SLO clone

SLO clone project is a guitar amp project based heavily on Soldano SLO. There are some other guitar amps (at least Peavey 6505 and Weber VST Heather) based on the model, this project is my version of it. There will be a few mods here and there but not too many. The parts i am planning to buy will be high quality so i am expecting the amp to sound great!

Great info for making this amp and purchasing the parts can be found from the SLOclone Forums.

30.5.2008

I got the first parts a few days ago: The PCB boards, two of them, the main board and power supply board. It's possible to build this amp PTP too but i decided to go PCB as the original is PCB. Nice PCBs, thanks Smashguitars!

Today i ordered the chassis (white with black lettering) and the cabinet (snakeskin pattern tolex) from Weber VST. Weber's Heather amp's chassis and cabinet is quite close to the original. They should be here in a few weeks i guess.

I have ordered the transformers and the choke already too but it can take up to 8 weeks to get them. The transformers are made by O'Netics and they are considered to be about the best you can get for your SLO clone (real SLO uses DeYoung Mfg. transformers but they are custom built for Soldano and not available for public). O'Netics specially make a set suitable for SLO. O'Netics make transformers for THD, Soldano, Club and other boutique amp builders.

3.7.2008

Update, update! Today i received most of the electric components from Uraltone. Last week i already got the chassis from Weber. I ordered the cabinet also from Weber but i haven't got it yet, i wonder where it's going because it left Weber at the same time with the chassis. Fedex status says 'In Transit' so i really hope it's still travelling somewhere and not lost. Though i don't need it exactly now.

Immediately after i laid down the components on the carpet some inquiring minds came and started investigate the stuff. They didn't say anything as usual. They just did their thing and looked at me like they wanted some explanation of what is going on.

6.7.2008

I have made some progress. The boards have been mostly filled (at least the main board, the power board is still missing the big caps, diodes and a few resistors). I ordered some additional (pretty much the rest) components from Mouser to complete the boards and few things are still coming from Uraltone. The boards are also ready to be attached to the chassis and i will do it as soon as i finish the boards. The heaters have been wired and yeah it was some piece of work, it took a couple of hours to complete. All the hardware, Cliff jacks (for insulation from chassis), Alpha pots, switches, tube sockets (Belton, very good quality btw, easy to work on) have been attached so i'm getting ready to wire the boards and everything else (after i finish the boards).

I decided to go with Mallory 150 signal caps because i heard they are a bit more vintage, a bit more middy and softer high end than Orange Drops 715p's. I also got (mostly) carbon film resistors for compromise between stability, noise and tone.

I'm gonna try first how the traditional AC heater voltage works and decide then later if i want to change that for elevated or even DC heater voltage.

10.7.2008

Finally the cabinet arrived, two weeks after the first package. I called several times to Fedex and they say they lost the shipping info for that package although there is my name and addrress clearly printed on the box. Anyway it's here now. I also received the Mouser stuff i ordered. I have been going forward with the chassis by wiring the switches, input jack and some pots. Now that i can (again almost) complete the boards i can go on more freely.

Here is a pic of the cabinet, i wanted to try it with the chassis already. The cabinet is a bit shorter than small box Marshall cabinet but then a bit deeper. It measures 592 mm (W) x 230 mm (H) x 230 mm (D). Now this is something that made me think twice, it has a snakeskin pattern tolex (it's plastic, not real) which is a kind of classic look for SLO and which may not be really my style (morally) but as long it's not real it's okay i guess (Marshalls have fake animal skin tolex too but how many of us think it that way, snakeskin tolex is just so obvious).

One of the investigators is here again doing their job.

3.8.2008

Okay, i have been doing a lot since the last update but i have just been lazy to update here. However i have taken pictures every now and then. So here is one series of pictures.

And the power board is ready too by the way, there's just no pic of it. The height of the big capacitors on the power board are just low enough to fit inside the chassis. It seems that now i have everything but the transformers and the choke, i hope i will get them during the August.

15.8.2008

I had to re-order the transformers and the choke. This time i did it directly from O'Netics. However there's another at least 8 weeks waiting but that's okay, anyway i have no choice. I want quality and O'Netics are the ones to get.

6.11.2008

Still there? It's been some time. Alright, received a word from O'Netics that the transformers are ready but they were still waiting for the mounting hardware, they should arrive this week. Then they will pack and ship ASAP. Great, can't wait to finish the amp!

24.11.2008

On Saturday i received an email from O'Netics that the tranformers and the choke has been shipped. Finally it seems that i can finish the amp soon.

