| Triod lover |
| I just finished my mighty little amp using GM-70 last week,am a newbie in this forum,any comment pls advice. |
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| Tweeker |
| A link to your project or more details about it please? |
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| Triod lover |
Hi.Tweaker
I do not have a link to my project,i use 12HG7 as a driver thru 100H. choke load and feed thru GM70,the chassis size is 12x19 inch.,i 'll post some photo.
Arth. |
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| Triod lover |
| The look inside my amp |
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| kevinkr |
| Looks very nice. How about a little more description and some schematics? :D |
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| rcavictim |
| quote: | Originally posted by Triod lover
I just finished my mighty little amp using GM-70 last week,am a newbie in this forum,any comment pls advice. |
Really nice job there! What output xfmers did you use? What is the plate load Z? You are using ultralinear G2 connection to OPT yes? |
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| kevinkr |
Hi rcavictim,
The GM70 is a triode so he obviously won't be running it in UL as there is no screen grid.. I've included the data sheet as an attachment.
I'm actually thinking about getting a pair of these at some point to design and build an amplifier around.
I have heard a lot about a supposedly better sounding copper plate version of this tube. Standard plate afaik is graphite. Anyone have any thoughts on this? Triod Lover which version of GM70 do you use? |
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| HollowState |
Very nice construction and wiring job. I like the combination of wood and metal for the chassis too.
| quote: | | You are using ultralinear G2 connection to OPT yes? |
I thought GM-70s were triodes.
Victor
PS, yup, Kevin confirmed it. If I didn't have as many tubes as I do, I'd buy a few of these too. They sure look cool. |
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| Triod lover |
Hi..RCAVICTIM,KEVINKR,HOLLOWSTATE
Thank you all for the compliments,GM-70 is a very stable and tough like a tank it is a pure triode no G2,the output is the Electra-print load impedance is 5k.,the sound is very sweet and has a very good bass,the sound stage is just like watching the concert!!!,anyhow,i just burn-in for two weeks i think this tube will need another week or so to get it ready to rock n roll.One con about my amp is it so hot,especially living in Thailand that the temperature quite hot all year!!.I wish i lived in U.S.A or CANADA to get my amp as the heater as well. |
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| Triod lover |
Hi...Kevinkr
The GM70 that i used is a copper plate,i test both graphite and copper plate and prefer copper plate much more!!! it has a better tonal balance for me(my opinion anyway). |
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| kevinkr |
Some parts of the USA are quite hot as well, and even where I live in the summer the temperature outdoors exceeds 32 C quite regularly, and gets to 40 C sometimes. We have no AC so I avoid using even the 300B amplifier when it is very hot, which because of its tube regulated supplies throws off quite a lot of heat.
It's cold outside now, but my basement listening room is always warm until outside is below 0 C..
Good to hear about the copper plate version, I have seen them being sold on eBay by reputable sellers (one or two I have dealt with before) so I think I will try a pair sometime soon.
How much power do you think you are getting, what is plate current and voltage for example? |
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| rcavictim |
Sorry all. I am suffering from mentalpause. I somehow thought the GM70 was a euro version of the 813. My mistake. I`d love to pick up some GM70`s but the GM dealers over here in Canada just sell mostly unecessary garbage which the planet could live just fine without if they completely stopped today.
BTW, anyone got a single RCA 813 they can spare? I`ve been wanting to build a SE amp and I finally found my pair that were misplaced for ten full years and to my dismay one has an open filament. I`d go to my closest RCA dealer but alas the RCA dealers over here in Canada just sell mostly unecessary garbage (Thompson CSF) which the planet could live just fine without if they completely stopped today. |
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| Tweeker |
Ive heard graphite plate GM70 sounds much better (than cold GM70 graphite tube) when run hot, use full 125 watts dissipation.
Graphite plates can and should be run to a dull red glow (which you may not see over this tubes light bulb like heater) in order to getter. |
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| Triod lover |
Hi...all
You figue right!!! the hotter the better for this lantern! ,i think the sweetest spot for ma the V.plate around 800 volt. the current approx. 110 M.A the sound just right.,for investment and sound quality i love the copper plate,but be awared of the plate dissipation is lower than the graphite. |
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| Triod lover |
| Am going to leave this forum a few days,today am going to BANGKOK,anyhow i'll check it regulary,i post a pic of GM70 copper plate singing a song of Diana Ross the sound very smoothhhhh!!! |
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