I'm waiting for Paul Barker to move onto the GM100 once he has perfected his 212 amp!
I'm thinking that SE parafeed is the way to go with my 833s as it will allow me to tweak the bottom end response. And sinking 250mA through a choke will be easier than paying for a custom SE OPT ...
ciao
James
I'm thinking that SE parafeed is the way to go with my 833s as it will allow me to tweak the bottom end response. And sinking 250mA through a choke will be easier than paying for a custom SE OPT ...
ciao
James
the thread continues
Hi Unison845, Protos amd James D,
i was not able to reply earlier....sorry.
Unison845: just saw your post # 113. What a great display of options. Tantalising..... And about the thoriated tungsten filaments: they are extremely brittle AFTER they are used. So if the tube is NOS/NIB you're quite safe. If they have some hours on them NOT ! I found out the expensive way when a lot of this transmitting tubes were shipped to me transatlantic. I cheacked some ham-sites and they report the same. And they should know for they have decennia of experience.
In Russia they are still making great stuff. Not only the GM70 and the 6C45, but for sure there is more to find. I'had a look (and even listen) to the GU-81. Waste of time, avoid it ! It's a huge beam-tetrode (833-size), but the sound was quite dissapointing. A shame.
Protos: i believe you've found enough feedback to stop considering those "300B's on anabolics". Price and quality are seriously negative compared to well proven transmitting tubes. Still available. And there are even modern transmitting tubes which are ruggedised and do sound good (GM70). I am not against those new 300B-variants, but trying to squize how-many-watts (?) out of such a tube is basicly wrong. Or stop calling these 300B's !
Use the 300B in a schematic for what it is supposed to do:
- as a final triode in a low power amp;
- as a driver is a more exotic configuration;
For i do like the sound / availability / choices / ease of use / etc of a 300 b. I'll include a night picture of my driver tube, the Valve Art 300B-98C. Earlier in this thread is a daylight picture. But during the night it gives a nice optic display as well.
With regards,
Reinout
Hi Unison845, Protos amd James D,
i was not able to reply earlier....sorry.
Unison845: just saw your post # 113. What a great display of options. Tantalising..... And about the thoriated tungsten filaments: they are extremely brittle AFTER they are used. So if the tube is NOS/NIB you're quite safe. If they have some hours on them NOT ! I found out the expensive way when a lot of this transmitting tubes were shipped to me transatlantic. I cheacked some ham-sites and they report the same. And they should know for they have decennia of experience.
In Russia they are still making great stuff. Not only the GM70 and the 6C45, but for sure there is more to find. I'had a look (and even listen) to the GU-81. Waste of time, avoid it ! It's a huge beam-tetrode (833-size), but the sound was quite dissapointing. A shame.
Protos: i believe you've found enough feedback to stop considering those "300B's on anabolics". Price and quality are seriously negative compared to well proven transmitting tubes. Still available. And there are even modern transmitting tubes which are ruggedised and do sound good (GM70). I am not against those new 300B-variants, but trying to squize how-many-watts (?) out of such a tube is basicly wrong. Or stop calling these 300B's !
Use the 300B in a schematic for what it is supposed to do:
- as a final triode in a low power amp;
- as a driver is a more exotic configuration;
For i do like the sound / availability / choices / ease of use / etc of a 300 b. I'll include a night picture of my driver tube, the Valve Art 300B-98C. Earlier in this thread is a daylight picture. But during the night it gives a nice optic display as well.
With regards,
Reinout
Attachments
parafeed and ultra-parafeed
Hi Tubeman,
the 810....nope....never seen a audio-amp with that one. Lot's of 805's, 211's and 845's. And not to forget the 813 (in triode). Why not ? I believe James D gave a good reply on that. AND the 810 is still used in a lot of ham-transmitters. The current Chinese production is not comparable with the "old" American ones....so prices of nos 810 is quite high. Still not in the 845-price territory (scaring !), but certainly a point of consideration.
What are you going to do: pressing on with the 833-idea or pick another transmitting tube ?
Make a wise choice. The parts will not be free !
