Vemuram - Jan Ray

mmolteratx · Post by **mmolteratx** » 07 Mar 2013, 03:21

Got this earlier this afternoon.

DSC_0008 by mmolteratx, on Flickr

DSC_0013 by mmolteratx, on Flickr

DSC_0017 by mmolteratx, on Flickr

DSC_0019 by mmolteratx, on Flickr

DSC_0021 by mmolteratx, on Flickr

DSC_0024 by mmolteratx, on Flickr

DSC_0028 by mmolteratx, on Flickr

mmolteratx · Post by **mmolteratx** » 07 Mar 2013, 03:31

And here are pics of the caps I measured, and the trace routing since it's a 4 layer board.

mmolteratx · Post by **mmolteratx** » 07 Mar 2013, 03:54

Actually, screwed up typing one of the values in. 12k in the tone control should be 1k2. Mods, can you swap these?

candletears7 · Post by **candletears7** » 07 Mar 2013, 04:52

Timmy?

skywise · Post by **skywise** » 07 Mar 2013, 06:55

candletears7 wrote:Timmy?

It's Japanese, so probably 拓海 (Takumi).

candletears7 · Post by **candletears7** » 07 Mar 2013, 07:22

Timmy-san, then.

apollomusicservice · Post by **apollomusicservice** » 07 Mar 2013, 07:35

VR is point R9-R10-C12 right?

mmolteratx · Post by **mmolteratx** » 07 Mar 2013, 08:16

apollomusicservice wrote:VR is point R9-R10-C12 right?

Yup.

IvIark · Post by **IvIark** » 07 Mar 2013, 08:27

I've removed the first scheme you posted. Cheers Matt

Eisy · Post by **Eisy** » 07 Mar 2013, 11:28

Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...

p.eat · Post by **p.eat** » 07 Mar 2013, 11:34

Eisy wrote:Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...

+1 . The voltage divider is also missing a label for vref.

Nice work, btw!

IvIark · Post by **IvIark** » 07 Mar 2013, 13:03

Vero'd. And so another £300 rip off, no doubt some people will be stupid enough to buy it.

and one using a standard trimmer and with an extra switch to give you the option to also select the "compressed symmetrical" setting on the Timmy.

apollomusicservice · Post by **apollomusicservice** » 07 Mar 2013, 13:57

D6 on schem = D5 on board

IvIark · Post by **IvIark** » 07 Mar 2013, 14:46

Yes, I excluded the LED resistor so my numbering is different

I don't follow the scheme numbering convention because I don't number the main components. Of course I could have kept the diode numbering the same anyway, but I do it in a way that will cause me the least amount of work in the future, and I can guarantee I'd spend more time answering questions about whether I forgot to include a diode because of the missing number, than I will from people who notice the protection diode has the number given to the LED in the schematic.

Think of it as "based" on Matt's scheme

mmolteratx · Post by **mmolteratx** » 07 Mar 2013, 15:56

Eisy wrote:Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...

Yup. Removed and measured to be sure. It's definitely odd.

Eisy · Post by **Eisy** » 07 Mar 2013, 16:55

mmolteratx wrote:
Eisy wrote:Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...
Yup. Removed and measured to be sure. It's definitely odd.

Ok, thanks.

Maybe this is why the Jan Ray does not sound like a Timmy on the first view.
I guess this odd voltage divider will change the gain structure a lot.

dano · Post by **dano** » 07 Mar 2013, 17:24

Eisy wrote:
mmolteratx wrote:
Eisy wrote:Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...
Yup. Removed and measured to be sure. It's definitely odd.
Ok, thanks.

Maybe this is why the Jan Ray does not sound like a Timmy on the first view.

Could be the bass cut section, the trim pot in parallel with the 9K1, vs the Timmy and it's fixed 3K3 (iirc ? ). Plus a different value on the treble pot ?

mmolteratx · Post by **mmolteratx** » 08 Mar 2013, 00:23

Actually, thanks to an anonymous tipster, I realized that one of the bias resistors R10 was indeed mislabeled. Went back and checked my pictures and sure enough, LCR meter said 7k5 and I just misread the 7 as a 1 when I typed up the schem.

: Vemuram Jan Ray def schematic

dano wrote:
Eisy wrote:
mmolteratx wrote:
Eisy wrote:Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...
Yup. Removed and measured to be sure. It's definitely odd.
Ok, thanks.
Maybe this is why the Jan Ray does not sound like a Timmy on the first view.
Could be the bass cut section, the trim pot in parallel with the 9K1, vs the Timmy and it's fixed 3K3 (iirc ? ). Plus a different value on the treble pot ?

No, it's entirely in the different treble control. The bass response is exactly the same, all the trimmer does is vary the effective value of R4, which sets the gain of the stage. The treble control on the Jan Ray lops off everything above 2.8kHz at -6dB/decade at max. The Timmy's control at minimum does the same, but at 10.6kHz. Just use the Timmy's control in a different range and you've got a Jan Ray.

Realfi · Post by **Realfi** » 08 Mar 2013, 01:58

mmolteratx wrote:Actually, thanks to an anonymous tipster, I realized that one of the bias resistors R10 was indeed mislabeled. Went back and checked my pictures and sure enough, LCR meter said 7k5 and I just misread the 7 as a 1 when I typed up the schem.

[ Image ]

dano wrote:
Eisy wrote:
mmolteratx wrote:
Eisy wrote:Thanks to mmolteratx for tracing.
But are you sure about the values of R9/R10? Looks a bit odd to me and very mis-biased...
Yup. Removed and measured to be sure. It's definitely odd.
Ok, thanks.

Maybe this is why the Jan Ray does not sound like a Timmy on the first view.
Could be the bass cut section, the trim pot in parallel with the 9K1, vs the Timmy and it's fixed 3K3 (iirc ? ). Plus a different value on the treble pot ?
No, it's entirely in the different treble control. The bass response is exactly the same, all the trimmer does is vary the effective value of R4, which sets the gain of the stage. The treble control on the Jan Ray lops off everything above 2.8kHz at -6dB/decade at max. The Timmy's control at minimum does the same, but at 10.6kHz. Just use the Timmy's control in a different range and you've got a Jan Ray.

Loving watching this over at TGP..

So how many Timmy copies is that now?

dano · Post by **dano** » 08 Mar 2013, 09:34

mmolteratx wrote: No, it's entirely in the different treble control. The bass response is exactly the same, all the trimmer does is vary the effective value of R4, which sets the gain of the stage. The treble control on the Jan Ray lops off everything above 2.8kHz at -6dB/decade at max. The Timmy's control at minimum does the same, but at 10.6kHz. Just use the Timmy's control in a different range and you've got a Jan Ray.

What I was thinking with the bass cut is it depends where the trimmer is factor set. Plus you'd have to wonder why they have added a trimmer in parallel with a fixed resistor, I can think of two reasons, they couldn't source a 5K trimmer (unlikely) or , they wanted for some reason to make the circuit look a little different from the Timmy and add some mojo control to it..

Good work on this, think i'm going to buy a 'proper' Timmy this year.

Vemuram - Jan Ray [traced]