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Old 25th January 2014, 04:11 AM   #741
jpak is offline jpak  United States
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Quote:
Originally Posted by 45 View Post
In my opinion the LL1627 is the best choice because can be used for minimal loss (0.25 dB power loss). The LL1664 or the LL1623 at 3.3K and 3K connectio nare second best with 0.5 dB power loss. THe LL1664 has the advantage of the lower price at least.
The LL1620 is used at 0.8 dB power loss. Usable but not ideal. It's a waste especially considering the already low Pout of the amp. If you want to try the LL1627 I have a pair and you could borrow them.
What primary would you choose for LL1627?
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Old 25th January 2014, 07:32 AM   #742
45 is offline 45  Italy
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Quote:
Originally Posted by jpak View Post
What primary would you choose for LL1627?
2.3K which is a bit higher actually. It's almost 5K per tube.
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Old 18th March 2014, 05:14 AM   #743
H.Michi is offline H.Michi  Japan
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Default Battery biased 4P1Lx3 PSE Single stage stereo amp

Battery biased 4P1L x 3 PSE Single stage stereo amp

As I have got the pre-ordered OPT (XE-20s) from ISO-Tango in last December. So I decided to build a 4P1L x 3 PSE Single stage Stereo amp (experimental) as I do have a pre-amp which can deliver higher output voltage (over 70V rms) and condenser coupled output), yet with low impedance.
At first, I tried grid leak resister 200K ohm for fixed bias as a standard circuitry, and its output power came out only 4.5W due to the fact of the grid current starts flowing out, so that its bias voltage heads to deeper. It should be pointed out that this 4P1L tends specifically to flow out grid current..
Then, I made another try to replace the grid leak resister with a grid choke.
The outcome was of a minor improvement because of the bias PSU was not strong enough for sustaining lower impedance status...

Finally, I introduced an idea of Battery (14 units of size AA Battery in series for 21 V). Fortunately, the output power jumped up to 7W, and that its sound became further upgraded namely in clarity!
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Old 18th March 2014, 06:27 AM   #744
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This is really interesting! You are helping all who love the 4P1L with your experiments. Many thanks for that.

I want to try 3x4P1L with my Audio Note Trans-152 OPT, which is 2.5K. I use LL1660 interstage and filament bias.

What output would you expect from this arrangement?
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Old 18th March 2014, 11:53 AM   #745
H.Michi is offline H.Michi  Japan
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Hi Andy,
Thank you for your comment.
I am sure you can get the same amount of output power: 7~8W with inter-stage and filament bias. I guess your arrangement would be more effective to the grid rectifier current.
In my case, the output power was 8W based on the driving voltage of 23.5V rms .
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Old 20th April 2014, 09:02 AM   #746
H.Michi is offline H.Michi  Japan
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Default 4P1L x 3 PSE upgraded (10W in A2 class)

I replaced the battery biasing with a7119 as a direct coupling cathode follower with CCS on my experimental 4P1L PSE amp and that the plate voltage on the 4P1L raised to ca 280V in A2 class.
As a result, the output was increased to 10W with non clipping and that its THD has been improved in all output ranges.
The 4P1Ls in use are running in between 8.5W~9W of plate dissipation.
For verify the durability of 4P1Ls, I shall continue to run on the above conditions for the time being.
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Old 20th April 2014, 09:42 AM   #747
painted is offline painted  Luxembourg
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Your power supply is an inspiration. Remarkable that the -133V does not inject ripple at the penthodes' grids.
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Old 20th April 2014, 02:24 PM   #748
H.Michi is offline H.Michi  Japan
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The amp is very quiet any time.
The purpose of a resister 510k is for secure rush current for the 4P1Ls during start up phase.
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Old 20th April 2014, 03:01 PM   #749
Abszero is offline Abszero  United States
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Quote:
Originally Posted by H.Michi View Post
I replaced the battery biasing with a7119 as a direct coupling cathode follower with CCS on my experimental 4P1L PSE amp and that the plate voltage on the 4P1L raised to ca 280V in A2 class.
As a result, the output was increased to 10W with non clipping and that its THD has been improved in all output ranges.
The 4P1Ls in use are running in between 8.5W~9W of plate dissipation.
For verify the durability of 4P1Ls, I shall continue to run on the above conditions for the time being.
Very nice amp.
How is the transition from A1 to A2 impacts the sound?
Looking at the distorsion chart, you might be able to improve it by choosing a better operating point. I would try to choose the OP in such a manner that both sides swings equally( if for example use -15V then the swing is from +15 to -45, and you dont reach beyond -45V where linearity decreases dramatically). Just a thought.
Best,
Radu
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Old 21st April 2014, 09:08 AM   #750
H.Michi is offline H.Michi  Japan
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Hi Abszero,
I do not sense anything particular in sounding at the transition from A1 to A2.
I love its pulsive sound in particular.
Hiro
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