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Edited: May 18, 2022

Is it better to buy an A12 or A10 and then apply Mods ?

Hello from France,

I found the YT channel from Stephe, and decided to get my first Tubes Amp

I plan to apply Stephe mods to get a much better Amplifier

A12 price is the double of A10 price (500$ versus 240$ on China-hifi-audio website)

As far as I could find, main differences between them seem to be the quality of the OutPut transformers ( perhaps others ones ??...)

Do you think that the a12 quality and sound is worth its price ?

Regards, JC

@Stephe, thanks a lot for your great videos and Website !

11 answers5 replies

16 Comments

bill

Jun 01, 2022

The A10 is very similar to the A12. This list is supposedly for the A10 mods tweaked from Skunkie's A12 mod. I only wish she could clear up alotta confusion with us A10 buyers trying to follow her lead. This mod is assuming you have the non-printed circuit board version and have the hand soldered, point-to-point version of the A10.

I am not a techie, but have a friend that can handle the mods for low cost, after I gather the parts. Some resistors and caps are hard to find. Facsimiles must be found online.

Junkman George

Mar 06

Replying to

You can do the mod to the printed circuit board version, but it's not as easy, and is a bit tricky.

kanumera1

Jun 01, 2022

@bill , is this list to mod from A10 to A12, or the list from A10 to Skunkie A12 mod ?

bill

Jun 01, 2022

Ron Cochran is his name.

FB group is "Reisong tube amplifier Boyuurange audio ".

Contact him and he will provide his parts list.

(Too bad Skunkie seems to avoid much assistance with the A10 parts info...oh well)

bill

May 31, 2022

Trying to gather the parts list for an A10 mod....(list with manufacture info sourced from someone on a FB group for Reisong amps).

Lotta stuff is unobtainium......wish I had the knowledge to figure out a work around for the caps and resistors that are on many months BO status. Only ONE source found for the 220uF 25V caps.....in Japan....but they want $40 just to ship two of them to Texas. Sheesh. cancelled order.

kanumera1

Jun 01, 2022

Replying to

@bill Thx a lot

Junkman George

Mar 06

Replying to

Bill, if you are upgrading the 220uf caps on the EL34 to the 470uf the mod calls for, just re-use the removed 220's.

Thetubestore.com has caps, I checked Parts Express, but they are catering to the transistor crowd.

Edited

Skunkie

Mar 06

•

Replying to

I need to clarify: when you reduce the size of the cathode resistors to 250 ohms, you HAVE to increase the side of the EL34 bypass caps or you will lose a lot of the low frequency response. Also, this 470uf/35V cap is the min voltage. you can easily sub a 50-100V part. And yes for the driver tube bypass cap you can just move the 220uf cap that was originally on the output tube there. And to the question/complains about not providing a parts list for the A10, it's because there is no change to the parts list. The ONLY difference is rewiring the heaters to use 12AX7 or simply leave the A10 heaters alone and use the tubes it comes with. Attached is a diagram I have shared on the heater wiring several times in other places. Also I have been told there are 2 versions of the A10, one is point to point and the other uses PC boards, they are not the same. These super cheap ones are likely the PC board version which also use different/cheaper output transformers from the point to point wired A10/A12.

Edited

ECHO

May 23, 2022

I hope that I'm not breaking any rules here by informing you of another forums old thoughts on this amp. Boyuu A10 with EL34B, 6P3P, 6CA7 | diyAudio Have a look in here.

ECHO

May 22, 2022

I found a few take a look at these drawings

bill

May 23, 2022

Replying to

My novice untrained eye sees the 220V power input... Are all the components inside the same for a 120 V version? Thanks

kanumera1

May 22, 2022

I checked a10 and a12 schematics. Only a few resistors differences If I remember. If someone can tell how to mod an A10 to 12, It would be great .

bill

May 22, 2022

Replying to

I have a friend that is great at rehabbing old tube vintage AM radios...and he's glad to do this mod for me....but he's hesitant unless we can get a sketch of the A10 (not A12) mods. I know they are very similar, but he's not sure of it w/o the correct schematic. Looked all over the internet....cannot find. Hoping Skunkie responds to me email request about this.

bill

May 21, 2022

I just purchased an A10. Wish Skunkie would publish a markup of these mods for the A10, for us non techies.