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Any experience or opinion about 300B/EL34 Chinese DIY Kit ...

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Please share any experience or opinions about what we can see at this 300B DIY Kit from China :

Luxury Single Ended Class A Tube Amp Amplifier DIY Kit for HiFi Match 300B Tube | eBay

I have no relevant experience with tube amps , but I would like to start something (a stereo power amp) and that kit is quite interesting for me :)

My diy speakers are arround 98 dB efficiency and I already have a processor / preamplifier with RCA outputs (Yamaha Aventage RX-A2040)

I would like to buy also their recommended power transformer, tubes (Psvane 300B HiFi) and chocking coil ... all these from the same supplier as kit. Links are in the presentation of the kit.

The output transformers I would like to buy from TOROIDY or EDCOR, and btw any recommendations for these?

Does it make sense all these for a 300B stereo power amp? obviously my budget is (very) low ...

Thank you :)
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6sn7 srpp into 300b is kinda sad. This seller has no imagination and probably lots of Chinese 6sn7's and 300b's to sell.

If your budget is low, then best stay away from 300b. There are better and cheaper single ended projects that will yield better results for your 98db speakers.
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From what I have read, 300B single ended powers are highly regarded (of course they speak about expensive brands / projects ...) and yes is true that 300B are really expensive, not budget friendly :(

I compared this 300B kit with some other projects found on internet and seems is quite close to some nice proven done projects ... I was glad about having a PCB and was going to ask for assembled one.
Also I think to swap the 6SN7 with other quality tube ... which one still search about! :)
with EL34 and 6V6 I found some kits, but the power per channel is arround 5W ...

regarding 6L6 how about this?
6L6 SE Tube Amplifier Kit 10+10W (Stereo)_Power Amplifier Kit_Tube Amplifier Kit_Analog Metric - DIY Audio Kit
could really reach 10W per channel?

can't find a sale shop for kit or price for the Red Light District 15W PP Amplifier !?

regarding 300B SE ... Jesus Christ! don't tell me that 250-300GBP OT are the only choice! for a good quality sound ... really, no other choices for OT arround 80-100USD !? for a nice 300B SE power ...

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Forgot to mention that I would like 8 - 12W per channel from a power tube amplifier ... and I like what I have read about Class A Single Ended projects!

Can this power be reached with other tubes? meaning other SE kits?

It all depends on the voltage, RL of OT and Anode current Ia setting, so you must purchase the correct power transformer and OT for the power out you require. I think the standard config is not more than 7W per channel, should be able to drive your speaker IMO. So there should have a mean to set the bias of 300b also. say varying the cathode resistor.



Typical Class A amplifier parameters.

Ua -Ug Ia -RL Pout 2nd
V --V -mA -Ω-W ---db
200 42 30 2000 3 --20
200 39 40 2500 2.6 26
250 55 30 2000 4.9 18
250 52 40 3000 4.0 26
250 50 50 2500 4.4 26
250 48 60 2000 4.7 30
250 48 60 2700 5.0 26
250 45 80 1500 5.0 26
300 65 40 2500 6.7 20
300 63 50 2000 7.2 21
300 63 50 3000 6.1 26
300 61 60 2400 6.6 26
300 58 80 1700 7.5 26
350 76 50 3600 7.8 26
350 74 60 2000 10.2 21
350 74 60 3000 8.3 26
350 74 60 4000 7.0 30
350 71 80 2200 9.6 26
400 91 40 5000 8.4 26
400 89 50 1000 11.5 21
400 89 50 4000 9.4 25
400 87 60 3500 10.5 26
400 84 80 2500 12.5 25
450 104 40 6000 9.5 26
450 102 50 5000 10.7 27
450 100 60 4000 12.5 26
450 100 60 5500 10.1 30
450 97 80 2000 17.8 21
450 97 80 1000 14.6 26
450 97 80 4500 11.5 31
Edcor transformers are ok, but for near the same money or a bit more you can get Transendar or James. You can always upgrade later along with better 300b. IMHO a triode connected pentode will never sound like a 300b. I would rather listen to a PSE triodes like a 6BX7 or 6H30.
"IMHO a triode connected pentode will never sound like a 300b."

You probably haven't listened to curve tracer selected "triode"/pentodes. Like all tubes, including 300B, their curves are all over the place quality wise. You need a curve tracer to find something good. Like this pentode:


  • Perfect_Triode.jpg
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Tried a lot of "triode"/pentodes...not for me. I don't listen to a curve tracer, but to music. Note that I said IMHO. Different strokes for different folks. I have to agree that cheap 300b sound....well cheap. But so do Chinese 6V6, 6L6, EL34, KT88, etc. The tubes you refer to are vintage NOS and always sound better than new production. He was asking about the TOROIDY or EDCOR transformers and looking for a kit. If he wanted a pc board kit, I'm not sure he will want to DIY...but he might and I hope he does.
Plate characteristics are plate characteristics, the curve tracer doesn't lie. i.e. Your ears or anything else for that matter doesn't care if the tube's cathode is directly heated or indirectly heated, linearity of the device is all that matters. For example, the 12AU7 was I believe supposed to be the noval equivalent/replacement to the octal 6SN7, yes at specific operating points they may have similar transconductance and plate resistance but look at the plate curves and you will see the difference. The 6SN7 has nice and even grid steps where as the 12AU7 grid steps are spaced further from -4v to 0v and increasingly get more compressed the further to the right you go on the graph, this causes an increase in distortion.

People "roll" tubes for a reason, the difference in these plate curves from device to device even within the same production run can be audible and or measurable.

EDIT: You can have your 300b's, I will take the 6HJ5 any day of the week ;)
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That kit still leaves you with the output transformers, power supply , power transformer and chassis. If you are going to source all of those pieces you might as well go point to point wiring. Running kt88 single ended pentode like the RH Universal is excellent sounding. I have built 3 of those and 1 used Edcor outputs which were very nice. The design is uncomplicated and simple to do hardwired point to point. The kt88 is far easier to drive to full power than a 300b which means there is only one tube for the driver. Output power is around 10 to 12 watts depending on the operating voltages. If you google RH universal, you can read all about it.
I think you (the OP) are being far more worried than you should be about output power. If you have 98db efficient speakers, you can run 2 watts and not have any issues. Most 300B amps will put out around 5 watts. I am using a RH2a3 amp on a pair of 91db efficient speakers with no issues what so ever. I cannot turn the amp all the way up without using hearing protection. Just my 2 cents worth....

If this is your first foray into tube amps and you want to build a diy kit or something of that ilk, listen to what the other members are telling you. El84, 6v6, etc... will get your feet wet and allow you to make a better judgement as to what you like the amp to sound like without breaking the bank.
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