings. Go crazy!
If anything, the discussion and/or criticism should be focused on whether it is ethical (or tasteful?) for someone in this society to spend this much on stereo gear. It may be obscene to spend this much on an amp, but I tend to believe that folks can do what they want with their own money as long as it's no skin off my back.
I can't blame Rowland for catering to this market. If the market exists, the amp lives up to Rowland's standards for sound and build quality, and it's sale brings in a good profit then the company would be stupid if they didn't make and sell the line. It's just good business sense.
I don't think, therefore, that any ire can be directed towards Rowland. They're making a product for a specific market segment that's willing to pay the asking price. If any of the readers don't happen to fall into that group, I don't think badmouthing Rowland for selling to that specific market segment is a productive way of looking at it.
Best,
KT
Bridged/ balanced amps have advantages
Concerning balanced audio gear.
.
.
In my case where my direct out modified Behringer DEQ2496 uses the AK4395 dac chip which has true balanced outputs right through from the digital filter, sending a balanced signal to a true balanced/ bridged amp has many technical advantages. The least of which is the balanced cables. The big deal for me is that I can get an ultra clean implementation of a true balanced/ bridged 3875 amp in order to very cleanly double the otherwise anemic 30 watts that they are capable of into an 8 ohm speaker so that an affordable chip amp can finally try to reach the sonics of my more powerful amps. I agree that most other home audio gear that can use balanced cables is adding extra circuits on each end that you don't want, just in order to balance a 3 foot cable, making the balanced connection sound worse, not better. But, when it comes to amps, running bridged/ balanced is a great step foward as long as you are ready to double the cost of the amp, which, with these chip amps is minimal to begin with.
Concerning balanced audio gear.
.
Itinitus said:
.
In my case where my direct out modified Behringer DEQ2496 uses the AK4395 dac chip which has true balanced outputs right through from the digital filter, sending a balanced signal to a true balanced/ bridged amp has many technical advantages. The least of which is the balanced cables. The big deal for me is that I can get an ultra clean implementation of a true balanced/ bridged 3875 amp in order to very cleanly double the otherwise anemic 30 watts that they are capable of into an 8 ohm speaker so that an affordable chip amp can finally try to reach the sonics of my more powerful amps. I agree that most other home audio gear that can use balanced cables is adding extra circuits on each end that you don't want, just in order to balance a 3 foot cable, making the balanced connection sound worse, not better. But, when it comes to amps, running bridged/ balanced is a great step foward as long as you are ready to double the cost of the amp, which, with these chip amps is minimal to begin with.
Re: Bridged/ balanced amps have advantages
Backside is that a balanced amp will see half of the the actual speaker impedance
One possible benefit could be that you can obtain the same output with LESS voltage
Other than that I believe its actually the smaller amps that have superiour sonics
But being a chipamp it could very well mean that the raised power does have some benefits
With regards to the power supply LCAudio(LarsClausen) once had some interesting suggestions
Something with double supply, which had a drawback, being capacitance would be halfed, hence a big cap with twice the voltage was placed across, + to -
sendler said:
Backside is that a balanced amp will see half of the the actual speaker impedance
One possible benefit could be that you can obtain the same output with LESS voltage
Other than that I believe its actually the smaller amps that have superiour sonics
But being a chipamp it could very well mean that the raised power does have some benefits
With regards to the power supply LCAudio(LarsClausen) once had some interesting suggestions
Something with double supply, which had a drawback, being capacitance would be halfed, hence a big cap with twice the voltage was placed across, + to -
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