| beppe61 |
Dear Friends,
in the Sanken's web site I found this statement:" Darlington transistors do not require drive transistors".
I wonder why darlingtons are not much more common as they could be used in simpler circuits.
I mean 1 darlington can replace 1 drive bjt + 1 output bjt.
Am I missing something ?
And also high current darlingtons are available.
Any link to very simple topologies using darlingtons?
Thank you very much indeed.
Kind regards,
beppe61 |
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| richie00boy |
| A very good point. One issue is that they tend to be slower, and that reverse biasing the base to switch off quicker/cleaner is not possible. Also there is no control over the main transistors base-emitter resistor. |
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| lineup |
| quote: | Originally posted by beppe61
Dear Friends,
in the Sanken's web site I found this statement:" Darlington transistors do not require drive transistors".
I wonder why darlingtons are not much more common as they could be used in simpler circuits.
I mean 1 darlington can replace 1 drive bjt + 1 output bjt.
...
beppe61 |
Sure is possible very easy make of a strong power amplifier
covering well beyond 40 kHz with good sound quality.
Using powerful darlingtons, that can take a lot of heat!
This thread about the LAB10 Amplifier is only one fine example!
http://www.diyaudio.com/forums/show...&threadid=71292
:cool: :smash: |
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| beppe61 |
| quote: | Originally posted by richie00boy
A very good point.
One issue is that they tend to be slower, and that reverse biasing the base to switch off quicker/cleaner is not possible.
Also there is no control over the main transistors base-emitter resistor. |
Dear Sir,
thank you so much for your extremely kind and valuable reply.
First of all I must confess my almost complete ignorance in electronics.
Anyway this statement makes me think about the possibility to build a minimalist audio power amp with just 5-6 active devices.
It should be very interesting.
By the way, I noticed that darlington were more used in the past (I know of amps using them in the '80s).
I particular like one from the UK firm Albarry audio.
Just one pair of output darlingtons. Very very good sound indeed.
If only I could find the service manual ...
Thank you very much again.
Kind regards,
beppe61 |
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| beppe61 |
| quote: | Originally posted by lineup
Sure is possible very easy make of a strong power amplifier
covering well beyond 40 kHz with good sound quality.
Using powerful darlingtons, that can take a lot of heat!
This thread about the LAB10 Amplifier is only one fine example!
http://www.diyaudio.com/forums/show...&threadid=71292
:cool: :smash: |
Dear Sir,
thank you very much for the very interesting information.
To be honest I do not like the op-amp based preamp too much.
Any all discrete option for a let's say 60 W/8 ohm power amp?
It could sound great indeed, if minimalism is the way of course.
Thank you very much indeed.
Kind regards,
beppe61 |
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| richie00boy |
It depends what you mean by minimalism. If you mean physical small parts count then yes, but the same actual number of devices is there whether you use darlingtons or discrete drivers and outputs.
Darlintons can sound good and measure good. It's just that absolute ultimate performance is more readily available from discrete. |
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| beppe61 |
Dear Sir,
thank you so much again for your kind reply.
Let me explain my point of view hereafter.
>| quote: | Originally posted by richie00boy
It depends what you mean by minimalism.
I mean minimum number of active devices used in the best operational conditions. But I am not an expert at all.
I just like the idea on principle.
> ... but the same actual number of devices is there whether you use darlingtons or discrete drivers and outputs.
Well, so I was very wrong.
I wanted to reduce the number of active devices.
For instance, if I am not wrong again, at Sanken I understand they build power bjts that are multiple bjts in the same package (multiemitter or something like that).
I like this as well, of course always on principle.
> Darlintons can sound good and measure good.
This is my personal experience as well.
> It's just that absolute ultimate performance is more readily available from discrete. |
I am not looking for the "absolute ultimate performance" .
I am looking for a exceptional simple but nice sounding circuit.
I heard for instance some single mosfet class A power amp, but I did not like completely the lower frequencies, not powerful enough.
Thank you very much indeed.
