I have opened a webpage about this project
845 Amplifier with only two stages
Now I am waiting the final version of 2:1 Bartolucci interstage transformers
845 Amplifier with only two stages
Now I am waiting the final version of 2:1 Bartolucci interstage transformers
For the version 1 I cannot find other choice than this:
M-CAP® Supreme Silver / Gold & Oil 2.2uF 1200V dc
M-CAP® Supreme Silver / Gold & Oil 2.2uF 1200V dc
I have received the last Bartolucci interstage.
Finished all the measurements on both the versions.
845 Amplifier with only two stages
The version 2 have the same frequency band but give a better sound because does not use the interstage capacitor.
In both case the band is limited only by the output transformers.
Finished all the measurements on both the versions.
845 Amplifier with only two stages
The version 2 have the same frequency band but give a better sound because does not use the interstage capacitor.
In both case the band is limited only by the output transformers.
Finally arrived all the Bartolucci transformers to complete my 813/GM70 amp
813 / GM70 amplifier with Bartolucci transformers
813 / GM70 amplifier with Bartolucci transformers
Last edited:
2 stage GM70
Hello
Can I use these interstage transformer to drive my GM70 tube with D3A or with any other tube..
2 X SESCOM MI-13 INTERSTAGE TRANSFORMER | eBay
Unfortunately I can't afford to go with Tango interstage, I live on disability support unfortunately because I had car accident with bike.😱
I try to find some solution so I can put together my GM70.
Any help, comment welcome!😉
Greetings gabor
Hello
Can I use these interstage transformer to drive my GM70 tube with D3A or with any other tube..
2 X SESCOM MI-13 INTERSTAGE TRANSFORMER | eBay
Unfortunately I can't afford to go with Tango interstage, I live on disability support unfortunately because I had car accident with bike.😱
I try to find some solution so I can put together my GM70.
Any help, comment welcome!😉
Greetings gabor
Attachments
I think those would be worth trying if you have them, provided you aren't planning to run the GM70 in A2. With A1 you won't have to worry about DC current in the grid winding.
Hello
Thank you for your reply!
I do not have them but I can afford these or similar price interstage.
I want to be sure if I invest in them I can use them.
15K:15K a bit to high com pare to the 5K Andrea uses, I don't know.
I'll wait on more opinion. Or may be someone know better solution (what would feet better these amp)
Greetings gabor
Thank you for your reply!
I do not have them but I can afford these or similar price interstage.
I want to be sure if I invest in them I can use them.
15K:15K a bit to high com pare to the 5K Andrea uses, I don't know.
I'll wait on more opinion. Or may be someone know better solution (what would feet better these amp)
Greetings gabor
Hi!
They don't seem to be able to handle DC in the primary, at least nothing printed on them. Given their size they are probably not meant for DC. So they wouldbe good for parafeed drive only.
If you ask me for my opinion: use another tube. The D3A is a poor choice as a driver tube for transmitting output tubes IMHO
Thomas
They don't seem to be able to handle DC in the primary, at least nothing printed on them. Given their size they are probably not meant for DC. So they wouldbe good for parafeed drive only.
If you ask me for my opinion: use another tube. The D3A is a poor choice as a driver tube for transmitting output tubes IMHO
Thomas
Hello
Thank you for your opinion!
What would be your advise as a driver tube?
That would need interstage or with out?
Please let me know
You can send PM to gaborzoltan2@gmail.com
Greetings Gabor
Thank you for your opinion!
What would be your advise as a driver tube?
That would need interstage or with out?
Please let me know
You can send PM to gaborzoltan2@gmail.com
Greetings Gabor
Hi!
If you follow my posts on this forum, I'm advocating good headroom. At least 6dB. That means the driver tube should be able to deliver twice as much voltage swing as is needed to drive the output tube to full power.
Also keep in mind grid current effects start to kick in at bias voltages smaller than -1V. If you want to stay clear of that range, the available voltage from the D3A is limited.
Of course it all also depends on the op point of your ouput tube, that determines the required voltage swing.
Also depends on your gain requirements
This is a general choice which you probabaly should make together with the other points above to be able to determine your driver tube.
You can check the schematics on my blog for some ideas, especially the 211 amp schematic, which uses a 6HS5 driver
Thomas
If you follow my posts on this forum, I'm advocating good headroom. At least 6dB. That means the driver tube should be able to deliver twice as much voltage swing as is needed to drive the output tube to full power.
Also keep in mind grid current effects start to kick in at bias voltages smaller than -1V. If you want to stay clear of that range, the available voltage from the D3A is limited.
Of course it all also depends on the op point of your ouput tube, that determines the required voltage swing.
Also depends on your gain requirements
This is a general choice which you probabaly should make together with the other points above to be able to determine your driver tube.
You can check the schematics on my blog for some ideas, especially the 211 amp schematic, which uses a 6HS5 driver
Why start a public discussion, and then take it off line ??? The purpose of a forum is public sharing of opinions, no ???
Thomas
Hello Thomas
Some people does not want to share their experience in public, so for that reason I gave my email address.
I'm interested to see your, schematic. That is available on your personal website or somewhere on the forum?
Thanks one more time for your answer!
Greetings Gabor
Some people does not want to share their experience in public, so for that reason I gave my email address.
I'm interested to see your, schematic. That is available on your personal website or somewhere on the forum?
Thanks one more time for your answer!
Greetings Gabor
Hi gabor,
My 211 schematic can be found here:
VinylSavor: Making of a 211 Amplifier, Part 1: Planning
Assembly process of the amp:
VinylSavor: Making of a 211 amplifier, Part 2: Assembly
Final result:
VinylSavor: Making of a 211 amplifier, Part 3: Listening
There are other projects also on my blog, just browse through the various articles.
