"Out-Hacker" a Hacker GP42?

[ukvrshaun]

My audiophile friend has been pretty impressed with the sound coming from a 'recapped' Hacker GP42 I've just completed. (New transformer, Sprague Atoms and Orange Drops, some polystyrenes and silver micas and a handful of Kiwame resistors).

It has me thinking, how you would "Out-Hacker" a Hacker? What's the most you could get out of a 'one box' 60's inspired record player? What would be the limiting factor (or factors)?

I'd be interested to read your thoughts and ideas.

My only ground rules are valve amplification (and maybe pre-amplification), as a want to build a valve amplifier, a single full-range speaker and a 1/2" plywood / rexine box of any custom dimensions... with a carrying handle.

Thanks
Shaun

[unitaudio]

Hi Shaun. I would imagine the greatest limiting factor would be susceptibility to acoustic feedback due to the speaker being in the same box as the record deck. That's the biggest problem with one-box record players.

Certain models have appeared with as much as 12 Watts output but that appears to be the practical limit for this configuration.

I'd say it's alright to include a tweeter in the allowable specification as some portable record players had them.

Regards,
Paul

[Edward Huggins]

The Philco "Duet" from 1957 will out-Hacker-a- Hacker, with it's truly deep, reflexed designed cabinet Bass, low distortion and a non-harsh treble....

[RojDW48]

I am rather pleased with a Decca Decalian from the 40s. I replaced its 78 only deck with a Garrard 2025TC and sonotone cart and the old 6V6G single ended amp really delivers. I am reviving a GP42 at the moment (same deck and cart). They both sound very good. If pushed I would probably lean towards the Decca - it is, after all, about 70 years old. I hope I am working that well when I get there!

[stevehertz]

A rock solid cabinet complete with sound deadening panels would be a must. Then you need the best speakers that you can lay your hands on, a great (hifi (no stacking facility?)) deck etc. It would be an expensive undertaking for sure.

[ms660]

One idea would be to incorporate the loudspeaker into a detachable lid with a flying jack lead or whatever plug on it, socket could go on deck's base board, that way for normal volume the lid could remain attached for normal listening or detached if playing loud heavy bass stuff like Roy Docker's Mellow Moon Light

Lawrence.

[ukvrshaun]

Many thanks for your initial thoughts, including the alternative 'best' record players. I'll leave the GP42 as my reference, due to its current popularity, availability and the fact that I own one! I would still like some help on the high-level design decisions, as I'm not a vintage record player specialist, having moved sideways, somewhat, from Gramophones/78rpm at one end and Digital Electronics and Computing at the other end.

I've been considering the following:

- A 'very solid box' is required. The GP42 is pretty robust, it seems? I'm not sure I understand the need for 'sound-proofing', though. I'm intrigued by Edward's 'reflex designed cabinet bass', if he's got any more details.

- The GP42's amp design looks similar to other Push-Pull circuits I've studied. The valves used (ECL86) were lower cost items, I believe. I'm thinking about a Mullard 5-10 as offering a good all round improvement...

- Should I stick with a Ceramic Cartridge? MM would be preferable for choice (and it was just available back then, I think), but I'd need to pre-amp. I'm also not sure whether MM Cartridges will just pick up noise in this particular environment?

- I'm assuming I'll need to fit a transit screws/floating deck to maintain the 'portable' aspect? What would have been a 'step up' from an SP25?

- I've no experience of loudspeakers, I'll need to do some basic research, unless anybody can offer advice...

Thanks
Shaun

[ms660]

Problem is, upping the power output would usually up the weight.

Lawrence.

[dseymo1]

I've been thinking for a while along similar lines, and had in mind a Dual CS-505, which wouldn't mind being turned on edge, and an EMI 13*8 speaker. I think a MM cart is essential (and no more expensive than a good ceramic). Undecided over the amp, though. Practically, a Class D job would be sensible, but I agree that a 5-10 would be more fun. We'd be looking at a fair sized cabinet for that lot, though.
Speaker in lid is a good idea, as it could be designed as a proper cabinet.
These days, it would be reasonable to expect some sort of quick-release deck suspension, which wouldn't be too difficult to arrange.

[wd40addict]

IMHO the 3-3 sounds better than the 5-10. Why not out Crosely the Croselys too and make it stereo with a pair of 3-3s? The best sounding, easily obtainable, drivers tend to come from the car audio world. Could be a really nice project

Greetings from Stevenage!

PS: Edward is the Philco better that the Pye's?

[Edward Huggins]

Whatever you do, don't attempt to "tweak" your GP42. No point in adding a MM cartridge as you'll also need to add a pre-amplifier - and you'll be unlikely to hear any difference. The only tweak I would ever consider for this is to add a Tweeter (alas the otherwise adequate 10" x 6" Goodmans speaker "falls-off" rapidly at the higher frequencies) but there's no room for one. The GP42 has a sort of "reflex" vent of sorts, but not as well executed as that on the Philco. As is, the GP42 is certainly deserving of its reputation. I personally prefer the version with the Garrard 3000 autochanger fitted - a marginally better performer than the 2025TC.

