GM70 PP

[Nick]

The shoddiness is off the scale.

I think we have to agree that the shoddy is a logarithmic unit of measure, so there will always be space at the far end for more shoddiness. But agreed, very very high shoddy factor.

[Toppsy]

I agree with every thing Nick posted above.
You may give some consideration to caging those GM70 valves, especially if children come visiting.

[andrew Ivimey]

Ha! Let'em burn! This is high art.

[Mike H]

The shoddiness is off the scale.

Yes it's epic!

[simon]

Some pics. Hasn't got clothes yet.


GM70top.jpg


GM70front.jpg


GM70side.jpg


Ply is all baltic birch coz had some lying around. 1000V rated 2mm plugs and sockets carry HTs from PSU to audio chassis. An IEC plug carries the mains from PSU to audio and plugs into a socket under the HT caps on the finals filament module.

Brass furniture castors on the front as they can be seen with regular seat castors at the back.

Looking back at this post from 2022, and the following, I think the filament supplies are immediately beneath the top plate with the valves and OPT. The HT PS is the bottom layer. Did you have any issues with proximity of transformers and magnetic fields? I've had a few false starts with boxing up GM70 and this method makes a lot of sense to me.

How are the threaded bars fixed to the top plate? Is there a captive nut glued in the underside of the plate? I'm not sure if that would be strong enough considering the boat anchor beneath - perhaps the top plate is a laminate of two with the nut captive between the two?

[simon]

Hmmm, the photos didn't come through, maybe this link works

https://www.audio-talk.co.uk/phpBB3/vie ... 39#p198539

[izzy wizzy]

I agree with every thing Nick posted above.
You may give some consideration to caging those GM70 valves, especially if children come visiting.

Thank you. Just got to do a top venner job like you on the speakers.

We had 4 little ones over at Xmas around 5yo. They all escaped alive and un-burnt. We use the Cambridge A1 in the slot under the top unit for everyday like TV. I was more concerned about the turntable and arm but we've had little kids around for decades and no one yet has done anything to harm the system

[izzy wizzy]

Looking back at this post from 2022, and the following, I think the filament supplies are immediately beneath the top plate with the valves and OPT. The HT PS is the bottom layer. Did you have any issues with proximity of transformers and magnetic fields? I've had a few false starts with boxing up GM70 and this method makes a lot of sense to me.

How are the threaded bars fixed to the top plate? Is there a captive nut glued in the underside of the plate? I'm not sure if that would be strong enough considering the boat anchor beneath - perhaps the top plate is a laminate of two with the nut captive between the two?

Had more issues with the SMPS filaments and noise. There is a very very small buzz but haven't tried to get rid of it yet. Need to be very close to the speaker to hear it and they're quite sensitive. Yours probably more so. There's no noise from the output stage when isolated from the front end. Yet to investigate where that's coming from. Could be mag fields into the interstage txs.

Was surprised there's so little noise as it is tightly packed. Tried to keep the noisy things away from the sensitive stuff. Got more noise from ungrounded transformers cases/frames etc. Once all grounded, like they probably would be on a metal chassis, did it get quiet. It was way too noisy as first go until I did this.

If you check the pics at the bottom of the page https://izzy-wizzy.com/?page_id=58, the various blocks are outlined.

The top just sits on the threaded rods in location holes. The sides and back are screwed on and hold it together. It forms a rigid block which is easy to roll around. You're not picking it up by yourself! I roll it to the workshop and lift the top off to work on it. Top has a cradle to sit on upside down. It's a bit wobbly without the sides and back but it's been like that for years no issue. The top never fell off when unsecured, even wheeling it around.

[MistyBlue]

Absolutely loving the matching cosmetics of all your equipment.

SWMBO has had a major input to the design of it all as that's more her field than mine.

Always a good strategy.

Congratulations, very, very nice work!

[simon]

Thanks, got it.

Interesting about the IT and hum - you reminded me that when I played with 10Y IT 300B I had unacceptable hum. I can't remember now whether it was proximity to the HT tx or the OPT that caused it, but it needed to be about a meter away from whichever was causing it ISTR. Probably the HT tx. Maybe grounding the iron would have helped. Thomas Meyer uses this type of construction a lot, and fairly densely, so it's presumably just a matter of location and orientation. And lots of trial and error.

[RhythMick]

Is this a new level of shoddiness ?! I like it.

[jack]

The shoddiness is off the scale.

I think we have to agree that the shoddy is a logarithmic unit of measure, so there will always be space at the far end for more shoddiness. But agreed, very very high shoddy factor.

Yep. This is excellent. Perhaps we need a new scale... a deciVark (dV) maybe? Named after that paragon of beautiful hand-crafted making, Tatjana van Vark - the decibel is, after all, named after AG Bell.

So, one dV would be 1/10 as good as kit made by TvV which would perhaps be equivalent to "shoddy" and the base reference for logarithmic ratios...

[Nick]

Yes, and ideally 1dV would represent the minimum change in appearance that can be detected by an (average) human eye.

Maybe also have dVi and dVr to distinguish between comparisons from an image or in real life.

[Nick]

And to add to that, when I say "minimum change in appearance" I am not talking about a tell them apart comparison, but a change in the shoddyness between two things (or the same thing after a change).

[izzy wizzy]

I looked up Tatjana van Vark. Wow! Perfect ambassador for a measure of shoddy.

Thanks for all the lovely posts.