Kind regards,
beppe61 |
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| peranders |
| quote: | Originally posted by beppe61
Any all discrete option for a let's say 60 W/8 ohm power amp?
|
This is pretty nice and small! :nod:
http://mirand.dk/ |
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| beppe61 |
| quote: | Originally posted by peranders
This is pretty nice and small! :nod:
http://mirand.dk/ |
Dear Mr. Peranders,
thank you very much for the link.
Kind regards,
beppe61 |
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| forr |
It is not possible to have a good external control of the quiescent current of class B output stages when darlingtons are used as power devices. Sanken seems now to provide darlington with internal bias diodes for a good thermal compensation : a thirty years old demand of amplifiers engineers.
~~~~~~ Forr
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| beppe61 |
| quote: | Originally posted by forr
It is not possible to have a good external control of the quiescent current of class B output stages when darlingtons are used as power devices.
Sanken seems now to provide darlington with internal bias diodes for a good thermal compensation : a thirty years old demand of amplifiers engineers.
~~~~~~ Forr
§§§ |
Thank you very much Sir.
This could be one of the reason why darlingtons based audio power amps are not so common.
Nevertheless I have heard an old UK design one sounding very nice indeed.
Thank you very much again.
Kind regards,
beppe61 |
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| Christer |
Another example of a power amp using darlingtons is the swedish Sentec PA9, which is world famous in all of Sweden. :)
Although probably not in the state-of-the-art league, it is considered by many as a very good power amp, and is the reference amp of the swedish autiotechnical society. The design is probably about 15 years old. |
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| beppe61 |
| quote: | Originally posted by Christer
Another example of a power amp using darlingtons is the swedish Sentec PA9, which is world famous in all of Sweden. :)
Although probably not in the state-of-the-art league, it is considered by many as a very good power amp, and is the reference amp of the swedish autiotechnical society. The design is probably about 15 years old. |
Dear Mr. Christer,
thank you very much indeed for the kind and very valuable reply.
Any idea about even a basic circuit of the PA9?
Thank you very much indeed.
Kind regards,
beppe61 |
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| Christer |
| Sorry, I have no schematic for the PA9. I tried to google for it, but I didn't find any. I friend of mine has a pair of PA9 (they're monoblocks), but he currently lives on Iceland, so I don't have access to them for reverse engineering. Maybe if I ask him to take of photos of the PCB, it could be possible to reverse engineer? I did that with photos of the corresponding preamp SCA1. It is hard to do from photos, though, and usually impossible to se exactly what compnents there are. |
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| beppe61 |
[QUOTE]Originally posted by Christer
[B]Sorry, I have no schematic for the PA9. I tried to google for it, but I didn't find any. I friend of mine ...]
Dear Mr. Christer,
please do not worry about that.
Anyway as this amp is regarded to be very good sounding, it would be interesting to find out the general schematic.
I mean, the part number and the number of output devices are employed, the total number of active devices, its performances driving difficult loads, etc.
I googled as well and find some reviews in Swedish
http://www.faktiskt.se/modules.php?...article&sid=141
and some nice pictures of the PA9 monoblock and its mate, the SC9 preamp.
If only your friend had a service manual at hand ....
Anyway, thank you very much again.
Kind regards,
beppe61 |
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| Christer |
| quote: | Originally posted by beppe61
I googled as well and find some reviews in Swedish
http://www.faktiskt.se/modules.php?...article&sid=141
and some nice pictures of the PA9 monoblock and its mate, the SC9 preamp.
If only your friend had a service manual at hand ....
[/B] |
Strange, that one looks quite different from the ones my friend has, but I think there were two version of the PA9, but they didn't change the name, so probably it is the same basic design.
If I remember correctly, the ones my friend has are only 50 W, into 8 Ohms, but with good current capacity. I think there is only one pair of output devices, but I can't remember which types they are. It is nothing exotic, though, just some standard, easily available darlingtons.
You are right, of course, that the corresponding pre is SC9. My friend had the somewhat older SCA1, which I think had no corresponding power amp. The SCA1 is an interesting design, but hardly anything worth cloning. |
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| beppe61 |
Dear Mr. Christer,
thank you very much again for your appreciated reply.
