Hi,
I'm new to this forum and only 17 years old. I'm just wondering if anyone has, or can write up a very SIMPLE audio amp schematic using a 6AQ5 tube for a preamp and 1 6CA7 for the power amp. and I mean really simple, im looking for 1 input 1 output, maybe a single pot for Gain.
I have at my dispossle:
1 breadboard.
many assorted wires.
2 6CA7 power tubes.
1 6AQ5 tube
Many assorted resistor's, capacitor's,
switch's and diodes.
1 speaker,
1 microphone.
1 1m pot
1 10k pot
1 100k pot
2 1/4 inch female plug's
Ill be using any and all safety precautions when building this, im just looking for the simplest design for a audio amp curcuit.
I want to start out with just a preamp first and get the curcuit operational before adding in the 6CA7 tube, As I've read a single 6CA7 can produce 11 watts which should be sufficent
Any help with this little project would be GREATLY apreciated!!
Thank You,
Weston
I'm new to this forum and only 17 years old. I'm just wondering if anyone has, or can write up a very SIMPLE audio amp schematic using a 6AQ5 tube for a preamp and 1 6CA7 for the power amp. and I mean really simple, im looking for 1 input 1 output, maybe a single pot for Gain.
I have at my dispossle:
1 breadboard.
many assorted wires.
2 6CA7 power tubes.
1 6AQ5 tube
Many assorted resistor's, capacitor's,
switch's and diodes.
1 speaker,
1 microphone.
1 1m pot
1 10k pot
1 100k pot
2 1/4 inch female plug's
Ill be using any and all safety precautions when building this, im just looking for the simplest design for a audio amp curcuit.
I want to start out with just a preamp first and get the curcuit operational before adding in the 6CA7 tube, As I've read a single 6CA7 can produce 11 watts which should be sufficent
Any help with this little project would be GREATLY apreciated!!
Thank You,
Weston
You will need more 6AQ5's, but they can be had for a relatively low price. This is the Moebius that was suggested above.
http://www.audiotropic.net/Projects/Mobius/linePre6AQ5.gif
For more 6AQ5's check here:
http://www.surplussales.com/
I would check this tread out too since the 6AQ5 is more or less a 7-pin 6V6.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=102352&highlight=6V6
As for the 6CA7's, may I suggest the Tubelab Simple SE. A simple design with a full PCB available and lots of support from DIY Audio, both from builders and from the designer himself. You would have to invest in a 12AT7 but they are fairly cheap. If you hit surplus and garage sales you can probably find some, I picked some up for $0.25 each not to long ago. The 12AT7 can also be bought new for around $7 to $10. The 5AR4 rectifier is optional as the board also has previsions for SS diodes, but a new stock 5AR4 would run about $10 to $15. The majority of the parts can be ordered from Digikey or Mouser and there is a full build manual with parts list on the Tubelab site. All in all, using Edcor output transformers (the $20 ones, don't let the price fool you, great transformers), this amp can be built for around $200. Check out Allied for the power iron and some of the parts as well. It is also very friendly to tube rolling, with some tweaks it can use just about any octal out there.
http://www.tubelab.com/SimpleSE.htm
Could also go the other way, pick up some more 6AQ5's, and build this:
http://homepage.mac.com/planet10/forum/elCheapo-23jun06-map.gif
Great little amp that again would weigh in at around $200 mark, give or take, depends on what you already have.
Cheers
James
http://www.audiotropic.net/Projects/Mobius/linePre6AQ5.gif
For more 6AQ5's check here:
http://www.surplussales.com/
I would check this tread out too since the 6AQ5 is more or less a 7-pin 6V6.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=102352&highlight=6V6
As for the 6CA7's, may I suggest the Tubelab Simple SE. A simple design with a full PCB available and lots of support from DIY Audio, both from builders and from the designer himself. You would have to invest in a 12AT7 but they are fairly cheap. If you hit surplus and garage sales you can probably find some, I picked some up for $0.25 each not to long ago. The 12AT7 can also be bought new for around $7 to $10. The 5AR4 rectifier is optional as the board also has previsions for SS diodes, but a new stock 5AR4 would run about $10 to $15. The majority of the parts can be ordered from Digikey or Mouser and there is a full build manual with parts list on the Tubelab site. All in all, using Edcor output transformers (the $20 ones, don't let the price fool you, great transformers), this amp can be built for around $200. Check out Allied for the power iron and some of the parts as well. It is also very friendly to tube rolling, with some tweaks it can use just about any octal out there.
http://www.tubelab.com/SimpleSE.htm
Could also go the other way, pick up some more 6AQ5's, and build this:
http://homepage.mac.com/planet10/forum/elCheapo-23jun06-map.gif
Great little amp that again would weigh in at around $200 mark, give or take, depends on what you already have.
