Manzamp Build: Hold My Beer... I'm Goin' In

[dorrisant]

Manzamp build time!

I'm gonna try this... It's gonna go a bit slow by my standards... Be patient please. Let me know if you see anything wrong before I get too far ahead of myself.

I have a Tweed Bassman chassis and board ready. Designed it with info from here: https://ampgarage.com/forum/viewtopic.php?f=5&t=36212

I have a '59 Bassman Reissue PT (Hammond 290TX) but I don't think it will work perfectly with this because the filament winding is only good for 2A. I need around 4A with the Manzamp due to the higher filament load of the EL34s. I could go with a 290DX, but that would be cutting it close at 4A for filaments. I will likely use the 290TX and add a filament TX just for the EL34s. The HT will be a bit high (696v) , but I will use a "B+ MOSFET Reducer" to get it down to the correct HT.

The choke I have matches what is spec'd on the two schematics. I don't think I have an OT that I'd like to use here. I want to use the suggested 4k2 primary but have a choice of different secondary taps. I'm thinking of using a Hammond 1750M with 2, 4 and 8 Ohm taps. This is gonna be stuffed into a headshell, so I want it to play nice with different cabs.

I ordered the filter caps yesterday, they should be here within a week. I noticed the lack of availability for the reservoir caps in 10mm lead spacing. I ended up going with 7.5mm, but I don't think it will be a real issue. Also, I ordered 100uF caps for the reservoir, we'll see how that sounds and go from there.

Currently, I have a few things to do with my cash so it will be a bit before I order an OT.

The 5k dropping resistor is one of the few components left to procure. I have that tagged on another order that is in que.

Another note... The standoff spacing of my board design is a bit larger than what is pre-drilled with this chassis. I moved all 4 of those holes on my board to match the chassis. There are a couple of errors on the layout that need to be corrected too. For instance, the .1uF orange drops are mislabeled as 1uF. I will update the drawings here and on the files page linked above before too long.

[award70]

Did you etch the circuit boards or cnc?

Alan

[Guy77]

Manzamp build time!

I'm gonna try this... It's gonna go a bit slow by my standards... Be patient please. Let me know if you see anything wrong before I get too far ahead of myself.

I have a Tweed Bassman chassis and board ready. Designed it with info from here: https://ampgarage.com/forum/viewtopic.php?f=5&t=36212

I have a '59 Bassman Reissue PT (Hammond 290TX) but I don't think it will work perfectly with this because the filament winding is only good for 2A. I need around 4A with the Manzamp due to the higher filament load of the EL34s. I could go with a 290DX, but that would be cutting it close at 4A for filaments. I will likely use the 290TX and add a filament TX just for the EL34s. The HT will be a bit high (696v) , but I will use a "B+ MOSFET Reducer" to get it down to the correct HT.

The choke I have matches what is spec'd on the two schematics. I don't think I have an OT that I'd like to use here. I want to use the suggested 4k2 primary but have a choice of different secondary taps. I'm thinking of using a Hammond 1750M with 2, 4 and 8 Ohm taps. This is gonna be stuffed into a headshell, so I want it to play nice with different cabs.

I ordered the filter caps yesterday, they should be here within a week. I noticed the lack of availability for the reservoir caps in 10mm lead spacing. I ended up going with 7.5mm, but I don't think it will be a real issue. Also, I ordered 100uF caps for the reservoir, we'll see how that sounds and go from there.

Currently, I have a few things to do with my cash so it will be a bit before I order an OT.

The 5k dropping resistor is one of the few components left to procure. I have that tagged on another order that is in que.

Another note... The standoff spacing of my board design is a bit larger than what is pre-drilled with this chassis. I moved all 4 of those holes on my board to match the chassis. There are a couple of errors on the layout that need to be corrected too. For instance, the .1uF orange drops are mislabeled as 1uF. I will update the drawings here and on the files page linked above before too long.

Excited to see how this comes out. Looking good so far!

Regarding the 290DX. The 4amp filament is underrated. I have run it with an ODS and JJ EL34s and it handles it fine.
For some reason whenever I use a separate transformer for the filaments and leave the main transformers filaments unused I notice the amps sound a little different, most likely because of the lack of load. I am sure which ever you choose it will sound great.

And yes also how did you make the boards CNC or etch?