Let me reply between the lines.
>| quote: | Originally posted by Christer
Strange, that one looks quite different from the ones my friend has, but I think there were two version of the PA9, but they didn't change the name, so probably it is the same basic design.
If I remember correctly, the ones my friend has are only 50 W, into 8 Ohms, but with good current capacity.
I think there is only one pair of output devices, but I can't remember which types they are.
It is nothing exotic, though, just some standard, easily available darlingtons.
In my humble experience simple design can sound very very good indeed (transparent and with great imaging abilities).
I like the idea of a single pair of output devices/channel because it frees from the need of matching devices.
Of course this makes the choice of the devices a little critical (and also the choice of the speakers that should be easy to drive, differently from my present Dynaudio).
I am pretty sure that the PA9 are really great sounding units.
> You are right, of course, that the corresponding pre is SC9.
My friend had the somewhat older SCA1, which I think had no corresponding power amp.
The SCA1 is an interesting design, but hardly anything worth cloning. |
If you ever obtain any more information on the circuit of the PA9 please feel free to e-mail me directly.
Thank you very much indeed.
Kind regards,
beppe61 |
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| consort_ee_um |
hi beppe61,
I also thought of a simple amplifier as you describe. The problem of thermal compensation I solved by using schottky diodes which have a lower forward voltage but almost the same temperature drift as the darlingtons
So in this circuit the Bat54S doule schottkys would have to be attached to the heatsink. I have modelled it in Spice but not built it yet. |
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| beppe61 |
| quote: | Originally posted by consort_ee_um
hi beppe61, I also thought of a simple amplifier as you describe.
The problem of thermal compensation I solved by using schottky diodes which have a lower forward voltage but almost the same temperature drift as the darlingtons
So in this circuit the Bat54S doule schottkys would have to be attached to the heatsink. I have modelled it in Spice but not built it yet. |
Thank you very much Sir, for the very interesting schema.
Actually I am looking for an amp able to deliver at least 50-60 W/8 ohm and to drive adequately also demanding loads.
In my humble experience a very nice example is the Albarry M408.
Just a single pair of darlingtons at the output and a very very musical sound.
That would be a very interesting schema to study.
The best power amp I have experienced in my set-up so far.
Thank you very much again.
Kind regards,
beppe61 |
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| peranders |
| quote: | Originally posted by consort_ee_um
hi beppe61,
I also thought of a simple amplifier as you describe. The problem of thermal compensation I solved by using schottky diodes which have a lower forward voltage but almost the same temperature drift as the darlingtons
So in this circuit the Bat54S doule schottkys would have to be attached to the heatsink. I have modelled it in Spice but not built it yet. |
Very similar to the Alexander amp. See mine and the original AN211 or AN211 with better text |
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| beppe61 |
[QUOTE]Originally posted by peranders
[B]
Very similar to the Alexander amp. See mine ...
Dear Mr. Peranders,
if I am not wrong this is an headphone amp not a power amp.
Do you mean that it could be modified to serve as a power amp as well ?
Thank you very much for the most interesting links.
Kind regards,
beppe61 |
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| peranders |
I have made it like a headphone amp but the original is power amp. You have checked the application note?
The voltage/power limit is not set by the amp but by the transistors.
If you are interested I have also the very original paper by Mr. Alexander. The AN-211 is an edited version with all you want to know... but there is more :nod: |
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| peranders |
I will also point out that you see different kinds of output transistors. The expertize here does not recommend IBGT transistors which can be seen in the AN-211. Mr. Alexander has used different types but the main thing is that you can choose whatever you'll like, lateral or vertical mosfet's, BJT's, IGBT's :bigeyes: , tubes etc.
I have also the patent of the amp :nod: Rather boring to read. :yawn: |
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| consort_ee_um |
Hi Beppi61,
Using 2SB1560 and 2SD2390 as output devices, =/-30V supplies and 12V zeners in my circuit you could get 50 watts.
Out of interest I searched for Albarry m208 in this forum and found a couple of threads where you mention a bass problem. You suspect the Albarry amplifier.
