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Old 17th February 2006, 02:25 PM   #11
consort_ee_um is offline consort_ee_um  United Kingdom
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Beppe61
Further info here:
http://www.velleman.be/downloads/0/i...nual_k8060.pdf
I would buy the kit and throw away D3-D6(1n5404 3A) and use P600J 6A rectifiers. Throw away the 4700uF and use at least 10000uF
I would not fit the current limiting stuff D1,2 R5,6,16,17 T4,5
You would then have an amp similar to your beloved Albarrys!
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Old 17th February 2006, 02:37 PM   #12
richie00boy is offline richie00boy  United Kingdom
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is this any good?
Are you familiar with the Albarry then? How can you be sure it's a similar circuit?
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Old 17th February 2006, 02:45 PM   #13
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by consort_ee_um
Beppe61
1) Further info here:http://www.velleman.be/downloads/0/i...nual_k8060.pdf
2) I would buy the kit
3) and throw away D3-D6(1n5404 3A) and use P600J 6A rectifiers. Throw away the 4700uF and use at least 10000uF
4) I would not fit the current limiting stuff D1,2 R5,6,16,17 T4,5
5) You would then have an amp similar to your beloved Albarrys!
Dear Sir,

thank you so much for your very kind and precious reply.
I appreciate it greatly.
You have understood very well that in the end I am very intrigued about this cheap, simple but nevertheles very promising amp.
And the idea to get a performance similar to that one of the Albarrys intrigues me even more.
1) Thank you so much. What a spectacular set of instructions!
Very good user manual indeed.
2) Is this a sort of your endorsement of it?
3) OK. To upgrade the power supply. I understand that.
4) This I do not understand completely.
I have to bypass completely the components you list?
5) I tell you this.
I strongly think this could be an extremely instructive experience.
I would be very curious to test the two amps side by side.

Thank you very much again for your very kind and valuable support.

Kind regards,

beppe
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Old 17th February 2006, 03:36 PM   #14
sreten is offline sreten  United Kingdom
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Hi,

as others have stated its a Velleman kit.

I have one waiting to be put together. It will replace a blown
power amplifier board in a bass guitar Combo (amp+speaker).

As a Hi-Fi amplifier it has little to recommend it.

If you think it is a hifi amplifier you should read :

D.Self's "Power Amplifier Design Handbook".


For Hi-Fi the JLH class A site is a good place to start:

http://www.tcaas.btinternet.co.uk/index-1.htm

or here:

http://sound.westhost.com/

or buy D.Self's "Power Amplifier Design Handbook"
and read it cover to cover several times until it starts to make sense.

/sreten.
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Old 17th February 2006, 03:51 PM   #15
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by beppe61

4) This I do not understand completely.
I have to bypass completely the components you list?
beppe
Hi,

No. You simply omit them (do not fit them).

The amplifier will die the first time the output is accidently shorted.

/sreten.
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Old 17th February 2006, 05:43 PM   #16
consort_ee_um is offline consort_ee_um  United Kingdom
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Beppe61
That is the question:

I would be very curious to test the two amps side by side.

I think you would have trouble telling them apart
The Albarrys date from the 80's. I believe they have TIP142/147 devices. Since the performance of the amp tends to be dominated by these devices, The amps would be similar.
As others hint more modern devices enable better performamce but can you tell the difference between 0.02% and 0.002% distortion when the speakers have 0.2% anyway.
The issue of bass transients and current surges I got around by removing the current limiting components. However as Sreten points out if you short the amp output it will destroy it. Perhaps use some fuses. Start with 1 Amp and work up to the rated current.
Incidentally the Samson amp I think you currently use (is it the semi-pro type?) has a serious protection circuit that may be the cause of your problems.
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Old 17th February 2006, 07:29 PM   #17
sith is offline sith  Croatia
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Yup, this definitely seems Velleman...

As far as I can see in their brochure T4 & T5 are supposed to be mounted on heatsink.... Some sort of thermal protection??? Should there be some improvements in using other devices for driving output transistors, or can I use some other outpust instead of TIP's... Will I get any bennefits in paralleling output transistors?

