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Old 25th April 2012, 09:56 PM   #1
castorG is offline castorG  Italy
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Talking unison reserch s8, let's build it!

Hi everyone,
look what I found....the unison research s8!

</font></b></i>unison audio s8 845 single ended tube amplifier,octal 2a3,el34,ecc82,ecc88,kt88,300b,845 direct heated triode,mkp, ...

So..I posted the schematic. Now, is there anybody out there that can help me build this sweet jewel?

I'm not an expert in elecronics, so I'll build it with my uncle, but I need some help on finding all the needed pieces.

I was told by someone who knows a lot about tube amps to use a 5687 alimented at around 550v to drive the 845.

Ervin

ps. could please someone who knows how to do it rewrite the schematics on the computer?
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Old 26th April 2012, 11:48 AM   #2
hooman is offline hooman  Iran
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.for 845 or 211 you can use best driver but mor $.diy is not copy of unison tube ampdiy = best sound
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Old 26th April 2012, 12:29 PM   #3
castorG is offline castorG  Italy
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Quote:
Originally Posted by hooman View Post
.for 845 or 211 you can use best driver but mor $.diy is not copy of unison tube ampdiy = best sound
You mean I can spend better my money on investing them on a better diy 845 amp? Any suggestion?

ps. Don't you like the s8 schemtic? Do you think there is something that can be improved?
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Old 26th April 2012, 02:07 PM   #4
hooman is offline hooman  Iran
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my frind has tried to improve sound of unisun 8 .but at last made project 211 !!!you need good schematic .5r4 in power and best tube driver.
so unisun 8 just good for new customers in hifi.
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Old 26th April 2012, 09:38 PM   #5
lechuck is offline lechuck  Netherlands
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Quote:
Originally Posted by castorG View Post
You mean I can spend better my money on investing them on a better diy 845 amp? Any suggestion?

ps. Don't you like the s8 schemtic? Do you think there is something that can be improved?
Something could indeed be improved; The s8 does not allow class A2 operation due to the AC signal coupling of the output tube's grid.

Take a look at the schematics from Tubelab for the 845, you can find the schematics over here: 845SE

In his amplifier he drives the output tube's grid DC coupled with a mosfet. This arrangement allows for grid current to flow, which in turn allows operation into higher power levels (read the article for more information, it's quite a good read ).

Now this is where diy comes into play; If for example you like the idea of the ability to operate the output tube in class A2 mode but you don't like the pre descending driver stages, then change the driver stage. Or if you really like the amplifier layout but fear for mosfets affecting the sound, then change the amplifier to suit your needs and replace the mosfets with tubes capable of doing the same job.

Last edited by lechuck; 26th April 2012 at 09:41 PM.
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Old 3rd May 2012, 09:28 AM   #6
castorG is offline castorG  Italy
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In between the u.r. smart845 and the u.r. s8, what would you choose?
Here there are the smart 845 schematics:
Unison Research SMART 845

Ervin
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Old 3rd May 2012, 05:29 PM   #7
castorG is offline castorG  Italy
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Does anyone have the simple 845 schematics?
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Old 3rd May 2012, 05:39 PM   #8
lechuck is offline lechuck  Netherlands
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Quote:
Originally Posted by castorG View Post
In between the u.r. smart845 and the u.r. s8, what would you choose?
Here there are the smart 845 schematics:
Unison Research SMART 845

Ervin
Personally I would build neither of them, but that is because I am on the DC coupled / feedback-less road.

If I would have to choose between these two designs only, then I would prefer the S8 because of it's simplicity and my preference for the grounded cathode stages above SRPP stages.

Both designs have the drawback of only operating in class A1 which limits the output power and add's grid-blocking distortion when being overdriven. The design from Tubelab overcomes these problems and seems logical, effective and simple.

If I would build an amplifier with 845 tubes the Tubelab's design would be my first choice. However, I do not see myself building a 845 amp in the near future since I am happily on a different road

Last edited by lechuck; 3rd May 2012 at 05:43 PM.
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Old 3rd May 2012, 06:01 PM   #9
castorG is offline castorG  Italy
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>> Personally I would build neither of them, but that is because I am on the DC coupled / feedback-less road.

After a day spent reading I do agree with you, this is why I'm looking for the simply 845 schematics now, since it is a no feedback amplifier.

I do really appreciate your suggestion about the tubelab's 845 amp lechuk, but in my mind goes on only one thing: build an unison research amp, build an unison research amp, build an unison research amp! Don't ask me why please, I don't know the answer!

Any idea on where to find the schematic of the simply 845?

Ervin.
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Old 3rd May 2012, 09:10 PM   #10
lechuck is offline lechuck  Netherlands
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Quote:
Originally Posted by castorG View Post
>> Personally I would build neither of them, but that is because I am on the DC coupled / feedback-less road.

After a day spent reading I do agree with you, this is why I'm looking for the simply 845 schematics now, since it is a no feedback amplifier.

I do really appreciate your suggestion about the tubelab's 845 amp lechuk, but in my mind goes on only one thing: build an unison research amp, build an unison research amp, build an unison research amp! Don't ask me why please, I don't know the answer!

Any idea on where to find the schematic of the simply 845?

Ervin.
You could simply play around with the feedback of the U.R. circuits, or leave the feedback out.

If you have the resources; why not build several circuits and choose the one that sound best in your ears? I build my amplifiers initially on a wooden board so I can experiment with them and build the final amplifier based on what sounds best in my ears.

The expensive components for the different circuits are similar, you could use the same power transformer, output transformer and output tube for these circuits. The less expensive parts like resistors, caps and small tubes are not to expensive to get, and you could sell some of them off after your final build.

You could concern it to be a little bit more DIY than simply building an existing (and probably well proven) circuit, but with it's own (read commercial) limitations. If you experiment yourself you can end up with a much better amplifier, and you always have the possibility to revert to an existing circuit if it doesn't work out as well as you've hoped.

Have you ever listened to a U.R. 845 tube amp, or a 845 tube in general, before? It's a big tube with big voltages, not really a tube I would recommend to an un-experienced builder because of the risks involved.

- edit -

Almost overlooked your question From the appearance of the Simply 845 I would guess the circuit is not that much different from the Smart 845. While searching I also found out that this amplifier only put's out a merely 24 watt's per channel. Getting back to the design from Tubelab, he get's > 40 watt's per channel, and claims more than 50 watt's would be possible as well:
Quote:
Jack Eliano at Electra-Print (awesome transformers) told me that he is getting 60 watts out of a single 845, and the secret is in the driver. That conversation got me thinking. I performed some simulations with SEAmpCAD from Tubecad which reveal that power levels over 50 watts (without over stressing the tube) can be achieved if you have a driver that can put out 450 volts peak to peak and source 10 milliamps. To get 50 watts you need a 1200 volt plate supply, and the grid must be driven 60 volts positive (well into A2). Distortion levels remain low at these power extremes. Tube dissipation is well within tube specifications under all conditions.

Last edited by lechuck; 3rd May 2012 at 09:25 PM.
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