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EL34 Baby Huey Amplifier
EL34 Baby Huey Amplifier
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Old 4th September 2018, 02:21 PM   #11
bandol83 is offline bandol83  France
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Hello Prasi,

At least the back side is finished
We were lucky that the chassis was supplied with the big rectangular hole for the main connector already punched therefor we had only to make round holes... I have also put all the label on the top panel and it was not necessary to add text on the rear panel, we have made the same for the front panel

Yes I will give more information about auxiliary circuit as announced in the first post. The input selector module is part of 3 PCB designed to add convenient features to the amplifier and to convert a power amplifier in a complete amplifier with 4 inputs selector, volume control, standby power and infrared remote interface. I made the module as small as possible to facilitate their integration into the chassis.

The input selector module use 4 relays to switch input from CD, Tuner, Streaming and Aux. The control unit include a motorized pot with its driver and a MCU driving The 4 relays, 4 LED, and the standby 230 V AC relay, there is also the infrared detector. Finally the mini 5 V Power Supply will include the standby transformer, the 5 V regulator and the standby power relay.

All schematics and PCB are shown below

Best regards,
Marc
Attached Images
File Type: png PCB Input Selector 4 sept 2018.png (39.5 KB, 1534 views)
File Type: png Preampli control unit.png (861.8 KB, 1480 views)
File Type: png PCB Control panel 2.png (66.7 KB, 1528 views)
File Type: png PCB Mini 5V Power Supply.png (47.3 KB, 1474 views)
Attached Files
File Type: pdf Schema Input Selector.pdf (114.0 KB, 181 views)
File Type: pdf Schema Control Panel 2.pdf (113.4 KB, 158 views)
File Type: pdf Schema Mini 5V Power Supply.pdf (117.5 KB, 129 views)
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Old 4th September 2018, 07:13 PM   #12
prasi is offline prasi  India
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EL34 Baby Huey Amplifier
Hello Marc,
Thank you very much posting comprehensive data.
It really looks nice and compact for the functionalities it possesses.
very nice layout as well.
thanks
Prasi
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Old 4th September 2018, 07:19 PM   #13
silasmellor is offline silasmellor  Denmark
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EL34 Baby Huey Amplifier
Nice, i am warming up to this project. I am curious, any chance for interior shots of your amp, especially the PSU?
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Old 5th September 2018, 07:40 AM   #14
bandol83 is offline bandol83  France
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Hi Prasi,

Thanks for your kind words for the PCB's, coming from you, an expert on PCB, I appreciate a lot

Hi Silasmellor,

Here are two pictures of the inside of the amplifier, but it is still a work in progress, when it will be finished I will post more pictures...

For the power supply I definitely recommend the Toroidy transformer TSTA250/001 TSTA 0250/001 - Mains transformer for tubes - Shop Toroidy.pl which fit perfectly the need for this amplifier, if you want to make it visible there is a superb EXPO version with a chrome enclosure (see web). It is also available from TME with very reasonable shipment cost : TSTA 250/001 TOROIDY - Transformateur: toroidal audio | TME - Composants electroniques and the spec are here : https://www.tme.eu/fr/Document/57008...TOROIDY-EN.pdf
I have no interest in these Companies, but I have found that their transformers for power supply and for output are very well built and at a much lower price than other toroid transformer designed specially for audio like Plitron / Amplimo ! I have built my EL34 Baby Huey amplifier with the Hammond 1650N because I had them on my selves since many years and they are quite good, but for my next quad KT120 I have already bought the CFB2000PP : TTG-CFB2000PP - Tube output CFB transformer [2kOhm] Cathode Feedback Push-pull - Shop Toroidy.pl (see picture)...

Best regards
Marc
Attached Images
File Type: jpg Inside view 1 17 Aug 2018.jpg (259.2 KB, 1403 views)
File Type: jpg Inside view 2 21 Aug 2018.jpg (104.8 KB, 570 views)
File Type: jpg 6CA7 Toroidy.JPG (411.7 KB, 508 views)
File Type: jpg Transfo TOROIDY.JPG (412.7 KB, 474 views)
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Old 5th September 2018, 11:00 AM   #15
bandol83 is offline bandol83  France
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Some more precision about the PSU (see attached diagram) :

