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Old 10th April 2012, 04:36 PM   #501
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The 6DJ8 is prone to microphonics far in excess of any 12AT7. So you can make the 12AT7 sound more neutral.

90volts AC is kind of low but it will work.

The 6BX7 and 6BL7 both are good tubes, but when the output section saturates, there is not more than a watt or so of difference between them and the 6SN7.
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Old 10th April 2012, 05:08 PM   #502
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Default Thanks ATMA

Quote:
Originally Posted by atmasphere View Post
The 6DJ8 is prone to microphonics far in excess of any 12AT7. So you can make the 12AT7 sound more neutral.

90volts AC is kind of low but it will work.

The 6BX7 and 6BL7 both are good tubes, but when the output section saturates, there is not more than a watt or so of difference between them and the 6SN7.
Thanks for share your time.
King Regards.
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Old 11th April 2012, 12:28 PM   #503
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Quote:
Originally Posted by atmasphere View Post
You should be able to make that work in both cases.
Atma,
many thanks for reply.

As I said in previous post, I'm planning to build M60 with 12 6AS7G. I'm thinking to use 3 boxes for each channel, mechanically joined among them, so I don't use any interconnection cable and connectors.
As you can see in the attachment, the middle box contains amplifier section and lateral box PSU. All transformers (2 for output stage bridges, 6 for output stage tube filaments, 1 for input and driver stage, 1 for input and driver stage tue filaments) are placed into lateral boxes. So, I'm thinking to use layout as in the attachment to minimize current loss.
All filaments are heated in DC: transformers, bridges and the first CRC capacitors are placed in PSU units, then resistor and second capacitor in amplifier unit.
The same about output bridges supply: one capacitor only in PSU unit, resistor and the rest of capacitors in the ampli unit. A film cap will be placed close to each 6AS7G.
Also the same for input/driver stage: first capacitor in PSU unit, resistor, inductor and the rest of capacitors in amp unit.

Do you think is that the right way?

Andrea
Attached Files
File Type: pdf Chassis_Layout.pdf (79.2 KB, 116 views)
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Old 11th April 2012, 03:07 PM   #504
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what happened to the group buy?
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Old 11th April 2012, 04:57 PM   #505
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Hi! This afternoon I run the Switching power supply for the filaments, One PS 7,5 Volts 40A has a pot for change the voltage between 5 and 8 volts. I put 20 6AS7 paralleled during one hour. The system become warm but stabilized in tour around 40șC without rise.
I was afraid in cold system because the resistance near short circuit but run.
Now i will put the oscilloscope for watch for spurious signal. If this result I will avoid little transformer of 6,3 volt 50A.
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Old 12th April 2012, 07:31 AM   #506
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Quote:
Originally Posted by Villaw View Post
what happened to the group buy?
Formerly I asked twice for your above mentioned buyer's group and nobody said anything. While I Just getting the parts, I resolve partially the heaters. But maybe somebody want to integrate to this group and one of all the readers take control. For me one important thing are the Tubes, I need 20 x 6AS7G for each time I replace them plus 8 x 6H8C that is the practically more suitable because is reliable, cheap, undistorted, easy matchable, etc. Maybe somebody has a clue for them.
If you want to give continuity I will follow you.
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Old 12th April 2012, 07:48 AM   #507
Villaw is offline Villaw  Cyprus
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the ball is in Dr. Earfeelgood's (Ralph's) quarter!

Anyone else interested in a group buy for the cases at least? we need ten at least. If my memory serves me right the cases go for 450 USD each (you need two) but you get quality stuff with punched holes and look good for the family too.

Atma is selling the M-60 as a kit too costing 2100 US per monoblock if anyone is interested in a more all-rounded faster solution, and possibly financially less costly considering the time it takes in sourcing components.

So if anyone else is interested please raise your keyboard. Otherwise we forget about it and resort to metal fabrication.

dady- you can get conditioned tubes from Atma which go for 23 US, which is less than what other vendors charge.
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Old 15th April 2012, 11:36 AM   #508
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Hi all,
my project starts..
I have just got 32 Svetlana "C" winged 6H13C, so i'm thinking to use 18 output tubes/channel.
Do you think M60 driver stage can drive 18 output tubes?
Also, to parallel 6SN7 driver stage, should I simply join anode, grid and cathode of paralleled triodes?

Andrea
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Old 16th April 2012, 01:53 PM   #509
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Smile If you will use 18 you need four more plus 6AS7

Quote:
Originally Posted by andrea_mori View Post
Hi all,
my project starts..
I have just got 32 Svetlana "C" winged 6H13C, so i'm thinking to use 18 output tubes/channel.
Do you think M60 driver stage can drive 18 output tubes?
Also, to parallel 6SN7 driver stage, should I simply join anode, grid and cathode of paralleled triodes?

Andrea
And better if you get 72 for next change of tubes. Are you sure If seriously you need such monster in summer time? Rise the SPL in the loudspeakers with a couple of dB you win with at least 8 or more tubes. With 18 tubes for channel you take 300watt of power, but you heat 567watt only in filaments + 300 watts in idle power = 860watt (without music) and Imagine that if you build an amplifier of 300watt per channel the most possible is you gonna use it for at least 100 watt per channel. Sum another 200 watts you rise the KW.
If you have this living room and you waste this amount of energy for listen music probably you have a lot of money, and in this case is easy for get directly to Atmasphere a MA3 amp or best.
Anyway i guess with a parallel 6SN7, or use one 6BX7 or 6BL7 you drive better the final bridge of 18 AS7.
Best regards
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Old 16th April 2012, 03:27 PM   #510
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Quote:
Originally Posted by dady View Post
And better if you get 72 for next change of tubes. Are you sure If seriously you need such monster in summer time? Rise the SPL in the loudspeakers with a couple of dB you win with at least 8 or more tubes. With 18 tubes for channel you take 300watt of power, but you heat 567watt only in filaments + 300 watts in idle power = 860watt (without music) and Imagine that if you build an amplifier of 300watt per channel the most possible is you gonna use it for at least 100 watt per channel. Sum another 200 watts you rise the KW.
If you have this living room and you waste this amount of energy for listen music probably you have a lot of money, and in this case is easy for get directly to Atmasphere a MA3 amp or best.
Anyway i guess with a parallel 6SN7, or use one 6BX7 or 6BL7 you drive better the final bridge of 18 AS7.
Best regards
Hi dady,
I don't like high efficiency loudspeaker system, obviously my point of view. Actually I own a pair of Linn S.A.R.A., 4 ohm 87 db SPL, but I'm planning to build an open baffle speaker system using low efficiency driver (86-87 db SPL), so the situation do not change.
About power consumption, I know that I need 1 KW, but also I know that I need the same power to cook a pizza, so I believe that I'll eat one less pizza when I'll lesten to music. BTW I listen to music not much than one hour in a day, and not all days of the week.
I do not have enough money to get MA2 or MA3 amp, and I like to build my devices.
I'm very curious to know what Atmasphere think about this project.
Also I would like to know what Atmasphere suggests about driver stage to properly drive 18 tube/channel.

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