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Old 10th April 2015, 10:29 PM   #1
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Location: Paris
Default My last amplifier

Hi everyone,
I have just finished (2 weeks ago) my last amplifier I'm quite happy with the sound sharp and soft at the same time. And while its schematic of my own is quite original I give it to you if some one is interested by more details I can provide any informations.
It is a 70/80W AB with driven biasing.
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Old 11th April 2015, 11:51 PM   #2
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It seams nobody likes my amp, its a pity

Anyway I will say a little more:

The output stage (of an original topology) maintains a constant bias current of 250mA this current is maintained almost independently ot temperature and ouput current.

This ensure thermal stability, linéarity and low output impédance.

linéarité and output impédance are such that in previous version (which used same output stage) and that has been sounding very nicely in my living room for years; it was implemented with 0db NFB.

Here it does use significant amount of NFB with a blameless like front end. So I guess figure are very low.
It is certainly one of the best amp I haver ever heard.

I used ExpressPCB boards so files are available.
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Old 12th April 2015, 09:18 AM   #3
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Could you show some oscillographs and/or actual measurements?
Cheers,

Jacques
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Old 12th April 2015, 11:50 AM   #4
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The amplifier is design to work from scratch without any tuning (there is no trimmer). So I have only done steady state measurements to check conformance with simulations. These measurements where:
- Idle current which was: 258 & 253 mA
- Offset voltage which was : 0.9 & 1.5 mV
- Check of absence of any oscillation on output
- Several internal voltage measurements.
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Old 12th April 2015, 09:08 PM   #5
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An other strong point of this amplifier is that I completely avoided decoupling of supply rails on amp pcb.
Instead I use a pcb configuration with output very close to both supply rails this reduces induction of even harmonics and inductance of both output and suppy rails.
The front end has its own pair of (cleaner) supply rails.
Avoiding decoupling also helps a lot in keeping pcb amp ground clean. In this amp pcb amp ground only contains input and feed back network.
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Old 13th April 2015, 02:31 AM   #6
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Is that a Baxandall in the output stage ? Unique.

Does the OPS also "self clamp" on overload ?

OS
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Old 13th April 2015, 05:22 AM   #7
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Where is ground of load ?
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Old 13th April 2015, 05:53 AM   #8
dadod is offline dadod  Croatia
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Quote:
Originally Posted by SMourareau View Post
It seams nobody likes my amp, its a pity

Anyway I will say a little more:

The output stage (of an original topology) maintains a constant bias current of 250mA this current is maintained almost independently ot temperature and ouput current.

This ensure thermal stability, linéarity and low output impédance.

linéarité and output impédance are such that in previous version (which used same output stage) and that has been sounding very nicely in my living room for years; it was implemented with 0db NFB.

Here it does use significant amount of NFB with a blameless like front end. So I guess figure are very low.
It is certainly one of the best amp I haver ever heard.

I used ExpressPCB boards so files are available.
Why you are surprised of low interest, you don't show the schematic with the values?
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Old 13th April 2015, 06:38 AM   #9
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Location: Paris
The ground of load and in fact the whole output RLC net is on PSU board.
Here are the components (sorry for the layout):

QP4 BJT KSA1220A
QP8 BJT KSC1845
QV5 BJT KSC1845
QV6 BJT KSC1845
QP5 BJT KSC2690A
QP1 BJT 2SA1943
QP2 BJT 2SC5200
QP3 BJT 2SC5200
QV3 BJT BC549C
QV4 BJT BC549C
QP6 BJT BC559C
QP7 BJT BC559C
QRP1 BJT KSA992
QRP2 BJT KSA992
QRP3 BJT KSA992
QRP4 BJT KSA992
QRV1 BJT KSA992
QRV2 BJT KSA992
QV1 BJT KSA992
QV2 BJT KSA992
CBP removed
CP1 polypro 47pf 5,00%
CV1 polypro 100pf 5,00%
CV2 polyester 6.8uf 5,00%
CV3 polyester 6.8uf 5,00%
DP1 0.25A/75V BAW76
DP2 0.25A/75V BAW76
DP3 0.25A/75V BAW76
DP4 Zener 5v6 1N5919B
LBP 2uH
RP8 couche métal 15R 1,00% MRS25
RV1 couche métal 100R 1,00% MRS25
RV2 couche métal 100R 1,00% MRS25
RRP1 couche métal 1K87 1,00% MRS25
RRP2 couche métal 1K87 1,00% MRS25
RP7 couche métal 267R 1,00% MRS25
RV3 couche métal 267R 1,00% MRS25
RP3 couche métal 294R 1,00% MRS25
RP2 couche métal 590R 1,00% MRS25
RP5 couche métal 59R 1,00% MRS25
RP6 couche métal 604R 1,00% MRS25
RV5 couche métal 604R 1,00% MRS25
RRV2 métal métal 787R 1,00% MRS25
RRP3 couche métal 931R 1,00% MRS25
RRV1 couche métal 931R 1,00% MRS25
RRP4 couche métal 931R 1,00% MRS25
RBP1 couche métal 1R 5,00% MFP1
RBP2 couche métal 1R 5,00% MFP1
RP1 couche metal 1R2 5,00% MFP1
RRV3 couche métal 22K 5,00% MFP1
RRP5 couche métal 33K 1,00% MFP1
RRP6 couche métal 33K 1,00% MFP1
RP4 couche metal 100R 5,00% MFP2
RV8 couche métal 133K 1,00% RC55Y
RV6 couche métal 133K 1,00% RC55Y
RV7 couche métal 6K650 1,00% RC55Y
VP1 Shunt Reg. 10V LM4040-10
VP2 Shunt Reg. 2V5 LM4040-2.5
VV1 Shunt Reg. 2V5 LM4040-2.5
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Old 13th April 2015, 06:48 AM   #10
MiiB is offline MiiB  Denmark
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Sorry, you ask for interest, but don bother to make a schematic that people can relate to, then now you add a component list making it even harder to get a good impression, my gut feel is that if you want a qualified response then you have to make it easier to understand your thinking.
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