I have a question about the "ultra-grade plate chokes" you mentioned. In what way are they ultra grade compared to the chokes your using now? Are the Henry, and DCR specs the same as your current plate chokes?
Also interested in these plate chokes, both the older and newer ones..
Is there a roundabout price you could post, please.. 🙂
Is there a roundabout price you could post, please.. 🙂
They sell on eBay. Sometimes they are quite cheap and other times they inexplicably shoot up in price. I got a bunch of RCAs for $2 each recently, but the very next auction went for more than double that.
Just Back
Sorry I haven't replied for awhile. My niece (31) is in late 2nd stage Melanoma cancer and we've been helping out with babysitting as she goes through surgury. Hoping that this is it. Survival rates for 3rd stage are not good at all.
I still haven't posted the power supply, but I will get that out this weekend and then try to get some kit prices out when all the info comes back. I'm getting quotes on boards for PS now.
With respect to the ultra-grade chokes, they are using a cobalt iron core instead of standard (high quality) M6 grain aligned grade. I haven't compared the two on the bench or in the listening room yet, so I should do that. No sense in spending money if it doesn't improve the sound.
I think the standard plate chokes will be in the $25 range each and the power chokes around $15 each, but let me finish putting everything together before offering a full kit. There are several options and ways to do the PS kit--using 3 or 6 power chokes. See the technical results to choose which works best for you. I've also laid in a stock of vintage Sangamo 38,000uF (Filament Voltage) filter chokes, so those will be available also.
Sorry I haven't replied for awhile. My niece (31) is in late 2nd stage Melanoma cancer and we've been helping out with babysitting as she goes through surgury. Hoping that this is it. Survival rates for 3rd stage are not good at all.
I still haven't posted the power supply, but I will get that out this weekend and then try to get some kit prices out when all the info comes back. I'm getting quotes on boards for PS now.
With respect to the ultra-grade chokes, they are using a cobalt iron core instead of standard (high quality) M6 grain aligned grade. I haven't compared the two on the bench or in the listening room yet, so I should do that. No sense in spending money if it doesn't improve the sound.
I think the standard plate chokes will be in the $25 range each and the power chokes around $15 each, but let me finish putting everything together before offering a full kit. There are several options and ways to do the PS kit--using 3 or 6 power chokes. See the technical results to choose which works best for you. I've also laid in a stock of vintage Sangamo 38,000uF (Filament Voltage) filter chokes, so those will be available also.
May God Bless You.
Ya.. this hobby is of secondary important.
Take care and May God Bless You,
Zekk
Ya.. this hobby is of secondary important.
Take care and May God Bless You,
Zekk
hey-Hey!!!,
12B4 is one of my favourite linestage tubes. I just built another one. This one is SE😛P via a LTP/diff amp. B+ is linestage-nuts at 480V in order to get nearly 20 mA idle current through its 20k plate loads. I like the balanced signal; amps are all using XLR as well as the active cross-over.
cheers,
Douglas
12B4 is one of my favourite linestage tubes. I just built another one. This one is SE😛P via a LTP/diff amp. B+ is linestage-nuts at 480V in order to get nearly 20 mA idle current through its 20k plate loads. I like the balanced signal; amps are all using XLR as well as the active cross-over.
cheers,
Douglas
Hey douglas, are you able to talk about the topology of the Emotive 12B4 that you were involved with?
PSU Posted
Finally got the PS details posted. Go to http://galaxysetlabs.com/Designs/Designs_Top.htm & click on "Reference" and select the hyperlink in the "Low Henry Power Supply" text.
Next step is to post the parts list and kit. I'll be working on that this week, but at least you can now build the full amp with a little DIY magic.
Thanks for the thoughts. Looks like my niece is going to be OK.
Finally got the PS details posted. Go to http://galaxysetlabs.com/Designs/Designs_Top.htm & click on "Reference" and select the hyperlink in the "Low Henry Power Supply" text.
Next step is to post the parts list and kit. I'll be working on that this week, but at least you can now build the full amp with a little DIY magic.
Thanks for the thoughts. Looks like my niece is going to be OK.
Hi Coffeedj,
i have a couple of questions regarding your schematic:
http://www.galaxysetlabs.com/Designs/12B4ChokeFed.pdf
Do you use one OD3 per channel?
When using a normal amplifier with Rin of ~20K Ohm wouldn't it be better to have a load resistor of 100K+ after the coupling cap connected to ground?
Do you use your power supply for one or for both channels?
KR
Hauke
i have a couple of questions regarding your schematic:
http://www.galaxysetlabs.com/Designs/12B4ChokeFed.pdf
Do you use one OD3 per channel?
When using a normal amplifier with Rin of ~20K Ohm wouldn't it be better to have a load resistor of 100K+ after the coupling cap connected to ground?
Do you use your power supply for one or for both channels?
KR
Hauke
Yes there is one 0D3 per channel, and a common power supply feeding both. By using a separate Voltage regulater per channel you get channel isolation nearly equivalent to using two power supplys. In addition, we are driving these 12B4's at 21ma, so if a single channel of regulation was used it would have to be a pair of 874s, and you are back to two tubes for VR.
Re: output load--that would be fine if you want to do it and probably a good idea. I feed a 10K input impedance input, so the use of a load resistor is not necessary. If, however, you are going into a high impedance input then a 100K or even 10K load resistor is a good idea. The ouput impedance of 600ohms would dictate something in the 20 to 1 range, or about 10K.
