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Old 1st Dec 2020, 9:21 pm   #21
Tim
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Default Re: Mini lockdown project

Hi Doug.
If your teaching your bairn, how about a simple one valver using an ECL82 etc? Has all the essential basic elements, easy to build and get going.
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Old 1st Dec 2020, 10:24 pm   #22
dougietamson
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Default Re: Mini lockdown project

Quote:
Originally Posted by Tim View Post
Hi Doug.
If your teaching your bairn, how about a simple one valver using an ECL82 etc? Has all the essential basic elements, easy to build and get going.
I have a couple of ECL80 and ECL82, I used the ECL82 in a transformerless spring reverb, sound great too.

He's never soldered anything yet so he'll do some basic safety stuff and a bit of assembling components/soldering and some 'scope work tracing signals. We'll also do some woodwork for a small cabinet, again he's never done even the most basic of technical stuff. He can use some of the tools I made at school in the 70's, shame he didn't learn any wood/metalwork at school, we were in France for most of his school years where they don't do any practical learning.
I'll take him through how it's
Just before we moved back to Edinburgh we (Me, Mum and 2 kids) took 10 weeks off to do a road trip in a camper van from Adelaide to Cairns. I bought him a $20 guitar in a pawn shop in Adelaide for him to learn on, during lockdown he's really got into playing guitar and learning Beatles stuff (inspired by one of his former teachers)
He 's studying maths and astrophysics (maybe a future Brian May in the making!)

Doug
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Old 2nd Dec 2020, 9:56 am   #23
Valvepower
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Default Re: Mini lockdown project

Hi Doug,

Glad the info was useful.

The original plan for the bits Ďa this amp was to use two EL95ís and a Radiospares Hygrade output transformer (this is still an option at some point in the future), however this morphed in to the bits Ďa this amplifier Mk II, Iíve just made, using EL84ís and the Radiospares EL84 output transformer. I think there is an embryo thread in the Homebrew section, and Iíll post some pictures and eventually the circuit when Iím happy with it.

Another project is to make a Marshall JTM clone using 6V6ís this will be a JTM15Ö.

Now Iím semi-retired the time has come to tackle the round tuit jobs.

Ah, spring reverbsÖ thereís a unique sound that canít be easily recreated in the digital plug-in world.

Iím heading off topic here.

Regards
Terry
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Old 2nd Dec 2020, 1:23 pm   #24
dougietamson
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Default Re: Mini lockdown project

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Ah, spring reverbsÖ thereís a unique sound that canít be easily recreated in the digital plug-in world.

Regards
Terry
The best sounding spring reverb I've built is the one by Grant Willis from his valveheaven site, you can use just about any signal pentode (he recommends pulls from old TVs eg the EF80). It uses a constant current drive and no transformer for and the spring lines used for solid state drivers (the higher impedance type). Controls for dwell and reverb signal mix/balance, the dwell control drives the spring harder.
It sounds as good as the '63 Fender stand alone unit at £600!
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Old 2nd Dec 2020, 9:58 pm   #25
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Default Re: Mini lockdown project

Home now offer my op and our cleaner has brought a Roberts 701 for me to look at. SWMBO is out for most of tomorrow so hopefully I can have a good tinker with it. I don’t know how it’s misbehaving yet, as somehow I managed to resist the temptation. Well, I didn’t want to give the game away did I?
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Old 3rd Dec 2020, 11:44 am   #26
dougietamson
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Default Re: Mini lockdown project

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Home now offer my op and our cleaner has brought a Roberts 701 for me to look at. SWMBO is out for most of tomorrow so hopefully I can have a good tinker with it. I donít know how itís misbehaving yet, as somehow I managed to resist the temptation. Well, I didnít want to give the game away did I?
Should be small enough to hide easily

Luckily my other half refuses to go in the loft in case there are spiders, which the there is of course, huge big ones too, guarding my treasures.
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Old 3rd Dec 2020, 2:29 pm   #27
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Default Re: Mini lockdown project

Alas, was left a big pile of ironing to keep me out of mischief. SWMBO and no1 daughter out again tomorrow so perhaps then.
Similar situation regarding loft here. Fortunately!
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Old 4th Dec 2020, 10:12 am   #28
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Default Re: Mini lockdown project

Tim hope the OP went OK.

Doug,

Iíve got to be careful Iím not heading off topic hereÖ.

My experience with spring reverbs goes back to working at Roost in the 1970ís and fixing amplifiers at the local music shop. From memory the circuits we used were both or one half an ECC81 driving a small transformer with an ECC83 post amplifier. Spring reverbs were a nightmare in the combo amplifiers!

I vaguely remember the 6BR8 or was it 6BR7 doing reverb duties in some amplifiers - could have been Selmer or WEM?

Should have squirreled away some of the original Hammond Reverb trays along with Mullard EL34's.

Anyway, thatís enough memories for now!

Regards
Terry

Quote:
The best sounding spring reverb I've built is the one by Grant Willis from his valveheaven site, you can use just about any signal pentode (he recommends pulls from old TVs eg the EF80). It uses a constant current drive and no transformer for and the spring lines used for solid state drivers (the higher impedance type). Controls for dwell and reverb signal mix/balance, the dwell control drives the spring harder.
It sounds as good as the '63 Fender stand alone unit at £600
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Old 4th Dec 2020, 2:50 pm   #29
dougietamson
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Default Re: Mini lockdown project

I put together a quick test in my dev chassis of the 1st valve in the pre amp stage, mainly to test if the old Mullard and Mazda pulls in the junk box had any AF service life left in them.

All worked ok, I input a 200mV sine wave and got a nice clean 40V out and were flat (eyeballed only) up to 18kHz. All valves were within 10% of each other. Tried a couple of EF80s too.

Next I'll start a new thread to get help with the push pull section as I've already taken it way off topic

Doug.
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