The Secret Society of Lathe Trolls

Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

Anyone go a manual or info on the grampian type d feedback head???
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motorino · Joined: 24 Aug 2005 Posts: 194

i need too!
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Lewis D · Posted: Mon Jun 25, 2007 6:19 am Post subject:

Hey, I have the manual for the grampian amp that was made for the type D head. Includes power supply and schemtics. If you would like, I could email them to you.

Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

That would be perfect.. Can mail sump-warrior@hotmail.co.uk

Thanks alot. can see what grampian were thinking at the time .Would be nice to see about building one but 2007 electronics
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Lewis D · Posted: Mon Jun 25, 2007 6:52 pm Post subject:

This would cost mega money to make. The transformers on the power supply and the amp are huge. It takes two men to lift the power supply, no joke, thats how good the quality is. Huge valves!

But it would be great to make one, would be better than some transistor bit of crap off the shelf.

Thanks lewis

Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

Thanks for the circuit. going to have a look at a build of this update PSU but use amp circuit.. thanks again lewis ps. did ya scan it ya self if ya did thanks even more. If I do have a go I post step by step build
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motorino · Joined: 24 Aug 2005 Posts: 194

Thanks Lewis! Very Happy

i have more questions about the grampian type D, originally how much impedance have the driving coil? and feedback coil? its a feedback coil or what its that?

as it is limits in milliamperes for the cut coil? 800 ma peaks?

somebody has the original characteristics of frequency response of grampian D?

i dont have the RA7, i only have the cutterhead, i have a lot of questions after read a lot of post here, 1000 wats for a driving coil? its a joke? i have experience with big amps for PA, class A, B, the new concept of D...i have a clamp amperimeter...for destroy one beyma 21L50 you need 3 or 4 amperes (no dc) and have a 4 inches coil!

i believe if i put a 1000 hertz senoidal tone at -10db with a 1000 wats class A in a neumann sx74 few miliseconds...destroy...and i look its the best for the sound put in "hard tim" the amplifier!! +4dbs or more? wow, you can weld steel with a electrode with that 1000 wats amplifier

i believe im very confused, i burn a haeco sc2 few months ago, and i dont like burn my grampian d Rolling Eyes

any help?

thanks
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Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

3 to 4 amps at 180V full swing = 540W or 720W eq. 1000W PA. It states in manual never drive continus tone at full power will destroy head
150W valve power =250W trans power.I have rivera hammer320 valve it in real world is a loud as 500W class A and play all day,night,day ect. At Big volume no probs. Av killed many tranz amps Ha Ha Ha.
Grampian seems to:
it can swing 300v ish at 500ma on primary of output trans
trans may have 5:1 ratio ?

givs 60v 2.5A power 150W

trans 10:1

givs 30v 5A power 150W

Avo readings in manual are not actual voltages(AVO7 Not frequency comp.) of output on head terminals its just seems to be a setup reference without a Oscope Wattmeter ect.
Am still swatting up on valves but its Alll clearing now all the beers gone
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Lewis D · Posted: Wed Jun 27, 2007 9:52 am Post subject:

1000 wats? The amp is 150watts peak audio. Do not exceed 300ma. if you put in 800ma, the head will blow.

motorino · Joined: 24 Aug 2005 Posts: 194

thanks again Lewis! 300 ma..

i dont know a transistor amplifier works with 180 volts bus, normally use 100 volts

when i repair a amplifier and testing, i use a ac voltimeter ( for look the volts) osciloscope (for look the dc peak) a clamp amperimeter (for look the amperes) and a big resistor ( a old heating cooler )

Power= Volts x Amperes x Cos fi (normally 0,8 )

with all the measurements and the formula you have the power, if go up the volts the amperes go down, but you have the isolation problem...at the finish a similar problem

mmm....oracles, shamans, exoteric......
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Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

+-90v(180v) seem common as a supply if big amps +-50v(100) in smaller stuff
had a "no name china amp" for repair working V +-100v(200v) from psu was only 500W.wouldnt like my speakers on that!

sorry about maths at 2 mins after awake at a rough gusse

av found tranz for psu. hard bit sorted. amp parts seem easy to sorce. mate working out output tranz values he thinks it could push 200W w mega over engineering. says he seen output stage in a 10m ham linar. 2x811A in push pull running 50ohms load was rated at 200W.
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Lewis D · Posted: Thu Jun 28, 2007 6:41 am Post subject:

Where would you get the output transformer or would you get one made? Just to let you know, to build something of the same quility as the origanal, you would have to spend over £2,000 minimum. The transformers are huge. There is no plastic parts in this thing!! And it weighs a ton. The power supply and the amp are two seperate units. Sounds amazing tho.

Keep me posted,
Lewis

motorino · Joined: 24 Aug 2005 Posts: 194

i will made all the electronics..

i like this amp.. http://sound.westhost.com/project101.htm
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Lewis D · Posted: Thu Jun 28, 2007 7:38 am Post subject:

Oh yes I forgot to tell you that the original and anything of that time was not built on PCB. If you build this amp on PCB, the quility will not be as good. You should really hand wire this amplifier for best results.

Lewis

Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

found a RCA ex. mil tranz for job is rated bigger then orig. £40
psu stand about £100
amp £300 to £400 depend on sorce of valves
old large cases £10 each ex mil.

output tubes 811a £10 each(china) £100 pair(nos ex. mil)

caps ect cheap ex mil.

not many thing made in 1950 had a pcb Even my Rivera valve amp hardwired and its made in 1999 by a G.peff he signed inside!
output trans can be custom made for around £200 prob most exspensive part but looking at a 3S industries output tranz as used in rivera £180.
local mil. surplus has stacks of high power tube electronics at cheap prices for ham bands this amp uses these parts.
The Ex mil. stuff is of very high quality like the parts used by grampian.
The mains transformer I found is out of a mil. radio rack had one massive valve in center must be 24inch long 12inch glass bulb in middle force air cooled. prob 1Kw! or more It had 2 of these transformers in it friend has the other he loves very big valve amp for ham radio. he is very good with valves he 75!!
Thanks again lewis for info.. wouldnt be poss with out it..
p.s. What lathe do you have?? mine is the one in the picture but come with on head or amp hence building one to keep it RETrO.
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Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

Lewis Thanks for the intrest.. have orded input and output transformers valve sockets, caps ect. have found a case for the psu. so should look at construction some time next week..
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Lewis D · Posted: Tue Nov 13, 2007 10:37 am Post subject:

Hey, hows the amp coming along? I'v been getting good results on my system at the moment. I have been doing cuts for poeple in my school and other disk jockeys. I also recently got another R.A.7 amplifier, but yet to plug it in. I also installed a Lyrec motor into my Presto 8DG, steady as a rock! All valve system and sounds great!

Lewis

Amp Doc · Joined: 21 Jun 2007 Posts: 109 Location: UK

Hi lewis very busy at moment at work so not got anything done to the amp. have made a active RIAA network though and am runing one of the 500w lateral n channel mosfet amp modules I make no feedback yet but gives good results so cant wait till I get time to use feedback.
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