Cheers
James
The Moebius looks very inticing, I think I will go for that.
I've changed my plans for this little project, since I own and run a recording studio out of my home I think ill try and make just a preamp for the microphones, no power amp. which means I wont need the 6CA7's. Anyone know where I can get 4 mounts for the 4 6AQ5's?
Oh and before I go for 6AQ5's im wondering if I should go with better tube's? perhaps some 12AX7's? Any suggestions on better preamp tubes?
I'll also need this to have balanced inputs & outputs aswell.
How can I add in transformer balancing to the in's and outs on the moebius schematic? What transformers will I need?
And thank you for helping me out here, I appreciate it!
Weston
I've changed my plans for this little project, since I own and run a recording studio out of my home I think ill try and make just a preamp for the microphones, no power amp. which means I wont need the 6CA7's. Anyone know where I can get 4 mounts for the 4 6AQ5's?
Oh and before I go for 6AQ5's im wondering if I should go with better tube's? perhaps some 12AX7's? Any suggestions on better preamp tubes?
I'll also need this to have balanced inputs & outputs aswell.
How can I add in transformer balancing to the in's and outs on the moebius schematic? What transformers will I need?
And thank you for helping me out here, I appreciate it!
Weston
och the noo...
ummm, with all the little changes you suggest, suddenly you don't have a moebius any more... I think you need to more clearly define your design goals. Either this project is aimed at maximising the use of available parts, or you ar eprepared ot start from scratch. Either it is a pre- for a specific use (a microphone being substantially different to a CDP as a source) or its an integrated for pleasant noodling. Good luck - and welcome to the DIY toobies dillema!
ummm, with all the little changes you suggest, suddenly you don't have a moebius any more... I think you need to more clearly define your design goals. Either this project is aimed at maximising the use of available parts, or you ar eprepared ot start from scratch. Either it is a pre- for a specific use (a microphone being substantially different to a CDP as a source) or its an integrated for pleasant noodling. Good luck - and welcome to the DIY toobies dillema!
I don't know much about mic preamps so can't help you there. However if this will be used for mics I would shy away from the 6AQ5, Poinz (and I am sure others) found them to be microphonic in the Moeb preamp, now he is playing with 6T4's. If this will be used for home audio and you need balanced you could try something like this:
http://www.nutshellhifi.com/Raven-MarkII.gif
Transformers from Lundahl but Sowter also makes some specifically for this line amp.
Like I said, for mic I can't help much, but I can say you could look to Lundahl for mic iron too. Also Electra-Print, great iron and custom wound to whatever you need; Jack is a great guy too, just an added bonus. If you have 12AX7's great, but they are a "hot" tube so NOS prices are sky high. Luckily they are also still made by lots of tube companies. 12AT7's deserve a look, along with maybe 12AZ7's, 12AY7's, 6SL7's, EF86's, 6J7's...all medium high to high gain triodes and petodes. 6J7 for example was used for years by RCA in high gain low noise photo input sections on theater amps. The EF86 is kind of a continuation of this tube, different specs and 9-pin, but still low noise high gain. NOS EF86's command high price points, but are also still made today. (I may regret saying this, but it seems this tube is fairly undiscovered, or maybe disliked, IDK) NOS 6J7's can still be had on the cheap, the down side is a cap to deal with, but no worries, it is just a grid cap. I would go out on a limb and say that the 6J7's bests the popular 6SJ7.
Cheers
James
http://www.nutshellhifi.com/Raven-MarkII.gif
Transformers from Lundahl but Sowter also makes some specifically for this line amp.