Reading the threads it seems to me that your problem is with the speakers as the Albarrys are capable of a lot of output at the bass end.
If you could borrow some speakers with known good bass you could test them on your system which I think you would find is satisfactory. |
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| forr |
The HiFi News 1978 Linsley-Hood amplifier uses darlington in a triple à la Quad configuration (nice sound, an interesting configuration for bass and medium). Power devices were 2N2501/2N3001.
I think Krell used darlington followers in some of their class A (well, as claimed by the manufacturer) amps.
~~~~~~ Forr
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| beppe61 |
Dear Mr. Consort_ee_um,
thank you so much for your extremely kind and valuable reply.
Please let me be more precise hereafter.
>[QUOTE]Originally posted by consort_ee_um
[B]Hi Beppi61, Using 2SB1560 and 2SD2390 as output devices, =/-30V supplies and 12V zeners in my circuit you could get 50 watts.
Very interesting.
In the weekend I will try to study the circuit more in depth.
> Out of interest I searched for Albarry m208 in this forum and found a couple of threads where you mention a bass problem. You suspect the Albarry amplifier.
No. It is just the opposite.
I found the bass performance of the Albarry pretty remarkable out of just a single pair of darlintons.
It is my current amp that have a very weak bass.
I think some sort of current limiting circuit is the culprit.
I will try to upload the schema because I would like to try to by-pass this circuit.
> Reading the threads it seems to me that your problem is with the speakers as the Albarrys are capable of a lot of output at the bass end.
Actually the woofers of my speakers are of the very inefficient kind. With the Albarrys they sound just fine and pretty enjoyable.
> If you could borrow some speakers with known good bass you could test them on your system which I think you would find is satisfactory.
That is indeed my current dilemma: switching for a powerful amp or change the speakers?
I suspect my Dynaudio are "dynamically" compressed in some way.
I am afraid that also increasing power could lead to some distortion.
But as I said with the Albys they were just fine.
Thank you very much again.
Kind regards,
beppe61 |
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| beppe61 |
Dear Mr. Peranders,
thank you so much for your very friendly and valuable support.
I will take me the weekend to study the AN.
Anyway I understand it deals with a power amp.
> Originally posted by peranders [/i]
I will also point out that you see different kinds of output transistors.
The expertize here does not recommend IBGT transistors which can be seen in the AN-211.
Mr. Alexander has used different types but the main thing is that you can choose whatever you'll like, lateral or vertical mosfet's, BJT's, IGBT's :bigeyes: , tubes etc.
That is very interesting indeed.
Sometimes I wonder about the possibility to exchange the type of the output devices in some circuits available in the web.
It seems to me that mosfets and bjts are the devices more popular nowadays.
> I have also the patent of the amp :nod: Rather boring to read. :yawn: [/QUOTE]
As I maybe said previously I find your projects of a very high level indeed.
My sincere congratulations.
Kind regards,
beppe61 |
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| beppe61 |
Originally posted by forr [/i]
The HiFi News 1978 Linsley-Hood amplifier uses darlington in a triple à la Quad configuration (nice sound, an interesting configuration for bass and medium).
Power devices were 2N2501/2N3001.
I think Krell used darlington followers in some of their class A (well, as claimed by the manufacturer) amps.
~~~~~~ Forr
§§§ [/QUOTE]
Dear Mr. Forr,
thank you very much for the kind advice.
I have to say that my question was generated by the idea that very simple topologies (very few active components) can be designed with darlingtons.
I am always dreaming to the ultimate minimalist approach with a strong single output pair.
Thank you very much indeed.
Kind regards,
beppe61 |
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| beppe61 |
| quote: | Originally posted by lineup
Sure is possible very easy make of a strong power amplifier
covering well beyond 40 kHz with good sound quality.
Using powerful darlingtons, that can take a lot of heat!
This thread about the LAB10 Amplifier is only one fine example!
http://www.diyaudio.com/forums/show...&threadid=71292
:cool: :smash: |
Dear Sir,
please excuse me for having dismissed your kind and very valuable suggestion with all haste!
Do you have built anything following the schematic ?
