Hi
I am a newbie who is getting brave to build a first tube power amp.
I've been reading some posts about 6bg6/ga tubes with much interest. And I decided to build a power amp with these tubes. And I just ordered a few of them. I do have a pair of opt that are around 8k. Would you point me to some schematics that I could use? I am not looking for a high power. I will be happy with 15-20w. I would like to try triode pp. However, I am very open to your suggestions. I rather have a good sounding amp than to insist on my ignorance. Finally, my speakers are 16ohm and 90+ efficient.
Thank you.
I am a newbie who is getting brave to build a first tube power amp.
I've been reading some posts about 6bg6/ga tubes with much interest. And I decided to build a power amp with these tubes. And I just ordered a few of them. I do have a pair of opt that are around 8k. Would you point me to some schematics that I could use? I am not looking for a high power. I will be happy with 15-20w. I would like to try triode pp. However, I am very open to your suggestions. I rather have a good sounding amp than to insist on my ignorance. Finally, my speakers are 16ohm and 90+ efficient.
Thank you.
look for 6l6 / 807 / 1625 circuits.
Ping Shoog and Miles for info on 807 circuits - they have done a fair bit with them.
In triode and according to the spec sheet you are stuck with a 350V B+ limit and hence not a lot of grunt, HOWEVER - with TV tubes, the datasheet screen (and in fact any) maximums can often be, ahem, conservatively disregarded.
See tubelab's posts for the bleeding edge of this black art.
Do your OPTs have a 16 ohm tap?
Ping Shoog and Miles for info on 807 circuits - they have done a fair bit with them.
In triode and according to the spec sheet you are stuck with a 350V B+ limit and hence not a lot of grunt, HOWEVER - with TV tubes, the datasheet screen (and in fact any) maximums can often be, ahem, conservatively disregarded.
See tubelab's posts for the bleeding edge of this black art.
Do your OPTs have a 16 ohm tap?
aardvarkash10
Thanks for the reply.
Yes, my Opts have 16 ohm tap. And I've done some researches in the past few weeks and found a couple that looked manageable to me.
First http://hollowstate.netfirms.com/DIY_files/777.gif I do have three questions though.
1. Would this circuit suitable for 6bg6?
2. How can I make it a fixed bias amp?
3. And what are those 2 6GX8 in the circuit? Do I need that?
I know these questions may sound pretty stupid. But that's where I am now as a newbie
.
Second http://www.joeltunnah.com/images/6L6amp_schematic.JPG
It looks simple enough for me to follow. But he is using 3.k OPT and mine are 8ks. So, I don't know if the circuit will be suitable for me. May be there is a quick fix that I don't even know about.
I have emailed Shoog before for a different top. He is a great guy. I will definitely email him for this project.
Thanks again.
Thanks for the reply.
Yes, my Opts have 16 ohm tap. And I've done some researches in the past few weeks and found a couple that looked manageable to me.
First http://hollowstate.netfirms.com/DIY_files/777.gif I do have three questions though.
1. Would this circuit suitable for 6bg6?
2. How can I make it a fixed bias amp?
3. And what are those 2 6GX8 in the circuit? Do I need that?
I know these questions may sound pretty stupid. But that's where I am now as a newbie
.Second http://www.joeltunnah.com/images/6L6amp_schematic.JPG
It looks simple enough for me to follow. But he is using 3.k OPT and mine are 8ks. So, I don't know if the circuit will be suitable for me. May be there is a quick fix that I don't even know about.
I have emailed Shoog before for a different top. He is a great guy. I will definitely email him for this project.
Thanks again.
If you have to ask, you really don't want that
Magic eye tube (volume indicator in this particular circuit). No, you don't need it.
You are talking about these specific tubes from this vendor, right?
6BG6 To 6L6 Vacuum Tube List
If you just ordered any old 6BG6GA, you should not assume they can be substituted for a 6L6/807.
6BG6 To 6L6 Vacuum Tube List
If you just ordered any old 6BG6GA, you should not assume they can be substituted for a 6L6/807.
You MIGHT have some tubes that have big internals stuffed in them, for example I bought a batch of 19BG6GA's a while back and some of them were the big plate versions that is typically called "Super 6BG6GA" on the forum. If I were you I would either find a way to verify this or probably play it safe and build a design for true 6BG6GA's, or something designed for 20W sweep tubes.
Even the "Super" version doesn't like to be abused in triode, I found that out the hard way.
Jeff
Any suggestions? I am getting more confused!!!
Could you tell me what you mean by "abuse"? I am not following you at all.
And how about this one then?
http://www.pimmlabs.com/web/Tabor3s.gif
Thanks
Even the "Super" version doesn't like to be abused in triode, I found that out the hard way.
Really? Do you know if was plate dissipation or screen voltage that did them in?
