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Old 30th July 2011, 10:09 PM   #121
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Elvee: In post 106 you state that ...Q7 has to be biased... The way Q7 is drawn it is a diode. Could you elaborate please.
Thanks, E
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Old 31st July 2011, 08:59 AM   #122
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by mickeymoose View Post
Elvee: In post 106 you state that ...Q7 has to be biased... The way Q7 is drawn it is a diode.
It is indeed connected as a diode, and for the servo to operate and remain in its linear range, that diode has to be forward-biased by the collector current from Q13.
That diode can then play its role of compensating Q2's Vbe.
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Old 8th August 2011, 02:45 AM   #123
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Elvee, I am going to put together a square wave generator hopefully by the end of the week. I have a lot going on, so don't be surprised if it is a bit longer.

I am also in the process of putting together a +-35VDC power supply for these and altering the resistor value you spoke of. When that happens I will let you know how it goes. Still playing this every day, and still sounds simply amazing.
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Old 8th August 2011, 05:57 PM   #124
Elvee is offline Elvee  Belgium
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Originally Posted by odysseybmx414 View Post
Elvee, I am going to put together a square wave generator hopefully by the end of the week. I have a lot going on, so don't be surprised if it is a bit longer.
This is not essential, but it will allow to you to fine-tune the compensations, if required
Quote:
Still playing this every day, and still sounds simply amazing.
I am glad you enjoy it, that's the way it's supposed to work.
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Old 10th August 2011, 01:23 PM   #125
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Quote:
Originally Posted by odysseybmx414 View Post
Elvee, I am going to put together a square wave generator hopefully by the end of the week. I have a lot going on, so don't be surprised if it is a bit longer.

I am also in the process of putting together a +-35VDC power supply for these and altering the resistor value you spoke of. When that happens I will let you know how it goes. Still playing this every day, and still sounds simply amazing.
Hi odysseybmx414, I'm following your review this amplifier with - +35vdc, what the updates now and how it sound? I'm waiting for your next review. Thanks.

Regards,
Boyet
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Old 11th August 2011, 09:37 PM   #126
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Originally Posted by boyet0173 View Post
Hi odysseybmx414, I'm following your review this amplifier with - +35vdc, what the updates now and how it sound? I'm waiting for your next review. Thanks.

Regards,
Boyet
Actually, I have a PCB sitting in etchant right now. It is 7 2200uF capacitors per rail. Just waiting on a mouser order which should arrive any day. I will review in a few days.

Elvee, forgive my ignorance, I tried to figure it out for myself. At +-35V, will I have to change the BC546/556Cs that I am using?
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Old 12th August 2011, 03:19 AM   #127
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2n3055 only claims 60V CEO, you are gonna have to change that too.
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Old 12th August 2011, 03:55 AM   #128
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Originally Posted by kenpeter View Post
2n3055 only claims 60V CEO, you are gonna have to change that too.
I am and have been using MJW21196. I couldn't speak of this circuit using 2n3055.

I wasn't sure of the actual voltages the small signal transistors are seeing.
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Old 12th August 2011, 05:37 PM   #129
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by odysseybmx414 View Post
Elvee, forgive my ignorance, I tried to figure it out for myself. At +-35V, will I have to change the BC546/556Cs that I am using?
Of the BC's, only one will see the full supply voltage: Q13.

At a total supply of 70V, it will see ~67V, and the BC546's Vceo is rated at 65V, thus in theory too much.

But if +/-35V really is the upper limit of your supply, you run no risk using one.

If on the other hand there is a risk your supply drifts higher than 70V, you would be well advised to use a 100V or 80V type, like the MPSL01 or the 2N5550 for example.

Note that Q12 should preferably be identical to Q13.

Other BC's see at most half the total supply and need not being substituted.
The BD's and the 2N3019 are OK too.
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Old 12th August 2011, 06:13 PM   #130
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Quote:
Originally Posted by Elvee View Post
Of the BC's, only one will see the full supply voltage: Q13.

At a total supply of 70V, it will see ~67V, and the BC546's Vceo is rated at 65V, thus in theory too much.

But if +/-35V really is the upper limit of your supply, you run no risk using one.

If on the other hand there is a risk your supply drifts higher than 70V, you would be well advised to use a 100V or 80V type, like the MPSL01 or the 2N5550 for example.

Note that Q12 should preferably be identical to Q13.

Other BC's see at most half the total supply and need not being substituted.
The BD's and the 2N3019 are OK too.
Alright, thanks. Also note that I do not use BD's. I'm using 2SB649's as the drivers to the MJW21196's.

So, the changes will be:

--Power supply to +-35VDC
--Q12,Q13 to 2N5551 (Or is KSC1845E better? (much higher hFE, but low Ic))
--R21 to 56K
--D8,D9 changed from 2x12V to 2x15V


Should be up and running within two or three days hopefully.
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