Okay it has been awhile since I looked at my specs.
Here is a photo of the transformers I used for reference.
So I used Hammond 274BX 375-0-375 HT not 400 as I stated earlier. Choke 158M 10h 100mA.
OT Hammond 1645 4k I believe.
The new tubes are much better then the microphonic NOS.
EH 150 Build Completed
Moderators: pompeiisneaks, Colossal
Re: EH 150 Build Completed
You do not have the required permissions to view the files attached to this post.
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Postscript-Cranked Her Up
For those who built this amp and any others interested, that 200 ohm cathode resistor and the 5R4GYB rectifier dragged my voltages down considerably below what I thought it would. 325-0-325 PT, which is much less than the original design.
B+ off the 5R4 was only 370. Plates & screens were 355. I had to change the 100K dropping resistor to 43K to get the right voltages on the 6SQ7s. 43K? Yes there is such a thing, at least there was in carbon comps. Yellow-orange-orange.
So now I have B+ off the rectifier at 365, plates/screens at 350, 6N7 PI at 163/163, nicely matched, V1 & V3 at 127V and V2 at 185V. Cathodes are in the right areas. Voltage on the 200 ohm 6L6 cathodes is 25. No noticeable microphonics from any of the 6SQ7s.
Even with only 350Vp/Vs, and with 2mA thru each screen resistor (470R 5W Mills), Pa is still 104% of 19W. Those old '40s amp guys were real cowboys!
However, it sounds awesome! I never heard a vintage P12N up close before. Even the "clean" channel can get some real hair on it. The mic/overdrive channel is really great. I used a 51K resistor/50K pot on the distortion channel 1M/100K voltage divider. I put the pot on the faceplate.
I also tried it with a GE 5AR4, lo and behold 395 Vp/Vs, but Pa was 134%. I have ordered a 5V4G to see if the 15V or so less is manageable. If I like that I will have to switch the 6L6GAs to Tungsol 5881s (real ones not Tungsolskis) as they can handle the cathode current.
Note: I don't use a 5U4G because my PT only has 2A on the 5V winding.
B+ off the 5R4 was only 370. Plates & screens were 355. I had to change the 100K dropping resistor to 43K to get the right voltages on the 6SQ7s. 43K? Yes there is such a thing, at least there was in carbon comps. Yellow-orange-orange.
So now I have B+ off the rectifier at 365, plates/screens at 350, 6N7 PI at 163/163, nicely matched, V1 & V3 at 127V and V2 at 185V. Cathodes are in the right areas. Voltage on the 200 ohm 6L6 cathodes is 25. No noticeable microphonics from any of the 6SQ7s.
Even with only 350Vp/Vs, and with 2mA thru each screen resistor (470R 5W Mills), Pa is still 104% of 19W. Those old '40s amp guys were real cowboys!
However, it sounds awesome! I never heard a vintage P12N up close before. Even the "clean" channel can get some real hair on it. The mic/overdrive channel is really great. I used a 51K resistor/50K pot on the distortion channel 1M/100K voltage divider. I put the pot on the faceplate.
I also tried it with a GE 5AR4, lo and behold 395 Vp/Vs, but Pa was 134%. I have ordered a 5V4G to see if the 15V or so less is manageable. If I like that I will have to switch the 6L6GAs to Tungsol 5881s (real ones not Tungsolskis) as they can handle the cathode current.
Note: I don't use a 5U4G because my PT only has 2A on the 5V winding.
-
RJ Guitars
- Posts: 2663
- Joined: Tue Nov 14, 2006 3:49 am
- Location: Los Alamos, New Mexico
- Contact:
Re: EH 150 Build Completed
David,
that is truly a prize piece of art with some very cool vintage technology. Very nicely done and thanks for sharing your info.
rj
that is truly a prize piece of art with some very cool vintage technology. Very nicely done and thanks for sharing your info.
rj
Good, Fast, or Cheap -- Pick two...
http://www.rjguitars.net
http://www.rjaudioresearch.com/
http://diyguitaramps.prophpbb.com/
http://www.rjguitars.net
http://www.rjaudioresearch.com/
http://diyguitaramps.prophpbb.com/
-
Cliff Schecht
- Posts: 2629
- Joined: Wed Dec 30, 2009 7:32 am
- Location: Austin
- Contact:
Re: EH 150 Build Completed
Want.
I am definitely adding the EH-150 to my list of builds this fall. I also want to build a Gibson GA100 and an RCA theremin (last one is sort of a pipe dream..).
I am definitely adding the EH-150 to my list of builds this fall. I also want to build a Gibson GA100 and an RCA theremin (last one is sort of a pipe dream..).
Cliff Schecht - Circuit P.I.
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Wish List
A Theremin! That is quite a challenge I think, Cliff, but you can probably do it.
The Princeton Reverb chassis/cab is the right size, but in retrospect I might have reversed the position of the can cap and the choke, because the choke feeds both the plates and the screens. Of course if you use the steel Mojotone knockoff chassis you won't have that option. I must recommend RJ's aluminum Princeton chassis. It's blank but 3/32" aluminum is a LOT easier to cut than the Mojo 16 ga. steel chassis, and RJ's is also much cheaper. I think he made a dozen of them, don't know how many he has left.
