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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 03 Sep 2017, 20:27 
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Alex Q wrote:
Is this a good starting point to build the C3g Headphone amp(The PS in the schematic will not be use)?I will be using the same PS that Matt designed for the 12AU7/6SN7 Headphone amp,I'am thinking of adding another 159R Choke and a Capacitor in the PS will this be Ok?The reason i want to use Matt PS design incase the C3g will not be as good as the 6SN7 i can reuse the PS to build the 12AU7 version which i plan on building for work.

Thanks!
Alex


I'm surprised this small tube will drive 32ohm headphones. Is that true? Usually a bigger power tube is required. If so I'm really suprised.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 03 Sep 2017, 20:31 
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I very rarely use any shielded wire except between phono stages. Very rarely in amps.

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PostPosted: 03 Sep 2017, 20:48 
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Suncalc wrote:
Alex Q wrote:
... hopefully this time i can cleanup my rat's nest wiring style.
Whereas I am always supportive of people cleaning up their wiring a little bit (but be careful not to take it too far) I am less sanguine about the widespread use of shielded wire. In exterior cabling where ground connections are set, it is very beneficial, but inside an amp it is very easy to set up noise inducing ground loops. I generally prefer simple wiring, well dressed within the chassis and maybe simple twisted pair for input signal runs.

Just my opinions on the matter.


I guess i will just shorten most of the wires specially those twisted ones they are long and i will put those resistors and capacitors flat closer to the chassis surface instead of them pointing up/upright.Thanks Matt!

Alex


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PostPosted: 03 Sep 2017, 21:11 
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mwhouston wrote:
Alex Q wrote:
Is this a good starting point to build the C3g Headphone amp(The PS in the schematic will not be use)?I will be using the same PS that Matt designed for the 12AU7/6SN7 Headphone amp,I'am thinking of adding another 159R Choke and a Capacitor in the PS will this be Ok?The reason i want to use Matt PS design incase the C3g will not be as good as the 6SN7 i can reuse the PS to build the 12AU7 version which i plan on building for work.

Thanks!
Alex


I'm surprised this small tube will drive 32ohm headphones. Is that true? Usually a bigger power tube is required. If so I'm really suprised.


I'am using an adapter that i made for the C3g in Matt's Circuit not the one i posted,I build the C3g amp based on the circuit that i posted i don't like the sound of it really high gain and flat sounding to my ears that is(Took it apart and build another one of Matt's circuit).The C3g in Matt's circuit(6SN7 version)with adapter is quiet and smooth it drives my Sony MDR-XB700(24 ohms) with no problem the gain is there i don't need to turn the volume that high sometimes switching from HD650 to XB700 i don't even need to touch the volume.

Alex


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PostPosted: 04 Sep 2017, 05:39 
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Hi Matt,
Since i'am rebuilding the amp i would like to add a CURRENT meter how/where to connect this meter and i have two choices 100ma DC/250ma DC meter?Thanks!

Alex


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PostPosted: 04 Sep 2017, 10:20 
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Alex Q wrote:
Since i'am rebuilding the amp i would like to add a CURRENT meter how/where to connect this meter and i have two choices 100ma DC/250ma DC meter?
If you want to show supply current, the meter would go in the B+ supply line after the second capacitor (100µf) and before it breaks up to feed the four individual filter stages. As the load current is only 41mA per driver triode, the total current is in the neighborhood of 85mA (41mA + 41mA +1.5mA +1.5mA) so the 100mA meter should work well.

If you look at the front of the 6EM7 Vertical amp here, you'll see that I used a 100mA linear scale meter for the ≈40mA power stage load and it works out fine.
Attachment:
meter.jpg
An 85mA current would still be fine with a meter like this.

However, if you have one of the current meters with the logarithmic scale, like this one:
Attachment:
meter2.jpg
Then I would recommend that you use the 200mA meter just so that the needle isn't so far over to the right edge.


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PostPosted: 04 Sep 2017, 10:56 
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Location: Canada
Suncalc wrote:
Alex Q wrote:
Since i'am rebuilding the amp i would like to add a CURRENT meter how/where to connect this meter and i have two choices 100ma DC/250ma DC meter?
If you want to show supply current, the meter would go in the B+ supply line after the second capacitor (100µf) and before it breaks up to feed the four individual filter stages. As the load current is only 41mA per driver triode, the total current is in the neighborhood of 85mA (41mA + 41mA +1.5mA +1.5mA) so the 100mA meter should work well.

If you look at the front of the 6EM7 Vertical amp here, you'll see that I used a 100mA linear scale meter for the ≈40mA power stage load and it works out fine.
Attachment:
meter.jpg
An 85mA current would still be fine with a meter like this.

However, if you have one of the current meters with the logarithmic scale, like this one:
Attachment:
meter2.jpg
Then I would recommend that you use the 200mA meter just so that the needle isn't so far over to the right edge.


Ok i will look into it,Thanks again Matt!

Alex


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PostPosted: 06 Sep 2017, 20:20 
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Hi Matt i remembered you mentioned "Something in the input acting like an antenna" that might be my noise/hum issue.Instead of redoing the first amp that i build from your Schematic i decided to rewire the second amp because this one is noisier,I started on the RCA input jack cable i cut it shorter and moved it away from the Transformer to my surprise it's now DEAD QUIET no more further rewiring for this Amp at least it's a bit neater than the first one.The Power supply for this second Amp(hammond 270FX) is from my C3g build that did not work well ,The only question i have is is it ok to run this Power supply with 2 159R choke and removed the 250R resistor?The final B+ is 292VDC.Thanks Again!

Alex

In this pics you can see the SHIELDED Wire for the RCA Jack is long and the input Jacks are beside the Transformer.
Attachment:
IMG_0837.JPG

Attachment:
IMG_0789.JPG

In this pics you can see i cut the shielded wire short and moved the RCA Jacks right behind the Input tube in this configuration the AMP is Dead Quiet.


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PostPosted: 06 Sep 2017, 22:52 
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Alex Q wrote:
s it ok to run this Power supply with 2 159R choke and removed the 250R resistor?
Kind of overkill from a filtering perspective, but it should work fine.

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PostPosted: 07 Sep 2017, 14:06 
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Suncalc wrote:
Alex Q wrote:
s it ok to run this Power supply with 2 159R choke and removed the 250R resistor?
Kind of overkill from a filtering perspective, but it should work fine.

Ok Thanks again!


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