Just bought a 50/60s valve preamp, did I get ripped off?

[ivansc]

(grin) I bought a GAP 73 pre and it works just fine.

£350 for the front end of a geriatric Ferrograph?

[MrSedor]

Hi

I solved the problem resoldering the last old double capacitor. There is no more oscillations. I think the polarity of the new capacitors was wrong and I probably damaged them, so I m waiting for new ones.
But I have another issue replacing the tubes. One of the olds mullard EF86 cannot be changed by a EH EF86, it's cause a lot of hum. I don't understand, the new tube is correct and I try with another EH EF86 with the same result...

[Insomniaclown]

Hmmm, could be a bias issue. I would measure the plate and screen voltages on the original EF 86, then plug in the replacement and see what you get. Did it come with a schematic of any kind?

Use caution when measuring voltages! Sorry, got to say it. If you don't post for a few weeks, I'll get worried.

[snod_donkey]

Originally Posted by MrSedor

Hi

I solved the problem resoldering the last old double capacitor. There is no more oscillations. I think the polarity of the new capacitors was wrong and I probably damaged them, so I m waiting for new ones.
But I have another issue replacing the tubes. One of the olds mullard EF86 cannot be changed by a EH EF86, it's cause a lot of hum. I don't understand, the new tube is correct and I try with another EH EF86 with the same result...

What make of valve are you fitting in? If its ok with the old valve then the amp is ok. If you are using nasty modern Russian made valves that may be a problem.... If you fit a crap hummy valve to the right hand side EF86 socket which is the mic pre it will be very much boosted through the next preamp stage. I had the same problem fitting modern valves so used British made Mullards in the end which was much better. Cost a bit more but the sound was fantastic

[SWAN808]

here he is again. Im curious how these sound - not a bad deal...

Vintage Valve Mic Preamp - STEREO UNIT - Mike Preamplifier - Ex BBC | eBay

[SEED78]

my mono one was £290.

I'm not pre expert by a long way - but so far I like it. not really put in the hours with it yet as have been focusing on other aspects on my studio. first impressions is its got a decent amount of gain, not too noisy, not too muddy or too colored.

If more clued up at the time I might have continued to save up cash and invested in a dual channel DAV, but those are twice the price.

These are not just the front end of a Ferrograph - they have had other work done to them.

[ivansc]

Apart from hooking up a power supply and of course the external connectors,what else has been done?
I cant see anything other than that in his ads.

Still think you would be better off with a GAP7 3pre for the same sort of money AND you get a full warranty & no thirty,forty, fifty year old components.

[dkelley]

Originally Posted by ivansc

Apart from hooking up a power supply and of course the external connectors,what else has been done?
I cant see anything other than that in his ads.

Still think you would be better off with a GAP7 3pre for the same sort of money AND you get a full warranty & no thirty,forty, fifty year old components.

agreed, but it's cool since it seems to be in working shape. as long as psu caps and other electrolytics aren't about to leak all over or dry out then all should be good.

maybe not a sonically amazing piece, but fun all the same to have.

[SEED78]

yeah it was a semi daft buy, I did mention I bought it before even knowing about the GAP73... didn't actually choose this over the GAP - I'd rather have saved up for a DAV now that I think clearer - hay ho - its far from crap, sounds decent - worst purchases could have been made.

[RebornOnline]

Originally Posted by SEED78

g-r-e-a-t - just found out about the golden ages pre 73

Mega-facepalm! It's probably the most talked about pre-amp on the whole board

[SEED78]

I know... very strange i missed it, I've seen nothing BUT talk of GAP 73 since obviously ha ha! still, what I have is far from bad so not loosing too much sleep yet.

[harrypurser]

I have a pair of these (60s) preamps, bought from the same Ebay guy. IMO, not ideal as a 'main' pre. The sound is very coloured, with a bit of a hump at around 150-200 Hz and another at 1.5-2 kHz (I think), and there's some roll-off above 10 kHz. If you want to record a pop vocal, look elsewhere. Where these excel are on drums (apart from OHs), bass and electric guitar.

However, the best use for these seems to be for synths rather mics in my studio. Another poster mentioned that the strength of these pres is the low end and I would agree. In fact, you could pretty much use ANY synth on bass duties if tracked through one of these, because they extend and solidify bass without any flabbiness.

SEED78 - I think that these are actually fantastic bargains, but you will +definitely+ need something else for more general duties.

[SEED78]

enjoyed mine so far.


good to hear an endorsement on drums and bass - any thing that adds beef to those chains is always appreciated!

[EvLoutonian]

Hey guys,
Nice to find some info on these here.
I have a couple of these old Ferrograph pre's here (in Melb, Australia) that I've been meaning to rack up for some fun in the tube front end action department, but I'm not too sure exactly which parts of the circuit are in the signal path and which aren't, once removed from the tape recorder side of things. I can see that the Analogue Addicts guy(s) remove a lot of components from the ones they're selling.
If any of you guys could post detailed pics of the inside (underside and top of the chassis) that'd be uber helpful!

Thanks,
Evan

[snod_donkey]

I have purchased the stereo version which is a different circuit then the mono units. The mono ones sound fantastic on my vintage synths and drum machine but i also wanted something else for vocals. I found the stereo unit was flatter with more gain and very very quiet in the background noise dept. so quiet i thought it want working!! Way i look at it is yes its old and built with vintage components... thing is these very components are exactly what are found in the top end systems. New china crap or vintage hi end British? I know where my moneys going

This is the unit i have eBay - The UK's Online Marketplace

[EvLoutonian]

Hmm, well, I look forward to seeing some images of the underside of the chassis if anyone can provide it?

So I can try this work on my couple of old Ferro pre's.

Cheers!
Evan.

[EvLoutonian]

PS. Am I right in my understanding of the circuit, which is that actually there is no input transformer in use in the audio path of this kind of re-working of the circuit?

If you look at the original circuit notes, there is an input transformer, but this was used on the return from the tape playback head, into tube 1 of the circuit.

And the large output transformer is only really used for the (low power single ended EL84) speaker output.

[EvLoutonian]

Here is a page with the Series 5 (very detailed) User Manual (with schematics) and a bunch of other Ferrograph notes and manuals:

Ferrograph Tape Recorders

A great resource!

And you will see in the series five manual a good explanation of how the whole unit works.