Cheap Tube Amp Kits?

I have seen many cheap tube amp kits for sale on Aliexpress and eBay. I realise that these kits will probably have lower quality components and likely not perform to advertised specs. My question is are these worthwhile purchasing to gain building experience before attempting one of the projects on this website or are they just a waste of money?

7 answers0 replies

7 Comments

Just Me

Feb 11, 2023

I would say yes, build one. There is one that I am building right now. On YouTube, xraytonyb has done a thorough job of building and testing it, and it does perform to spec. The components are reasonably high quality, except maybe the volume pot and one power supply cap that I will replace. It comes with a 115V transformer now. I am hoping that will be close enough to work ok. My wall outlet is exactly 120V.

You can see the building and testing by xraytonyb in detail here:

Part 1: https://www.youtube.com/watch?v=lkImhOoAnSA

Part 2: https://www.youtube.com/watch?v=fD83Oi6gCUs

Part 3: https://www.youtube.com/watch?v=0nDsGJn_BEM

Note that the amplifier kit has been updated to remove the loudness circuitry, which was the first modification that xraytonyb made. The loudness switch and the associated circuitry are gone now thankfully. The rest remains unchanged.

If you order from AliExpress, you will see large differences in the price for the same amplifier kit. I chose the lowest price seller, and we have been having a little communication difficulty. Make sure you are comfortable communicating with the seller BEFORE you buy, in case it arrives with missing parts or damage. Try chatting with the seller using the messenger tool before buying. You can also find the amp kit on ebay, but at higher prices.

https://www.aliexpress.us/item/3256804139705130.html

The new building instructions and Q&A can be found in this discussion thread:

https://www.diyaudio.com/community/threads/6p14-el84-amplifier-kit-building-questions-before-i-build-maybe-during-if-i-do.394962/

Mine took just 6 days to ship from Hong Kong to Florida. Here it is:

Also on YouTube, xraytonyb built another one of the inexpensive amp kits that also turned out quite well for him. He did a 10-part video series on it called "Electronics 101-1/2."

https://www.youtube.com/watch?v=YqD_4tkRcts

mddawson

Feb 11, 2023

Replying to

Thanks for the "Electronics 101-1/2." recommendation, I will watch them in preparation for my kit. I ended up ordering an FU50 kit from Aliexpress (https://www.aliexpress.com/item/1005004910994491.html) I have found two YouTube series showing construction but one is in Korean and the other in Thai so I can only go by the visuals. Both had dented shielding on one of the transformers but their seller supplied replacement covers (both show how to replace them in their videos). One had a cap die after around six months so I will be ordering a complete set of Vishay or Kemet caps (and any out of spec resistors) for it once it arrives. The main power transformer appears to be 230v which is close enough to my 240v mains to not cause an issue.

Just Me

Feb 11, 2023

Replying to

Can you give me links to the videos? I'd like to see the kit quality. I looked at that FU50 amp but passed it up because it's single-ended (8W) and has a rectifier tube that I didn't want to fiddle with. The one I bought has a tiny bit more power at 12 watts and no rectifier tube to deal with. I'm leaving off the "magic eye" tubes because they are just there for decoration.

If you watch the whole electronics 101-1/2 it will take you about 10 hours. It took me several days to get through it.

mddawson

Feb 11, 2023

Replying to

Here is the Korean playlist (no speaking but all the on screen captions are in Korean): https://www.youtube.com/watch?v=nUK4sOOE7WQ&list=PLnyQFHUSljIpCy0KD6aTbms7K0Mb5Krhx Here is part 1 (of 6) of the Thai series. This guy does a better job IMO as he insulates the longer resistor leads and seems to take more care with wire placement: https://www.youtube.com/watch?v=kSG8v8h-E-M Both YouTubers have the main power transformer spaced from the top of the case leaving a gap. I am assuming that removing the four nuts on the transformer could affect the plates so I am thinking of drilling larger holes and using spacers around the nuts to secure it to the case.

kudju

Jan 24, 2023

You can have fun building this 10-16$ 6j1 buffers from ebay or aliexpress. Just type in the search bar for 6j1 buffer and you will find plenty

mddawson

Jan 24, 2023

Well Stephe's video on 110v transformers answered part of my question as all the kits I have seen operate at either 110v or 220v. So a bucking transformer or replacing the amps main transformer will need to be factored in. https://www.youtube.com/watch?v=38GS-K776_8

Moonfish

Jan 24, 2023

Replying to

Hi! Maybe you can start with a low voltage kit like this; https://nl.aliexpress.com/item/33010234920.html?spm=a2g0o.productlist.main.31.508b3d80fUR9LB&algo_pvid=d53428b5-089e-4107-aa30-04af7baeeccc&algo_exp_id=d53428b5-089e-4107-aa30-04af7baeeccc-15&pdp_ext_f=%7B%22sku_id%22%3A%2267151228592%22%7D&pdp_npi=2%40dis%21EUR%2115.87%2112.38%21%21%21%21%21%402100b20d16745333380756852d06ef%2167151228592%21sea&curPageLogUid=6Z1d7i3tLVe6