Does the aluminum chassis make a difference? Probably but I'd have to duplicate it in the Mojo steel chassis to prove it, and that's not on my list.
It's also not an optimal layout for this circuit, which necessitated the short runs of coax. Even so it hums a bit on the overdrive channel, but not to where I need to do anything about it. The clean channel doesn't hum. Both have a little hiss from the carbon comp resistors I guess.
I used a .001uF bypass cap on the tone control. The original was .00075, but Tino Zottola's book shows .002 there. The tone control as wired increases the bass as you turn it up, CW. Would you get mo' better bass with .002?
Crosstalk from the tweed mixer (anode mixer)? Maybe. Something seems to be going on between the two channels but I haven't taken the time to figure it out. Does not seem to affect performance tonewise, and I have dimed both channels individually. It is a surprisingly LOUD little bugger!
If you do use this platform, I would recommend you have the speaker mounting baffle cut for a 12" speaker, and, if you can spring an extra $200 for a real vintage P12N with an original cone you won't regret it!
The Princeton Reverb chassis/cab is the right size, but in retrospect I might have reversed the position of the can cap and the choke, because the choke feeds both the plates and the screens. Of course if you use the steel Mojotone knockoff chassis you won't have that option. I must recommend RJ's aluminum Princeton chassis. It's blank but 3/32" aluminum is a LOT easier to cut than the Mojo 16 ga. steel chassis, and RJ's is also much cheaper. I think he made a dozen of them, don't know how many he has left.
Does the aluminum chassis make a difference? Probably but I'd have to duplicate it in the Mojo steel chassis to prove it, and that's not on my list.
It's also not an optimal layout for this circuit, which necessitated the short runs of coax. Even so it hums a bit on the overdrive channel, but not to where I need to do anything about it. The clean channel doesn't hum. Both have a little hiss from the carbon comp resistors I guess.
I used a .001uF bypass cap on the tone control. The original was .00075, but Tino Zottola's book shows .002 there. The tone control as wired increases the bass as you turn it up, CW. Would you get mo' better bass with .002?
Crosstalk from the tweed mixer (anode mixer)? Maybe. Something seems to be going on between the two channels but I haven't taken the time to figure it out. Does not seem to affect performance tonewise, and I have dimed both channels individually. It is a surprisingly LOUD little bugger!
If you do use this platform, I would recommend you have the speaker mounting baffle cut for a 12" speaker, and, if you can spring an extra $200 for a real vintage P12N with an original cone you won't regret it!
Re: Wish List
David,David Root wrote: Crosstalk from the tweed mixer (anode mixer)? Maybe. Something seems to be going on between the two channels but I haven't taken the time to figure it out. Does not seem to affect performance tonewise, and I have dimed both channels individually. It is a surprisingly LOUD little bugger!
Wired as shown there seems to be some interaction between the OD channel and the clean channel. A test for this would be to be playing on the clean channel and rotate the OD volume and see if you hear any change in the background. I find the volume comfortably loud and in no way fatiguing with a 1x12 combo cab (open back).
-
Cliff Schecht
- Posts: 2629
- Joined: Wed Dec 30, 2009 7:32 am
- Location: Austin
- Contact:
Re: EH 150 Build Completed
I have 2 Jensen's that I want to shove in a cab. Both sound sorta lame by themselves but strangely nice together. IIRC the two of them are oddballs, a PM12C and a P12S from the 50's (the former has very little info on the web about it). Hopefully I can locate a cheap/decent 2x12 cab to mount those in.. Is a P12N a higher wattage speaker? Both of the ones I have are maybe 9-12W a piece..
Also with enough help I could tackle a tube theremin. The hard part would really be finding some good UV224 and UV227 tubes for a decent price as well as figuring out the interstage xfrms and massive coils. It's pretty ridiculous to try to use such ancient tubes in a build though. Even Mr. Moog himself went for modern equivalents with his designs back in the 50's because I think even by his time the original RCA tube types were getting rare. Now they're impossible to find..
Also with enough help I could tackle a tube theremin. The hard part would really be finding some good UV224 and UV227 tubes for a decent price as well as figuring out the interstage xfrms and massive coils. It's pretty ridiculous to try to use such ancient tubes in a build though. Even Mr. Moog himself went for modern equivalents with his designs back in the 50's because I think even by his time the original RCA tube types were getting rare. Now they're impossible to find..
Cliff Schecht - Circuit P.I.
Re: EH 150 Build Completed
It is some pretty build David.
I can' help but wonder whether you can get rid of the coax. Forgive me if my tone here sounds pushy -- not meant that way, just thinking out loud that it might be worth trying.
So, just a few ideas for you to consider, FWIW. I'm not saying this would necessarily work or be an improvement. I am one of those people who isn't fond of coax. That's all...
Phil
I can' help but wonder whether you can get rid of the coax. Forgive me if my tone here sounds pushy -- not meant that way, just thinking out loud that it might be worth trying.
