The soldering at the ground point didn't look that good. I made it with a to small soldering iron, so it didn't melt like it should. I had to use my largest one:
Worked out fine
An externally hosted image should be here but it was not working when we last tested it.
Worked out fine
Early on in this thread (post #2) SY wrote:
<<The one modification I'd make is to put a trimpot in the nulling resistor string to adjust out the noise more perfectly- the ratio of the resistors is very sensitive to tube gain.>>
Being the newbie that I am, can someone identify which is the "nulling resistor string" referred to here.
I'm thinking of the 2 resistors (100K) in series with the .47uF capacitor from B+ on the 2nd stage of the preamp at:
http://www.tubecad.com/2005/January/blog0030.htm
Is this correct?
Thanks,
Joe A
<<The one modification I'd make is to put a trimpot in the nulling resistor string to adjust out the noise more perfectly- the ratio of the resistors is very sensitive to tube gain.>>
Being the newbie that I am, can someone identify which is the "nulling resistor string" referred to here.
I'm thinking of the 2 resistors (100K) in series with the .47uF capacitor from B+ on the 2nd stage of the preamp at:
http://www.tubecad.com/2005/January/blog0030.htm
Is this correct?
Thanks,
Joe A
Yes that is correct.
Here is the post where John Broskie shows how to calculate resistors values. Inserting a potentiometer would allow you to dial in precisely.
http://www.tubecad.com/2005/July/blog0051.htm
Thanks Bas for yr reply and info.
I have another question please. Orignally I intended to build the Aikido with ECC88 and 5687 but since the 5687 consumes so much heater current I decided on using 12SL/N7 with a 12V heater regulated supply rated at 2A.
If I use this heater supply for an ECC88 - 5687 Aikido can I wire the 2 5687s for 12V heaters in parallel (each at 0.45A) and the 2 ECC88s in series (at 0.365A) parallel with the 5687s? This way I would have (I'm thinking) 2 x 0.45A and 0.365A - a total of 1.265A @ 12V.
My question is "Will this imbalance between the 0.45A and 0.365A across the 12V supply affect the correct functioning of the valves?
Thanks
JA
I have another question please. Orignally I intended to build the Aikido with ECC88 and 5687 but since the 5687 consumes so much heater current I decided on using 12SL/N7 with a 12V heater regulated supply rated at 2A.
If I use this heater supply for an ECC88 - 5687 Aikido can I wire the 2 5687s for 12V heaters in parallel (each at 0.45A) and the 2 ECC88s in series (at 0.365A) parallel with the 5687s? This way I would have (I'm thinking) 2 x 0.45A and 0.365A - a total of 1.265A @ 12V.
My question is "Will this imbalance between the 0.45A and 0.365A across the 12V supply affect the correct functioning of the valves?
Thanks
JA
Now I have finished the amp. It looks like this:
I get sound, but I also get hum So I started to think about the heaters. They are 6,3VAC for all tubes. The transformer has 6,3V with a centertap. I use the two 3,15V in series to get 6,3V
I hadn't locked the heater potential at all, so I tried what I had: centertap --> 55ohm --> ground. The hum was reduced a bit
Now I'm thinking about a better method to do it.
Maybe two resistors in series between ground and B+, and connect the heater between the resistors?
Which potential do I want for the heaters? 80V?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I get sound, but I also get hum
So I started to think about the heaters. They are 6,3VAC for all tubes. The transformer has 6,3V with a centertap. I use the two 3,15V in series to get 6,3VI hadn't locked the heater potential at all, so I tried what I had: centertap --> 55ohm --> ground. The hum was reduced a bit
Now I'm thinking about a better method to do it.
Maybe two resistors in series between ground and B+, and connect the heater between the resistors?
Which potential do I want for the heaters? 80V?
Hi Olle,
Nice work - please post some pictures of your amp assembled.
Regarding your heater, please have a look at this link. It is from Broskies site and is the same as written in the Rev. B file I sent you. It is written from page 1 - 2.
http://www.tubecad.com/Aikido_9-pin_Mono_Rev-A_PCB.pdf
Hope this helps.
Karsten
Nice work - please post some pictures of your amp assembled
. Regarding your heater, please have a look at this link. It is from Broskies site and is the same as written in the Rev. B file I sent you. It is written from page 1 - 2.
http://www.tubecad.com/Aikido_9-pin_Mono_Rev-A_PCB.pdf
Hope this helps.
Karsten
Mixing 6.3V & 12.6V Heaters
Okay - with regard to my question in post #67 I found the answer in JB's pcb construction manual @:
http://www.tubecad.com/Nine-Pin_Aikido_PCB.pdf
Basically yes, valves with different heater voltages can be wired as suggested in the above post, i.e. Assuming a 12.6V PS, 2 x 12V heater valves can be wired in parallel and 2 x 6.3V heater valves in series, all across the heater supply.
JA
Okay - with regard to my question in post #67 I found the answer in JB's pcb construction manual @:
http://www.tubecad.com/Nine-Pin_Aikido_PCB.pdf
Basically yes, valves with different heater voltages can be wired as suggested in the above post, i.e. Assuming a 12.6V PS, 2 x 12V heater valves can be wired in parallel and 2 x 6.3V heater valves in series, all across the heater supply.
