Yet Another 183 (Sort of w/HRM) In Progress

[David Root]

Just finished another day of slow progress on this one. Planning multiple FSW including HRM/Non-HRM and FET/NOR. Also includes buffered loop a la Normster. Had to cut the CE chassis for the loop Send/Return & separate OD master. Will use faceplate/backplate.

Custom PT w/6V3 relay winding for 5V relays. 340-0-340 HT, 7.5A heaters.

[dreric]

Very Impressive!

Great build! One of Jason's PT?

Eric

[67plexi]

David, Looks great so far keep up the good work.

I dig your resistor choice,will you use the 5v relays on the HRM board ???

Just asking I'm starting a HRM my self.

I used on of Jasons PT and the relay taps were only 3-0-3. 6v total not 12v

installed a 12v transformer workes great.with the foot switch now.

Thank you, Steve.

[M Fowler]

Looking very good David and that HRM board looks great. I see I need to follow your lead and get some good resistors for my build.

Mark

[David Root]

Thanx guys, the PT is a custom Heyboer that is the same mounting centers as a Twin PT but the lamination stack is 1/4" thicker. I ordered five, kept two. Mark took one, and CHIP and telecaster took the other two. That way we got a good price break.

The OT is a Magnetic Components JMP 100W.

Steve, I will be using the two 5V relays on the HRM board. That's what leaves me the space to cram in four more in the space between it and the pots. I changed one thing on Jason's HRM board, I put SIP tracks on the board, glued in with CA glue, then just fitted the relays into the SIP sockets rather than soldering the relays directly to the board. I have had one relay fail in another amp and being able to pop that dead one out and pop another in to a DIP socket was really cool. I had to use SIPs on these relays because they're so small and no-one makes "DSIPs" with 0.2 pin spacing. I'll post some pix of those later.

Those NOS Piher resistors I bought on Ebay from a guy in Bologna Italy, Alberto Bario, very knowlegeable with huge inventory, also some Iskra (you'll see the 3K3 cathode resistors on V1A and V2A are Iskra, he was out of Pihers). The 220K 1/2W, 68K 2W and 100K 1/2W were not cheap but those are the Marshall guys must-haves, everything else was 40 cents or 80 cents. I never used them before but I've been listening to them for years in my '77 Marshall head.

I will probably have some relay questions as I get into it, I never did more than three in one build before. If anyone has done a HRM/Non-HRM relay I'd appreciate some tips.

[Structo]

Looks great David!
Can't wait to see the final product.

I wasn't aware that CE was selling four preamp chassis?

[Colossal]

Fantastic David! Can't wait to see more.

[M Fowler]

I wasn't aware that CE was selling four preamp chassis?

Tom at one time CE was selling your choice three or four preamp tube chassis.

Mark

[dreric]

David

I have a couple of questions.

The PS board is one of those early ones fro Jason that had an extra string for reverb or loop, right? When I first looked it seemed like you where using solens on V3 to drop the PS. Am I mistaken? The picture are good but not good enough to see all the values.

I've had good experiences with Alberto, seems all the stashes of pihers, bleyschlags and iskra are over seas now

You use of caps and resistors of difference brands / sonic choices far exceeds my understanding of the signal path and where these choices make a difference. It would be great if you shared your thoughts or thinking process regarding your component selection.

Thanks

Eric

[David Root]

dreric, yes the PS board has an extra pair of cap spots for buffered loop or reverb. I used it for the buffered loop, they are two 22uF 450V Rubycons. I cut one board trace and added a wire to split the two caps apart, and used the paralleling resistor spot for the dropping resistor. If you look hard on the right side of the board you should be able to see where there is an extra pin out hole right below the original one.

BTW I wondered why the boards Jason sells now don't have that extra spot. I like it and I have two of them left.

On the Pihers I wish I could claim "esoteric HAD-level knowledge" on where to put them vs. the non-Pihers, but the truth is really somewhat more prosaic.
I know to put them on all grids in the main signal path. I did that. I did not use them in the FX loop circuit, because a good loop is supposed to be uncolored, transparent if you will. Otherwise the sound would be different with/without it in circuit. That's why the red PRP metal films there, because they are uncolored, transparent and quiet. Likewise the Solen 630V aluminum film caps, ditto.

I discussed it with Tony, he said the slope resistor is also a good spot for a Piher.
I put them on the plates and cathodes of V1 and V2 because I bought them! I went thru the schematic of #183 and bought every resistor that could conceivably be considered part of or maybe influencing the signal path. That's all. I bought 270K grid leaks but could only get 1W. Then they wouldn't fit under the .05 caps so I used the PRP 1/2W 270Ks there. I also used Takman CFs on the PI because I didn't have any 110K Pihers and I didn't want to mix them. Using 1/2W there gives a little more 2nd harmonic distortion which never hurts.

The HRM board doesn't have any Pihers in it because I didn't have them when I populated the board! May have to revisit that.

FWIW I think that HAD did a lot of this, ie using what he had on hand. He was probably too cheap to pay NOS prices for Pihers, but, unlike me, he had enough knowledge to get the tone he wanted by tweaking what he had to work with.

[ToneMerc]

He was probably too cheap to pay NOS prices for Pihers, but, unlike me, he had enough knowledge to get the tone he wanted by tweaking what he had to work with.

Keep in mind that 30 yrs ago, surplus 10-15 year old resistors where just that.

You should have asked, I would sent you some 270's that would have fit.

TM

[David Root]

Well, that's true too. Maybe there just weren't a lot of them in North America then.

The only guys who seem to have serious inventory now in Pihers, Iskras and Beyschlags are all in Europe apparently.

Thanx for the offer. Do you think Pihers would make a difference in that position?

[ToneMerc]

Well, that's true too. Maybe there just weren't a lot of them in North America then.

The only guys who seem to have serious inventory now in Pihers, Iskras and Beyschlags are all in Europe apparently.

Yes, that's mainly due to the country of origin. Very few American products contained these resistors.

Pihers-Spain
Iskra-Yugoslavia
Beyschlag-Germany

Months back I found a nice selection of Pihers in Spain, the problem is the guy won't ship to North America unless I buy at least 150 Euros worth.

I have a 1966 Vox Italian wah that has Pihers in it. IMHO, you cannot clone the very early ones and not use these resistors.

[ToneMerc]

Thanx for the offer. Do you think Pihers would make a difference in that position?

No, not really. When I built my #183 I tried to get as close as possible to what HAD used and there's only one Piher in it. I'm getting a board ready for my next build and I'll be using a few Pihers strategically.

TM

[David Root]

I didn't think so either. I'm not trying to duplicate #183, just use a proven circuit to build what Tony Albany told me would be a killer amp with all the Pihers in it. My '77 Marshall 2204 sounds killer and it's full of Pihers, so that was it! Of course I think the old Mullards help too.

Maybe we should organize a group buy from your Spanish source, to get to 150 Euros, that's about $220 I think.