I very like the POWER AMPLIFIER section in particular.
Using powerful darlington I could build a very interesting power follower and try it with different voltage gain stage topologies.
Please tell me some more (or if you are aware of oher links of the same kind).
Please excuse me again but I am as impetuos as ignorant.:D
Kind regards,
beppe |
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| psychosteve |
i got some velleman K8060 kits they are quite good and use tip142/147 darlingtons as the output pair.
id post the scem. but i have not got a scanner, any way , at £15 for the complete kit, minus heat sink and transformer its worth a look at.
ps, does anyone have experiance of paralleling darlingtons?? |
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| beppe61 |
| quote: | Originally posted by psychosteve
i got some velleman K8060 kits they are quite good and use tip142/147 darlingtons as the output pair. id post the scem.
but i have not got a scanner, any way , at £15 for the complete kit, minus heat sink and transformer its worth a look at.
ps, does anyone have experiance of paralleling darlingtons?? |
Dear Sir,
thank you so much for your extremely kind and valuable reply.
I will study deeply the kit you mention.
Have you built it personally ? How does it sound ?
I would like to explain my interest for simple amps using just a single pair of darlington in the output stage.
During the last 6 months I have tried a number of integrateds and power amps in my system to drive a quite demanding pair of Dynaudio speakers.
Most failed to give an adequate bass response (i.e. fast, deep, powerful and damped).
The best power amp I listened in my system has been two English monos rated 45W/8ohm that I had the opportunity to open and see inside.
I could see in each mono:
1) a toroidal transfo made by ILP type:5322 S.N.:2102
2) two good sized filter caps
3) 7-8 small plastic case bjts (in TO92 case I think)
4) a single pair of TIP146/TIP141 per channel.
This has been by a long margin the best amp I tried in my sistem.
On this basis I am now very interested in very simple topologies.
My dream would be to find a kit of a power amp with just 4-5 bjts that could be used along with the output pair of point 4).
This kit with a very powerful power supply could have the potential to sound very good IMHO.
The sound of the monos pair I mention it is very good even with demanding speakers.
The monos have been circulated among a number of audio friends of mine.
Every time the judgement has been positive to say the least.
If I were good at cloning that woudl be my target.
As I said I will study all the minimalist design I found that could be used to that single darlington output pair.
Thank you very much again for your very valuable advice
Kind regards,
beppe |
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| psychosteve |
http://www.diyaudio.com/forums/show...&threadid=73701
yes i built them my self, they sound good, damping factor is quoted as <800, freq resp 3hz to 200khz (-3db) so i wasnt expecting zen type quality, but they drive eminence delta15,s REAL GOOD.
breif circuit description, bc640 longtail pair input, bc639 class a driver, bc547 bias compensation, bc547/557 curent amp, tip142/147 darlington output.
total of 6 bc type plastic case transistors and two tip darlingtons
hope this helps some, espesh the other thread, id upgrade the caps in the kit anyway, it says that in the manual !!! transfo required is meant to be +/-30v at 120va, i went up to 300va per pair, without the on board diodes.
see you soon, steve.. .. |
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| beppe61 |
| quote: | Originally posted by psychosteve
http://www.diyaudio.com/forums/show...&threadid=73701
1) yes i built them my self, they sound good, damping factor is quoted as <800, freq resp 3hz to 200khz (-3db) so i wasnt expecting zen type quality, but they drive eminence delta15,s REAL GOOD.
2) breif circuit description, bc640 longtail pair input, bc639 class a driver, bc547 bias compensation, bc547/557 curent amp, tip142/147 darlington output.
total of 6 bc type plastic case transistors and two tip darlingtons
3) hope this helps some, espesh the other thread, id upgrade the caps in the kit anyway, it says that in the manual !!! transfo required is meant to be +/-30v at 120va, i went up to 300va per pair, without the on board diodes.
see you soon, steve.. .. |
Dear Mr. Steve,
thank you so much for your extremely kind and valuable reply.
1) I like very much the simplicity of the kit and the nice lay-out.
So they can output some current. Good.
2) Very good. I like simple circuit greatly.