Like I said, for mic I can't help much, but I can say you could look to Lundahl for mic iron too. Also Electra-Print, great iron and custom wound to whatever you need; Jack is a great guy too, just an added bonus. If you have 12AX7's great, but they are a "hot" tube so NOS prices are sky high. Luckily they are also still made by lots of tube companies. 12AT7's deserve a look, along with maybe 12AZ7's, 12AY7's, 6SL7's, EF86's, 6J7's...all medium high to high gain triodes and petodes. 6J7 for example was used for years by RCA in high gain low noise photo input sections on theater amps. The EF86 is kind of a continuation of this tube, different specs and 9-pin, but still low noise high gain. NOS EF86's command high price points, but are also still made today. (I may regret saying this, but it seems this tube is fairly undiscovered, or maybe disliked, IDK) NOS 6J7's can still be had on the cheap, the down side is a cap to deal with, but no worries, it is just a grid cap. I would go out on a limb and say that the 6J7's bests the popular 6SJ7.
Cheers
James
Hi, Thanks for all the info everyone!
Victoria:
Sail number? huh?
aardvarkash10:
Well, my design goal did change I was just planning on tinkering iwth some tubes, but i figured if I can manage to build a preamp for $200, I would do that, since I need preamp's in my studio for recording and most preamp's that are 100% tube are anywhere from $500 to $7,000. The "Moebius" looked like a good schematic I just figured that I could add to it and make it have balanced in's and out's since that is a requirment since studios need 100% hum/noise-free conditions. I am more of starting fom scrap parts, I would like to find out what else I need and how much it would cost to build a modified Moebius.
JPeitzman:
Thanks for the heads up on the 6AQ5's, however the Raven is a bit more complex I dont think im skilled enough to build something like that. and im not sure about using different tubes in the "Moebius"? Not sure about compatibility. Like I said im new to this forum and am fairly new to tube circuit designs.
What would you suggest for a better audio qaulity tube that is compatible with the "Moebius"?
Stuey:
Thanks!
Thank you all for your help!
Weston
Victoria:
Sail number? huh?
aardvarkash10:
Well, my design goal did change I was just planning on tinkering iwth some tubes, but i figured if I can manage to build a preamp for $200, I would do that, since I need preamp's in my studio for recording and most preamp's that are 100% tube are anywhere from $500 to $7,000. The "Moebius" looked like a good schematic I just figured that I could add to it and make it have balanced in's and out's since that is a requirment since studios need 100% hum/noise-free conditions. I am more of starting fom scrap parts, I would like to find out what else I need and how much it would cost to build a modified Moebius.
JPeitzman:
Thanks for the heads up on the 6AQ5's, however the Raven is a bit more complex I dont think im skilled enough to build something like that. and im not sure about using different tubes in the "Moebius"? Not sure about compatibility. Like I said im new to this forum and am fairly new to tube circuit designs.
What would you suggest for a better audio qaulity tube that is compatible with the "Moebius"?
Stuey:
Thanks!
Thank you all for your help!
Weston
hiya lightning
whatever you do, you'll learn from it! Speak with poinz about the moebius - he's very accomodating and approachable, just ping him on this forum and wait a day or two - he will come through. He has tried a range of different tubes in the design and has some ideas on what alternatives will and won't work. I have one half built myself (usual story - fired with enthusiasm and held back by ignorance...) and will be using "available tubes" that will be identified after breadboarding. THere are a couple of techniques to get your balanced input - look for the easiest to source and impliment, then give it a go! Input transformer is probably the quickest solution...
whatever you do, you'll learn from it! Speak with poinz about the moebius - he's very accomodating and approachable, just ping him on this forum and wait a day or two - he will come through. He has tried a range of different tubes in the design and has some ideas on what alternatives will and won't work. I have one half built myself (usual story - fired with enthusiasm and held back by ignorance...) and will be using "available tubes" that will be identified after breadboarding. THere are a couple of techniques to get your balanced input - look for the easiest to source and impliment, then give it a go! Input transformer is probably the quickest solution...
No worries, I am still pretty new here too. As for different tubes, just about any tube will work in a SRPP arrangement like the Moeb. Last I knew Poinz was liking the 6T4 because it used the same socket and specs similar to the 6AQ5 but is a lot less microphonic; also a triode so the socket is wired a bit different but not a big problem. I will attach the schematic of the Moeb with the 6T4's in place of the 6AQ5. I am not sure though if you use it for mics if the Moeb will give you enough gain. That is why I mentioned the 6SL7, 12AX7, 12AT7, and EF86, much higher gain and still low noise.