I have been listening to GC, Elliots DOZ and Elector Hexfet amp, can this one be compared to any of above???
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Old 17th February 2006, 07:57 PM   #18
ilimzn is offline ilimzn  Croatia
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T6 absolutely must be mounted on the heatsink, for T4 and 5 there would be no real benefit in doing so. It is doubtful they will protect the output stage anyway. They could if the circuit was somewhat altered into a first order SOA approximation foldback protection, but then if it ever does go into limiting, it will sound horrible. So, it's atrade-off of sorts...
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Old 18th February 2006, 05:18 PM   #19
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by consort_ee_um
Beppe61
1) That is the question: I would be very curious to test the two amps side by side.
I think you would have trouble telling them apart
2) The Albarrys date from the 80's.
I believe they have TIP142/147 devices.
3) Since the performance of the amp tends to be dominated by these devices, The amps would be similar.
4) As others hint more modern devices enable better performamce but can you tell the difference between 0.02% and 0.002% distortion when the speakers have 0.2% anyway.
5) The issue of bass transients and current surges I got around by removing the current limiting components.
However as Sreten points out if you short the amp output it will destroy it. Perhaps use some fuses.
Start with 1 Amp and work up to the rated current.
6) Incidentally the Samson amp I think you currently use (is it the semi-pro type?) has a serious protection circuit that may be the cause of your problems.
Dear Sir,
thank you very much again for your always kind and really valuable support.
I have to say that after reading your comments I can well understand you are a very knowledgable expert and I sincerely trust you.
Thank you very much for sharing your knowledge with me.
1) As the original kit has those current limiting components I really think that the bass response of the Albarry would be very much stronger, using equal power supply of course.
2) The Albys have a single output pair of TIP141/146 actually.
Very similar components I think. With similar specs as well.
3) This is very interesting because differently I thought that the circuit before the output devices gave the sound quality (timbral accuracy, soundstage, transparency) and the output only the brute force (i.e. current to drive the load).
Your words turn over my belief. Thank you very much.
4) your point is perfectly clear. Then is very difficult to understand all these discussion about sonic differences about amps with similar specs.
5) And THIS is a point that is very fundamental to me.
If removing those current limiting devices (ie. diodes I think) can give me the bass of the Albarrys with the Velleman kit I am done.
I am even prepared to take some risk.
Of course while checking the heatsink temperature.
Anyway I always avoid of shorting the outputs in any case, also with an overprotected amp .
I could put some fuses on the voltage rails as you very well say.
The MAIN problem for me is that given a schematic I really cannot point-out the current limiting devices that must be removed to increase the current delivery.
6) I strongly think you have hit the center of the problem.
Looking at the Samson schematic it seems to me that a similar current limiting circuit is present.
But I am not sure of course being quite ignorant.
Please excuse me if I take the liberty of ask your consultancy.
If I scan the circuit could you analyze it for me and say which would be the components to remove to increase its current output?
I like the sound of Samson but its bass response is quite weak in comparison to that of the Albarrys.
Besides I have some last questions:
1) Do you think it could be wiser to build the Velleman kit and modify as you said for an higher current output or instead modify the Samson?
2) Could you recommend (also privately if you prefer) instead another nice (and not too expensive) power amp without current limiting and so with a solid bass to solve my problem of weak bass response?
As you can well understand I am not looking for an high end solution, just a more solid sound that gives "body" to instruments, to make my system play piano as a piano and not like a cello.
An amp with balls. Ok. I said that.
If it is not the most refined of the amps I do not worry.
Besides I would be extremely interested to know your tastes on audio equipment (i.e. to get some info on your current play-back system, or a sort of list of recommended components).
I confirm that reading your directions I have learnt to trust in you completely.

Thank you sincerely.
Kind regards,

beppe
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Old 18th February 2006, 07:52 PM   #20
consort_ee_um is offline consort_ee_um  United Kingdom
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Hi Beppe
The output devices, because they are slower than the rest of the electronics tend to dominate the frequency response and higher frequency distortion characteristics. The other electronics decides the low frequency distortion and power supply rejection etc.

I think the easiest and best route for you is to try removing the output protection circuits of your Samson amp. This could be as simple as snipping the lead at one end of a resistor.

If you email me the circuit I will identify where to make the cuts. I will try to do it so you could restore it easily in the unlikely event that it does not do the business
I will also check if the Samson design is robust enough to allow this.
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