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Old 28th October 2013, 01:13 PM   #21
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Hai Rieds,
can you make it Triple Darlington output?
with symmetric VBE, MJE340+350 or BD139+140...

Regards
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Old 28th October 2013, 01:52 PM   #22
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Quote:
Originally Posted by borys View Post
Mile
I just was wondering if there is anythink special in diamond topology, diamond buffers are all over the net, so I just added 2 current sources and tef stage into it and it worked just fine and is simple. The results are there SR around 60u/us and thd nearly not mesurable:

BG3 - diamond amp - simple

I was thinking how to improve the input stage but I have lack of knowlage and ideas.

Your amp is very interesting, buffored front stage is really good idea (I will defenetley build it).
There is one think that I do not know how to explain, I did listening tests of 2 nearly same circuits (one has toshibas TO92-mod second has 2n5xx1 tranies), there was audiable diffrence heard strigt away in bass area, the one with 2n5xx1 was bit deeper and more soft.
Another think - I just had changed 2 resistors in second diamond stage (reducing biasing by 50%) and harmonics character has changed totally - I do not know if this is specyfic case of my circuit or kind of diamond topology characteristics. It looks like that there is a way to fine tune the amp with listening test.

In your amp prapobly there will be a way too to fine tune the amp with listening sessions. I would put j-fets at input buffer anyway.
Simple schematic work good but need more tuning than complex circuit, I think my schematic is also simple.
I suggest to revert resistors value on your diamond amp, R12/R13 and R11/R14.
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Old 28th October 2013, 01:58 PM   #23
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Originally Posted by Rieds View Post
I tried the schematic on ltspice.
I replaced R10K with 1K8 & added some capacitors for amp stability.
Nice work, thanks for correction, I revert 10k and 2k2 on my schematic. I will use some different compensation for stability.
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Old 28th October 2013, 02:13 PM   #24
borys is offline borys  Poland
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Quote:
Originally Posted by Rieds View Post
I tried the schematic on ltspice.
I replaced R10K with 1K8 & added some capacitors for amp stability.
If you put big compensation caps the amp will be slower.
Just replace in first stage amplifiers 5.6k resistors with 2.2k, than 1.8k with 3.3k in second stage and amp will remain stable with only one pair 33pF caps, and will be much faster.
FFt looks nice.

Mile
Thanks for advice, You are right, the second stage is bit warm (50deg) so I will swap resistors values.
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Last edited by borys; 28th October 2013 at 02:20 PM.
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Old 28th October 2013, 03:01 PM   #25
Rieds is offline Rieds  Indonesia
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Quote:
Originally Posted by JOHN BALI View Post
Hai Rieds,
can you make it Triple Darlington output?
with symmetric VBE, MJE340+350 or BD139+140...

Regards
I think You don't need 'Triple Darlington' or triple emitter folower, if you need high power you can replace the driver with the bigger transistor like MJE15034/35 or 2sc5200&2SA1943.

Regards.
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Old 28th October 2013, 03:32 PM   #26
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Quote:
Originally Posted by borys View Post
Mile
Thanks for advice, You are right, the second stage is bit warm (50deg) so I will swap resistors values.
Second stage must be warm, use heatsinks.
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Old 28th October 2013, 03:42 PM   #27
Rieds is offline Rieds  Indonesia
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Quote:
Originally Posted by borys View Post
If you put big compensation caps the amp will be slower.
Just replace in first stage amplifiers 5.6k resistors with 2.2k, than 1.8k with 3.3k in second stage and amp will remain stable with only one pair 33pF caps, and will be much faster.
FFt looks nice.

Mile
Thanks for advice, You are right, the second stage is bit warm (50deg) so I will swap resistors values.
I tried your idea, PA is stable, the vas current decrease to 8mA .
thanks for the advice

Regards

Last edited by Rieds; 28th October 2013 at 03:46 PM.
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Old 28th October 2013, 03:56 PM   #28
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Quote:
Originally Posted by Rieds View Post
I think You don't need 'Triple Darlington' or triple emitter folower, if you need high power you can replace the driver with the bigger transistor like MJE15034/35 or 2sc5200&2SA1943.

Regards.
No, I don't think so... I thought TD or TEF just like you now(for more power),
but
more gain there at output stage mean less stress to VAS stage &
lower the distortion

I have build one, it is from apex too (AX-17 or 20)
MJE340+350 ---> 2SA1837+C4793 ---> 2SA1493+2SC5200
They are quite stable this arrangements, I've also changed to
MJE340+350--->MJE15032+15033--->2SA1216+2SC2922
and I prefer this one, more rugged (the heat is not so hot when biased 100mA)
The above is more warmer in the sound & hotter the heat sink with same bias.
I thing it might be the same here, try to build one & you know what I mean

ps: I can't simulate like you do, but I think should try sometime
do you mind to try to simulate it now? TEF or TD...?

Regards
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Last edited by JOHN BALI; 28th October 2013 at 04:00 PM. Reason: bro Rieds mohon coba disimulasi ya, yg Triple Darlington
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Old 28th October 2013, 04:52 PM   #29
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Quote:
Originally Posted by Rieds View Post
I tried your idea, PA is stable, the vas current decrease to 8mA .
thanks for the advice

Regards
Diamond differential current decrease to 8mA (4mA per MPSA), vas current decrease to 15mA.
Regards
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Old 28th October 2013, 05:55 PM   #30
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Quote:
Originally Posted by borys View Post
If you put big compensation caps the amp will be slower.
Just replace in first stage amplifiers 5.6k resistors with 2.2k, than 1.8k with 3.3k in second stage and amp will remain stable with only one pair 33pF caps, and will be much faster.
FFt looks nice.

Mile
Thanks for advice, You are right, the second stage is bit warm (50deg) so I will swap resistors values.
or replace 10R resistors with 33R in second stage...
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