For a monitor or something of that nature it should work great. It gives a nice low Zout (aprox 200 ohms i think) and enough drive to push fairly long cables. Of course the Raven will do the same as far as being able to drive anything, but is more complex and will cost a lot more. Balanced in and out can be done on the Moeb by using input and output transformers. You don't need gaped outputs either, just get some nice parafeed output iron and a nice cap. If you went that route I would say talk to Jack at Electra-Print or Kevin at K&K Audio (Lundahl).
Check out Bottlehead too. Kits through them are reasonably priced, offer awesome performance, and Doc B. might be able to give you some advice on something custom. He has a custom version of the Seduction Phono to be used with tapes so maybe he can whip something up custom for mics and send it to you as a kit. You would get something that you know will be well designed but can still put together yourself. For a line amp the Foreplay is also a great kit with lots of options available to it. Just some options!
Cheers and happy listening / good luck building!
James
edit: http://www.bottlehead.com/
For a monitor or something of that nature it should work great. It gives a nice low Zout (aprox 200 ohms i think) and enough drive to push fairly long cables. Of course the Raven will do the same as far as being able to drive anything, but is more complex and will cost a lot more. Balanced in and out can be done on the Moeb by using input and output transformers. You don't need gaped outputs either, just get some nice parafeed output iron and a nice cap. If you went that route I would say talk to Jack at Electra-Print or Kevin at K&K Audio (Lundahl).
Check out Bottlehead too. Kits through them are reasonably priced, offer awesome performance, and Doc B. might be able to give you some advice on something custom. He has a custom version of the Seduction Phono to be used with tapes so maybe he can whip something up custom for mics and send it to you as a kit. You would get something that you know will be well designed but can still put together yourself. For a line amp the Foreplay is also a great kit with lots of options available to it. Just some options!
Cheers and happy listening / good luck building!
James
edit: http://www.bottlehead.com/
Attachments
Forgot this little snip. Make the output transformer balanced output and add something at the front to accept balanced input...just something else to muddy up the waters!
http://www.tubecad.com/2007/05/08/cathode-coupled amplifier with output transformer.png
Here is the full entry, go down near the bottem.
http://www.tubecad.com/2007/05/blog0106.htm
Cheers
James
http://www.tubecad.com/2007/05/08/cathode-coupled amplifier with output transformer.png
Here is the full entry, go down near the bottem.
http://www.tubecad.com/2007/05/blog0106.htm
Cheers
James
Just a note on those sockets:
Don't use the Chinese 7-pin mini with the 2-piece ceramic body held together by the center terminal; the ones that every vendor seems to have. They are the pitz, and only grip the pins the first time or two. I got a Mœbie rejected from review by a very prestigious online 'zine because of those damned things. Very humiliating.
Auwe!
Poinz
Don't use the Chinese 7-pin mini with the 2-piece ceramic body held together by the center terminal; the ones that every vendor seems to have. They are the pitz, and only grip the pins the first time or two. I got a Mœbie rejected from review by a very prestigious online 'zine because of those damned things. Very humiliating.
Auwe!
Poinz
Ok, I've attached a modified version of the Moebius.
I'm not sure if this will work, kind of guessing. Do you think that would work for balancing? (this is the 6T4 version)
I'm also not sure what transformers to use for the balancing.
Also, i'm not certain if I would need any modifications to the power supply curcuit to handle 2 sides, left and right and the 4 tube's it would have to power?
Thanks,
I'm not sure if this will work, kind of guessing. Do you think that would work for balancing? (this is the 6T4 version)
I'm also not sure what transformers to use for the balancing.
Also, i'm not certain if I would need any modifications to the power supply curcuit to handle 2 sides, left and right and the 4 tube's it would have to power?
Thanks,
Attachments
To my knowledge it looks good except that I am pretty sure you don't need the 18k resistors on the output. Also I am sure it is fine but you could play a bit with the value of the cap on the output.
This is just off the top of my head for a 1:1 input (no additional gain needed) the LL1690 for input; LL1676 or LL1674 for output, Lundahl options. There are others out there more versed in low level transformer selection than I; also like I said, off the top of my head.
Cheers
James
This is just off the top of my head for a 1:1 input (no additional gain needed) the LL1690 for input; LL1676 or LL1674 for output, Lundahl options. There are others out there more versed in low level transformer selection than I; also like I said, off the top of my head.
Cheers
James
The transformer on the input looks superfluous to me, since the circuit takes a single-ended signal on the input grid. You might as well just connect whichever pole of the balanced input to the grid that gives you the polarity out that you want, and float or ground the other side as happens with the transformer. Am I missing something? I admit that I am inexperienced at balanced operation.