Reinout
Hi Tubeman,
the 810....nope....never seen a audio-amp with that one. Lot's of 805's, 211's and 845's. And not to forget the 813 (in triode). Why not ? I believe James D gave a good reply on that. AND the 810 is still used in a lot of ham-transmitters. The current Chinese production is not comparable with the "old" American ones....so prices of nos 810 is quite high. Still not in the 845-price territory (scaring !), but certainly a point of consideration.
What are you going to do: pressing on with the 833-idea or pick another transmitting tube ?
Make a wise choice. The parts will not be free !
Reinout
(ultra-)parafeed
Hi James D,
EXACTLY my thoughts when i was doing the theory for my 833 amp. Happily i had Vacuum Tube Valley issue 16 where Lynn Olson had a great explanation of all types of configurations: from "standard" single-ended via UltraPath (registered !) to Parallel Feed (your thoughts) to Ultra Parafeed.
I'll enclose a small excerpt of the article. It's a periodic table of topologies and is simply GREAT. Thank you Lynn Olson !!
During my audio-history i've learned that repeating the same tube can be very tricky. You enhance both the good AND the bad qualities. The same is with schematics. Doing a three-stage amplifier with three times the same schematic can be boring to make and/or to listen to. So looking at the table of topologies and doing some calculations i came up with:
- 6SN7 push pull (input)
- 300B se (driver)
- 833 ultra parafeed (output)
And the same is done with the transformers. I picked different lamination-materials in almost each stage. Simply to get the best material at the right place:
- mumetal input transformer (very fast fast and detailed but prone to saturation: input !);
- permalloy-49 interstage between 6SN7 and 300B (great combination of speed/datails and saturation);
- M6X as interstage between 300B and 833 (this material can have serious punding and will not saturate);
- M6X output. I wished i had a HUGE permalloy core, for it needed to be wound for 1 kV+. No flimsy wires here ! The size permalloy i wanted was not available. So i "stuck" with M6X; and that does not "hurt".
And that M6X opt was way smaller than in a normal SE configuration for now the laminations had no air gap / there was no chance on DC / etc etc. The whole opt became less critical. Of course there is a down side: introduction of a parallel feed coil (which you wanted to do anyway) and a cathode-transformer bypass capacitor. That sucker is a tricky item: it took time to get a correct one ....and later a good sounding one. See it on the bright side: you can much easier chance the sound-character with that single cap than chanching the whole schematic/transformer.
Mix'n match !
Try to pick up a copy of the No16 Vacuum Tube Valley; it's worth it.
And i'm very very interested in your thoughts / schematic of your 833 amp.
With regards,
Reinout
Hi James D,
EXACTLY my thoughts when i was doing the theory for my 833 amp. Happily i had Vacuum Tube Valley issue 16 where Lynn Olson had a great explanation of all types of configurations: from "standard" single-ended via UltraPath (registered !) to Parallel Feed (your thoughts) to Ultra Parafeed.
I'll enclose a small excerpt of the article. It's a periodic table of topologies and is simply GREAT. Thank you Lynn Olson !!
During my audio-history i've learned that repeating the same tube can be very tricky. You enhance both the good AND the bad qualities. The same is with schematics. Doing a three-stage amplifier with three times the same schematic can be boring to make and/or to listen to. So looking at the table of topologies and doing some calculations i came up with:
- 6SN7 push pull (input)
- 300B se (driver)
- 833 ultra parafeed (output)
And the same is done with the transformers. I picked different lamination-materials in almost each stage. Simply to get the best material at the right place:
- mumetal input transformer (very fast fast and detailed but prone to saturation: input !);
- permalloy-49 interstage between 6SN7 and 300B (great combination of speed/datails and saturation);
- M6X as interstage between 300B and 833 (this material can have serious punding and will not saturate);
- M6X output. I wished i had a HUGE permalloy core, for it needed to be wound for 1 kV+. No flimsy wires here ! The size permalloy i wanted was not available. So i "stuck" with M6X; and that does not "hurt".
