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Cheap Chinese 6P3P kit

Squidward said:
BinaryMike brings up concerns that the original schematic is based on an inferior output transformer and would be best used as presented.
Click to expand...

My comments were intended to mean that I'm wary of designs that leave the OPT outside the feedback loop. The amp kit under discussion here does, in fact, include the OPT inside the loop. Maybe I confused things by airing my suspicion that feedback magnitude may be undesirably low.
 
Big & Pink

To clarify, in case the discussion of the transformer inside or outside the feedback loop is confusing you.

First to be clear. The amp you purchased has the transformer inside the feedback loop. BinaryMike is making the point that he believes designs of this type have an output transformer that is of sufficiently high quality that when used in this type of design, in this manner, they do not cause negative reliability and performance issues. (I.e. unwanted oscillations or other issues). This is a good thing. His comment (as I read it at least) about designs where the transformer was left out of the feedback loop was that he would suspect the reason for leaving it out was that it it might cause those unwanted problems if it was included. Some low quality transformers can do that.

Basically he was saying he thought the kit would have at least fair to middling quality outputs. (At least that's how I read it.)

Shelly_D

By the way, some folks do not like the type of feedback scheme used here, apparently (judging from his remarks I'm guessing) Squidward is one of those, however some of us do like that scheme. I like it because when properly implemented it lowers the output impedance, flattens the frequency response and reduces the output distortion. How do you know if its properly implemented? Listen and decide if you like it. There are some indicative tests that can be done but ultimately its your ears. I view it as a matter of taste.

Build it the way it comes, see what you think. If you want to experiment, post back and get some ideas for changes. track the mods yo make so that you can go back if want. Remember, its your system and it needs to sound good to you.

Have fun with the build.

Shelly_D
 
I would also suggest build it as originally designed as well.

But like Squid I to prefer local feedback verse loop an even more so when you
can leave that output transformer out of the mix easy enough like yu can here.

Local feedback gives same benefits of loop, like lowering the output impedance,
flatten the frequency response and reduces the output distortion, just another
way to implement it.

Not saying I don't use loop and from the output of the tranny back up, an even
like how it can workout, I just prefer not to when it can be done nicely.

I've attached the mod Squid was mentioning to try on this amp, after you build
it up an listen stock you might want to try this simple tweak an see how it may
may perform for you. (this is the schem someone posted of yur amp, I modded)

..
 

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Shelly_D

Thank you for your input! Your explanation has cleared the fog that was going over my head.

I know nothing about feedback in tube amps, pros/cons theory and practical implementation. With Keggers suggested tweak hopefully I will be able to hear and understand the difference the change makes.

I don’t have high expectations for this amp and I doubt it could best my ST-70 I built. My main goal is to better understand simple schematics and how to tweak them under the expert tutelage of the local tube gurus.

I plan to build it stock and then go from there.

Kegger/Shelly, I appreciate your suggestions and input.

Thanks :thmbsp:
 
sled108 said:
How can the Prices on either of These be Right?
Click to expand...

On the preamp its only 1 power transformer, inexpensive Chinese chassis, simple gain circuit without tone controls and tubes that have not escalated in price due to popular demand. Couple that with low parts count and inexpensive design costs for the circuit itself and you get a reasonable price. Note that it is also a line level preamp only, no phono section.

Shelly_D
 
Oh Yes, I know that there is no Phono Section...The real Question is if it's worth an extra $100 to get a Proven, Built Pre-Amp with Phono...Such as the Yaqin MS-12B?
 
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Hello allllllll, I AM THE SELLER! Glad to see that you are discuss our products. Yes they are really great kit for tube amp lovers. Best of all it brings a lot of fun of DIY. You can solder it, change the tubes, modify the circuit, listen to it, all as your won wish. A TOday a customer in Australia told me that he was very happy with the result. His friend guess the amplfier cost at least $800 after listen to it without looking at it.

There are some other great kits for more serious audio DIYers:
 
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Hey Ray....Well, I must say That is Most Reasonable...Any chance of a Phono Pre-Amp Kit in the Future?
 
Seems like a few bargains to me - now I'll have to throw in some of these in the pot along with the K-12M - sooner or later pull the trigger on a kit or two.
Having a 2A3 amp and a K-12m that's been upgraded, I find it not easy on deciding on something to build for a next tube piece, amp wise.
More rainy days are coming and I wouldn't mind building a couple kits.
That 6P3P is looking interesting, but in no hurry on what to decide on.
 
siliconray said:
Hello allllllll, I AM THE SELLER! Glad to see that you are discuss our products. Yes they are really great kit for tube amp lovers. Best of all it brings a lot of fun of DIY. You can solder it, change the tubes, modify the circuit, listen to it, all as your won wish. A TOday a customer in Australia told me that he was very happy with the result. His friend guess the amplfier cost at least $800 after listen to it without looking at it.

There are some other great kits for more serious audio DIYers:

------------

Edited my moderator.. (KEGGER)

While it is nice to see a manufacturer come in an check things out..

Without being an AK sponsor you can't advertise your wares, if you
would like to become a sponsor PM me for further details..
Click to expand...

I tried the one. 6n9p+EL34B SE 13Wx2 Hifi Tube Amplifier kits
Never did get it to work. Keg and I spent a few days talking about it. I forget what wire it was but one of the wires on the PT got so hot I refused to complete the kit not to mention you had to drill holes to get the transformers to fit. The chassis is Stainless steel and is a real pain to drill.
 
Hmmm. The nice gold binding posts in the completed unit photos turn into red and black plastic in the parts break-out photos.
 
gcgst said:
Hmmm. The nice gold binding posts in the completed unit photos turn into red and black plastic in the parts break-out photos.
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I noticed that too. The gold ones really do make it look nice.

I guess if I decide to order one of these I will be prepared to test everything before any assembly is done.
 
coman61 said:
I tried the one. 6n9p+EL34B SE 13Wx2 Hifi Tube Amplifier kits
Never did get it to work. Keg and I spent a few days talking about it. I forget what wire it was but one of the wires on the PT got so hot I refused to complete the kit not to mention you had to drill holes to get the transformers to fit. The chassis is Stainless steel and is a real pain to drill.
Click to expand...

Hey what you should do is get that thing to me, I'm sure we could sort it out.
 
Finally what appears to be a decent tube amp kit that does not require you selling your kids to afford it.

The main reason I have not really built tube amp kits is because until these kits the prices of even a basic tube amp kit except maybe the cheap ones Antique Electronic Supply sells or sold was well out of my price range and also well above what I think is reasonable to pay for a tube amp kit.

Main reason the price is so low is the manufacturer probably does not use the ridiculously expensive audiophool grade electronic components, but rather uses normal components which more than likely sound just as good as the audiophool grade components do. The larger size of the expensive audiophool grade caps make them more susceptible to picking up hum or causing feedback.

More than likely the amp will sound fine as is. Only thing about going ultra linear is you loose some output power.
 
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