I can suggest either 01A or 112A. Both are 0.25A filament types like the 71A, which makes battery heating easy, which might be a consideration if you're building this for low level stage.
Shane.
Shane.
Hi Ceglar,
01a is my first choice if I would to add a driver stage in front. I'm planning to built a single stage 71a preamp for start.
It would be a 100K step volume pot > Lundahl LL1674 1:4 step up > 71A > Tamura A-4714 with 5k primary and 600ohm secondary.
2nd stage would be taking out the Lundahl step up and add a driver stage for 71A.
My objective doing this is to compare 71A tube with 45 as preamp by using Tamura A-4714 as line transformer.
My system consist of :
Turntable : Garrard 301
Tonearm : SME 3012 S2
Cartradge : Denon DL 103 Pro
Phono Stage : Audio Image - multi curve
Preamp : 45 with Tamura A-4714
Power amp : 300B
Speaker : Tannoy Westminster TW
01a is my first choice if I would to add a driver stage in front. I'm planning to built a single stage 71a preamp for start.
It would be a 100K step volume pot > Lundahl LL1674 1:4 step up > 71A > Tamura A-4714 with 5k primary and 600ohm secondary.
2nd stage would be taking out the Lundahl step up and add a driver stage for 71A.
My objective doing this is to compare 71A tube with 45 as preamp by using Tamura A-4714 as line transformer.
My system consist of :
Turntable : Garrard 301
Tonearm : SME 3012 S2
Cartradge : Denon DL 103 Pro
Phono Stage : Audio Image - multi curve
Preamp : 45 with Tamura A-4714
Power amp : 300B
Speaker : Tannoy Westminster TW
I wonder how much gain you really need, whats the signal level at the output of your phono stage with average program material?
71A biased at -40V can swing more than enough to drive 300B, linearly, and still with headroom. Rp is decent enough and 20mA Ip is good to drive the Cin of 300B without any slew rate issues. Battery heated, its a nice quiet DHT driver.
I like LL7903 as 1:4 to 01A DC 71A IT 2A3/300B. Nice quiet and simple enough.
Regards,
Shane
I have no idea about your proposal, as I don`t know about LL1674.
Try to just replace existing 45 tube with a 71A?
The 71A single stage with fillament bias hold the signal pass to a minium.
Regards
Hiro
Try to just replace existing 45 tube with a 71A?
The 71A single stage with fillament bias hold the signal pass to a minium.
Regards
Hiro
Ceglar,
DL 103 output is 0.3mV,my phono stage is at 60db and it has a gain of 67db. I suppose there is 0.3v output from phono.
My current 45 preamp is done as:
S&B TX-102 TVC (configure with +6db) > lundahl LL1674 1:4 step up >
45 DHT > Tamura A-4714 with 600 ohm output.
As poweramp :
6n1 mu follower > 45 DHT > Tango NC20F > 300b > Tango 3.5k output trans.
I do think my current set up have enough gain and head room.
I'm not going to have enough gain or head room if I would to replace my 45 preamp with a single stage 71a preamp without the 1:4 step up.
I quest a 2 stage 71a preamp is the solution.
Cheah
DL 103 output is 0.3mV,my phono stage is at 60db and it has a gain of 67db. I suppose there is 0.3v output from phono.
My current 45 preamp is done as:
S&B TX-102 TVC (configure with +6db) > lundahl LL1674 1:4 step up >
45 DHT > Tamura A-4714 with 600 ohm output.
As poweramp :
6n1 mu follower > 45 DHT > Tango NC20F > 300b > Tango 3.5k output trans.
I do think my current set up have enough gain and head room.
I'm not going to have enough gain or head room if I would to replace my 45 preamp with a single stage 71a preamp without the 1:4 step up.
I quest a 2 stage 71a preamp is the solution.
Cheah
You can replace 45 driver stage with 71A, my friend tried and he chose 71A. he used Lundahl (unknow) - 71A - LL1677-300B - XE20s.
I did amplifiers and pre-amplifiers with 45.
- Power: 417a-45-James transformers.
- Pre: Lundahl 1544a (or 6j5) - 45 - LL1692A.
I like the sound power amplifiers 45 but low power (I test with Fostex 208 BLH speaker). With pre45 I failed, may be my preamp schematic is not good.
Cheer.
I did amplifiers and pre-amplifiers with 45.
- Power: 417a-45-James transformers.
- Pre: Lundahl 1544a (or 6j5) - 45 - LL1692A.
I like the sound power amplifiers 45 but low power (I test with Fostex 208 BLH speaker). With pre45 I failed, may be my preamp schematic is not good.
Cheer.
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I had completed my 71a preamp few months back. It sounded fantastic !
Well worth the effort.
Cheers,
Cheah
Well worth the effort.
Cheers,
Cheah
LCL filter is always good for 71A. I replace 71A RCA with UX-171A Cunningham/RCA for my preamp. It get more microphonic but sound is fanstastic. I did improve filament filter with bigger capacitor and better B+ with more henry choke so hum noise become minimum, < 1mV
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Hi!
I ended up building a partial kit from Thomas Mayer(Vinylsavor). As usual, he use all passive filtering with LCLCLC for B+, LCL for filament.
Cheers,
Cheah
Hi!
I ended up building a partial kit from Thomas Mayer(Vinylsavor). As usual, he use all passive filtering with LCLCLC for B+, LCL for filament.
Cheers,
Cheah
Woo, looks very nice and good parts 🙂 .
Thank tcqanh , I use 10,000uF/16v for first capacitor .
My choke measured with different values on the same gauges henry with 20H and 100H meter. I test with 10H/125mA Hanmond .
* 20H meter :
- Hanmond is 6.02 H
- My choke is 13.52
* 200H meter :
- Hanmond is 9.9 H
- My choke is 21.2 H
My choke measured with different values on the same gauges henry with 20H and 100H meter. I test with 10H/125mA Hanmond .
* 20H meter :
- Hanmond is 6.02 H
- My choke is 13.52
* 200H meter :
- Hanmond is 9.9 H
- My choke is 21.2 H
Attachments
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Thomas take always complicated PSU. So they become very big 🙂
How is your schematic ?
This meter uses different sample frequencies, 1Khz and 100Hz for scale 20H, 100H sequentially. So you will get diffenrent results.
They uses four 6AX4... looks like this:
VinylSavor: Single Ended Amplifier Concept, Part 5
VinylSavor: Tube of the Month: The 6AX4
Hi!
Complicated? no! They are usually quite simple. Big, uuumh, yes 😉
But I did try to scale down a bit in my latest entry level preamps.
Best regards
Thomas
Complicated? no! They are usually quite simple. Big, uuumh, yes 😉
But I did try to scale down a bit in my latest entry level preamps.
Best regards
Thomas
I like 6AX5/6X5 instead of 6AX4. So I need only 1 tube and PSU is a much more simple. Choke input is my favorite, cause of its regulatory current. 🙂
Hi!
I prefer the bridge rectifier, hence the need for 4 diodes. In my simple preamps I also use rectifiers like 6AX5 or 6BY5, but augmented with two silicon diodes for a bridge
Best regards
Thomas
I prefer the bridge rectifier, hence the need for 4 diodes. In my simple preamps I also use rectifiers like 6AX5 or 6BY5, but augmented with two silicon diodes for a bridge
Best regards
Thomas
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