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Old 30th July 2018, 01:42 PM   #11
andrewlebon is offline andrewlebon  India
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Hello valery
greetings just wanted to ask you if MJL4281/4302 can be used as i have
bought them and do the 1381/3503 E grade transistors have to be matched
warm regards
Andrew
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Old 30th July 2018, 01:50 PM   #12
vzaichenko is offline vzaichenko  Russian Federation
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VHex+ amplifier modules, kits and boards
Quote:
Originally Posted by andrewlebon View Post
Hello valery
greetings just wanted to ask you if MJL4281/4302 can be used as i have
bought them and do the 1381/3503 E grade transistors have to be matched
warm regards
Andrew
Hi Andrew,

Yes, 4281/4302 are good to go with.
1381/3503 matching makes sense, although don't try to match them too precisely. In fact, if hFE differs less than 2 times - it's ok.

Cheers,
Valery
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Old 30th July 2018, 02:07 PM   #13
J.M.K is offline J.M.K  France
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Default Building it

Quote:
Originally Posted by vzaichenko View Post
Hi JMK,

Simpelstark is a rather special amplifier. The "core" of it is an ultra-linear amplifier with the "standard" 29db voltage gain and no global feedback loop.
On top of that, it's equipped with Only Distortion Negative Feedback (18db loop gain), crystallizing the error signal and injecting it at the input of the OPS, mixing it with the VAS signal at 180 degrees phase shift. That's the point where the error signal is subtracted from the VAS output signal, although it corrects the overall error of the amplifier, as this kind of arrangement is equivalent to the global loop of 18db in principle.

The amplifier provides very natural sound throughout the whole audio frequency range without any coloration or "highlighting" any parts of it. We call it a "Delicate Sound" amplifier. Real hi-end

This is a class AB setup, but the OPS arrangement is sort of non-standard - its a "constant gm" type of OPS with the EF driver stage running at 110mA of quiescent current (class A), and then a couple of pairs of common emitter "supporting" transistors, running at just 20-30mA each.

The output impedance of the amplifier is close to 0.05 ohm, resulting in the damping factor of around 150 with 8 ohm speakers. I deliberately keep it not too high - too much of control over the speaker is not always good. In general, "the more is the better" statement is incorrect with regards to the damping factor.

+/- 47.5 V DC unregulated is ok, although we have never practically tested this amplifier with SMPS power supplies. I don't see any issues though.

We don't use any MOSFETs in this version of the amplifier - the OPS purely consists of the BJT power transistors (one pair of 0281/0302 and two pairs of 3281/1302 in each channel).

IPS requires one pair of 2sk246/j103 jFETs, relatively rare, but still available these days.

The kits are available in our store.

Let me know if you will have some more questions

Cheers,
Valery

P.S. BTW, you can see an overall topology in the comments to my post on FB:
Just finished testing and measuring the... - Virtual Zero Audio Store | Facebook
Thanks for this quick and detailed answer.
Is there anything special needed for the building?
All parts provided with the kit (beside heatsinks) ?
Is it possible to have a look at the building manual ?

JMK
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Old 30th July 2018, 07:49 PM   #14
vzaichenko is offline vzaichenko  Russian Federation
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VHex+ amplifier modules, kits and boards
Quote:
Originally Posted by J.M.K View Post
Thanks for this quick and detailed answer.
Is there anything special needed for the building?
All parts provided with the kit (beside heatsinks) ?
Is it possible to have a look at the building manual ?

JMK
Hi JMK,

All the parts will be provided for building the amplifier modules. PSU and COntrol System modules are the separate kits, but as I understand you've got those things in place already.

Setup procedure will be described in the building manual. This is a relatively new product, so the manual is in the final stage of development now - I will let you know as soon as it's done in a few days.

Cheers,
Valery
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Old 31st July 2018, 08:13 AM   #15
odie1427 is offline odie1427  Brunei
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Hi Valery,


I just order a PCB board, but i cannot download the build guide, could you please direct me to the link? or maybe can attached the file here.


thanks,
odie
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Old 31st July 2018, 11:19 AM   #16
vzaichenko is offline vzaichenko  Russian Federation
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Quote:
Originally Posted by odie1427 View Post
Hi Valery,


I just order a PCB board, but i cannot download the build guide, could you please direct me to the link? or maybe can attached the file here.


thanks,
odie
Hi Odie,

Thank you for your order. I have opened the downloads area for you.

Please click the "Building Guides" link under the DOWNLOADS title at the bottom of the homepage and download the building guide for VHex+ Classic amplifier.

Let us know if you will have some questions on the build.

Cheers,
Valery
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Old 4th August 2018, 10:11 AM   #17
vzaichenko is offline vzaichenko  Russian Federation
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VHex+ amplifier modules, kits and boards
Default Simpelstark PLUS V1.3 Building Guide

Gentlemen,

The building guide for Simpelstark+ V1.3 is ready and available in the DOWNLOADS area of the web-store.
It's available to all the registered customers (please login or create an account).

Cheers,
Valery
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