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Old 18th August 2013, 08:04 PM   #731
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Default TO-3 revisited

In post #706, I did write that I did not hear tonal difference between the latest TO-3 system and a previous non TO-3 symasym system.

Today I must re-write this statement, the input was the cause that no difference could be heard (in post #706 the source was of low quality).

The current session was with a DDDAC 1794 NOS DAC, here the TO-3 system had deeper bass and better overall performance as the non TO-3 symasym.

All credits to Rudi.

The TO-3 system is not at my place no more (makes you wonder why I did not test better), now the quest continues.

Grtz

Bert
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Old 23rd August 2013, 04:53 AM   #732
RKH is offline RKH  United States
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Default TO-3 Symasym up and running

I just finished this amp and have a couple of hours run time on it. It is extremely quiet (and I know as I have very noisy mains.) So far, good at low volume, very good at higher volume.

Apple lossless (iTunes w/PureMusic) --> Mac Mini (optical out) --> Cambridge Audio DACmagic --> Sansui CA2000 -->TO-3 SymaSym --> MJKing Open Baffle (Fostex Full Range and Eminence Alpha-15A)

Next up... I'm going to add my Aikido (with 6CG7s) pre-amp. Then I'll fold in my OPUS DAC etc.

Rudi's boards and build guide are the best!

By the way, I have a very big (800 VA) transformer so I'm using the DIYAudio softstart circuit as well.
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Old 27th August 2013, 05:39 PM   #733
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Thank you for your kind words, Ryan.

The TO3-SYMASYM is - at least in my ears and the ears of those who built it - one of the highlights of this forum, and - believe me -
I have re-enigineered a lot of AMPs being presented in this forum.

The TO3-SYMASM is playing emotions, dynamics, deep black bass and smooth heights, producing the "Philly Sound" of the 80th.

I have - in the meanwhile - layouted a version, which is much more compact, but I wonder, if I will offer it as a group-buy.
Doing a group-buy means a very lot of work for me.

Best regards - Rudi
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Old 27th August 2013, 06:30 PM   #734
mcds is offline mcds  Tuvalu
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One suggestion I'd like to make is that a future layout allows easy implementation of a separate power supply for the front end.
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Old 28th August 2013, 09:26 AM   #735
rephil is offline rephil  Europe
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Quote:
Originally Posted by Rudi_Ratlos View Post
Thank you for your kind words, Ryan.

The TO3-SYMASYM is - at least in my ears and the ears of those who built it - one of the highlights of this forum, and - believe me -
I have re-enigineered a lot of AMPs being presented in this forum.

The TO3-SYMASM is playing emotions, dynamics, deep black bass and smooth heights, producing the "Philly Sound" of the 80th.

I have - in the meanwhile - layouted a version, which is much more compact, but I wonder, if I will offer it as a group-buy.
Doing a group-buy means a very lot of work for me.

Best regards - Rudi
Hi Rudi,

It is a very good idea to think to offer this new release as a group-buy . You have good ideas Rudi !

So if you do a new group-buy, I am in for many of all boards you will provide.

I have great fun with the boards I have got from you : my SymAsym is slowly growing. Recently I got able to drill - as should be - the alu L profile in order to fit the TO3 devices, and until now this has been a no go for me. I have partly populated one board, and I have stil a few problems. Here it is.

BTW, did you try the MKT 1822 22uF with the SymAsym ? I have some problems with the MKT 1822 10uF : I have two of them, and they don't measure the same on my bridge this varying the test frequency. I am willing to fit the the MKT 1822 22uF as I have plenty of them home, and two of them that neasure the same in varying the frequency would be for me easy to get ... IMO the frequency measurement of this condensator has to do with the goodness of sound of the SymAsym.

The second problem is matching the output transistors. With what parameters did you do that ? I believe that it is at 55mA, getting the hFE within 5%. Did you get also the vBE within some (how much) mV for them ?

Thank you for your reply .

Best regards

rephil
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Old 28th August 2013, 10:33 AM   #736
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@mcds: the PCB-layout already includes CAP-multipliers to provide smooth and stable voltages for the frontend, and the CAP-multipliers
are doing a very good job.
@Rephil: I measured my TO3s with a collector current of 100mA (adjusted by the CCS of my test-rig).
The main function of the input capacitor is to block DC voltage.
I myself am using a 3.3F Vishay MKT.

Best regards - Rudi_Ratlos
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Old 30th August 2013, 02:04 PM   #737
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Gentlemen, to offer you the current layout of the TO3-SYMASYM in a group-buy will cost a lot of money per PCB,
since the layout needs tooling costs!

But I will offer you a PDF-file of the solder-layer to "Do-it-Yourself".
The size of the PCB is 139,7 x 112,4 mm.
If you need further instructions, how to build: tell me.

Best regards - Rudi_Ratlos
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Old 30th August 2013, 08:35 PM   #738
rephil is offline rephil  Europe
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Quote:
Originally Posted by Rudi_Ratlos View Post
Gentlemen, to offer you the current layout of the TO3-SYMASYM in a group-buy will cost a lot of money per PCB,
since the layout needs tooling costs!

But I will offer you a PDF-file of the solder-layer to "Do-it-Yourself".
The size of the PCB is 139,7 x 112,4 mm.
If you need further instructions, how to build: tell me.

Best regards - Rudi_Ratlos

Hi Rudi,

Thank you for this very nice gift. Yes I will give it a try later, but I will need also the silk screen in order to understand where the components are placed. Thank you Rudi !

It is again a very nice board that you did !

BTW, I measured the TO3 that you provided matched to me : they are really very well matched : hFE difference <1% ! and the Vbe is also very good between pairs : difference <1mV ! How many transistors did you measure in order to get such a good result ?

IMHO you could match at 50mA (I did do the measurement too) : the values of hFE are practically the same as for 100mA, the Vbe match the same as previously, obviously at other values.

Again thank you for your SymAsym and the boards and components I did get from you! I am more than happy to get soon a working SymAsym with all what you provided to us .

Best regards

rephil
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Old 1st September 2013, 05:22 PM   #739
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Quote:
Originally Posted by mcds View Post
One suggestion I'd like to make is that a future layout allows easy implementation of a separate power supply for the front end.
Jumper1 can be used to feed the front end from a separate power supply.
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Old 3rd September 2013, 03:41 AM   #740
RKH is offline RKH  United States
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Unhappy Ooops

My amp went to the dark side. I don't know what precipitated things but I have a suspicion it started in my pre-amp.

Regardless, can someone give me some advice on how to diagnose and resurrect this amp?

Symptoms: Lots of crackling static on output.

Strategy:
check for shorts on output transistors and heatsink
check rail voltages
check bias settings
check output offset voltage...

From this point on I could use some help. I'm really disappointed that this happened. If the chain of events is as I suspect, it is totally my fault.

Thanks (in advance) for your help
Ryan
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