So, just a few ideas for you to consider, FWIW. I'm not saying this would necessarily work or be an improvement. I am one of those people who isn't fond of coax. That's all...
Phil
You do not have the required permissions to view the files attached to this post.
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: EH 150 Build Completed
Cliff, the P12N was Jensen Chicago's most powerful speaker, I believe, rated for 50W.
I've never heard of the P12C or P12S, only P12R, P12Q, P12P & P12N.
At about 10W or so each this amp could easily blow them both out.
Tino Zottola in his book writes that he measured 30W "with a clean input of 500Hz into 8 ohms". That is with his PT, which was "375-0-375 at 75 mA". I kind of think that should read 175 mA because at 400Vp/Vs those 6L6Gs pull about 140mA between them at idle. 28.5V across 200 R. I used a
325-0-325 at 150mA.
For a cabinet I recommend the Avatar 2x12 open back. It has a Dumble style oval hole and sounds great. Not too pricey either.
Colossal, thanx for that tip, I will try it out.
Phil S, I think I erred on the conservative side with the coax. I will try disconnecting the shields one by one and see what happens, thanx for the suggested routings too.
I think the hum I'm getting on the overdrive channel is from the extra tube in line and the fact that they are all non-humbucking heaters.
I've never heard of the P12C or P12S, only P12R, P12Q, P12P & P12N.
At about 10W or so each this amp could easily blow them both out.
Tino Zottola in his book writes that he measured 30W "with a clean input of 500Hz into 8 ohms". That is with his PT, which was "375-0-375 at 75 mA". I kind of think that should read 175 mA because at 400Vp/Vs those 6L6Gs pull about 140mA between them at idle. 28.5V across 200 R. I used a
325-0-325 at 150mA.
For a cabinet I recommend the Avatar 2x12 open back. It has a Dumble style oval hole and sounds great. Not too pricey either.
Colossal, thanx for that tip, I will try it out.
Phil S, I think I erred on the conservative side with the coax. I will try disconnecting the shields one by one and see what happens, thanx for the suggested routings too.
I think the hum I'm getting on the overdrive channel is from the extra tube in line and the fact that they are all non-humbucking heaters.
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
.002 tone bypass
I tried the recommended .002 uF tone bypass cap. Mo' better bass!
Re: EH 150 Build Completed
The only issues I had was OD channel oscillation that I was sure was due to the 1m/100k voltage divider but nothing worked to tame it.
I got some Chinese 6SQ7 tubes and that did the trick. I do have some hum issues but with a PTP build I was expecting some. I have the amp on the bench right now looking to see where I can change things some.
Mark
I got some Chinese 6SQ7 tubes and that did the trick. I do have some hum issues but with a PTP build I was expecting some. I have the amp on the bench right now looking to see where I can change things some.
Mark
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: EH 150 Build Completed
Mark, let us know what you find out. I have had no issues with my 6SQ7GTs, but I have not tried out metal case 6SQ7s either.
A really old guy (in his mid 80s 10 years ago) who ran a tube shop in Salt Lake City on Main & 17th, where I lived then, told me that metal case tubes were no good because they overheated and failed. If they were routinely abused by this kind of circuit I could see that.
Fortunately he also sold me about a dozen used 6L6GC RCA blackplates for $10 each so I can't bitch. Three or four of them have gone to Valvehalla since then but I still ain't bitchin!
A really old guy (in his mid 80s 10 years ago) who ran a tube shop in Salt Lake City on Main & 17th, where I lived then, told me that metal case tubes were no good because they overheated and failed. If they were routinely abused by this kind of circuit I could see that.
Fortunately he also sold me about a dozen used 6L6GC RCA blackplates for $10 each so I can't bitch. Three or four of them have gone to Valvehalla since then but I still ain't bitchin!
Re: EH 150 Build Completed
I used some Westinghouse metal can 6SQ7s which I really like. I actually preferred their tone to some JAN 6SQ7GTs (glass jacket). But I did find the metal cans to be on the microphonic side. I used a trimmer to find the sweet spot for the OD channel where I used a metal jacketed 6SQ7. They do run quite hot (as did a metal can RCA 6N7 which I used in the PI). I rolled a number of 6SQ7s and 6SQ7GTs and even had a DOA which was a bummer. I got a bunch of the new issue Chinese 6SQ7s to try for my next build.David Root wrote:A really old guy (in his mid 80s 10 years ago) who ran a tube shop in Salt Lake City on Main & 17th, where I lived then, told me that metal case tubes were no good because they overheated and failed. If they were routinely abused by this kind of circuit I could see that.
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: EH 150 Build Completed
There does seem to be an interaction between the two channels, but it only seems to affect the hum/noise level as far as I could see. I found no tonal difference in the clean channel by cranking up the overdrive volume pot. Not the other way either.
But I do like that .002 cap!
But I do like that .002 cap!
Re: EH 150 Build Completed
The only metal can I have is the 6N7 which I now have glass tube to use. But the new Chinese 6SQ7 are used by the HiFi guys so I figured they have to be good. 
Next the hum.
Mark
Next the hum.
Mark