And that M6X opt was way smaller than in a normal SE configuration for now the laminations had no air gap / there was no chance on DC / etc etc. The whole opt became less critical. Of course there is a down side: introduction of a parallel feed coil (which you wanted to do anyway) and a cathode-transformer bypass capacitor. That sucker is a tricky item: it took time to get a correct one ....and later a good sounding one. See it on the bright side: you can much easier chance the sound-character with that single cap than chanching the whole schematic/transformer.
Mix'n match !
Try to pick up a copy of the No16 Vacuum Tube Valley; it's worth it.
And i'm very very interested in your thoughts / schematic of your 833 amp.
With regards,
Reinout
Attachments
Hi Reinout,
Many thanks for your thoughts and the L.O. info. Lynn writes some very interesting stuff. I'll work through your email in detail later but I thought I would quickly post my latest thoughts on the circuit and its evolution.
I like to use push pull circuits, even differential circuits in my designs. Not exclusively but most of the time so the driver is push-pull. I also like to try and use only two stages in a power amplifier - mainly to minimise the build up of higher distortion products.
I like to use a lot of transformers as I find the breaking of ground planes between stages beneficial and I prefer the sound of IT coupling to any other.
Having decided with the 833 that I was going to end up with an SE output stage (mainly due to power supply cost considerations and I wanted to see how a big valve would cope in SE) I thought the driver stage would be the main challenge... In a way I was right as I couldn't get a high gain, high current driver with sufficently low distortion for my liking. I wanted to use a pair of PL802 in triode mode as drivers - 316a put me onto them and they have very nice performance - see Pete Milletts tests. They worked very well as a push pull pair up to about 100V output at 30mA but I wanted a bigger step down and more like 100mA drive minimum. I tried different valve combinations but none would give me the required performance in one stage. Thinking back to my ss design days, when I needed to boost single stage performance I went to cascode config. so I started looking at a differential cascode for the drivers. That lead me into the recent thread here where SY, Frank et al had debated the merits and performance of the LTPC. I was hooked! The only thing was to keep the output impedance down for the stage so I ended up with a pair of PL802s in triode mode for the lower valves and a pair of 2A3s for the upper valves. Now I have good gain and a +/- 150V , low distortion and low output impedance driver stage so I can use a 6:1 step down transformer and drive the 833 from a 60ohm source impedance. I have only simulated the design so far but it looks very promising. Of course the distortion spectra from the cascode diff pair is not as simple as a normal diff pair would be but it's not too bad and it is very low level at normal signal level.
Well that and the parafeed thoughts are where the design is today and here is the circuit drawing so far. I would be very interested in any comments. ciao
James
Many thanks for your thoughts and the L.O. info. Lynn writes some very interesting stuff. I'll work through your email in detail later but I thought I would quickly post my latest thoughts on the circuit and its evolution.
I like to use push pull circuits, even differential circuits in my designs. Not exclusively but most of the time so the driver is push-pull. I also like to try and use only two stages in a power amplifier - mainly to minimise the build up of higher distortion products.
I like to use a lot of transformers as I find the breaking of ground planes between stages beneficial and I prefer the sound of IT coupling to any other.
Having decided with the 833 that I was going to end up with an SE output stage (mainly due to power supply cost considerations and I wanted to see how a big valve would cope in SE) I thought the driver stage would be the main challenge... In a way I was right as I couldn't get a high gain, high current driver with sufficently low distortion for my liking. I wanted to use a pair of PL802 in triode mode as drivers - 316a put me onto them and they have very nice performance - see Pete Milletts tests. They worked very well as a push pull pair up to about 100V output at 30mA but I wanted a bigger step down and more like 100mA drive minimum. I tried different valve combinations but none would give me the required performance in one stage. Thinking back to my ss design days, when I needed to boost single stage performance I went to cascode config. so I started looking at a differential cascode for the drivers. That lead me into the recent thread here where SY, Frank et al had debated the merits and performance of the LTPC. I was hooked! The only thing was to keep the output impedance down for the stage so I ended up with a pair of PL802s in triode mode for the lower valves and a pair of 2A3s for the upper valves. Now I have good gain and a +/- 150V , low distortion and low output impedance driver stage so I can use a 6:1 step down transformer and drive the 833 from a 60ohm source impedance. I have only simulated the design so far but it looks very promising. Of course the distortion spectra from the cascode diff pair is not as simple as a normal diff pair would be but it's not too bad and it is very low level at normal signal level.
