DIY Tube Preamp - Page 3

G · 12th November 2002, 06:28 AM

To get your feet wet I would (personally) recommend that you get the Bottlehead Foreplay, build it, tweak it and then go for the "build it from scratch" preamp (or amp). The Bottlehead site can be found here:

http://www.bottlehead.com/

There is a forum with lots of experienced "Foreplay builders" as well as a plethora (did I say that?) of tried and true tweaks for the preamp. This will get you smelling solder fumes and get your feet wet and is a good design. Whichever path you choose, enjoy.

FBLEAGH · 12th November 2002, 10:30 AM

I just a response from harbuch on the transformer

$112.15 as EI or $77 as toroid.

add 10% for GST in Australia.

good price ??

As for G's post, i looked at the bottlehead foreplay and i know there is heaps of info out there on it , but i would rathe get right in there and build one from scratch. I've already learnt heaps just in researching this much

I tend not to learn as much from kits as i dont have to nut it out to start with.

Cheers
Fbleagh

timc · 12th November 2002, 12:20 PM

Hi Fbleagh,

The transformer prices sound reasonable to me, better than
anything I have been able to find in Australia.

What was the spec? Was it similar to what Brett posted for your original project?
Primary: 230V
Secondary 1: 330V - 0 - 330V at 100 mA for the B+
Secondary 2: 6.3V at 2A for the GZ80
Secondary 3: 8V at 1.5 A for the signal tubes

Regards,
Tim

Joel · 12th November 2002, 03:08 PM

FBLEAGH,

Since you're new to tubes, please start off on the right foot and realize that there is no need to spend lots of money on tubes. Get a "used/tested good" pair of 6sn7's and be on your way. Also, two 6CG7, or even four 6J5's are options if you can't find cheap 6sn7's. Preamp tubes almost never go bad, and due to the number of people obsessed with "NOS", you can pick up used ones for very little cash. You will never know the difference (because there is none).
Just because RCA put a red colored base on a tube doesn't mean it "sounds" better, or works any better.

To answer your question, there is no difference in sound between brands either. Have fun.

Joel

FBLEAGH · 12th November 2002, 08:38 PM

timc, yeah it was the same spec as the one listed above

ie.
Primary: 230V
Secondary 1: 330V - 0 - 330V at 100 mA
Secondary 2: 6.3V at 2A
Secondary 3: 8V at 1.5 A

I am finding that there is much larger range of 12ax7's out there compared to the 6sn7's

are they a good tube ? I know there is a difference in pinouts etc but what sonic differnfce or different driving attributes do they have ?

fdegrove · 12th November 2002, 08:43 PM

Hi,

Quote:

To answer your question, there is no difference in sound between brands either. Have fun.

You can just as well claim that half the population is deaf???

I'm not to claim one tube is better then the other,but saying there that there is difference?

Get real,please.

Joel · 12th November 2002, 08:44 PM

There is a difference in gain. 6SN7 has an ideal voltage gain of 20, 12AX7's is 100. As far as "drive" - I assume you mean current capablity? - 12AX7's idle at under a milliamp, 6SN7's at 8 or 9.

Any old tube manual would be a good investment for you. They are cheap.

Joel

Joel · 12th November 2002, 08:48 PM

Quote:

Originally posted by fdegrove
You can just as well claim that half the population is deaf???
I'm not to claim one tube is better then the other,but saying there that there is difference?

Frank, the phenomena is called a "mass delusion", and is quite well documented. It's like when 500 people see a UFO at the same time...

Get real? My thoughts exactly.

Cheers,
Joel

fdegrove · 12th November 2002, 08:50 PM

hi,

I agree,we are all deaf.

FBLEAGH · 14th November 2002, 11:22 AM

Ok i've been doing more thinking and research.

2 questions

1) instead of getting a custom xformer for this, is there a multi purpose tube transformer i can get ?? ie one i can use on later projects ?? i would imagine lots of secondaires that u can combine.

2) are there any other designs that are worth looking at ?? other topologies etc ?? I jsut want a nice sounding preamp, that i can tweak and modify later, but is a good starting point.