1) The EL34 Baby Huey PCB include already the rectifier, the capacitor and the resistor filters for the high voltage, the input current source, the output bias and the driver voltage
2) Even if you can supply the heater directly from the 6.3V AC outputs of the power transformer, I recommend to use a 6.3V DC approach to have no hum at all from the 50 or 60 Hz main. Today DC/DC converter are so cheap that it should be an error not to take advantage of them, but don't hesitate to take a big one, like 20 A, because their specification are very exaggerated : 1 PC DC 300 W 20A CC CV Courant Constant Reglable Step Down Converter Tension Buck Z09 Drop ship dans Circuits integres de Composants electroniques et Fournitures sur AliExpress.com | Alibaba Group
3) It is always recommended to use a main filter like a Schaffner FN2010-3/06 (for 230 V line) to cancel the industrial noise carried on the main : https://www.mouser.fr/ProductDetail/...W4m3t3Ww%3d%3d
4) A CTN resistor will also be a good decision to protect the power transformer and the capacitors during power up...
5) The third 6.3 V output can be used to generate auxiliary power supply for devices like the 1.999 V voltmeter used to test bias. Again with the low price of these voltmeter it is a better solution than to connect multi-meter to test points, and it solve the problem of location of these test points
6) Of course, if you are using the standby module, the transformer must be connected via the power on relay !

Best regards,
Marc
Attached Images
File Type: jpg DC DC Converter 20 A.JPG (322.8 KB, 525 views)
File Type: jpg 6 CA7 Baby Huey Toroidy.JPG (710.5 KB, 551 views)
Attached Files
File Type: pdf Cablage EL34 Baby Huey 05092018.pdf (513.2 KB, 336 views)
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Old 7th September 2018, 01:53 AM   #16
Vunce is online now Vunce  United States
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EL34 Baby Huey Amplifier
Hello Marc,

Have you tried using a choke in the power supply?
I was wondering if there would be any improvement.
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Old 7th September 2018, 05:42 AM   #17
jcastellano is offline jcastellano  Spain
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Default Chokes

Hi,
I have used the Hammond 159v in each channel instead of R27 10 ohms 4w resistor and I am very happy with the results. Also, I recommend using 500v caps in the power supply section if using 275v ac supply. This is because, at the initial start of the amplifier the dc voltage goes higher than the nominal 400v caps, it is only for a little time but I feel this degrades the cap ability to filter, also when the amplifier is stabilized around 385v dc, this value is in my modest opinion very near the nominal limit of the psu caps. I changed them to 500v ones and also no regrets. Absolutely silent amp.

Read carefully the info regarding the 500v caps because their value are little bit different than the 400v counterparts, I think this is due to limitations in size. I ordered wrongly the same mf value but in 500v and they didn’t fit in the pcb so I had to install them outside and used cables to the pcb solder points.

I am going to make some photos during this weekend to show the inners of my build. I am going to make another set of pcbs but using boutique parts to check if the sound can be improved but it’s very difficult because it is a really very good amp. Thanks Marc and Gingertube and everybody who have made this possible.

Regards,

Jorge
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Old 7th September 2018, 07:02 AM   #18
silasmellor is offline silasmellor  Denmark
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EL34 Baby Huey Amplifier
Hey Marc, thanks for the info that is perfect. I am already a fan of toroidy PTs, which I’ve used for a couple of projects so that seems like sound advice. Being new to tube amps (only built a Bassman 5f6 so far), what is the preferred way to rectify the 6,3v tap for the heaters?
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Old 7th September 2018, 09:17 AM   #19
Vunce is online now Vunce  United States
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EL34 Baby Huey Amplifier
Quote:
Originally Posted by jcastellano View Post
Hi,
I have used the Hammond 159v in each channel instead of R27 10 ohms 4w resistor and I am very happy with the results. Also, I recommend using 500v caps in the power supply section if using 275v ac supply. This is because, at the initial start of the amplifier the dc voltage goes higher than the nominal 400v caps, it is only for a little time but I feel this degrades the cap ability to filter, also when the amplifier is stabilized around 385v dc, this value is in my modest opinion very near the nominal limit of the psu caps. I changed them to 500v ones and also no regrets. Absolutely silent amp.
Hi Jorge,

Thanks for the detailed information! I had very good results substituting the resistor for a choke in a Tubelab SSE.
I also have Mundorf Tubecaps rated at 550v that I will try with the Baby Huey, they are very large

Regards,
Vunce
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Old 7th September 2018, 02:23 PM   #20
Soonerorlater is offline Soonerorlater  United Kingdom
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I picked up a pair of small chokes (partridge ?) and used them to replace the 10 Ohm resistors in my EL84 baby Huey, didn't hear much difference in the sound stage. It was very good anyway. Really needed to scope the output for a change in filtering.
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