18.12.2008

A week ago i received the transformers and the choke. However some of the parts were a bit damaged during shipping. The choke bobbin flange was broken and transfomers' end bells had a few dents. I sent email to O'Netics and they immediately told me they will send replacement parts FREE OF CHARGE: new end bells for the transformers and a new choke. That's customer service! So i still have to wait for a while to get the new parts. I will continue to build the amp then.

28.2.2009

I emailed O'Netics awhile ago to ask about the stransformer covers and choke. They replied that they haven't sent them yet because they found out that Finland's voltage is 230 V (their power transformer is made for 220 V or 240 V). While it was agreed that it would quite okay to use the 240 V transformer tap, they decided to make me and one other customer here in Finland a new power transformer. They said it would take a few weeks to complete. I will receive the choke then also.

25.4.2009

I got email from O'Netics that the power trasnformers have been shipped. I should get my choke too. This would be all FREE OF CHARGE. O'Netics has been suffering from supply chain problems as many companies carry little or no inventory nowadays. It's been long time but i do understand their problem to delivery. Soon it has been a year since i started my project though the last 8 months i've been only waiting. Soon mommy soon i assume!

22.5.2009

I received my new power transformer (for 230 V line voltage) and choke 2 weeks ago. No problems with shipping this time. Yesterday i spent some time to resume my project. I attached the transformers and choke to chassis. Now i can continue making the rest of the wiring. Since i haven't been able to build my amp for some time i have forgotten many things about it. I hope i can remember all important things and not make any stupid mistakes. I also talked to the other Finnish guy (Mikko) who got the same transformers for his amp and he said the output transformer might be a bit bass heavy (at least for his taste). Let's see how i like it.

28.8.2009

A lot have been happening since May. I spent my summer working "elsewhere". First in friend family's laundry business while they were out of country. Then bought an apartment and decided to renovate it throughout. This week i resumed my project again and was happy to complete the wiring for now. I am saying 'for now' because i haven't tried to turn it on yet. I still have to check everything and learn how to switch it on the first time.

29.8.2009

Ok, the amp works... somehow: There's a lot of oscillation, hiss and buzz. When i set the output impedance to 16 ohms i can get rid of the oscillation. The poweramp tubes are also hot, too hot. Regardless of the bias pot position the plates are turning red after awhile. The good news is, i can hear the guitar through the amp and it does sound good. Furthermore channel switching is working fine. Now i hope i can manage with the troubleshooting.

9.10.2009

Yesterday i brought the amp to a professional amp tech Olli Kaske, Midi Factory Ky (suggested by Mikko, the guy who purchased the same O'Netics transformers i did). He found a few foundational problems from my amp: First of all the OT primary wires were wrong way (opposite phase), that's were the enormous oscillation came from (amp's negative feedback was actually positive). Secondly the optocouplers' power supply was NOT grounded at all. In the schematic this is clearly stated that the ground connection must be made, PCB's other ground connections are not connected to optocouplers' power supply. Last thing was that poweramp bias point was not very close where it should be. This was corrected by adding two resistors, one 47 kohm resistor in parallel with R67 (220 kohm) and one 39 kohm resistor in series with VR11 the bias pot (50 kohm). Thank you Olli Kaske!

I fetched the amp back today and yes it working like it should be... for a few minutes. I was playing the amp at home when suddenly the Overdrive channel lost some of it's drive. I was thinking to myself this amp project is not meant to be easy. The Normal channel was working like it should be so i was thinking the problem must in Overdrive preamp section. I removed all the preamp tubes and put them back thinking it could be a contact problem. Did not solve the problem. Then i removed two first preamptubes and replaced them with known good ones. Tadaa! All the drive was back.

Obviously i haven't been able to open the amp much (volume wise) at home. But the amp sounds quite awesome. I must also say that this is truly a master volume amp, attenuator doesn't do any justice for it, tried it also. Normal channel clean is nice, beatiful and totally usable. Ovedrive channel is strong and thick, pretty much like what i have imagined (my reference with this amp is Eric Clapton's tone in the time of Journeyman album and on the following tour which i was happy to witness, specially take a listen to the song Bad Love).

I try to record some samples soon.

10.10.2009

Samples:

23.11.2009

I added FX loop level switch to decrease the default level from + 4dB to 0dB when needed. I started to keep my Lexicon LXP-1 in the loop to give a nice Plate reverb.

I also made a footswitch (with a LED) to change between the Normal and Overdrive channel.

Overall i have started to like this amp a lot. It's a kind of scary because i used to like only vintage style non master volume amps before. This amp has made me to realize that master volume can be made well when designed into an amp. I still don't like the idea where a master volume is added thoughtlessly to any amp.