183 Build Report

[UltraHookedOnPhonix]

HI Joost , excelent build , compliments!!!!
Can you tell me the code of your trimpot? they are from mouser?
Thanks

Thanks!

Search with, "201XR" at Mouser and DigiKey.

[ToneMerc]

HI Joost , excelent build , compliments!!!!
Can you tell me the code of your trimpot? they are from mouser?
Thanks

Thanks!

Search with, "201XR" at Mouser and DigiKey.

Thanks, I won't rsid the surplus places anymore looking for the thumbwheel trimmers.

[grtamp]

Thanks! UHOP
great!!!

[Joost]

Well, those wires aren't routed any differently than those found in a real ODS. The amp is very quiet and doesn't pop with either relay engaged.

I wasn't aware of relays being a source of noise and that routing wires in this fashion could cause problems, including tone loss. Please tell me what these problems are and how an electronic switch is inherently noisy.

The wires coming from the pre board snake around the preamp ground and behind the PAB relay, just like Dumble did it. In fact, using the JLDDI approach is something I try to follow rather closely.

Well an amp designer told me this recently. This is what google told me :"Isolation and EMI
As you might expect, Mechanical Relays offer superior electrical isolation.   But when it comes to Electromagnetic Interference (EMI), mechanical relays act as an antenna and drive EMI directly back into anything that is controlling it.  This is where solid state relays really have mechanical relays beat.  Solid State relays on the other hand offer superior EMI and electrical isolation.  Any application that involves highly inductive switching should ONLY use Solid State relays."

[Structo]

Nah, they work fine and have done so for 40 years.

[David Root]

UHOP, thanx for your response. I think part of this is attributable to my #124 running at ~36 mA idle w/6L6GC rather than 30.3 with EL34. That's 24 mA difference +/- which has to be reflected in the Vp @ idle.

Maybe I can get 460 Vp or so out of the M-C PT? If I put in a separate filament transformer for the 12AX7s that might help by reducing the overall load on the PT.

[David Root]

I decided to look at a custom Heyboer PT. Colossal, thanx for the tips.

Laydown, 3" x 3 3/4" centers (same as Twin reverb PT)

340-0-340 @ 500mA. Should give 465V at idle with 4xEL34 and 4X12AX7.

3.15-0-3.15 @ 7.5A (supports 4xEL34 and 4x12AX7 for internal buffered loop)

6.3-0 @ 350mA for 5V relays (or 12V if you use a voltage doubler). Good for 3 relays even at 12V.

If anyone is interested I may get additional units, PM me. I am in Canada, not sure if Heyboer will drop ship in the US or not, did not ask them that yet!

[talbany]

Dave
I believe I posted this a while back but why go custom?..

http://www.mojotone.com/amp-parts/trans ... ransformer

I spoke with Heybor way back about this and they told me that this PT can handle 6.5a in the filament winding no problem..HT says 450 but they told me 500ma.. I've used this transformer on several builds with 4X34's with no trouble..It doesn't come with the 5v tap for the relays but if it's cheaper to get this one and add your relay transformer,this one will work....

Tony

[tele caster]

Out of stock Tony, thanks for the tip though. I've been holding off on buying the pt. Shipping might be high to Canada, Mojo isn't my favorite vendor because of their shipping rates.
Dave, what is the price for that heyboer transformer? I might be interested if they can ship to Ontario.

[ER]

It's not a lay down, but using these on my current 4xel34 build;
http://www.edcorusa.com/products/728-xpwr127_120.aspx
http://www.edcorusa.com/products/456-cx ... -1_7k.aspx
The price is good, we'll see how they sound.

-E

[David Root]

Thanx Tony, tele, ER. I will let you know what the Heyboer pricing is.

I have two std. Twin Mag. Cpts. 40-18004 in stock but I am concerned that they may not give me 465 Vp @ idle with four 12AX7s. The relay PT is not a problem, I have one suitable.

M-C lists HT @ 465mA @ 320-0-320. The Mojotone spec is 340-0-340 but it is not clear if that is at idle or at rated mA. So there is some uncertainty in my mind regarding the 465 Vp. Perhaps I worry too much. But I have learned over the years to pay attention to detail!

[David Root]

Heyboer quoted me

5 pcs @ $ 90.00 each
2 pcs @ $ 105.00 each
1 pc @ $ 118.00 each

Delivery approx 2 to 3 weeks after ordered.


I will ask them about drop-shipping. I might get five if others are interested, that is a good price compared with Mojotone, who are $106 ea. without the 6.3V relay winding.

I also forgot to specify the bias tap voltage. Will confirm that.

[David Root]

Heyboer will drop ship within the US or Canada. To Canada is $24. I would guess about half that within CONUS.

I just ordered five units @ $90 each plus shipping. I am keeping two units. If you want one let me know, PM me. I have a US bank account, we lived there for 25 years until two years ago, so no need for international money orders etc.

Bias tap is 55V, BTW.

Heyboer advised drop shipment to US addresses are by UPS @ 12.75. Canada is USPS.

[grtamp]

Mercury FBFTP/MT have 7A on filament , but it's much expensive!

[David Root]

If you want one, don't wait too long. I have three committed and one "interested", so only one is left without a potential home.