3) It helps a lot indeed. Very kind of you. Thank you very much indeed.
If I understand well you advice to increase capacitance in the power supply and the VA rating of the transformer. Good.
I don't understand the subject of "on board diodes" anyway.
What do you mean with that?
Thank you so much again.
Kind regards,
beppe |
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| psychosteve |
A/C from transformer goes to the board and is rectified and smoothed at the amp. if you want to bridge a pair of amps, like i did, dont solder the diodes to the board, but use a single package bridge rectifier at the transformer, along with caps, then take +/- DC voltage to each board.
if you only using a single amp, not bridged, follow the kit instructions. caps in the kit are 3300uf 50v, but there is space on there for 4700uf 50v which is what the manual suggests for the upgrade. personaly i doubled up with 2 x 3300uf and paralled with 200nf, the choice is yours.
hope this clears things up a bit, see you soon, steve.. .. |
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| beppe61 |
| quote: | Originally posted by psychosteve
1) A/C from transformer goes to the board and is rectified and smoothed at the amp.
2) if you want to bridge a pair of amps, like i did, dont solder the diodes to the board, but use a single package bridge rectifier at the transformer, along with caps, then take +/- DC voltage to each board.
3) if you only using a single amp, not bridged, follow the kit instructions.
caps in the kit are 3300uf 50v, but there is space on there for 4700uf 50v which is what the manual suggests for the upgrade. personaly i doubled up with 2 x 3300uf and paralled with 200nf, the choice is yours.
4) hope this clears things up a bit, see you soon, steve.. .. |
Dear Mr. Steve,
thank you so much again for your kind and precious help.
1) 2) 3) I think to do the same as you did without bridging, with very big transformer and caps (something like 15.000uF I have at hand-they are very good Siemens).
4) Completely.
Thank you very much indeed.
Have a nice day,
beppe |
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| richie00boy |
Hi Steve good to see you again,
What load impedance are you running the bridged amp into? I think you will run into trouble into 4 ohms, as each amp will see a 2 ohm load. Bridged you might see 200W RMS into 8 ohms. |
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| psychosteve |
hey richie00boy, yes its good to be back,
they run into a modified PA cab, runs fine at 6ohms, but then the amps run 2 x AMD athalon sink and fans each. and the bridge circuit has a 1k ohm multi turn preset res with the wiper as input so i can fine ballance the input to an ne5532 dual op amp, one inverting one as buffer non inverting.
with a 300va 30/30 volt transfo it pushes the speakers and they are suposed to be rated to 400watts rms, they sound loud, and they can drive heavy comp cone speakers which is what beppe was looking for.
hows the gain clone doin richie?
see you soon, steve.. .. |
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| psychosteve |
ps, richie00boy do you know what the problems of paralleling darlingtons are, apart from being a bit slow, and needing to use current forcing resistors? cos for the price of the kit it may be worth blowing one up trying to get more out of the amps, tip 142/147, is i think, 10 amp 125 watt package so they quite sturdy.
see you soon, steve.. .. |
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| richie00boy |
You should be OK paralleling darlingtons with current sharing resistors. The issue would be that the amp voltage amplifier stage might start to struggle driving the extra load though. Not only that the current limiting circuitry would need to be adjusted.
Glad you seem to be having success with a 6 ohm load and bridged operation, but you really are running on a knife edge there. I'll bet the amp current limiting circuitry is working overtime.
I also think you don't need to run the pot after the splitter as the outputs should be very well matched anway. The pot is likely to give you trouble later down the line as it gets dirty and noisy. |
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| psychosteve |
yes its probly pushing it a bit, ah well...
the pot is a high quality ceremet sealed unit, so should last a while, the pot is the splitter, input goes to the wiper, one end of the res goes to inv opamp, other end of res goes to buffer opamp.
i only put it in to make sure of equal drive, and i had the pot left over from the same idea i had for running parrallel stk chipamps.