As I have stated in the past the 807, the 1625, and the 6BG6 were all derived from the 6L6GA. Yes some 6BG6GA's were stuffed with 7027A guts but most were not and unless this can be verified by visual comparison, you must assume that you have 19 watt 6BG6's. The 6BG6 is not a true sweep tube and does not behave like most sweep tubes. Many sweep tubes opreate with screen voltages in the 150 volt range. The 6BG6 needs more voltage to operate.
The 6BG6 can be assumed to be a 6L6, a 6L6G, a 6L6GA, or even a 6L6GB. it is NOT a 6L6GC. A schematic for any of the first 4 versions can be used. Note that all of these tubes are rated for 270 volts on the screen including triode operation. I have pushed this to 300 volts in triode, and some tubes will take much more but this is not a given.
The Tabor is probably one of the better designs for this tube type. It is also one of the more complicated and easy to mess up. There are multiple power supplies and CCS circuits and a simple mistake in any of these can fry several parts.
The 6BG6 can be assumed to be a 6L6, a 6L6G, a 6L6GA, or even a 6L6GB. it is NOT a 6L6GC. A schematic for any of the first 4 versions can be used. Note that all of these tubes are rated for 270 volts on the screen including triode operation. I have pushed this to 300 volts in triode, and some tubes will take much more but this is not a given.
The Tabor is probably one of the better designs for this tube type. It is also one of the more complicated and easy to mess up. There are multiple power supplies and CCS circuits and a simple mistake in any of these can fry several parts.
Pushing the screens far beyond their 350 volt rating.
The screens were crying out.
I'm thinkin' you could run these tubes pretty hard with a regulated screen supply.Jeff
Hi George
Thanks for the reply.
English is not my strength and lack of electronic knowledge is not helping me.
Shoog sent me a thread that contains modified version of Tabor. I am studying it really hard now.
Thanks guys
YaHO!
Thanks for the reply.
I should have read other 6bg6ga threads more carefully. I got excited and bought $50 worth of "regular" 6bg6s.
English is not my strength and lack of electronic knowledge is not helping me. That helps a lot!
Actually it looks too challenging for me. It's way above my skill. Do you have any suggestions? Something simple and sound good?
Shoog sent me a thread that contains modified version of Tabor. I am studying it really hard now.
So that's call abuse!
Thanks guys
YaHO!
Shoog's version of Tabor
Here is the Shoog's version of Gary Pimm's Tabor amp. The power supply looks much simpler for me to follow. Hey Shoog, thanks for your kind help!
Shoog supplies 300V to the 807s. So the 6bg6s will not be abused! Right?
http://www.diyaudio.com/forums/atta...my-tabor-clone-finished-tabor-clone-final.jpg
I do have a few questions though.
1. What adjustment do I need to make in order not to use input stage transformer?
2. How can I have one regulating tube per channel.
3. Would you tell me where is the CCS in this circuit? I need to recalculate the current set resistor. But I need to find the circuit first. I thought I was looking for something like this http://www.electro-tech-online.com/...v-out-voltage-regulator-circuit-0to30vreg.jpg
I can't find it. If I don't need it that's fine too.
Well, that reveals my ignorance for the day. I guess that should give me a start.
Thanks again for all your help and patience.
Yaho
Go World cup! May the best team win!
Here is the Shoog's version of Gary Pimm's Tabor amp. The power supply looks much simpler for me to follow. Hey Shoog, thanks for your kind help!
Shoog supplies 300V to the 807s. So the 6bg6s will not be abused! Right?
http://www.diyaudio.com/forums/atta...my-tabor-clone-finished-tabor-clone-final.jpg
I do have a few questions though.
1. What adjustment do I need to make in order not to use input stage transformer?
2. How can I have one regulating tube per channel.
3. Would you tell me where is the CCS in this circuit? I need to recalculate the current set resistor. But I need to find the circuit first. I thought I was looking for something like this http://www.electro-tech-online.com/...v-out-voltage-regulator-circuit-0to30vreg.jpg
I can't find it. If I don't need it that's fine too.
Well, that reveals my ignorance for the day. I guess that should give me a start.
Thanks again for all your help and patience.
Yaho
Go World cup! May the best team win!
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Just to add interest and confusion, Gary's latest take on the Tabor concept is 100% solid state and his input splitter is a take off on his CCS board. Haven't a clue how he does it, but if we agitate him with a barrage of emails he might drop some hints.
The SS amp is just spectacular sounding, uses a nickle core interstage and a 6.6k K push pull OPT from a level 3 Karna set. Taking the Fets up to tube voltages and using transformers makes the amp sound like a tube amp without the usual noise and distortion issues, very sweet, very clear and extremely revealing.
Bud
The SS amp is just spectacular sounding, uses a nickle core interstage and a 6.6k K push pull OPT from a level 3 Karna set. Taking the Fets up to tube voltages and using transformers makes the amp sound like a tube amp without the usual noise and distortion issues, very sweet, very clear and extremely revealing.
Bud
That transformer is the phase splitter. I think he used a mains toroid, might be a good idea to use it if you're going with this design.
Jeff
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