The 18K resistor across the output is the loading resistance. The circuit 'likes' to see 15-17K as a load for best sound. Lighter (higher) will sound a little tight and shallow, and heavier (lower ohms) will start to sound a little soft and 'tubey'. The 18K is for the standared 100K or so tube amp Zin. For guys who will be driving a sand amp with 20-25K Zin, I use a 39K or 47K there.
I mentioned in the other 6AQ5 thread that I have found The Answer for power transformer duty, the Antek AN-0232. It's a 25VA toroid with two 32V secondaries which will give 68-70V in series at our 7W burn. Voltage doubler rectification and the same filter, 135-140Vdc for the B+. It also can be used for any wall voltage, having dual 115V primaries. I'll try to draw a picture in the next day or two.
Aloha,
Poinz
The 18K resistor across the output is the loading resistance. The circuit 'likes' to see 15-17K as a load for best sound. Lighter (higher) will sound a little tight and shallow, and heavier (lower ohms) will start to sound a little soft and 'tubey'. The 18K is for the standared 100K or so tube amp Zin. For guys who will be driving a sand amp with 20-25K Zin, I use a 39K or 47K there.
I mentioned in the other 6AQ5 thread that I have found The Answer for power transformer duty, the Antek AN-0232. It's a 25VA toroid with two 32V secondaries which will give 68-70V in series at our 7W burn. Voltage doubler rectification and the same filter, 135-140Vdc for the B+. It also can be used for any wall voltage, having dual 115V primaries. I'll try to draw a picture in the next day or two.
Aloha,
Poinz
Ok, I think I got enough information on parts, Thanks for the info on the lundahl transformers JPeitz, I'll look into them.
Now I need some other information... like:
Whats the freq response of this preamp?
Whats the max gain before clip?
Whats the line out? -10dBV or 4+dBu?
Whats the maxium output level?
Whats the signal to noise ratio?
Whats the range of the gain pot? (in dB's)
That is infact if anyone knows these spec's
Thanks,
Now I need some other information... like:
Whats the freq response of this preamp?
Whats the max gain before clip?
Whats the line out? -10dBV or 4+dBu?
Whats the maxium output level?
Whats the signal to noise ratio?
Whats the range of the gain pot? (in dB's)
That is infact if anyone knows these spec's
Thanks,
Anyone? Anyone!?
Whats the freq response of this preamp?
With the 6T4 and 2.2µF on the output, 10Hz - 200KHz +0 -1dB
Whats the max gain before clip?
This is a meaningless spec. The gain, under all circumstances, is ~6 (15dB)
Whats the line out? -10dBV or 4+dBu?
This is a pro spec, the meaning of which I do not know.
Whats the maxium output level?
Vg-k is 1.6V, so at the 6.0Av, the circuit will swing 9.6Vpk at the onset of soft clipping, or 6.8Vac (Vrms).
Whats the signal to noise ratio?
Hum + noise is constant at ~20-40µV (.02 - .04mV), depending on the individual tubes, so S/N will depend on signal level.
Whats the range of the gain pot? (in dB's)
Circuit range, with the pot, is from 0 output to full 6.8Vac output. In dB, of course, this would be approximately equal to infinity (minus the hum+noise value). This amounts to (in hi-fi terms) another non-spec.
Aloha,
Poinz
Whats the freq response of this preamp?
With the 6T4 and 2.2µF on the output, 10Hz - 200KHz +0 -1dB
Whats the max gain before clip?
This is a meaningless spec. The gain, under all circumstances, is ~6 (15dB)
Whats the line out? -10dBV or 4+dBu?
This is a pro spec, the meaning of which I do not know.
Whats the maxium output level?
Vg-k is 1.6V, so at the 6.0Av, the circuit will swing 9.6Vpk at the onset of soft clipping, or 6.8Vac (Vrms).
Whats the signal to noise ratio?
Hum + noise is constant at ~20-40µV (.02 - .04mV), depending on the individual tubes, so S/N will depend on signal level.
Whats the range of the gain pot? (in dB's)
Circuit range, with the pot, is from 0 output to full 6.8Vac output. In dB, of course, this would be approximately equal to infinity (minus the hum+noise value). This amounts to (in hi-fi terms) another non-spec.
Aloha,
Poinz
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.