aikido problem

jayme · 18th October 2006, 07:37 PM

Ok. Just finished my Aikido-based preamp, using 4 6SN7s.

I plugged it in...and a bit of hum, and it is volume-knob level dependent.

But, the big problem is that the GAIN is outrageous...I barely move the volume-knob from the lowest level and the music is waaaay too loud.

The 6SN7 Aikido should give me around 20DB of total gain, which is not too much off of my Grounded Grid at 12DB of gain. And, on that preamp...I can use the entire range of the volume knob...

I am lost...Any thoughts as to where to start investigating?

HollowState · 18th October 2006, 07:44 PM

Hi jayme,

Just off the top of my head, it sounds like you have a wiring error. Recheck everything around the area of the control, including the control itself. Also proper grounding.

Victor

jayme · 18th October 2006, 08:28 PM

I had one loose connection on the board...fixed that which took care of the variable hum. There is still a bit of hum...but it's not bad now.

But the overall gain is still an issue.

My pot is wired correctly, and grounded. The rest of the ground connections check out.

ErikdeBest · 18th October 2006, 09:28 PM

Hi Jayme

Are you able to measure in and output at the same time (using a 2 channel osciloscope)? Play a 1V RMS tone and see what exactly is coming out at the output. Or maybe just a DVM with fine AC reading...play a 60Hz tone (simple DVM's measure the best at this range, I've been told), measure input...don't change anything and than measure output. Crude, but can shed some light!

Erik

jayme · 18th October 2006, 09:59 PM

I have a DVM, but no oscilloscope. I'll try to measure the output voltage...

I have found that my B+ is higher than I expected, at 337V. I was shooting for around 300V. I have 330R grid resistors, with 1000R cathode resistors on the input tubes and 300R cathode resistors on the output tubes.

I am new to tube math...does the higher B+ give a larger swing to the signal output voltage?

Geek · 18th October 2006, 10:01 PM

Quote:

Originally posted by jayme
But, the big problem is that the GAIN is outrageous...I barely move the volume-knob from the lowest level and the music is waaaay too loud.

That part almost sounds like you have a linear pot (B) rather than an audio taper (A) type in there.

Original Burnedfingers · 18th October 2006, 10:12 PM

jayme,

My point to point 6sn7 is very quiet. My speakers are over 100db
1W 1M and I can barely hear a very slight hiss if I get my head touching them.

As stated above you need to check the VC to see what the taper is. I run CD's at about 9-10 oclock setting without problems.

With respect to tubes.... the 5692's are sweet but the Russian 1578 is even better. The 1578 carries two numbers as its a military grade tube. 6N8S/1578 Nice tube with a nickle base. I picked up two pair on ebay.

jayme · 18th October 2006, 10:13 PM

It's the standard pot from the Transcendent Grounded Grid kit...I used a stepped attenuator in that project instead of it.

So, I am pretty sure it is a Audio Taper pot...

tinear9 · 19th October 2006, 01:26 AM

The Aikido gain s/b about half the MU (10 in this case, not 20). Puzzling.

jayme · 19th October 2006, 02:03 AM

Quote:

Originally posted by tinear9
The Aikido gain s/b about half the MU (10 in this case, not 20). Puzzling.

Yes, a gain of 10 (which equates to 20dB).

http://tubecad.com/2006/05/blog0064.htm

18th October 2006, 07:37 PM	#1
jayme diyAudio Member Join Date: Sep 2005	aikido problem Ok. Just finished my Aikido-based preamp, using 4 6SN7s. I plugged it in...and a bit of hum, and it is volume-knob level dependent. But, the big problem is that the GAIN is outrageous...I barely move the volume-knob from the lowest level and the music is waaaay too loud. The 6SN7 Aikido should give me around 20DB of total gain, which is not too much off of my Grounded Grid at 12DB of gain. And, on that preamp...I can use the entire range of the volume knob... I am lost...Any thoughts as to where to start investigating?

19th October 2006, 01:26 AM	#9
tinear9 diyAudio Member Join Date: Aug 2003 Location: Phoenix, AZ	Aikido Gain The Aikido gain s/b about half the MU (10 in this case, not 20). Puzzling.

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18th October 2006, 07:44 PM	#2
HollowState diyAudio Member Join Date: Aug 2006 Location: Taxland, New Jersey	Hi jayme, Just off the top of my head, it sounds like you have a wiring error. Recheck everything around the area of the control, including the control itself. Also proper grounding. Victor

18th October 2006, 08:28 PM	#3
jayme diyAudio Member Join Date: Sep 2005	I had one loose connection on the board...fixed that which took care of the variable hum. There is still a bit of hum...but it's not bad now. But the overall gain is still an issue. My pot is wired correctly, and grounded. The rest of the ground connections check out.

18th October 2006, 09:28 PM	#4
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Hi Jayme Are you able to measure in and output at the same time (using a 2 channel osciloscope)? Play a 1V RMS tone and see what exactly is coming out at the output. Or maybe just a DVM with fine AC reading...play a 60Hz tone (simple DVM's measure the best at this range, I've been told), measure input...don't change anything and than measure output. Crude, but can shed some light! Erik

18th October 2006, 09:59 PM	#5
jayme diyAudio Member Join Date: Sep 2005	I have a DVM, but no oscilloscope. I'll try to measure the output voltage... I have found that my B+ is higher than I expected, at 337V. I was shooting for around 300V. I have 330R grid resistors, with 1000R cathode resistors on the input tubes and 300R cathode resistors on the output tubes. I am new to tube math...does the higher B+ give a larger swing to the signal output voltage?

18th October 2006, 10:12 PM	#7
Original Burnedfingers diyAudio Member Join Date: Nov 2002	jayme, My point to point 6sn7 is very quiet. My speakers are over 100db 1W 1M and I can barely hear a very slight hiss if I get my head touching them. As stated above you need to check the VC to see what the taper is. I run CD's at about 9-10 oclock setting without problems. With respect to tubes.... the 5692's are sweet but the Russian 1578 is even better. The 1578 carries two numbers as its a military grade tube. 6N8S/1578 Nice tube with a nickle base. I picked up two pair on ebay.

18th October 2006, 10:13 PM	#8
jayme diyAudio Member Join Date: Sep 2005	It's the standard pot from the Transcendent Grounded Grid kit...I used a stepped attenuator in that project instead of it. So, I am pretty sure it is a Audio Taper pot...

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