Traynor Yvm-1 Sandbox Overdrive

[aab0mb]

Nice place you have here, guys.

I’ve been reading for a while but figured It was time to post.

A while back I put out an ad on craigslist offering to buy broken musical gear. As luck would have it, I managed to pick up a YVM1 for super cheap. At first I brought it up to factory spec just to see what I could do but it was pretty bland because it was normally a PA amplifier.

I had poked at it a little bit and converted one of the inputs to AB763 style But I didn’t have the right components for the tone stack And it was pretty bland overall. In the last couple of weeks I’ve been experimenting with 5f6a and Plexi set ups which is something new for me.

While pondering what to do with all of the extra preamp tubes I decided to take an extra tube and wire it as a double overdrive section after the plexi tone stack. The attached schematic reflects the current set up.

I had no knowledge of Jeff putting out all the ODS variants so I was tickled when I found his D’mars and Marshumble type circuits. We talked a little bit about having the tone stack of the plexi right before the dumble overdrive and possible interactions but we agreed we would probably get more useful insight by starting a thread here.

It sounds pretty good overall with a large range of tones and the usual tweaking can be expected. I need to order some parts to work on the power supply and adjust some preamp plate voltages etc. I scrapped this build together with salvage parts in a lot of cases. At other points there are vintage mustard caps. A strange contrast!

I’m wondering if anyone wants to chime in on the design and note any glaring flaws or oversights that a noob like myself might make?

As it stands the build quality is of a transient nature but I’m trying things right now in order to finalize a notion of the final build. I’m still not convinced of the topology itself and may allocate the preamp tubes to a traditional Dumble design with a built in Dumblelator.

I thought this design was cool because it was a little bit different and I already had the plexi so figured why not try it first before converting the whole thing to classic Dumble topology.

Thanks to the Forum and Jeff (Tubenit/10thTx) especially. Most fun I’ve had in months!

-Aaron-

[mhuss]

The only think that stands out to me is the 135k slope resistor in the tone stack - that seems high. This is normally 33k in a Marshall and 56k in a tweed Bassman, 100k in a later Fender without a cathode follower.

Be very careful with your grounding, a multi-stage gain setup like this will be very prone to oscillation. Use a star ground, or a bus ground connected to the chassis at only one point near the inputs. I'd also recommend using another B+ RC decoupling stage for the "gain" triodes, "E" or whatever.

[thetragichero]

these old traynors (i have messed around with a yba1 and yba1a) are fantastic!
is this similar to those where all you have to do to access the chassis is removed four bolts and pull the top off? an absolute stroke of GENIUS for those of us who like to tweak amps. one of them came with the original xf2 mullard power tubes, and they still tested STRONG. marshall guys pay GOOD money for em
just lovely gigantic hammond iron. nice score!

[aab0mb]

The only think that stands out to me is the 135k slope resistor in the tone stack - that seems high. This is normally 33k in a Marshall and 56k in a tweed Bassman, 100k in a later Fender without a cathode follower.

Be very careful with your grounding, a multi-stage gain setup like this will be very prone to oscillation. Use a star ground, or a bus ground connected to the chassis at only one point near the inputs. I'd also recommend using another B+ RC decoupling stage for the "gain" triodes, "E" or whatever.

Right you are, sir! I wanted to try out the Dumble tone stack so I separated the bass and mid controls and used the closest value I had to the 150k slope resistor he used. I cobbled this build together from salvage so in a lot of cases I used what worked to get the electrons flowing haha ! As luck would have it, i enjoy the 135k slope more than the 68k i had dropped in there before. I feel like it helps mitigate some of the boomy low end and smooth out the highs a bit. I was looking at the Plexi, 5f6, and the Manzamp and kind of goulashing (is that a word?) them as I went along. A real MUTT! But mutts are some of the best companions

Surprisingly, for having all cloth covered wire and zero attention payed to layout and lead dress this amp is nearly silent when a healthy amount of gain is applied. Factory grounding scheme seems to be working for the time being. It's quieter than some of my combo amps on clean settings. As mentioned, this is kind of a sandbox build at the moment so i can try some topologies that i've not tried before.

You read my mind about adding the extra node to the power section. I think I have some an 8-10k and 20uf that could stand in for now.