Cheers
Guy

[dorrisant]

Did you etch the circuit boards or cnc?

Alan

I used the CNC.

Excited to see how this comes out. Looking good so far!

Regarding the 290DX. The 4amp filament is underrated. I have run it with an ODS and JJ EL34s and it handles it fine.
For some reason whenever I use a separate transformer for the filaments and leave the main transformers filaments unused I notice the amps sound a little different, most likely because of the lack of load. I am sure which ever you choose it will sound great.

I think I will hold out and get the 290DX then. Thanks for the help.

Duely noted though. Next time I split the filaments like I suggested, I will have to tack in the TX wiring so it can be reversed later to test that theory. It might be subtle, but I I'd like to find out now that you mentioned it.

[award70]

I used the CNC.

They turned out really nice!

[dorrisant]

I got the power supply caps in and added a 5k1 to the dropping string. I'm going with 100uF reservoir caps for the moment.

The 100uF 100v is a bipolar cap... Didn't realize that at the time of ordering. Should be just fine, unless I am spacing on something there.

[dorrisant]

Does anyone have plans or drawings for a Tweed Bassman headshell? All I can find relates to a combo cab.

[ic-racer]

That is really coming along nice!

[ThePanda]

Sweet build!

I am going to take ideas from the Manzamp and roll them into my 5F6a build!

What did you use for the 1-22H inductor?

Is it really 1-22H and not 1-22uH?

[dorrisant]

Sweet build!

I am going to take ideas from the Manzamp and roll them into my 5F6a build!

What did you use for the 1-22H inductor?

Is it really 1-22H and not 1-22uH?

I ended up using a 3H inductor. I found this value by reading through ic-racer's original post...

https://ampgarage.com/forum/viewtopic.p ... e7#p237487

Thanks for showing us your schematic. The clips sound good too.

I was a little confused by the choke 1-22Hy in the first stage. What does that achieve and did you include it in your amp?

When I wrote that posted schematic up I was considering any value from 1 to 22 Hy. What I finally installed was three x 1Hy wired in series. So 3Hy in the amp presently.

So, the thought process is that the biggest axial chokes are about 1hy and he has more than one on the chassis. So, it is probably a series wiring. If he used parallel it would be to reduce the d/c resistance, but we already have the cathode resistor in the circuit, so the d/c resistance is probably not what he was tweaking by using 3 or 4.

Could he have used three or four 0.25 Hy chokes to make 1Hy? Yes ,but why bother when a 0.25 choke is as hard to find as a 1hy choke?

So, the components in the picture look like a few chokes or inductors stacked together. To figure out how they might work in the circuit I studied this diagram of an active tone circuit using a 22Hy inductor. What I did was to forget about the treble side of the tone circuit and just wired the bass side as a putative fixed bass boost.

Does it do anything in my circuit?

Personally, I am digging this amp so much I at the point of not wanting to touch or 'tweak' it one bit. I threw a set of used tubes on it for start-up and don't even want to change those out at this time. I have only played an amp sounding like this in my dreams.

[ThePanda]

Sweet build!

I am going to take ideas from the Manzamp and roll them into my 5F6a build!

What did you use for the 1-22H inductor?

Is it really 1-22H and not 1-22uH?

I ended up using a 3H inductor. I found this value by reading through ic-racer's original post...

https://ampgarage.com/forum/viewtopic.p ... e7#p237487

I found some 4H inductors. These are surprisingly hard to find.

Where are you all sourcing yours?

20241029_161926.jpg

[dorrisant]

I got mine from a member her on TAG via the For Sale section. I bought a bunch (only two of the 3H), can't remember who though. Maybe someone will remember who it was.

A quick search says you can use one of these:

https://www.mouser.com/ProductDetail/42 ... 42TM018-RC

"i did a little research on the guitar forums, specifically about varitone circuits that use 3H inductors and found a thread about one guy that uses very small audio signal tranformers that are basically 3H inductors. he mentioned that the Xicon #42TM018-RC is a 1:1 transformer that measures 3H on both sides, and end to center tap on each side measures 1.5H. i bought two of them (just to have a spare!) from Mouser for $4.89 each + shipping and they arrived today for testing."

I updated the current price.

Quote was from here:

https://www.talkbass.com/threads/acoust ... rs.810974/