Well that and the parafeed thoughts are where the design is today and here is the circuit drawing so far. I would be very interested in any comments. ciao
James
Attachments
Hello James,
What kind of plate chokes are you using for the 833A? I am interested also in building a parafeed amp but never try yet. I have couple good PP 100W transformer that I would like to use for a parafeed SE. This would worth a try since there are not may 100W SE xformer out there. A 100W SE 450 TL would be awsome.
What kind of plate chokes are you using for the 833A? I am interested also in building a parafeed amp but never try yet. I have couple good PP 100W transformer that I would like to use for a parafeed SE. This would worth a try since there are not may 100W SE xformer out there. A 100W SE 450 TL would be awsome.
Hello Unison 845,
A parafeed 450 would indeed be awsome! I guess after that it's a GM100...
The chokes I am going to use are custom designs by Benny Glass of AquaBlue. They are designed for a 300B PSE amp. and are 120H at 160mA. So that would give me 60H at 320mA for the 833. Not cheap but good value. AquaBlue Iron list
Benny has some very intereting designs on his site including some nice 845 amps - both PP and SE parafeed.
I'll look forward to seeing your 450TL amplifier
ciao
James
A parafeed 450 would indeed be awsome! I guess after that it's a GM100...
The chokes I am going to use are custom designs by Benny Glass of AquaBlue. They are designed for a 300B PSE amp. and are 120H at 160mA. So that would give me 60H at 320mA for the 833. Not cheap but good value. AquaBlue Iron list
Benny has some very intereting designs on his site including some nice 845 amps - both PP and SE parafeed.
I'll look forward to seeing your 450TL amplifier
ciao
James
Thanks, James.
Yup, the choke plus the output transformer for parafeed is not cheap. Have you ever look at the plate of the output tube of a parafeed amp to see how it looks with square wave? I guess that depends on the characteristic of the choke both high and low frequency.
I am still gathering parts for the 450TL amp, which run about 1200V and 200-250ma bias.
Yup, the choke plus the output transformer for parafeed is not cheap. Have you ever look at the plate of the output tube of a parafeed amp to see how it looks with square wave? I guess that depends on the characteristic of the choke both high and low frequency.
I am still gathering parts for the 450TL amp, which run about 1200V and 200-250ma bias.
if audio fails.... (1)
Hi all,
so if your 833-based amp fails you can always built your own tesla coil with it.
No....this is not at my house; my 833's are up and running with music. I found these pictures surfing across the web. Still interesting: again the "spot" on the anode is clearly visible.
What kind of amp would this be ? Class Z ?
Reinout
Hi all,
so if your 833-based amp fails you can always built your own tesla coil with it.
No....this is not at my house; my 833's are up and running with music. I found these pictures surfing across the web. Still interesting: again the "spot" on the anode is clearly visible.
What kind of amp would this be ? Class Z ?
Reinout
Attachments
pl802 cascode
Hi James D,
now that's interesting. Indeed you need a low impendance driver in order to "feed" the powerhungry grid of the 833. With my 300b plus 4:1 stepdown interstage i ended up with 44 ohm.
Differential cascode is new to me. It looks well up to the task (= giving enough mA's at low impendance and voltage swing). But this is uncharted terrain for me. As are the PL802's. Again: never heard them. Can you blame me ? There are so many tubes out there..... The 2A3 is simply great. But quite variable with different brands. And there is even a monoplate-version. But i believe then we're talking serious money. I've heard that the Sovtek 2A3 was good; it looks almost like a 300B.
About push-pull: very handy, it takes a lot of trouble / underpowering / transformer-issue's away. I did not went that far to built a 833 in push-pull, but wanted to have the very handy DC-free operating way of PP to take the load of the output transformer. So that's why i came up with parafeed. Which became ultra-parafeed in the end. 833 PP....how many Watts ? In class B the tube data tells me 1650 Watts !
