Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on April 03, 2020, 04:34:28 pm
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Hi guys, The Covid 19 has hit downunder, we're fairing quite well compared to the rest of the world so far.
But we are suffering hugely in the work place due to social distancing.
I just got laid off and now on the unemployment line, thankfully the government has put in place a stimulus package for the next six months.
So some time on my hands....and some junk laying around the shed to generate some cash.
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I'm changing the cathode bias output to fixed bias and removing one of the 7pin sockets (not sure which one atm)
I am anticipating some problems due to the size of the chassis and the amount of gain on the 6AQ6 valves.
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just got laid off and now on the unemployment line
all the trades guys here quit going to the union shop, but they got a hellava gray market going under the table, I love creativity :laugh:
you can drive a pair of 6AQ6's from 1 AX7, maybe take out 2 sockets :laugh:
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Hey shooter, I'm a carpenter/builder by trade and 58yo, it will be interesting to see what the building industry will be like in 6 months.
There is already too many tradies now working for shit wages because there is not enough work.
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Most I know are 30-50, they're making honest money fixin uncle Pete's place for CASH only, then Bob calls and wants......., catch a mess of fish and you made it another week in world 3.0 :icon_biggrin:
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tim, sorry to read about your employment situation. hoping thing get better soon for you.
--pete
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that looks like a good design. i like 6aq5 they make smooth od tone. i like how you got one stage , tone stack, recovery from ts loss then an extra gain stage and a cathodyne p.i. i like those split load p.i. they give that great lo-fi tubey goodness. thats one reason imho the tweed deluxe sounds so good. that amp should scream like a banshee. have fun. i am furlough myself, i am a union electrician here in new orleans and havent worked in two weeks, i already modded one amp, fixed 2 others, rebuilt/restored a 1935 rca 225 radio including complete refinishing, well today i put stain on the console tommorrow it gets lacquer. good luck
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Sorry about your employment plight Timbo. I'm a similar age and was 9 months 'between jobs' 2 years ago. Many people laid off on this side of the ditch now too. Soundbytes yet?
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Hi Timbo
Have you considered a career change? You do really nice amp work. :headbang: :smiley:
Or at least part time in Custom amp building.
In Canberra we have builders who have gone bust and others who can't find enough hands/hours in the day to do the building work :dontknow:
Anyway love your amp work and all the best with your employment prospects.
Kind Regards
Mirek
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Thanks guys for the support, I'm sure something will come along.
Wiring is just about done, just need to go over it again and it's ready for a kick start.
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Hi guys, The Covid has fired up well.
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Voltages are good.
The 6AQ5 plate voltage is about what I expected with the SS rectifier.
As per the data sheet 250v on the plates and -15v bias, so nearly -17 and 277v on the plates should have it bias about right.
Sound wise it's a bit bright so a tweak on the TS (50p) may need to be increased.
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Sound wise it's a bit bright so a tweak on the TS (50p) may need to be increased.
looks like you'd want a 220-270pF for that part.
between V1b and V2a you have a .001uF coupling cap with 56K grid leak for V2a which results in a 2.4KHz low freq. rolloff - might want to look there. :dontknow:
.01uF to 56K has f-3dB ≈ 280Hz
.022uF to 56K has f-3dB ≈ 130Hz
.047uF to 56K has f-3dB ≈ 60Hz.
bumping R from 56K to 100K will approximately halve the rolloff frequency in the above. e.g., .01uF to 100K ≈ f-3dB of 160Hz
--pete
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Thanks mate, Upped that 50p to 300p and replaced the .001u with a .022u.
Much bettera.
:icon_biggrin:
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Hi guys, Unfortunately Covid 19 lingers.....
BUT, the Covid 10 is done.
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:icon_biggrin:
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Nice build!
I'm a carpenter/builder by trade and 58yo, it will be interesting to see what the building industry will be like in 6 months.
I was working the beerbaitngas last week, the commercial contractors are slammed, but the home builder/repair guys are getting spanked with $50 plywood! A few have been buying lumber straight from the local log to lumber guys. The problem, If it hasn't been blessed by the Govmnt, it won't pass inspections, so the work around for interior , just don't pull permit. creativity is what won the west :icon_biggrin:
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Really nice cabinet work! That's something I'm not very good at...
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Thanks guys.
Time fly's, I have now been employed for nearly 12 months. :icon_biggrin:
Great job doing house reno's and new builds for a local builder.