ADDED MOD: Being that this circuit isn't a normally discussed design here, I'm in the wilderness, so to speak. There will be some interactions and frequency response issues by moving the tonestack from the normal ODS placement, I assume. That being said, I applied a small 100pf shunt resistor to the wiper of the Drive pot to ground. My drive pot being 250k means that when Drive is maxed the low pass filter created by the 100pf to ground creates a filter right around 6k-7k in order to shave off some of the fizzy highs and ice pick attack while keeping lower gain sounds more sparkly like normal. Between the bright cap on channel one input and the shunt cap on the drive, a person can balance some of the high frequency content by listening and balancing both knobs to a degree. By not using shielded cable (yet!), I'm saving a few PF of capacitance through the circuit so hopefully the 250k drive and the small shunt can help to make up for that and provide some tweaking options.

I found that the presence has a hair trigger and tuning it to the sweet spot is essential to get some of the harmonics, strain and moaning sounds that are possible in these styles of overdrive amps.

[aab0mb]

these old traynors (i have messed around with a yba1 and yba1a) are fantastic!
is this similar to those where all you have to do to access the chassis is removed four bolts and pull the top off? an absolute stroke of GENIUS for those of us who like to tweak amps. one of them came with the original xf2 mullard power tubes, and they still tested STRONG. marshall guys pay GOOD money for em
just lovely gigantic hammond iron. nice score!

Fantastic, indeed! In my amp you pull the four bolts and the chassis can slide out like a kitchen drawer. Very convenient as it flips around on the slide rails if needed. So if i need to work on the front control panel wiring I just pull the whole chassis and slide it back in backwards about half way or so to hold it.

Yes the iron in this thing is substantial. One of the reasons I'll most likely keep it forever. Just something cool about it

Speaking of tubes, mine came with some Phillips brand tubes one of which I had placed in the cathode follower slot. I just so happened to stumble on some ratings for tubes working in that slot and Phillips was the worst. Can't handle as high a voltage at the cathode apparently? I had one GE and three Phillips tubes so I stuck the GE in the CF slot in hopes of not burning up a tube! JJ EL34's in the power section and so far so good with those.

I stole the 8ohm EVM 12L (go Minnesota!) from my Blues Jr ( I know, I know) and placed it in a sizable 1x12 cab I have in the rotation. Running it off the 4 ohm tap as that's all I have but it sounds really good so far. The Blues Jr got a cool Rola (i think) alnico from a Hammond organ courtesy of Rich at Minnesota Organ Service. Amazing guy who does some amazing work. He works with some sluggers for sure. He once told me he used to throw away pallets of ao-35's, the little Carmen Ghia type amps. Someone could have built a career on those!

[Colossal]

He once told me he used to throw away pallets of ao-35's, the little Carmen Ghia type amps. Someone could have built a career on those!

Dr. Z did build a career on those amps

[aab0mb]

He once told me he used to throw away pallets of ao-35's, the little Carmen Ghia type amps. Someone could have built a career on those!

Dr. Z did build a career on those amps

Glad someone caught the nod

I have an AO-35 waiting in the wings. Looking forward to it!

[Colossal]

Should be a fun amp. Lots of possibilities in those chassis.

[aab0mb]

I had an extra 500v 20uf cap and a 5k resistor handy so I dropped those in for an extra node on the power rail at the very end. As it sits, everything in front of the phase inverter is running on the same node.

With 8 triodes what is the best way to allocate my power nodes in an amp like this while considering signal path etc? Should I add an extra node because of all the stages?

[10thTx]

I had an extra 500v 20uf cap and a 5k resistor handy so I dropped those in for an extra node on the power rail at the very end. As it sits, everything in front of the phase inverter is running on the same node.

With 8 triodes what is the best way to allocate my power nodes in an amp like this while considering signal path etc? Should I add an extra node because of all the stages?

I would want the clean channel to have it's own filtering and the OD channel to have it's own filtering. So in the example you posted, clean would have a node E and OD would have a node D.

IF you are concerned about voltages being lowered too much you can always do some like in this schematic and run a node E off a node C

with respect, 10thtx

[aab0mb]

I had an extra 500v 20uf cap and a 5k resistor handy so I dropped those in for an extra node on the power rail at the very end. As it sits, everything in front of the phase inverter is running on the same node.

With 8 triodes what is the best way to allocate my power nodes in an amp like this while considering signal path etc? Should I add an extra node because of all the stages?

I would want the clean channel to have it's own filtering and the OD channel to have it's own filtering. So in the example you posted, clean would have a node E and OD would have a node D.

IF you are concerned about voltages being lowered too much you can always do some like in this schematic and run a node E off a node C

with respect, 10thtx

Thanks a ton, friend. I have all the nodes hooked up and will try your suggestion. I had a chance to try the amp at proper volume and it’s sounding great so far!