You like transformer-coupling.....we can talk ! I really like it and have had very good results with this type of connecting amplifier-stages to each other.
This summer we (girlfriend + me) are planning to visit Rome. Is your amp up-and-running then ? Maybe it is unwise to switch the amps on in summer (just kidding). I'm almost afraid about the heat-output this summer. During the wintermonths it was no big issue. But they're only a couple months "old" and never seen a warm summer day.
If you ever happen to visit the Netherlands: your welcome !
Reinout
Included a picture of the E96 interstage and E126 output transformer (opt). They are impressive in sound as well in size. E96....normally that's already a hefty output transformer.
I asked the transformer-winder to make the lead-out wires of the opt NOT connecting to soldering taps but as a bundle of wires coming straight out of the winding. That way i was able to solder the opt straight to the loudspeaker binding posts.
Hi James D,
now that's interesting. Indeed you need a low impendance driver in order to "feed" the powerhungry grid of the 833. With my 300b plus 4:1 stepdown interstage i ended up with 44 ohm.
Differential cascode is new to me. It looks well up to the task (= giving enough mA's at low impendance and voltage swing). But this is uncharted terrain for me. As are the PL802's. Again: never heard them. Can you blame me ? There are so many tubes out there..... The 2A3 is simply great. But quite variable with different brands. And there is even a monoplate-version. But i believe then we're talking serious money. I've heard that the Sovtek 2A3 was good; it looks almost like a 300B.
About push-pull: very handy, it takes a lot of trouble / underpowering / transformer-issue's away. I did not went that far to built a 833 in push-pull, but wanted to have the very handy DC-free operating way of PP to take the load of the output transformer. So that's why i came up with parafeed. Which became ultra-parafeed in the end. 833 PP....how many Watts ? In class B the tube data tells me 1650 Watts !
You like transformer-coupling.....we can talk ! I really like it and have had very good results with this type of connecting amplifier-stages to each other.
This summer we (girlfriend + me) are planning to visit Rome. Is your amp up-and-running then ? Maybe it is unwise to switch the amps on in summer (just kidding). I'm almost afraid about the heat-output this summer. During the wintermonths it was no big issue. But they're only a couple months "old" and never seen a warm summer day.
If you ever happen to visit the Netherlands: your welcome !
Reinout
Included a picture of the E96 interstage and E126 output transformer (opt). They are impressive in sound as well in size. E96....normally that's already a hefty output transformer.
I asked the transformer-winder to make the lead-out wires of the opt NOT connecting to soldering taps but as a bundle of wires coming straight out of the winding. That way i was able to solder the opt straight to the loudspeaker binding posts.
Attachments
Hi Unison 845 and Reinout,
I have looked at the plate of the output tube when using parafeed - and it is interesting at the edge of the passband. A bit more interesting than usual. Have a look at Bill Ramsey's analysis of the parafeed stage. He gives a calculated phase plot that explain a lot of what one sees... Mathematical Derivation of the Parafeed Output Stage
Within the passband the parafeed stage looks no worse than the usual IT coupled SE amp.
PL802 are a valve I had used in my early TV days but had ignored until recently 316a mentioned how nice they are as triodes. A mu=70 and S=40mA/V makes for an interesting beast! Pete Millett did some interesting work testing high transconductance pentodes as audio amplifiers.
High Gm pentodes
I guess the art of the cascode is choosing the right combination of valves for lower and upper devices - it easy to let the output impedance shoot up with all the problems that causes for integration downstream...
I tend to use the 6B4G NOS tubes or Sovtek 2A3. I haven't tried any of the expensive 2A3s yet and prefer the Sovtek to the chinese varients I have used so far.
I keep looking at the 833 in push pull. It is very tempting as I really like DHT PP amps... But it would be such a beast! I'm also working on a 211 Cathode follower push pull design that should have similar power output characteristics to the 833. I want to see if the CF PP gives a real advantage over normal PP (this will be my 845 PPamps) and SE at the same power level with real world speakers (i.e not my full range open baffles...)