[RojDW48]

I am inclined to agree with Edward here. You won't hear a significant improvement from any of the usual mods because the GP42 is just about there already. You could, of course, keep an eye open for the GP42 extension speaker and go for stereo that way (I haven't revived the speaker on the one I am repairing yet so I can't comment on the quality). The big gains are to had from older RPs with top quality amps but ancient and noisy autochangers or single speed 78rpm decks. They can be improved with a more modern deck and newer, sometimes better cartridge (assuming, of course, that the output matches the input!) and still maintain their viability as portable RPs. The boxes of the decent old RPs, in my experience, are pretty robust. I was astonished by the 70 year old Deccalian's ability to belt out the Doobie Brothers, close to the pain threshold, without buzzing or booming! If you want anything much more than a pleasing improvement in quality, I would have to suggest that you look at the traditional (not portable) hi-fi system.

[ms660]

You could save weight by going live chassis, a couple of 50L6's should put out a fair whack, those with other suitable phase splitter, amplifier valves would reduce dropper dissipation if using a diode dropper or alternatively use a capacitor dropper.

Lawrence.

[Edward Huggins]

Originally Posted by wd40addict

PS: Edward is the Philco better that the Pye's?

Which Pye unit are you referring to? One of their best compact record players was the Pye "Super Black Box", but this was not a portable.

[ukvrshaun]

Some additional insights into my motives.

I'm definitely not touching the GP42! This would be a separate unit. My primary goals here are to learn about valve amplification and hand-build a 60's style (mono) record player. Although this started as a 'thought exercise', I do like ambitious challenges! I tend to seek lots of opinion and advice first and take my time before starting construction. This is also more about the discovery than the result, to a certain extent.

I think my initial premise is that the quality of the GP42 amplification can be improved (at some cost) and that there are advantages to using a MM Cartridge (again with additional cost). I'd also now add 'adding a tweeter' to that premise. These are the areas I'm most interested in for information and thoughts.

Ultimately, I'd be happy with a record player 'that I made', even if, in the end, I couldn't out-Hacker a Hacker!

Shaun

[cmjones01]

Originally Posted by ukvrshaun

I've no experience of loudspeakers, I'll need to do some basic research, unless anybody can offer advice...

Yes, start here. The loudspeaker and its cabinet will make by far the biggest difference to the sound of the record player. After that, improvements to the cartridge, arm, suspension and deck will be next. It's the places where electricity meets mechanics that have the largest impact.

Any changes to the amplifier will be relatively hard to hear, unless what's already there is grossly inadequate or is faulty. Push-pull ECL86s are already as hi-fi as you're likely to want, as long as the output transformer is big and well-designed enough.

Using boutique resistors and capacitors will make no measurable or audible difference, again unless the originals were faulty. The big wins are not in the electronics!

Chris

[Radio tirana]

Hi Shaun
I agree with Chris
Not much wrong with the amplifier from a GP42 IMHO if anything it's the loudspeaker that lets it down slightly. I have added small tweeters to my own Hacker Cavalier and AL15 amplifier fixed between the speaker and the front grill to extend the frequency response. I have also been down the magnetic cartridge and solid state preamplifier route but was not happy with the result, the rumble from the motor and rim drive were reproduced too faithfully and the extra gain increased the mains hum to an unpleasant level. I experimented with different ceramic cartridges and on balance I think the BSR SC12M gives the best performance.
I much prefer the models fitted with a SP25 to the 2025/3000 series decks.
The Hacker has a great sound unmolested and I love playing 60s and 70s music on it good and loud.
Good luck with your project I like the concept.

[saxmaniac]

I would be in favour of a magnetic cart. I am listening to my hacker at this moment and the mag cart makes no difference to sound quality on this but the main reason for changing was to be kinder to the records and I'm not sure you can get a decent new crystal cart at any price? Please correct me if I'm talking rubbish!

[Edward Huggins]

A good ceramic cartridge e.g. Acos GP96 or a Sonotone 9TA/HC tracking at the correct weight c.3.0 grams is not going to cause any more damage than a MM! There is a limit to how light that Garrard tone arm can track anyway.

[dazzlevision]

Originally Posted by unitaudio

Hi Shaun. I would imagine the greatest limiting factor would be susceptibility to acoustic feedback due to the speaker being in the same box as the record deck. That's the biggest problem with one-box record players.

On the Decca Deccalian/4, with EL84 push-pull output, the amplifier's output was limited unless an extension loudspeaker was connected (which muted the internal one).