And the kit idea is pretty much out as i cna do this much much cheaper as DIY. I have my sources

Cheers
FBleagh

12th November 2002, 06:28 AM	#21
G diyAudio Member Join Date: Apr 2002 Location: Belleville, IL.	To get your feet wet I would (personally) recommend that you get the Bottlehead Foreplay, build it, tweak it and then go for the "build it from scratch" preamp (or amp). The Bottlehead site can be found here: http://www.bottlehead.com/ There is a forum with lots of experienced "Foreplay builders" as well as a plethora (did I say that?) of tried and true tweaks for the preamp. This will get you smelling solder fumes and get your feet wet and is a good design. Whichever path you choose, enjoy. __________________ Gavin

12th November 2002, 08:50 PM	#29
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	ALL ELSE BEING EQUAL. hi, I agree,we are all deaf. __________________ Frank

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12th November 2002, 10:30 AM	#22
FBLEAGH diyAudio Member Join Date: Sep 2001 Location: Sydney, australia	I just a response from harbuch on the transformer $112.15 as EI or $77 as toroid. add 10% for GST in Australia. good price ?? As for G's post, i looked at the bottlehead foreplay and i know there is heaps of info out there on it , but i would rathe get right in there and build one from scratch. I've already learnt heaps just in researching this much I tend not to learn as much from kits as i dont have to nut it out to start with. Cheers Fbleagh

12th November 2002, 12:20 PM	#23
timc diyAudio Member Join Date: Aug 2001 Location: Melbourne/Australia	Hi Fbleagh, The transformer prices sound reasonable to me, better than anything I have been able to find in Australia. What was the spec? Was it similar to what Brett posted for your original project? Primary: 230V Secondary 1: 330V - 0 - 330V at 100 mA for the B+ Secondary 2: 6.3V at 2A for the GZ80 Secondary 3: 8V at 1.5 A for the signal tubes Regards, Tim

12th November 2002, 03:08 PM	#24
Joel diyAudio Member Join Date: Oct 2002 Location: Brooklyn, NY	FBLEAGH, Since you're new to tubes, please start off on the right foot and realize that there is no need to spend lots of money on tubes. Get a "used/tested good" pair of 6sn7's and be on your way. Also, two 6CG7, or even four 6J5's are options if you can't find cheap 6sn7's. Preamp tubes almost never go bad, and due to the number of people obsessed with "NOS", you can pick up used ones for very little cash. You will never know the difference (because there is none). Just because RCA put a red colored base on a tube doesn't mean it "sounds" better, or works any better. To answer your question, there is no difference in sound between brands either. Have fun. Joel

12th November 2002, 08:38 PM	#25
FBLEAGH diyAudio Member Join Date: Sep 2001 Location: Sydney, australia	timc, yeah it was the same spec as the one listed above ie. Primary: 230V Secondary 1: 330V - 0 - 330V at 100 mA Secondary 2: 6.3V at 2A Secondary 3: 8V at 1.5 A I am finding that there is much larger range of 12ax7's out there compared to the 6sn7's are they a good tube ? I know there is a difference in pinouts etc but what sonic differnfce or different driving attributes do they have ?

12th November 2002, 08:44 PM	#27
Joel diyAudio Member Join Date: Oct 2002 Location: Brooklyn, NY	There is a difference in gain. 6SN7 has an ideal voltage gain of 20, 12AX7's is 100. As far as "drive" - I assume you mean current capablity? - 12AX7's idle at under a milliamp, 6SN7's at 8 or 9. Any old tube manual would be a good investment for you. They are cheap. Joel

14th November 2002, 11:22 AM	#30
FBLEAGH diyAudio Member Join Date: Sep 2001 Location: Sydney, australia	Ok i've been doing more thinking and research. 2 questions 1) instead of getting a custom xformer for this, is there a multi purpose tube transformer i can get ?? ie one i can use on later projects ?? i would imagine lots of secondaires that u can combine. 2) are there any other designs that are worth looking at ?? other topologies etc ?? I jsut want a nice sounding preamp, that i can tweak and modify later, but is a good starting point. And the kit idea is pretty much out as i cna do this much much cheaper as DIY. I have my sources Cheers FBleagh

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