Rome is a fantastic city with lots of amazing things to see - and very romantic. I doubt I will have my 833 finished this summer as I am moving back to the UK. I resigned from my job over Christmas and I am working out my notice period now. It's funny but I seem busier than ever since resigning...
Give me pm when your coming over and if I'm still here it would be nice to meet. I lived in the Netherlands for six years - had a great time. I occasionally get back so I'll come knocking!!!
I love the Tesla coil pics - but they scare me! One of my jobs as a junior engineer with Decca was to help test their ceramic insulators. I had to stand in a huge Faraday cage with the insulator under test connected to a 500KW transmitter and then spray water over the insulator to cause rf arcing!!! Then the insulator was examined for damage. Great when it worked like that but every now and then the arc would come back down the water stream towards you... It would normally earth around you as one had rubber kit on and used a plastic water gun but it is dammed scary to have a mini lighting strike going on around you!!!
Your transformer pics are great! E96 for an interstage is over the top! Twice the size of my office amp OPT...
ciao
James
I have looked at the plate of the output tube when using parafeed - and it is interesting at the edge of the passband. A bit more interesting than usual. Have a look at Bill Ramsey's analysis of the parafeed stage. He gives a calculated phase plot that explain a lot of what one sees... Mathematical Derivation of the Parafeed Output Stage
Within the passband the parafeed stage looks no worse than the usual IT coupled SE amp.
PL802 are a valve I had used in my early TV days but had ignored until recently 316a mentioned how nice they are as triodes. A mu=70 and S=40mA/V makes for an interesting beast! Pete Millett did some interesting work testing high transconductance pentodes as audio amplifiers.
High Gm pentodes
I guess the art of the cascode is choosing the right combination of valves for lower and upper devices - it easy to let the output impedance shoot up with all the problems that causes for integration downstream...
I tend to use the 6B4G NOS tubes or Sovtek 2A3. I haven't tried any of the expensive 2A3s yet and prefer the Sovtek to the chinese varients I have used so far.
I keep looking at the 833 in push pull. It is very tempting as I really like DHT PP amps... But it would be such a beast! I'm also working on a 211 Cathode follower push pull design that should have similar power output characteristics to the 833. I want to see if the CF PP gives a real advantage over normal PP (this will be my 845 PPamps) and SE at the same power level with real world speakers (i.e not my full range open baffles...)
Rome is a fantastic city with lots of amazing things to see - and very romantic
. I doubt I will have my 833 finished this summer as I am moving back to the UK. I resigned from my job over Christmas and I am working out my notice period now. It's funny but I seem busier than ever since resigning...Give me pm when your coming over and if I'm still here it would be nice to meet. I lived in the Netherlands for six years - had a great time. I occasionally get back so I'll come knocking!!!
I love the Tesla coil pics - but they scare me! One of my jobs as a junior engineer with Decca was to help test their ceramic insulators. I had to stand in a huge Faraday cage with the insulator under test connected to a 500KW transmitter and then spray water over the insulator to cause rf arcing!!! Then the insulator was examined for damage. Great when it worked like that but every now and then the arc would come back down the water stream towards you... It would normally earth around you as one had rubber kit on and used a plastic water gun but it is dammed scary to have a mini lighting strike going on around you!!!
Your transformer pics are great! E96 for an interstage is over the top! Twice the size of my office amp OPT...
ciao
James
Hello James,
I just bought a 450TL so my 450TL amp project is a go since now I got all the components, but it has to wait until I finished a 845 Transformer coupled Preamp.
I think we are on the frequency James, I intended to use the 6B4G on my 450TL amp also, I am still debating on the input tube.I got quite a few 2A3 but 6.3 volts transformer are easier to find.
I just bought a 450TL so my 450TL amp project is a go since now I got all the components, but it has to wait until I finished a 845 Transformer coupled Preamp.
