Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Scsoul on December 03, 2016, 03:15:32 pm
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what pt requirments do you guys use for a pair of 6aq5? i wanna build
A amp witph apair of 6aq5s and 3 12ax7 diode recto 250 to 270 plate voltage
Cathiode biased thanks mark
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6AQ5
(http://i.imgur.com/yJfe5FB.jpg)
EL90 (same tube)
(http://i.imgur.com/NwwlrCB.jpg)
Franco
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http://el34world.com/charts/Schematics/files/gibson/Gibson_ga17rvt.pdf (http://el34world.com/charts/Schematics/files/gibson/Gibson_ga17rvt.pdf)
Gibson Scout (GA17RVT) carried 300v on plates of 6AQ5's.
If you can find a PT that is 250-0-250 & use an old 5Y3GT, you might be OK with that having around 275v.
OR ............ 190-0-190 and use a 5V4 for around 230v. If you went solid state rectifier using diodes , maybe around 270v?
I would want a PT with at least 100ma.
275-0-275 & old 5Y3GT = about 300v same as Gibson Scout. You could install a VVR to lower plate voltages. I did this with a HoSo56 using 6AQ5's.
With respect , Tubenit
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http://www.musikding.de/Power-transformer-230V-230V-20V-63V (http://www.musikding.de/Power-transformer-230V-230V-20V-63V)
Primary 230V
secondary 230V 0,12A, 20V 0,12A (or 230v + 20v = 250v AC @ 120mA)
secondary 6.3V 4A
but this only if you are on this side of the pond
Franco
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Since Doug doesn't carry a PT that will keep the voltages under 275v & has 100ma or more, here is a source that has a 190-0-190 PT.
http://www.ebay.com/itm/PT190-2i-380Vac-POWER-TRANSFORMER-TUBE-240Vac-190-0-190Vac-120mA-/162279436680 (http://www.ebay.com/itm/PT190-2i-380Vac-POWER-TRANSFORMER-TUBE-240Vac-190-0-190Vac-120mA-/162279436680)
With respect, Tubenit
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thanks tubnit forgot about MPS, Those look great, i have some fender blues jr output transformers i was gonna try. i have a huge stash of 6aq5 i wanna get into. Was looking at soho and d-lite with 6aq5 built into 1 8inch combo thanks mark
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I truly hope you will share your results with us along with photos. The HoSo56 with 6AQ5's was a very expressive and touch sensitive amp.
IF I were doing a D'Lite with 6AQ5's, I would do something like a non-adjustable VVR where the plates and screens of the 6AQ5's were seeing 250v but the V1 plates were seeing 160-180v range. In other words, the VVR would just be lowering voltages on the power tubes.
With respect, Tubenit
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Here is an idea to consider that I think could be a great sounding amp. One might want to use 100k/1.5k plate/cathode resistors on V1 to get the voltages a little higher for a good clean tone.
With a 275-0-275 PT and a 5Y3GT, you could probably get by without a VVR? You should have around 300v on the 6AQ5 plates and the Gibson Scout had 305v on the plates. So, I am thinking you might be OK?
with respect, Tubenit
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after going through my Power power trany i found a couple good candidates one 280-ct-280 that i use a ez81 and should work fine for a 10 watter and a couple 170-170 that with diode shoud get me in 300 ballpart i got these cheap from fleabay and as i reacll in a el84h build therse were very close 300vdc so i guess i tray with 4 6aq5 build for around 20watts so its the tale of 2 builds, not sure what opt to use yet for for 4 6aq5 i have some 30watt ots that are 5.9k for 30 watt id assume a 40watt ot would be to large which ive found oversized ot isnt the way to go might try a hammond ao 43 chassis ot
Tubnit would you happen to have drill plas for a soho? im love on garolte and cant aforn a mess up? mark