音響制作工藝 DIY Audio Craft

My friend just back from USA and bring me some very nice China made vintage 6H8C (6SN7). He said, it sound very nice and better than all his 6SN7.

I am a 6SN7 collector. I love these small twin-triode can have so nice sound!! Really rare!! Even 12AU7 have similar specification as 6SN7, but I love 6SN7 sound much more!!

I want to know if the 6SN7 really great? Then I take out my favor NWT CV1988 (B65) and Ken-Rad VT231 (Grey glass) and the new Shuguang Treasure CV181, Chi-ping (Shuguang OEM) CV181, and Shuguang 1970's 6H8C and many Audiophile love, the RCA red base 5692 for compare!!

I have some more 6SN7, but we did compared some time ago, like the RCA, GE, Tungsol...etc They all are far away quality than the above tubes. So, to save time, we don't compare them any more!!

Let a look on some photo first

I don't want to post the result. Since it make many collector disappointed.

Yes...my friend are right. His vintage Nan-jing, China made 6H8C really great!! Many China website said the 1958 production is the best. But we pick 6 pairs, from 1958, 59, 60, 61, 62 and 63 to compare. His 1963 and 64 sound different with others. They are structural same. But sound really better. More details, better bass control and very very natural sound!!

So, big different on different year production? No!! a little different only.

To compare with Chi-ping, they are very close. Same characteristic, very balance and details. For current production, I said the Chi-ping CV-181 is the best. The Shuguang Treasure CV-181 look very nice and sound also very details. Even the most details on the upper frequency!! Better air and high. But worse bass compare with others!!

That is the 6SN7 cascode drives 245 power amp. The rectifiers are 83. These amp have switch for high voltage supply. So, we only switch the HV when change tubes!!

This amp only work on 250VDC B+ self Bias. So, it only output around 1W.

So, How about other 6SN7?

Ken-RAD VT-231, has dark gray glass costing inside. Sound very smooth and very details. Very similar to Treasure CV-181 and even more rich mid-high and more bass sound. Very good collection if you lack of high-frequency details. IF you cannot get this tube in acceptable price, the Chi-ping CV-181 sound nearly the same!! No mater characteristic and tone balance. But look completely different.

RCA Red base 5692: This tube has been a dream on some years ago. But, some comments said it is not as good as many others. OK, I would like to test it again. The result is not perfect, but very excellent performance. It sound very similar to the Ken-RAD VT-231 and even more mid-high details. I would say it has very good bass like the Ken-RAD VT-231 and Chi-ping CV-181. Another very excellent tube and worth for your collection.

NWT-CV1988 (B65): Oh!! I forgot take a photo of it. Yes, it is the best in my collection. Let report it with photo later!! A simple comments: Perfect on tone balance, details, and powerful bass control.

To Summary my test: The Nan-jing 6H8C 1958-1964 are all similar sound. Only a few (structural same) with some different. Anyway, all those tubes are worth for collection at current price level (i.e. Around US$20 each) They perform as good as current high-end production. But look not so nice!! I am not sure if earlier or later production are as good as them, but my collection only cover that years.

I would say the Nan-jing 6H8C (1958-1964) is "Poor-man-CV1988/CV181"

Chung, 8/July/2010

Chung,

Good testing for 6SN7. How about CBS 5692?

Is it your new power amp 245? Good looking.


Freeman

I did not test all my 6SN7. Since we don't have enough time.
The CBS brown base 5692 tested not as good as RCA red base 5692. So, I did not test it again here!!

The 245SE Power amp is Mr Hui's project. But, I design the circuit for him. A simple cascode 6SN7 RC coupling to 45. B+ 250V only. The output transformer are vintage China product. Power transformer is low cost one, similar to my selling filament and choke!!

Due to low B+, the output around 1W only. But still very powerful, not far away as my 300B (8W).

It sound very very details. I would say unbelievable!! To bad, I did not collect any 245 or even 45!!

Chung