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Simple Hybrid tube amplifier with MOSFET output
Simple Hybrid tube amplifier with MOSFET output
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Old 11th April 2019, 04:09 PM   #1
bandol83 is offline bandol83  France
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Default Simple Hybrid tube amplifier with MOSFET output

Hi,

For the Baby Huey amplifier (designed by yvesm and gingertube) I have made 3 different PCB, one very simple for two ECL86 or PCL86, a more complicated one for one ECC83 and two EL84 with a MOSFET driver stage and a similar schematic but for EL34 output tubes to have more power ( EL34 Baby Huey Amplifier ) ... I was not only impressed by the quality of the sound of these little amplifiers but also by the huge interest of the audio community and with the help of Prasi more than 500 boards have been produced for these PCB

After this experience, when I read somewhere that the Simple Quasi Complementary MOSFET Amplifier (designed by Ranchu32) sounded a little like a tube amplifier ( Very simple quasi complimentary MOSFET amplifier ) I could not resist and I decided to make a PCB to test it... I was not disappointed at all

An other experience with My MOSFET Amplifier designed for Music (designed by Mooly) witch also impressed me ( My MOSFET amplifier designed for music. ) finished to convince me that a "Best of both World" solution could be to make an Hybrid Amplifier which will use tubes in their best job to increase voltage and transistors with their capability to drive high current at low impedance therefor we could avoid the expensive and heavy output transformers

During my build of the Quasi I had the chance to have a lot of support from Hugh (AKSA) and we discussed the hybrid amplifier. From these discussions I have designed not one but two PCB : rev.5 is the original project with a current source and Rev.5 HD is Hugh suggestion to use a mu-follower stage...

Now that I have finally received the PCB I will start to build and test them

Cheers,
Marc
Attached Images
File Type: png PCB Hybrid amplifier Rev.5.png (155.0 KB, 1371 views)
File Type: png PCB Hybrid amplifier Rev.5HD.png (141.0 KB, 1370 views)
File Type: jpg Photo PCB Hybrid amp.jpg (179.8 KB, 1357 views)
Attached Files
File Type: pdf Schema Hybrid amplifier Rev.5.pdf (143.9 KB, 461 views)
File Type: pdf Schema Hybrid amplifier Rev.5HD.pdf (141.0 KB, 347 views)
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Old 11th April 2019, 07:40 PM   #2
Francois G is offline Francois G  United States
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I am following this project with great interest. Hopefully it works very well and satisfy your desire for the “best of both worlds”. Also hope Prasi would be involved in doing a GB. (I’m still, happily, working through my BH boards).

Two comments for your consideration, Marc.

1. Please consider designing your Quasi around current production output Mosfets. I had heard the supply status of those you have in the schematic is doubtful.

2. I see on the PCB that you make allowance for using the 6N1p. That is good, because I have seen many comments by gurus on this forum that ECC82 is not a very linear voltage amplifier. 6N6p would be even better, as would 6CG7 be.
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Old 11th April 2019, 08:34 PM   #3
soekris is offline soekris  Denmark
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Simple Hybrid tube amplifier with MOSFET output
Be aware that lateral power mosfets have a large and unlinear input capacitance and to reduce high frequency distortion, they should therefore be driven by a low impedance source, I don't know the output impedance of the tube driver, but even the gate resistors are too large....

Good alternatives to the now unavailable Hitachi Lateral Power Mosfets parts are Exicon, available at Profusion.

The output mosfet relay are a good choice, but they should be protected, t.ex. by a TVS.

The gate protection zeners should also have a series diode, otherwise they conduct when you don't want them to.
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Last edited by soekris; 11th April 2019 at 08:42 PM.
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Old 26th April 2019, 02:22 PM   #4
bandol83 is offline bandol83  France
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Location: near Bandol, French Riviera
Hi,

I have started to build this amplifier but I sill need some components and I just send an order to Mouser

While I have done this work, I made some changes for several resistors values that I show in this new schema... For the output transistors the lateral MOSFET from Renesas that I am also using on the Amplifier made for music from Mooly are doing well and as soekris say you can get equivalent from Exicon, they are only a little bit more expensive

The jumper selection for heater of the 6N1P can also be used to test other tubes like the 6FQ7 or 6CG7 ( https://s3.amazonaws.com/tubedepot-c...pdf?1400185580 ). The ECC99 could be also interesting ( https://www.jj-electronic.com/images.../pdf/ecc99.pdf ) with the jumper on the ECC82 position.

For the SSR protection I forget the TVS protection, it is stupid because I have done it on an other DC protection

Rgds,
Marc
Attached Images
File Type: jpg Hybrid en montage.JPG (471.3 KB, 1123 views)
File Type: jpg Photo DC protection bis Jan 5, 2019.JPG.JPG (640.1 KB, 1103 views)
Attached Files
File Type: pdf Schema Hybrid amplifier Rev.5.1.pdf (143.3 KB, 197 views)
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Old 26th April 2019, 04:29 PM   #5
Sodacose is offline Sodacose  United States
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Looks like a really interesting project! If you haven't looked at the Moskido designs, they're worth a glance as well. Similar goals and approach.

What kind of idle current are you planning in the output stage?
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Old 26th April 2019, 04:50 PM   #6
carlsor is online now carlsor  United States
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Simple Hybrid tube amplifier with MOSFET output
Default Also recommending the Moskido design

I also recommend the Moskido design. These sound amazingly musical.
I posted my experience and design in a DiyAudio thread.
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Old 26th April 2019, 08:49 PM   #7
ICG is offline ICG  Germany
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Location: I had a Déjà Moo - I've seen that BS before!
The main advantages of a hybrid amp are the higher power, no expensive output transformers and the non critical load impedance. At how much power roughly are we looking at?
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Old 28th April 2019, 07:57 PM   #8
stocktrader200 is offline stocktrader200  Canada
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I used the tubes 6922's before and after volume / balance driving an exceptional mosfet IRFP amplifier. The difference being tube amplification is not used to linearize the mosfet outputs and output offset / thump is not a problem.
This amp should sound very good.
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Old 29th April 2019, 06:54 PM   #9
nerdorama is offline nerdorama  United States
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Hello Marc,
You have probably been asked this by others but I would like to learn which PCB software you are using and the source you use for the PCB manufacturing. I have a board that I would like to have madel
thank you,
John
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Old 29th April 2019, 07:19 PM   #10
SemperFi is offline SemperFi  Wake Island
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Have you listened to this with and without the muting transistors on the output?
After done such a listen many years ago I have banned the use of transistors for muting. I only use relays if I bother with muting at all. I think the bad sound is due to the nonlinear capacitance of transistors. But perhaps todays transistors are much better?
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