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#2,285
hpasternack said:
I had an extra set of SymAsym boards and I decided to use them to rebuild an old amplifier. The layout is a bit unfortunate, but workable. Since the heatsink assembly was made for TO-3 transistors, I chose to use a set of 2ST2121/5949 outputs. The amplifier is unconditionally stable and has a 450kHz bandwidth.

Here we are, work in progress.

-Henry
Click to expand...
.... i am missing something here ...is this amplifier working without capacitors ? cause i cant see them in the foto ...still tha cables seem to be connected on boards

have i missed something ?

EDIT :looking at it once more seems that twisted cables are coming from the bridge to the boards and then another set of cables that is supposed to go to the capacitor banks ?

if you are planing to do this be aware that is a very bad practice .... from trafo you to bridge then from bridge to caps and then from caps to amp ...

let us know
kind regards sakis
 
Last edited:
#2,286
finished velleman k4010

hi there...
i am building velleman k4010 kits.
but i am having a problem with mine,
sound is pretty good but there are hum (at bass spk) and distortion (at treeble spk),
can anyone suggest what should i do?

this is my finished amp pics:
An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


i am having a ground loop problem with this finished amp.
 
#2,287
sakis said:
.... i am missing something here ...is this amplifier working without capacitors ? cause i cant see them in the foto ...still tha cables seem to be connected on boards

have i missed something ?

EDIT :looking at it once more seems that twisted cables are coming from the bridge to the boards and then another set of cables that is supposed to go to the capacitor banks ?

if you are planing to do this be aware that is a very bad practice .... from trafo you to bridge then from bridge to caps and then from caps to amp ...

let us know
kind regards sakis
Click to expand...

I understand your confusion! No, as I said, it's a work in progress. Lots of wires still waiting to be connected, plus the rectifier/capacitor board.

Here's a picture of the test setup I used to verify the performance with the ST transistors.

-Henry
 

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#2,288
sakis said:
.... i am missing something here ...is this amplifier working without capacitors ? cause i cant see them in the foto ...still tha cables seem to be connected on boards

have i missed something ?
Click to expand...

As Henry clearly states, "work in progress".
Since no capacitor bank has been installed and wires are not connected, this is not yet a working amp!
A closer look and everything is clear.
Regards,
Max.
 
#2,290
HP,
the test assembly shows your PSU connections.

You have at least two tappings from the PSU Zero Volts.
One on the left cap to the left channel and one on the right cap to the right channel. This is wrong.

The three wires from the PSU to each amplifier, zero volts +ve -ve, should be twisted as a triplet and taken to the amplifier as that triplet. At the amplifiers (since it's two channel) the triplet is Y split to form two sets of triplets. One set to each amplifier. Keep these final triplets as short as possible and use low resistance wire in the Zero volts between the two amp boards.
 
#2,291
Wengtech

Your amp looks to be slightly older revision of mine, i cant see any delay on relays or dc protection circuits.

I goy lucky with mine and it fired up first time and has been running great for a month or so, i have some scans of the latest manuals and component additions if they are any use to you.

best regards james
 
#2,292
hpasternack said:
I had an extra set of SymAsym boards and I decided to use them to rebuild an old amplifier. The layout is a bit unfortunate, but workable. Since the heatsink assembly was made for TO-3 transistors, I chose to use a set of 2ST2121/5949 outputs. The amplifier is unconditionally stable and has a 450kHz bandwidth.

Here we are, work in progress.

-Henry
Click to expand...
can you show me pcb.
thanking you
 
#2,293
masood said:
can you show me pcb.
thanking you
Click to expand...

The boards are the original SymAsym 5.3 design, as described here:

[wiki=http://www.lf-pro.net/mbittner/Sym5_Webpage/symasym5_3.html]%[/wiki]

I kept the board as is, but used the TO-3 outputs on sockets with short wires connecting them to the board.

Here is another diyAudio thread about a redesign of this PCB specifically to use TO-3 outputs:

[wiki=http://www.diyaudio.com/forums/group-buys/187592-3-symasym.html]%[/wiki]

With no offense intended to Mr. Bittner, who has designed by all accounts a very fine circuit, his original PCB design had some shortcomings and a number of improved layouts have been published. For instance, I have built AAK's dual output transistor version of the SymAsym with good results. If you search the forum you can easily find these discussions.

-Henry
 
#2,294
AndrewT said:
HP,
the test assembly shows your PSU connections.

You have at least two tappings from the PSU Zero Volts.
One on the left cap to the left channel and one on the right cap to the right channel. This is wrong.

The three wires from the PSU to each amplifier, zero volts +ve -ve, should be twisted as a triplet and taken to the amplifier as that triplet. At the amplifiers (since it's two channel) the triplet is Y split to form two sets of triplets. One set to each amplifier. Keep these final triplets as short as possible and use low resistance wire in the Zero volts between the two amp boards.
Click to expand...

Thank you for your very correct observation. If you were to zoom in on a high-resolution version of the photo, you would see the stubs of black wires adjacent to the transformer center tap connection on the bus wire between the capacitors. This is where the circuit board power grounds were originally connected. For a test lash-up, I was not concerned about punctillious grounding.

FWIW, the chassis with the power supply was a breadboard that I used for testing the complete amplifier before I eventually built this:

[wiki=http://www.diyaudio.com/forums/solid-state/96192-post-your-solid-state-pics-here-226.html#post2907972]%[/wiki]

The final version of my latest amplifier will have a dual-mono power supply with correct grounding and modern filter capacitors. (Those Sprague blue cans are 30 years old!)

-Henry
 
#2,295
AndrewT said:
HP,

The three wires from the PSU to each amplifier, zero volts +ve -ve, should be twisted as a triplet and taken to the amplifier as that triplet. At the amplifiers (since it's two channel) the triplet is Y split to form two sets of triplets. One set to each amplifier. Keep these final triplets as short as possible and use low resistance wire in the Zero volts between the two amp boards.
Click to expand...

triplets ? i don't think so Andrew always ground is supposed to be out of the "twisting" twist rails together yes but ground never with them .
 
#2,297
some little test with a hybride, mosfet dc driven by a 6C19 and a srpp 6N8, the 6C19 is not a cathodefollower but a plate follower driving the mosfets, I did need a high current low mu tube because of the mosfet capacity and to not to use feedback.

The printed circuit is made with a dremel, because it is just a tryout how a hybride without a cathodefollower sounds, this one has none, the 6n8 is not yet soldered that happens today.
 

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#2,298
kees52 said:
some little test with a hybride, mosfet dc driven by a 6C19 and a srpp 6N8, the 6C19 is not a cathodefollower but a plate follower driving the mosfets, I did need a high current low mu tube because of the mosfet capacity and to not to use feedback.

The printed circuit is made with a dremel, because it is just a tryout how a hybride without a cathodefollower sounds, this one has none, the 6n8 is not yet soldered that happens today.
Click to expand...

Wow, far out. I'm a great believer in hybrid amps. I'm guessing it should sound smooth.
 
#2,299
#2,300
I have now everything soldered, how it sound I do not now yet, a version of it with cathode follower works here for already 4 years, still with wires and no pcb.

this has a p follower to test, it is a pcb made with dremel, and some old parts for testing it, It is ready for the big test after cooling is ready, LM350 is also on board now with supply.

Do it work nicely I make a board for it.
 

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