JA
I wasn't pleased with my old scratched aluminum sides, so I made new ones in anodized aluminum! Looks much better:
Before:
New:
Karsten wanted new pictures of the amp assembled, but it have to wait a few days. I have a train to catch! Running now!
Before:
An externally hosted image should be here but it was not working when we last tested it.
New:
An externally hosted image should be here but it was not working when we last tested it.
Karsten wanted new pictures of the amp assembled, but it have to wait a few days. I have a train to catch! Running now!
I took a picture and plugged in the camera, and ran to the train. Now I'm putting up the picture over remote desktop at my home computer
I like the knobs! Old tandberg-gear from the 60's
An externally hosted image should be here but it was not working when we last tested it.
I like the knobs! Old tandberg-gear from the 60's
Hejsan Olle,
Yes, of course I would like som more pictures! Thanks a lot. I am quite sure that I am not the only one who likes to see a lot of DIY-pictures with tube gear
BTW, you wrote that you mounted the resistors for floating your heaters and that the hum was now reduced a lot. As I read it the hum didn´t totally disappear??? I was thinking if you remembered to mount the 0,1 uF capacitor across one of the resistors which is an essential part of floating the heaters?
Very nice pictures and I really like your design. I think it is both nice, funny and cool looking at the same time.
Cheers
Karsten
Yes, of course I would like som more pictures! Thanks a lot. I am quite sure that I am not the only one who likes to see a lot of DIY-pictures with tube gear
BTW, you wrote that you mounted the resistors for floating your heaters and that the hum was now reduced a lot. As I read it the hum didn´t totally disappear??? I was thinking if you remembered to mount the 0,1 uF capacitor across one of the resistors which is an essential part of floating the heaters?
Very nice pictures and I really like your design. I think it is both nice, funny and cool looking at the same time.
Cheers
Karsten
Tjenare Karsten!
There will be more pictures when I come home!
Yes, the hum was reduced, not gone!
And yes, I forgot the capacitor
I will try It right away when I come home! It might do the trick!
About the design: You described it very well!
The chassis is an old printer switch, which I modified a bit. From the beginning the sides was made of plastic...
The power transformer and the choke is taken from old radio gear from the 50's and 60's.
So is the knobs on the front side.
Do you know how I got the handle bars? I bought them cheap at IKEA.
It was a real coincidence i found them! I was walking by the kitchen section, and saw these.
They are normally mounted at kitchen doors, but I thought the suited my new amp!
This is my philosophy! DIY is great fun and doesn't have to be expensive!
This is the coolest printer switch I know!
There will be more pictures when I come home!
Yes, the hum was reduced, not gone!
And yes, I forgot the capacitor
I will try It right away when I come home! It might do the trick!
About the design: You described it very well!
The chassis is an old printer switch, which I modified a bit. From the beginning the sides was made of plastic...
The power transformer and the choke is taken from old radio gear from the 50's and 60's.
So is the knobs on the front side.
Do you know how I got the handle bars? I bought them cheap at IKEA.
It was a real coincidence i found them! I was walking by the kitchen section, and saw these.
They are normally mounted at kitchen doors, but I thought the suited my new amp!
This is my philosophy! DIY is great fun and doesn't have to be expensive!
This is the coolest printer switch I know!
How to reduce the gain of my Aikido
I know this is more like Ollebolle's thread but since my question concerns this preamp, I'm going to post it here.
I just finished my 12SL/SN7 Aikido (pt-2-pt) and it sounds good. It is still running in but there doesn't seem any nasties (hum, buzz, etc).
However, I have too much gain for my SE power amp (Morrison's 6SJ7 - 6L6GC). As soon as I slightly wind up the volume the sound becomes overbearing.
How can I reduce the gain without too much modifications? Will decreasing the volume pot to 22K (instead of 50K) help?
Thanks for comments and replies.
JA
I know this is more like Ollebolle's thread but since my question concerns this preamp, I'm going to post it here.
I just finished my 12SL/SN7 Aikido (pt-2-pt) and it sounds good. It is still running in but there doesn't seem any nasties (hum, buzz, etc).
However, I have too much gain for my SE power amp (Morrison's 6SJ7 - 6L6GC). As soon as I slightly wind up the volume the sound becomes overbearing.
How can I reduce the gain without too much modifications? Will decreasing the volume pot to 22K (instead of 50K) help?
Thanks for comments and replies.
JA
Regarding the hum:
in one of your pics you show the ground connected right to the chassis. Thats great, but can often be a bit hummy. It would be worth your while (and no harm) to use a pair of diodes wired back to back and then parallelled with a 10R/<5W resistor and a 0.01uF cap. See the rough schematic in the top right of the pic below which shows what I mean for an aleph I built. It makes a fair difference.
Use >1A rated diodes, >5W resistor and the cap, all at a high enough voltage rating to stand the B+/mains supply.
Fran
in one of your pics you show the ground connected right to the chassis. Thats great, but can often be a bit hummy. It would be worth your while (and no harm) to use a pair of diodes wired back to back and then parallelled with a 10R/<5W resistor and a 0.01uF cap. See the rough schematic in the top right of the pic below which shows what I mean for an aleph I built. It makes a fair difference.
An externally hosted image should be here but it was not working when we last tested it.
Use >1A rated diodes, >5W resistor and the cap, all at a high enough voltage rating to stand the B+/mains supply.
Fran