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Rogers HG88 mk3 Pick Up Adaptor

B

bob57

Active Member
Hi
Can anyone help me with the value of resistors and capacitors for the Gold Pick
Up Adaptor for the Rogers HG88 mk3 Amplifier.
I have tried 250p, 680p, 68k and 720k it plays but very bright and little bass.
I am using a shure M75 in a GL75 deck.
I am using the circuit diagram for the Rogers Cadet 3 as a posted on a forum on google. It said they were the same adaptors for both.
Hope someone can advise as I would like to see what this amp sounds like compared to more modern transistor amps.
Regards Bob
 
I also thought that the adaptors for the Cadet 3 and HG88 3 were the same.

I ran my HG88 with gold adaptor and an M75 (ED I think), and it was fine, no longer have it though. I still have a Cadet 3 and that I used with an M75ED and was fine too,

The HG88 3 is a very good amp, not much different to the Cadet 3, but with a more useful amount of power, possibly slightly better bass due to the larger output transformers.

I very much regret selling mine years ago. In my view it's better than many later transistor amplifiers.

Make sure that nothing is plugged into the tape out sockets, these are meant for very high impedance loads. Connecting a "modern" tape recorder to them will probably cut the treble by many dB.

Are you sure that speakers are connected in phase? What speakers are they?

Possibly, somewhere, I might have diagrams for the adaptors.
 
Speakers are bookshelf Bowers and Wilkins and they are connected in phase.
All the other inputs are sounding fine just the phono stage with the adaptor that do not seem right.
 
I don't know anything about the Rogers amps, but if a MM cart is very bright with no bass I'd instinctively try reducing capacitance. Try for 47k and as little capacitance as you can get and take it from there. Useful cart loading calculator here: www.hagtech.com/loading.html
 
Thanks Tony L, Not much good with the technical stuff, just had the adaptor made using a circuit diagram for the Cadet 3 Gold adaptor but just wanted to see if the component values were correct as one circuit shows a 250 cap and in the same position on a second circuit it shows a 2500 cap, not sure what difference that would make.
I was hoping someone might have knowledge of the Rogers Gold adaptor and could supply a circuit diagram and value of components to confirm that the one I had made was correct.
Regards Bob
 
Thanks Radfordman but I have circuit diagrams for the Cadet 3 and HG88 3 and niether of them shows the adaptor circuit.
Regards Bob
 
Found a small box with an adaptor and a spare metal cover in. The adaptor is a gold, and the spare cover is a silver, but I cannot guarantee that the right cover is fitted. Will take photos.
 
Hi Radfordman just checked your link and found that one fellow posted the values and connections and they tally with the one I had made so it looks like I have a problem somewhere else. Thanks all for your help.
Regards Bob
 
Is it worth sticking a meter over the phono input socket and just measuring what the cartridge is seeing from a load and capacitance perspective, that might give an indication if it is the right adapter or something really odd (e.g. for a ceramic cart).
 
It might, because the ceramic input should be very high impedance, say 1 to 2 M Ohm.

However, the response change by a change in load resistance or capacitance should not be that great. In fact Radford in the SC22 used a load resistance of 68K Ohm (I think), for the phono input.
 
Nothing wrong with the inbuilt module, I just have a good separate set-up so use that. I like these amps and had mine carefully restored.
 
There is a HG88 manual over on HiFiEngine that has cap values, a schematic etc, plus details of the phono modules (link). You'll need to register and log in to download it.

PS Does anyone know much about the history of these Rogers amps? I'm assuming it is the same Rogers that made all the speakers, i.e. Jim Rogers' company started in 1947. Was Jim the designer?
 
Jim Rogers, owned Rogers, I went to the factory in Catford quite a few times in the 60's, saw these amps being made, chassis corners were brazed up. Work of art.
 
It is a shame there is no decent in-depth history of Rogers online. Everything focuses on the LS3/5A, which was just a license build as far as Rogers were concerned, or the JR149, which was after the Rogers company had been sold on. From what I can piece together Jim was a thoroughly interesting and radical designer right from the start and really needs to be given similar credit and respect to say Peter Walker, Gilbert Briggs, Harold Leak etc. There doesn't even seem to be something as basic as a time-line and product itinerary.
 
Agreed, Jim knew what he was doing, nice bloke too. I have a Williamson power amp that was built at Rogers in the early days.

The is some stuff on the unofficial LS3/5a site about Rogers, but I don't think is says much about the Jim Rogers days
 
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