see you soon, steve.. .. |
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| richie00boy |
| Steve, you can actually remove the pot totally. It will be attenuating the signal very slightly (or a lot depending on the value of the pot and input resistors on your op-amps). Of course I'm assuming that you are simply driving a unity-gain buffer and a unity gain inverter... evn so, if you aren't you could convert them to unity gain easy. It really would be a better solution :) |
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| consort_ee_um |
| Steve, rather than paralleling the devices it might be worth using some more powerful transistors like 2SB1560 and 2SD2390. These have a better frequency response as well, but the compensation circuit might need tweaking to stop it oscillating! |
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| richie00boy |
| Steve, do you have any kind of thumps or pops when you switch the amp on? |
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| psychosteve |
richie00boy, yes i probly could do without the pot, the op amps are matched up to the drop through the pot, ie,, not unity, feedback is by 0.2% resisistors cutout from an old valve radio.
the idea was to set up with the pot then remove it once all the offset measurements had been done, but i never got round to it!!!
Consort, yes there is a small wheeze at power down, its very small and im not worried about damaging anything. when i ran the amps as single ended (not bridged into 6 ohm) they where quieter than a very quiet thing!!
thanks for the links, ill have a good look over the next few days.
see you soon guys, steve.. .. |
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| gmphadte |
Here is one schematic.
this one uses TIP130/5 and delivers 30watt into 4 ohms.
Gajanan Phadte |
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| aniceto |
i'm the owner of a sentec sca1 preamplifier, that is now broken
i'm desperately seeking for the schemas to repair it
here (in italy) the ex-distributor can't halp me, and no one seems to have this stuff
can someone help me in any way? |
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| beppe61 |
| quote: | Originally posted by aniceto
i'm the owner of a sentec sca1 preamplifier, that is now broken
i'm desperately seeking for the schemas to repair it here (in italy) the ex-distributor can't halp me, and no one seems to have this stuff
can someone help me in any way? |
I think you should start a new 3D with the subject:
sentec sca1 preamplifier schematic kindly requested
or something like that.
Maybe someone form Sweden can help you (it is a very popular brand over there).
Excuse me, do you have also the same brand monos amps?
Regards,
bg |
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| quote: | Originally posted by aniceto
i'm the owner of a sentec sca1 preamplifier, that is now broken
i'm desperately seeking for the schemas to repair it
here (in italy) the ex-distributor can't halp me, and no one seems to have this stuff
can someone help me in any way? |
This wellknown audio man
looks like have a lot of SENTEC stuff.
If you email him, he may send you a Sentec SCA1 diagram.
He has got SCA1 owner manual for free PDF download.
http://www.svalander.se/shoppen/sentec.htm
See also some hints by peranders in this post:
http://www.diyaudio.com/forums/show...4058#post234058
good luck! |
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| newsdesks |
| I have a set of T14's they |
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| newsdesks |
| I have a set of L100's which are exceptional. Musical and the best mid-range I have heard to date. |
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| Don S |
bg, the pass A40 is a great sounding amp that can drive most anything. On 33V rails it will deliver about 56W @ 8 ohms. It is simple to construct and easily meet all your needs. You can look it up at passdiy (dot) com/pdf/a40.pdf
Thanks, Don |
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| beppe61 |
[QUOTE]Originally posted by Don S
bg, the pass A40 is a great sounding amp that can drive most anything.
On 33V rails it will deliver about 56W @ 8 ohms.
It is simple to construct and easily meet all your needs.
You can look it up at passdiy (dot) com/pdf/a40.pdf
Thanks, Don
Dear Mr Don,
thank you very much for your kind suggestion.
On principle I do not like class A amps very much.
Reading through this forum I understand very good sound can be obtained from more efficient class AB amps as well.
The heat is usually enemy to parts (capacitors in particular) and heatsinks are expensive.
At present I am using a modified (better caps and transformer) little integrated (with darlingtons output pairs).
I like the overall sound but it lacks energy in the bass.
In order to break it in, I connected power resistors (200W/5ohm) to its output.
The amp gets very hot and the resistors stay cold.
A very bad result. I interpret this result as that of a very current limited amp.
This is unfortunate because for me a good current delivery is always a good thing.
Thank you very much anyway for your kind advice and kind regards,
beppe |
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