Also maybe of interest. my view on gain vs headroom vs power:
VinylSavor: Gain, Headroom and Power
and about op points:
VinylSavor: The search for that 'magical' operating point
Best regards
Thomas
My 211 schematic can be found here:
VinylSavor: Making of a 211 Amplifier, Part 1: Planning
Assembly process of the amp:
VinylSavor: Making of a 211 amplifier, Part 2: Assembly
Final result:
VinylSavor: Making of a 211 amplifier, Part 3: Listening
There are other projects also on my blog, just browse through the various articles.
Also maybe of interest. my view on gain vs headroom vs power:
VinylSavor: Gain, Headroom and Power
and about op points:
VinylSavor: The search for that 'magical' operating point
Best regards
Thomas
Hello Thomas
My plate voltage will be 900V, it is still OK to go with6HS5 tube.
I see U use Lundhal interstage, I think a pair of that I can afford.
I will study your amp after your answer about the 900V plate voltage.
I have some D3A at hand , also I have some12GN7A tubes. I won on ebay 4PC Sylvania 6HS5 tubes for $1 plus shipping. After I study Andrea amplifier with these tube I ask the seller to cancel the purchase.
I see U use stock Lundhal interstage not some special like Andrea.
Do you think with 900V plate voltage on GM70 I can drive with these tube?
Now is early morning 2:48 in Toronto, tomorrow I will do my home work.
Greetings Jeno
My plate voltage will be 900V, it is still OK to go with6HS5 tube.
I see U use Lundhal interstage, I think a pair of that I can afford.
I will study your amp after your answer about the 900V plate voltage.
I have some D3A at hand , also I have some12GN7A tubes. I won on ebay 4PC Sylvania 6HS5 tubes for $1 plus shipping. After I study Andrea amplifier with these tube I ask the seller to cancel the purchase.
I see U use stock Lundhal interstage not some special like Andrea.
Do you think with 900V plate voltage on GM70 I can drive with these tube?
Now is early morning 2:48 in Toronto, tomorrow I will do my home work.
Greetings Jeno
Hi!
Yes it would still work at 900V. Cathode resistor might need some adaption.
Also if you want to drive a GM70 I would not use the 4.5:1 step down ratio I used, but 2.25:1 which the Lundahl also offers. This is because you need a higher voltage swing at the grid compared to the 211.
The 2.25:1 step down will still provide a good low driving impedance of about 1kOhm and have good headroom.
You can contact me about parts for such projects I have most of the stuff available.
Best regards
Thomas
Yes it would still work at 900V. Cathode resistor might need some adaption.
Also if you want to drive a GM70 I would not use the 4.5:1 step down ratio I used, but 2.25:1 which the Lundahl also offers. This is because you need a higher voltage swing at the grid compared to the 211.
The 2.25:1 step down will still provide a good low driving impedance of about 1kOhm and have good headroom.
You can contact me about parts for such projects I have most of the stuff available.
Best regards
Thomas
Lundhal interstage, which one??
Hello Thomas
Right now probably I would be interested to get the interstage transformer.
If you have them, are you sell it in similar price like Lundhal? Any price offer?
These tubes and sockets available on Ebay as NOS.
I have some a 200mA 6Hy plate choke. Tested at 2500V. Also I have 4PC GM70 graphite plate, tube sockets, 3 enclosure for 2 mono block and separate power supp.
12PC Epcos b32361a2157j050 450VDC or 250AC 150uF all purpose MKP capacitor (new)
http://www.epcos.com/inf/20/50/ds/B3236X.pdf
Some electrolytic Nippon CC, Nichicon and Panasonic 450V type all 470uF or more.
Two Hammond 500V 30H 60mA choke etc.
At first I taught I will build these amp, but two many stage, I think that degrade the sound.
In case I go with your design can you help to get the right set up with 900V plate voltage?
Please let me know.
Thank you very much🙂
Greetings gaborbela
Hello Thomas
Right now probably I would be interested to get the interstage transformer.
If you have them, are you sell it in similar price like Lundhal? Any price offer?
These tubes and sockets available on Ebay as NOS.
I have some a 200mA 6Hy plate choke. Tested at 2500V. Also I have 4PC GM70 graphite plate, tube sockets, 3 enclosure for 2 mono block and separate power supp.
12PC Epcos b32361a2157j050 450VDC or 250AC 150uF all purpose MKP capacitor (new)
http://www.epcos.com/inf/20/50/ds/B3236X.pdf
Some electrolytic Nippon CC, Nichicon and Panasonic 450V type all 470uF or more.
Two Hammond 500V 30H 60mA choke etc.
At first I taught I will build these amp, but two many stage, I think that degrade the sound.
In case I go with your design can you help to get the right set up with 900V plate voltage?
Please let me know.
Thank you very much🙂
Greetings gaborbela
Attachments
Hi!
I will send you a PN about the prices of the stuff.
I can help you with getting the 6HS5 working. I have plenty experience with that tube. But be aware that such a project requires some knowledge about electronics and soldering skills. Don't just try to recycle the junk box parts. Such a project deserves selection of the right parts for the job. If cost is an issue, other designs might be a better choice.
Best regards
Thomas
I will send you a PN about the prices of the stuff.
I can help you with getting the 6HS5 working. I have plenty experience with that tube. But be aware that such a project requires some knowledge about electronics and soldering skills. Don't just try to recycle the junk box parts. Such a project deserves selection of the right parts for the job. If cost is an issue, other designs might be a better choice.
Best regards
Thomas