找回密碼
 註冊
查看: 12228|回復: 19

Seeking advice on driver tube for SE 300B

[複製鏈接]
oldbeandad 發表於 2007-7-6 09:35:02 | 顯示全部樓層 |閱讀模式
I am going to build a SE 300B on completion of my current project on a SE 211.  However, it is too hard for me to decide on which tube should be chosen to be the driver,  ECC32 or EL37?  For input stage, I would go with ECC32.  Any advice is appricated!
accphoto 發表於 2007-7-10 12:40:41 | 顯示全部樓層
Strange to use EL37 as a driver tube. It will " poluted " the sound of 300B as a triode SE. ECC32 is good to drive 300B but expensive.
 樓主| oldbeandad 發表於 2007-7-12 08:58:45 | 顯示全部樓層
It is so nice to see a response!  Thanks Accphoto!
You are right that EL 37 may not be friendly to 300B.  This is what I worry about and that is why I could not reach a decision yet.  As I search over internet and my old magazines, I found that some SE 300B schematics are having EL34/6L6 to be the driver tube. The Audiophile 125 edition (August 1996) and the 136 edition (July 1997) are examples.  Having an idea that EL37 sounds better than EL34 and 6L6 do, I consider to have it for the driver work.  But at the same time, I think it is too wasteful and I should let it do the work of power tube.  Anyway, I hope to see more comments and advice.
 樓主| oldbeandad 發表於 2007-8-23 10:01:36 | 顯示全部樓層
Well, there has been only one response so far.  Anyway, I have decided to go with ECC32 + 300B and this project is ready to go now because I just finished my se 211.  Attached are the pictures of my new born se211 and the main parts of 300B.

本帖子中包含更多資源

您需要 登錄 才可以下載或查看,沒有帳號?註冊

x
accphoto 發表於 2007-8-24 15:25:59 | 顯示全部樓層

300B amp

Hi,  I am in overseas and cannot response to your email. I have complete the construction of a 300BSE amp recently using Sunaudio 6sn7 driver tube but change the Main B+ to 420V for 300B, I recommend this circuit as I have compared this one to various 300B amp like audionote conquere and found that it sound better. I am also using premium parts like Jensen copper tube cap , RMG resisitor, Blackgate cap and Tango XE20S output. Cost me about 10,000 but it is worth as I have compared it to various amp like MC240, MC275, Marantz 8 . I found my taste is still prefer this 300B SE amp. My friend like it very much and take it in this home and work with JBL. I am now planning to work it as a mono-block. Hope this will help.
 樓主| oldbeandad 發表於 2007-8-26 11:05:11 | 顯示全部樓層
Wow!  Can you send me a copy of your schematic  for reference?  Among those available from web-sites, I like the one designed by Joseph Esmilla most.  You may go to www.heggeseth.com to have a look.  I think this one is very close to yours.

Oh yes, I am not residing in Hong Kong.  I wonder if you are in Canada too.
steve138 發表於 2007-8-26 12:46:48 | 顯示全部樓層
Dear cheaplow and accphoto
Here are three schematics for 300B single ended amplifier, do you think which is the best schematic. I am seeking your advice before I buy the parts. I am looking forward to receiving your advice. Thank you.
 樓主| oldbeandad 發表於 2007-8-27 01:35:25 | 顯示全部樓層
Steve, you don't need to wait for others' advice before buying parts/components.  When you come across good deals or good price offered, don't let them slip away.  No matter which schematic you  take,  you will need the transformers , caps and etc.  Well, I won't follow any schematic with exact component and value.  On completion of the building, we need to fine tune and adjust in accordance with the wave showed on oscillatescope.  If I strictly follow the schematic, I will never be able to taste the enjoyment from DIY.  I always hold the principle that for signal path, less component is the best.  But this does not apply to power supply unit because what we need in this unit is to supply pure and stable dc for the tubes in order to get the electrons jumped  smoothly and steadily to the plate inside the tube. So, Mr. Modi is absolutely right that isolated transformer is extremely important in audio hi-fi system.  Among the three schematics, I would try the top one first but cut off the 100K Tapper.  For power supply unit, I would perfer to having the one, which is not shown, with the third.  In fact, the third is the one that I mentioned, designed by Joseph Esmilla.  Direct coupling  is my cup of tea.  Anyway, all schematics are more or less the same.  Hope you enyoy your project.
accphoto 發表於 2007-8-28 17:44:23 | 顯示全部樓層
If you look at all those diagrams, they are effective the same principle thought the grip resistance are difference which 6Sn7 working on different working condition. The third diagram using a 880ohms cathod resistor so the 300B is working at a different condition then the other diagram. I had not tried this low cathod resistor as not all 300B suitable for such voltage. ( i was told that Full Music 300B should work at 1.1K instead) . Any way, i have attached my diagram that i have build but I have modified the B+ to 420V and using 1K cathod resistor for 300B to gain more power. Power Supply had also modified by using 2 Black Gate 100U x2.