I think we are on the frequency James, I intended to use the 6B4G on my 450TL amp also, I am still debating on the input tube.I got quite a few 2A3 but 6.3 volts transformer are easier to find.
A 450TL main amp driven by an 845 pre-amp
I just love it! What op point for the 845 were you thinking about? I've used then at points from Va 450Volts up and find them very nice at about Va=800V.
In my 211CF PP design I use 845pp as the voltage amp. driver stage. I need to swing about 600V p to p in that one and I know the 845s will do that just fine.
Thinking about possible front end valves for the 6B4G driving the 450TL. I really like the 6N6P driving 6B4G. There is a certain synergy about this combination that is very seductive. I tried a few other types from 6SN7 to 6S45s but liked the 6N6P the best. Just a thought and it might not have enough gain for this application...
ciao
James
I just love it! What op point for the 845 were you thinking about? I've used then at points from Va 450Volts up and find them very nice at about Va=800V.
In my 211CF PP design I use 845pp as the voltage amp. driver stage. I need to swing about 600V p to p in that one and I know the 845s will do that just fine.
Thinking about possible front end valves for the 6B4G driving the 450TL. I really like the 6N6P driving 6B4G. There is a certain synergy about this combination that is very seductive. I tried a few other types from 6SN7 to 6S45s but liked the 6N6P the best. Just a thought and it might not have enough gain for this application...
ciao
James
Hello James,
In the preamp the 845 will be running at 500-550V and 40-50ma bias. The transformer is UTC special that I bought from the flea market, I have used it with EL84 and it sounded very nice, so I have to build one for the 845.
I am going all out with this preamp, here are the features:
- Balance output.
- Phase reversal switch on Rca output
- Phono section.
- MC section with transformer.
- Remote control with Alps motor driven pot (I like this one)
- EM84 display
The picture below showed the preamp right after I finished mounting all components. The only think left is the wiring.
I might try your recomendation for the 6N6 tube for the 450TL, since I dont like the 6SN7 neither, none of my stuff used the 6SN7.
In the preamp the 845 will be running at 500-550V and 40-50ma bias. The transformer is UTC special that I bought from the flea market, I have used it with EL84 and it sounded very nice, so I have to build one for the 845.
I am going all out with this preamp, here are the features:
- Balance output.
- Phase reversal switch on Rca output
- Phono section.
- MC section with transformer.
- Remote control with Alps motor driven pot (I like this one)
- EM84 display
The picture below showed the preamp right after I finished mounting all components. The only think left is the wiring.
I might try your recomendation for the 6N6 tube for the 450TL, since I dont like the 6SN7 neither, none of my stuff used the 6SN7.
Attachments
... now that is what I call a pre-amp...
I like it! Very nice layout and features. Please let us know how it sounds once you have finished it. It started me thinking about pre-amps now...
Your 845s seem to have different structures? Are they made by different manufacturers?
BTW, the valve I use is the 6N6P and that is a russian beastie. It's quite different from the RCA 6N6 - just thought I ought to be clear about that.
My son uses 6SN7 in his 2A3 PSE amp. But then he says he has to be different from me
ciao
James
I like it! Very nice layout and features.
Please let us know how it sounds once you have finished it. It started me thinking about pre-amps now... Your 845s seem to have different structures? Are they made by different manufacturers?
BTW, the valve I use is the 6N6P and that is a russian beastie. It's quite different from the RCA 6N6 - just thought I ought to be clear about that.
My son uses 6SN7 in his 2A3 PSE amp. But then he says he has to be different from me
ciao
James
Hello James,
I just look at the 6N6P tube, and it is quite similar to the 12BH7 tube. Coincidence is that I used 12BH7 tube in most my amp, the 833, 845, and 250TL. I like the sound of the 12BH7 tube, but i might want to try something different in my 450TL, if not, I will stick with the 12BH7.
I just look at the 6N6P tube, and it is quite similar to the 12BH7 tube. Coincidence is that I used 12BH7 tube in most my amp, the 833, 845, and 250TL. I like the sound of the 12BH7 tube, but i might want to try something different in my 450TL, if not, I will stick with the 12BH7.