Re: output load--that would be fine if you want to do it and probably a good idea. I feed a 10K input impedance input, so the use of a load resistor is not necessary. If, however, you are going into a high impedance input then a 100K or even 10K load resistor is a good idea. The ouput impedance of 600ohms would dictate something in the 20 to 1 range, or about 10K.
New Amp Idea
I was listening to various tubes using my mulit-amp (http://www.galaxysetlabs.com/Designs/Designs_Top.htm and got to 'Power Amps' tab) and I was amazed at what a sweet sound the 6W6 tube has. The 12L6, 12W6, and 50L6 are all equivalent--the 25L6 and 35L6 are not, but that is a lot of options for a very inexpensive tube with great sound.
I expected it to be like a 6K6, but it is isn't. More like a cross between the SE sweetness of the 6V6G and clarity of the 6973. I'm going to build an amp using this tube in a parallel SE design, which should yield a little less than 8 watts. It has a very friendly 8.5V grid drive and low plate voltage with typical 45ma current. It could even be run in triple SE mode for 12W. This was originally designed to be a SE amplifier tube, but there is no reason not to look at a P-P design also. With the low voltage requirements it could be a real complement to a 12B4 amp, and even share a common power supply. With the cheap tube cost you could drive it hard and replace power tubes once a year--and probably get something like 22W in P-P mode with a single P-P pair. Make that a quad and you are getting serious tube power. I did notice that this tube really sings when it is driven hard--around 50-55ma per tube.
If there is interest I'll start a new thread.
I was listening to various tubes using my mulit-amp (http://www.galaxysetlabs.com/Designs/Designs_Top.htm and got to 'Power Amps' tab) and I was amazed at what a sweet sound the 6W6 tube has. The 12L6, 12W6, and 50L6 are all equivalent--the 25L6 and 35L6 are not, but that is a lot of options for a very inexpensive tube with great sound.
I expected it to be like a 6K6, but it is isn't. More like a cross between the SE sweetness of the 6V6G and clarity of the 6973. I'm going to build an amp using this tube in a parallel SE design, which should yield a little less than 8 watts. It has a very friendly 8.5V grid drive and low plate voltage with typical 45ma current. It could even be run in triple SE mode for 12W. This was originally designed to be a SE amplifier tube, but there is no reason not to look at a P-P design also. With the low voltage requirements it could be a real complement to a 12B4 amp, and even share a common power supply. With the cheap tube cost you could drive it hard and replace power tubes once a year--and probably get something like 22W in P-P mode with a single P-P pair. Make that a quad and you are getting serious tube power. I did notice that this tube really sings when it is driven hard--around 50-55ma per tube.
If there is interest I'll start a new thread.
coffeedj said:
Hi Coffeedj,
thanks for your reply 🙂
According to that:
http://www.galaxysetlabs.com/Designs/12B4ChokeFed.pdf
...your output voltage (from power supply for both channels) is 170-180V, isn't it?
...and each OD3 VR uses a single 470 Ohm resistor?
KR
Hauke
That is approximately correct. The actual supply voltage prior to the dropping resistor is not that important as long as it is about 180 (or more).
Calculate the correct dropping resistor by as follows:
Strike voltage for 0D3 is 160V and max voltage is 180V. Take 175 as your target voltage since the voltage will sag a little on connection to 12B4's.
Voltage drop = B+ supply - 175 (= VD)
Current is 21.5 ma X 2 = 43ma
R = V / I = (VD / 43) * 1000.
If for example filtered B+ output is 210V then the correct resistance is:
R = (210-175) / 21 * 1000 = 813.9. Round to 810 and test.
Note that 43ma through 810ohms is 1.5 Watts so use a 2 W resistor minimum. I recommend triple the wattage as a good rule of thumb to keep the resistor from drifting so use a 5 W resistor, or parallel two 2 watt 1.6K resistors.
R = (210 - 175 ) /
Calculate the correct dropping resistor by as follows:
Strike voltage for 0D3 is 160V and max voltage is 180V. Take 175 as your target voltage since the voltage will sag a little on connection to 12B4's.
Voltage drop = B+ supply - 175 (= VD)
Current is 21.5 ma X 2 = 43ma
R = V / I = (VD / 43) * 1000.
If for example filtered B+ output is 210V then the correct resistance is:
R = (210-175) / 21 * 1000 = 813.9. Round to 810 and test.
Note that 43ma through 810ohms is 1.5 Watts so use a 2 W resistor minimum. I recommend triple the wattage as a good rule of thumb to keep the resistor from drifting so use a 5 W resistor, or parallel two 2 watt 1.6K resistors.
R = (210 - 175 ) /
Dropping resistor.
Whoops: Note that I put 21 vice 43 in the denominator.
Example is correct: 810 ohms required.
Be sure to check voltage after circuit has run a while and everything is settled in. You may have to tweek the resistor up or down a little based on what you measure. You have to calculate expected voltage at the 0D3, it will be 150V reguardless, so use calculation to make sure that if it were a resistive load the voltage would be 170V.
If the 0D3 is not close to 150V you have the wrong value for the dropping resistor.
Whoops: Note that I put 21 vice 43 in the denominator.
Example is correct: 810 ohms required.
Be sure to check voltage after circuit has run a while and everything is settled in. You may have to tweek the resistor up or down a little based on what you measure. You have to calculate expected voltage at the 0D3, it will be 150V reguardless, so use calculation to make sure that if it were a resistive load the voltage would be 170V.
If the 0D3 is not close to 150V you have the wrong value for the dropping resistor.
Whoops again
Too late at night!
21 ma is correct denominator and you use two resistors--one to each 0D3.
Too late at night!
21 ma is correct denominator and you use two resistors--one to each 0D3.
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