Amp tinkerers and people who aren't afraid of 700 volts or so in here....

Moderators: Slowy, Capt. Black

User avatar
BY Anvil Amps Alan
#807839
Optical wrote:
jvpp wrote:
sizzlingbadger wrote:Yep, it doesn't mean much though (except its not burnt out), you would normally measure the impedance at 1Khz, usually about 8Kohms to 10Kohms for an EL 84 transformer.


Great, thinking this one might do?
https://www.amplifiedparts.com/products ... der-15w-8k

Only problem is that it is a single secondary. Would prefer the 4 & 16 ohm combinations


Get the 1760E instead of the 1750E


Brian Smith will make one with 4, 8, 16 Ohms.
Probably much cheaper than importing one.
User avatar
BY Anvil Amps Alan
#807840
Anvil Amps Alan wrote:
Optical wrote:
jvpp wrote:
Great, thinking this one might do?
https://www.amplifiedparts.com/products ... der-15w-8k

Only problem is that it is a single secondary. Would prefer the 4 & 16 ohm combinations


Get the 1760E instead of the 1750E


Brian Smith will make one with 4, 8, 16 Ohms.
Probably much cheaper than importing one.


The fender one looks a bit small which will impact on bass response.
User avatar
BY jvpp
#807973
Contacted Brian the transformer man, but no response yet. In the mean time here is the Bill Of Materials:
Notes:
- 1 extra valve for playing around
- All resistors 2W or less come in pack of 5
- Output TX for Fender Princeton chosen
- No Power TX found - add ?? $
- 1KOhm/5W wirewound missing (add $1.14)
- All prices in USA dollars
- All parts sourced from AmplifiedParts in USA
- no shipping costs added yet
- Fuse, jacks, knobs, mains connector, power switch, etc can be sourced locally

Is the total so far listed a reasonable price?

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User avatar
BY Slowy
#807974
Try a 12AX7 in V1. You may prefer it.

I don't. :D
User avatar
BY GrantB
#807976
I have dropped John a line, but it sounds like we are very advanced on the design. We'll see what he says.

In terms of a chassis, our singer works in a metal manufacturing operation. I would be happy to arrange the making of chassis through her....but we'd need a few to meet their minimum. I can also arrange face plates and rear plates.

So...is this turning into a group build thing? I can help pay for a prototype if it's needed?
User avatar
BY jeremyb
#807979
Forum kit build group buy sounds exciting!
User avatar
BY jeremyb
#807981
Slowy wrote:I already have one.


Yeah but stereo! :thumbup:
User avatar
BY Optical
#807982
jvpp wrote: - Output TX for Fender Princeton chosen


as mentioned, if you select the 1760E you get the 4,8 and 16R taps. The 1750E just has the 8R tap. As Anvil mentioned, you might want to find something with a heavier to be a closer match to the NZ spec one. Maybe even a 4xEL84 (~40W) spec output transformer and run it at half impedance.
Otherwise looks good.
User avatar
BY jvpp
#807983
Optical wrote:
jvpp wrote: - Output TX for Fender Princeton chosen


as mentioned, if you select the 1760E you get the 4,8 and 16R taps. The 1750E just has the 8R tap. As Anvil mentioned, you might want to find something with a heavier to be a closer match to the NZ spec one. Maybe even a 4xEL84 (~40W) spec output transformer and run it at half impedance.
Otherwise looks good.


Yes, but Amplified Parts don't stock it.... Will call Brian tomorrow and hopefully GrantB can get some more info from his guy re transformers as well.

More importantly, is the pricing acceptable or does it look expensive? I found AP very reasonable for previous purchases...
User avatar
BY jvpp
#807985
GrantB wrote:I have dropped John a line, but it sounds like we are very advanced on the design. We'll see what he says.

In terms of a chassis, our singer works in a metal manufacturing operation. I would be happy to arrange the making of chassis through her....but we'd need a few to meet their minimum. I can also arrange face plates and rear plates.

So...is this turning into a group build thing? I can help pay for a prototype if it's needed?


I will change the design ever so slightly to allow for fine tuning (assuming I am going to build one).

Once I have the transformers sorted and have their dimensions, I will put the chassis in Auto-CAD showing dimensions and locations of all cutouts.

Interested in face plate, not sure if there ever was a back plate? I think a prototype would be a good idea if a turret board was going to be used. If one sticks to the original layout and soldering method, then what can go wrong?

A group build thing - sounds like group sex almost
User avatar
BY Slowy
#807986
jeremyb wrote:
Slowy wrote:I already have one.


Yeah but stereo! :thumbup:

I have run a stereo rig. PITA to set up, divine to listen to.
User avatar
BY bender
#807987
GrantB wrote:I have dropped John a line, but it sounds like we are very advanced on the design. We'll see what he says.

In terms of a chassis, our singer works in a metal manufacturing operation. I would be happy to arrange the making of chassis through her....but we'd need a few to meet their minimum. I can also arrange face plates and rear plates.

So...is this turning into a group build thing? I can help pay for a prototype if it's needed?


Keen
User avatar
BY RectifiedAmps
#808013
How's the noise level on the original amp? There's certainly room for improvement in the grounding scheme, but it's not a complex circuit so it might not be worth it unless it has a noticeable hum. Assuming you have a centre-tap on the heaters/filaments in the DIY build, you could elevate it onto the EL84 cathodes to cut down some noise, but again- might not be necessary. Personally, I try to avoid multi-cap cans whenever possible and use separate capacitors instead - you can physically locate and ground them closer to the nodes they're feeding, which makes things tidier and usually quieter, too. Individual caps are also cheaper and easier to source, too.
User avatar
BY Conway
#808022
jvpp wrote:Contacted Brian the transformer man, but no response yet. In the mean time here is the Bill Of Materials:
Notes:
- 1 extra valve for playing around
- All resistors 2W or less come in pack of 5
- Output TX for Fender Princeton chosen
- No Power TX found - add ?? $
- 1KOhm/5W wirewound missing (add $1.14)
- All prices in USA dollars
- All parts sourced from AmplifiedParts in USA
- no shipping costs added yet
- Fuse, jacks, knobs, mains connector, power switch, etc can be sourced locally

Is the total so far listed a reasonable price?

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Your parts list misses the crucial vial of unicorn tears.
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