本帖子中包含更多資源

您需要 登錄 才可以下載或查看,沒有帳號?註冊

x
accphoto 發表於 2007-8-28 17:50:01 | 顯示全部樓層
This is my early version of 300B and now rest in my friend's home. He is quite happy at the moment.

I had also duplicate the circuit for EAR 734p and using it a phono amp at home.

本帖子中包含更多資源

您需要 登錄 才可以下載或查看,沒有帳號?註冊

x
steve138 發表於 2007-8-28 23:14:44 | 顯示全部樓層
I decided to try the first schematic first. Thank you for your recommendation.
 樓主| oldbeandad 發表於 2007-9-1 21:06:14 | 顯示全部樓層
Hello accphoto,  I have a schematic in below which is almost identical to yours except the value of B+ and  Cathode Resistor.  You may notice that the B+ supplied to the Plate of 300B is very close to what you have raised to (about 420 vdc) but the Cathode Resistor is having a value of 880 ohm.  According to the Data Sheet of TJ Fullmusic 300B and WE 300B, the Grid Voltage is -58v.  So, if you are having a plate current at 70mA, the Cathode Resistor would be 58v/70mA = 828.57 ohm, or round up to 830 - 840 ohm.  For JJ 300B and EH 300B, the Grid Voltage is -61v,  880 ohm (61v/70mA=871.4 ohm) appears to be the appropriate value for the Cathode Resistor should you like to have a plate current at 70 mA.  Anyhow, experience tells that such figures need to be adjusted in doing fine tune.  Would you mind to let me know the Grid Bias and Plate Current as well as which brand of 300B are with your amp. for reference?  Thanks.

本帖子中包含更多資源

您需要 登錄 才可以下載或查看,沒有帳號?註冊

x
accphoto 發表於 2007-10-2 23:28:04 | 顯示全部樓層
Dear Cheaplow,
Sorry for being late in answering you question. Since my first machine is no longer with me, I cannot measure the voltage. However, I have already built another machine using negative bias on the Grid, i found that 300B needs about -83V on China one in order to get a current of 70ma. For Full music , the negative bias needs to be much lower, so in order to achieve a 70ma working condition, I finally decide to add another transformer and give a negative voltage to the Grip, the Cathay resistor has been reduce to only 100ohms just for the sake of measuring the current flow. I am qiote sute that this will maximise the performance of each type of 300B.
steve138 發表於 2007-10-3 13:34:36 | 顯示全部樓層
Dear accphoto,
Would you tell me where to buy Tango output and main transformer?
Thank you.
accphoto 發表於 2007-10-3 23:52:01 | 顯示全部樓層
please send pm to me. I will send you the details.
 樓主| oldbeandad 發表於 2007-10-4 09:24:25 | 顯示全部樓層
Hi Accphoto
Thanks a lot for your information!  Oh yes, don't feel that you have an obligation to response to my message or answer any question.  As a matter of fact, we have a same hobby and it is our pleasure to share our experience.  We have our own job and may not have enough time to do what we want to do on time.  Me, I will be away for a while because I am going to leave for Europe day after tomorrow.  Yes, congratulations to you on your new born SE300B.  Wow, you know how much I admire you for being able to afford, both money and time, in building such a wonderful SE 300B?  Will you consider to grab a pair of WE 300B for it?  Hmmm, I still suspect that the plate current would exceed 70mA with -83v bias and a 100 Ohm cathode resistor.
steve138 發表於 2007-10-4 13:42:26 | 顯示全部樓層
Dear accphoto,

Please check e-mail.
accphoto 發表於 2007-10-4 22:10:31 | 顯示全部樓層
Dear Steve 138

Replied
accphoto 發表於 2007-10-4 22:13:29 | 顯示全部樓層
Hi Cheaplow,

Yes, I own a WE 300B and will put in it once run it. The current for the plate is 70ma as I am providing a negative voltage of -83V to the grid, that is why the cathod resistor value does not matter. I think it is more easy to control the plate current than using a fixed value of cathod resistor. Hope you have a nice trip..
steve138 發表於 2007-10-4 22:53:08 | 顯示全部樓層
Dear accphoto,
多謝指引。
您需要登錄後才可以回帖 登錄 | 註冊

本版積分規則

GMT+8, 2024-3-29 09:02 , Processed in 0.034275 second(s), 26 queries , Gzip On.

© 2001-2011 Powered by Discuz! X3.2. Theme By Yeei!

快速回復 返回頂部 返回列表